TWI910851B - Distributed power management devices and power distribution systems - Google Patents

Abstract

The present invention provides a distributed power supply management device (31) for managing one or more distributed power supplies. Each of the one or more distributed power supplies is connected to a power system and operates as a voltage source. The frequency and power relationship of each of the one or more distributed power supplies has a vertical characteristic and is adjusted so that the frequency command value (Fref) and the power command value (Pref) correspond to each other. The distributed power supply management device (31) includes: an AC frequency collection unit (313) for collecting AC frequency information of the power system and determining a representative value (Fmeasure) of the AC frequency based on the collected AC frequency information; and a frequency command value generation unit (315) for generating the frequency command value (Fref) of each of the one or more distributed power supplies based on the representative value of the AC frequency.

Description

Distributed power management devices and power distribution systems

This disclosure relates to a distributed power management device and power distribution system, and more specifically, to a method for generating control command values for each distributed power source when connecting one or more distributed power sources with vertical characteristics to an AC power distribution system, for example, with the installation of virtual synchronous generator control. In this disclosure, the plurality of distributed power sources include energy-generating machines (hereinafter also referred to as "energy-generating machines") that utilize renewable energy sources such as solar cells, and/or energy-storing machines (hereinafter also referred to as "energy-storing machines") such as fuel cells and batteries.

In recent years, with the goal of reducing environmental impact, the adoption of power generation systems utilizing natural energy sources, such as solar cells that do not emit carbon dioxide, has accelerated. Furthermore, to address power shortages following the Great East Japan Earthquake, the commercialization of systems with integrated batteries, systems using electric vehicles as batteries, and systems combining solar cells and batteries has been promoted. All of these systems utilize static inverters.

On the other hand, as the generation of renewable energy increases, the cost of power generation, including management costs, rises in thermal power plants, which serve as a regulating force, and therefore they are expected to be gradually shut down in the future. Synchronous generators used in thermal power generation and similar applications inherently possess a function of suppressing system frequency variations (referred to as inertial forces or synchronizing forces). Therefore, as the number of synchronous generators gradually decreases due to the closure of thermal power plants, ensuring system stability will become difficult.

To address the aforementioned issues, the development of virtual synchronous generator control technology, which enables static inverters to possess the functions of synchronous generators, has been promoted in various enterprises.

For example, Japanese Patent Application Publication No. 2019-176584 (Patent Document 1) discloses a method for setting the control parameters of a distributed power supply (more specifically, a static inverter) equipped with virtual synchronous generator control technology. Specifically, this document describes a static inverter that connects the distributed power supply to the power system based on either a required inertia value requested by the system user or a virtual inertia value calculated based on the specifications and operating state of the distributed power supply.

More specifically, the total virtual inertia value Jopt, obtained by summing the virtual inertia of each static inverter, is set as follows. First, the system linkage control device receives the virtual inertia value Jreq from the system user's request for distributed power. Then, based on the operating status and specifications of the renewable energy system, the system linkage control device sets the upper limit value Jmax, i of the virtual inertia relative to each static inverter, and the lower limit value Dmin, i of the virtual decay constant when the upper limit value Jmax, i of the virtual inertia is activated. Then, the system linkage control device determines whether the sum of the upper limit values Jmax,i, ΣJmax,i, is smaller than the required virtual inertia value Jrreq. When the sum of ΣJmax,i, is smaller than the required virtual inertia value Jrreq, the system linkage control device sets the total virtual inertia value Jopt suitable for the renewable energy system as Jopt = ΣJmax,i. On the other hand, when the sum of Jmax,i, ΣJmax,i, is larger than the required virtual inertia value Jrreq, the system linkage control device sets Jopt = Jreq. Furthermore, the total virtual decay constant value Doptimal (i.e., the optimal value) suitable for the renewable energy system has also been described in Patent 1 as being set using the same method. [Previous Art Documents] [Patent Documents]

Patent Document 1: Japanese Patent Application Publication No. 2019-176584

[The problem that the invention aims to solve]

According to Patent Document 1, the control parameters (i.e., the total virtual inertia value and the total virtual decay constant value) used for virtual synchronous generator control in a stationary inverter equipped with virtual synchronous generator control function are calculated and set using the method described above. While this method ensures the inertia of the system as intended by the system administrator, the following problems arise when load changes and power generation changes occur.

In other words, if load changes or power generation fluctuations occur, each distributed power source distributes excess or insufficient power according to its own virtual synchronous generator characteristics (i.e., droop characteristics). More specifically, each distributed power source (more specifically, a static inverter) simulates the operation of a synchronous generator based on the droop characteristics of virtual synchronous generator control, thereby supplying excess or insufficient power due to load changes or power generation fluctuations. At this time, each distributed power source determines the frequency of its output system AC voltage based on the difference between the power command value from the upper-level EMS (Energy Management System) and its own output power. On the other hand, the frequency of the system AC voltage is managed by high-capacity synchronous generators connected to the backbone system. In other words, high-capacity synchronous generators are superior to the frequency of the system AC voltage. Even if distributed power supplies equipped with virtual synchronous generators in the distribution system supply excess or insufficient power according to their droop characteristics, this has almost no impact on the frequency of the system AC voltage. Furthermore, the frequency of the AC system voltage supplemented by distributed power supplies equipped with virtual synchronous generators is determined based on the droop characteristics and the power command value from the higher-level EMS. Generally, the frequency of the backbone system varies by approximately ±0.2Hz from the rated frequency. On the other hand, distributed power supplies equipped with virtual synchronous generator control (i.e., distributed power supplies with drooping characteristics that operate as voltage sources) limit the upper and lower frequency limits of the AC system voltage they can fill to ensure stable operation, and the frequency range available to the backbone system is wider than their own frequency range. Therefore, when the frequency of the AC system voltage deviates from the frequency range that the distributed power supply equipped with virtual synchronous generator control can fill, there is a problem that the distributed power supply equipped with virtual synchronous generator control will stop.

This disclosure is a product developed to solve the aforementioned problems, specifically concerning a distributed power management device (i.e., a higher-level EMS). The purpose of this disclosure is to enable a distributed power management device to generate control command values in a power system equipped with multiple stationary inverters using virtual synchronous generator control. This ensures that even when the frequency of the AC system voltage changes due to variations in load consumption or power generation from renewable energy sources, the inverter will not deviate from the frequency range manageable by the vertical characteristics of the stationary inverter (which possesses virtual synchronous generator characteristics, more generally, vertical characteristics), and can operate continuously without stopping the stationary inverter. [Means for Solving the Problem]

According to one aspect disclosed herein, a distributed power supply management device is provided for managing one or more distributed power supplies. Each of the one or more distributed power supplies is connected to a power system and operates as a voltage source. The frequency-power relationship of each of the one or more distributed power supplies has a vertical characteristic and is adjusted so that frequency command values and power command values correspond to each other. The distributed power supply management device includes: an AC frequency collection unit that collects AC frequency information from the power system and determines a representative value of the AC frequency based on the collected AC frequency information; and a frequency command value generation unit that generates frequency command values for each of the one or more distributed power supplies based on the representative value of the AC frequency.

According to another aspect of this disclosure, a distributed power supply management device is provided for managing one or more distributed power supplies. Each of the one or more distributed power supplies is connected to a power system and operates as a voltage source. The frequency-power relationship of each of the one or more distributed power supplies has a vertical characteristic and is adjusted so that the frequency command value corresponds to the power command value. The distributed power supply management device includes: an AC frequency collection unit that collects AC frequency information from the power system and determines a representative value of the AC frequency based on the collected AC frequency information; and a power command value correction unit that corrects the power command value of each of the one or more distributed power supplies based on the representative value of the AC frequency. [Invention Benefits]

According to this disclosure, the frequency command value or power command value provided to each distributed power source is determined based on the measured AC frequency of the power system. Therefore, even when the frequency of the AC system voltage changes rapidly due to variations in load power consumption or solar radiation, such as the power supplied to the system from renewable energy generators, the distributed power source will not deviate from the frequency range managed by the stationary inverter equipped with virtual synchronous generator control characteristics (more generally, vertical characteristics), and can continue to operate without stopping the distributed power source.

The following describes each embodiment in detail with reference to the diagrams. In addition, the same or equal parts in the diagrams are marked with the same reference symbols, and the explanations will not be repeated in principle.

Embodiment 1 [Example of the Configuration of Distributed Power Management Device and Power Distribution System] Figure 1 is a block diagram showing the configuration of the distributed power management device of Embodiment 1 and a power distribution system having multiple distributed power sources controlled by the distributed power management device. Although a three-phase system is used as an example in this Embodiment 1, the distributed power management device of Embodiment 1 can also be applied to a single-phase system.

Referring to Figure 1, the power distribution system 1 includes: a substation 20; a main distribution line 24m, which is drawn from the substation 20; branch distribution lines 24a to 24d, which branch from the main distribution line 24m; and a plurality of automatic voltage regulators 23, which are connected in series on the main distribution line 24m. In this embodiment 1, an SVR (Step Voltage Regulator) is used as the automatic voltage regulator 23. Hereinafter, the automatic voltage regulator 23 will also be referred to as SVR23. Furthermore, the main distribution line 24m and the branch distribution lines 24a to 24d are collectively referred to as distribution lines 24. As shown in Figure 1, power distribution line 24 supplies power to users such as building 102, building 103, town A100a, town B100b, town C100c, town D100d, and factory 101, as well as the MW-level solar photovoltaic system (mega solar) power conversion device 27, battery power conversion devices 41a, 41b, and 41c, and synchronous generators 30a and 30b. The MW-level solar photovoltaic system 26 is connected to the MW-level solar photovoltaic system power conversion device 27, and batteries 40a, 40b, and 40c are connected to the battery power conversion devices 41a, 41b, and 41c, respectively.

Furthermore, the power distribution system 1 includes a plurality of voltmeters 22 (22a to 22x) connected to the main power distribution line 24m, a power distribution automation system 21, and a community energy management system (CEMS) 31. Hereinafter, the power distribution automation system 21 is also referred to as DSO (Distribution System Operator) 21. CEMS 31 is equivalent to the distributed power management device in this disclosure. In addition, the distributed power management system is referred to as such in that CEMS 31 includes DSO 21, battery power conversion device 41, and voltmeters 22, etc.

In this embodiment, each voltmeter 22 calculates the effective voltage value and frequency of the AC system voltage based on the voltage information of the distribution line 24 of the power distribution system 1. Each voltmeter 22 notifies DSO21 and CEMS31 of the calculated effective voltage value and frequency at a predetermined period (e.g., 1 minute period).

Furthermore, in this embodiment, each SVR23 notifies the distribution automation system (DSO) 21 of the touch position information, primary voltage information, and secondary voltage information at a pre-defined period. Moreover, during touch switching, the SVR23 notifies the distribution automation system (DSO) 21 of the touch position information, primary voltage information, and secondary voltage information non-periodically.

CEMS31 collects information on various measurement results, such as power consumption, from smart meters (not shown) installed at each user's location (i.e., town A100a, town B100b, town C100c, town D100d, building 102, building 103, factory 101) at a pre-defined cycle (e.g., 1 minute cycle). Furthermore, CEMS31 collects information on various measurement results, such as power generation, from the MW-level solar photovoltaic system power conversion device 27, synchronous generators 30a, 30b, and battery power conversion devices 41a, 41b, 41c at a pre-defined cycle (e.g., 1 minute cycle). At this time, CEMS31 notifies DSO21 of the aforementioned collected data as requested by DSO21. According to this embodiment 1, the communication cycle between CEMS31 and DSO21 is set to a 30-minute cycle.

Furthermore, although the communication cycle between DSO21 and CEMS31 is set to 30 minutes in the above description, it is not limited to this. For example, it could also be a 15-minute cycle or a 1-hour cycle. In addition, the communication cycle between each voltmeter 22 and the battery power conversion device 41 and CEMS31 is not limited to 1 minute. It could also be, for example, a 1-second cycle, a 10-second cycle, a 30-second cycle, a 2-minute cycle, etc.

Figure 2 is a block diagram of the CEMS31 shown in Figure 1. Referring to Figure 2, the CEMS31 has a communication circuit 311, a memory circuit 312, an AC frequency collection circuit 313, an operation plan generation circuit 314, a frequency command value generation circuit 315, a distributed power supply vertical characteristic management circuit 316, a data transmission generation circuit 317, and a CEMS internal control circuit 318.

The communication circuit 311 communicates with DSO21, each voltmeter 22, each SVR23, each user (i.e., town A100a, town B100b, town C100c, town D100d, building 102, building 103, town 100, and factory 101), MW-level solar photovoltaic system power conversion device 27, synchronous generators 30a, 30b, and battery power conversion devices 41a, 41b, 41c via communication line 25.

The memory circuit 312 stores various information obtained through the communication circuit 311, such as measurement results and status information of each distributed power source.

The AC frequency collection circuit 313 generates a representative value (Fmeasure) of the measured AC system voltage frequency based on the frequency measurement results of the AC system voltage received from voltmeter 22, the AC system voltage received from battery power conversion devices 41a, 41b, and 41c, and the AC system voltage received from MW-level solar photovoltaic system power conversion device 27. Furthermore, in this embodiment 1, the AC frequency collection circuit 313 outputs a representative value by calculating the average value of the AC system voltage measured by voltmeters 22a to 22x from the frequencies at various locations. In this way, the measurement errors of each voltmeter 22 are averaged.

Furthermore, the method for generating a representative value of frequency in the AC frequency collection circuit 313 is not limited to the above. For example, the output of a voltmeter 22 can be used as the representative value, or of course, the frequency measurement result of the AC system voltage measured by the battery power conversion device 41 or other distributed power sources can be used to determine the representative value. When the power distribution system 1 is an independent system, the representative value of AC frequency can also be the AC frequency collected from the distributed power source with the largest power capacity among a plurality of distributed power sources, or the distributed power source corresponding to the largest power command value among the power command values generated by the battery operation plan creation circuit 3141 of the operation plan creation circuit 314 described later.

The operation plan generation circuit 314 generates operation plans for the battery power conversion devices 41a, 41b, and 41c based on control commands from DSO21. In this embodiment 1, the operation plan generation circuit 314 generates a 24-hour operation plan at 30-minute intervals. Furthermore, the operation plan generation circuit 314 determines whether the operation plan needs to be modified based on measurement results and SOC (State of Charge) information collected from the battery power conversion devices 41a, 41b, and 41c in 1-minute increments. When it is determined that the operation plan needs to be modified, the operation plan generation circuit 314 then modifies the operation plan from DSO21 until the notification of the control command.

The frequency command value generation circuit 315 generates the frequency command value (Fref) based on the representative value (Fmeasure) of the frequency measurement result of the AC system voltage output from the AC frequency collection circuit 313.

The distributed power supply droop characteristic management circuit 316 manages the droop characteristics of the memory battery power conversion devices 41a, 41b, and 41c. In this embodiment 1, the distributed power supply droop characteristic management circuit 316 manages the virtual synchronous generator control parameters (i.e., speed regulation rate: Kgd, speed governor time constant: Tg, inertia constant: M, and braking coefficient Dg) as described later. Furthermore, the distributed power supply droop characteristic management circuit 316 can manage the droop characteristic itself, and can also be configured to manage the tilt angle ΔP/ΔF of the droop characteristic. Moreover, the droop characteristic of the distributed power supply is not limited to virtual synchronous generator control; it can be any droop characteristic with P (power) - F (frequency) characteristics. In addition, the distributed power supply droop characteristic management circuit 316 can also be configured to obtain control parameters (i.e., droop characteristics) from the virtual synchronous generator control circuit 4093 of the battery power conversion device 41 for management.

The data generation circuit 317 stores the operating plan output from the operating plan creation circuit 314 and the frequency command value (Fref) output from the frequency command value generation circuit 315. Furthermore, the data generation circuit 317 outputs the stored data to the communication circuit 311 based on the transmission command from the control circuit 318 within the CEMS. The communication circuit 311 transmits the data output from the data generation circuit 317 according to the control signal output from the control circuit 318 within the CEMS.

The control circuit 318 within the CEMS controls the operation of the communication circuit 311, memory circuit 312, AC frequency collection circuit 313, operation plan generation circuit 314, frequency command value generation circuit 315, distributed power supply vertical characteristic management circuit 316, and data transmission generation circuit 317 located within the CEMS 31.

Figure 3 is a block diagram of the operation plan creation circuit 314 within the CEMS31 shown in Figure 2. Referring to Figure 3, the operation plan creation circuit 314 includes a battery operation plan creation circuit 3141, a power generation prediction circuit 3142, a power consumption prediction circuit 3143, a battery operation plan correction circuit 3144, a power command value memory transmission circuit 3145, and a management circuit 3146.

The battery operation plan generation circuit 3141 generates operation plans (specifically, frequency command values and power command values) for the battery power conversion devices 41a, 41b, and 41c every 30 minutes and every 24 hours based on control command information from DSO21, power generation prediction results of the MW-level solar photovoltaic system 26 predicted by power generation prediction circuit 3142, and power consumption prediction information of users predicted by power consumption prediction circuit 3143. Here, the control information from DSO21 is the planned value (e.g., the plan for every 30 minutes and 24 hours) of the power consumed on the load side of substation 20 (i.e., the power supplied from substation 20 to the load side).

The power generation prediction circuit 3142 obtains 24-hour weather forecast information from a weather forecast server (not shown) via communication circuit 311. The power generation prediction circuit 3142 predicts the power generation of the MW-level solar photovoltaic system 26 based on the obtained weather forecast information, the clock information (year, month, day, and hour) inside the CEMS 31 (not shown), and the database information prepared for power generation prediction (not shown).

The power consumption prediction circuit 3143 predicts the total power consumption of each user based on the clock information (i.e., year, month, day, week, and hour) inside the CEMS 31 (not shown) and the database information prepared for power consumption prediction (not shown).

The battery operation plan correction circuit 3144 determines whether the operation plan needs to be corrected based on the charging and discharging power of the battery power conversion devices 41a, 41b, and 41c and the power command value information collected by the communication circuit 311. When it is determined that it needs to be corrected, it generates a correction value for the operation plan.

The power command value memory transmission circuit 3145 remembers the power command values of each distributed power source generated by the battery operation plan creation circuit 3141 and the battery operation plan correction circuit 3144, and outputs the power command values to the frequency command value generation circuit 315 according to the control signal output from the management circuit 3146 in the operation plan creation circuit 314.

The management circuit 3146 within the operation plan creation circuit 314 manages the operation of the battery operation plan creation circuit 3141, the power generation prediction circuit 3142, the power consumption prediction circuit 3143, the battery operation plan correction circuit 3144, and the power command value memory transmission circuit 3145.

Figure 4 is a block diagram of the AC frequency collection circuit 313 within the CEMS 31 shown in Figure 2. Referring to Figure 4, the AC frequency collection circuit 313 includes an averaging circuit 3131, a multiplier 3132, an adder 3133, a multiplier 3134, and a register 3135. As shown in Figure 4, in Embodiment 1, the AC frequency collection circuit 313 is configured to remove noise components from the output of the averaging circuit 3131 using a single IIR (Infinite Impulse Response) filter before outputting it.

The averaging circuit 3131 receives the frequency of the AC system voltage collected by the voltmeter 22 from the control circuit 318 within the CEMS at 1-minute intervals. The averaging circuit 3131 calculates the average value of the received AC system voltage frequency. The multiplier 3132 multiplies the average frequency output from the averaging circuit 3131 by the multiplication constant k output from the control circuit 318 within the CEMS. The adder 3133 adds the outputs of multiplier 3132 and multiplier 3134, and outputs the result to the frequency command value generation circuit 315 and the register 3135. The register 3135 stores the addition result of adder 3133. The multiplier 3134 multiplies the value of the register 3135 with the multiplication constant (1-k) and outputs the result to the adder 3133.

Figure 5 is a block diagram of the battery power conversion device 41 shown in Figure 1. Referring to Figure 5, the battery power conversion device 41 includes a voltmeter 401, a current meter 402, a first DC/DC conversion circuit 403, a first control circuit 404, a DC bus 405, a voltmeter 406, a current meter 407, a first DC/AC conversion circuit 408, a second control circuit 409, a voltmeter 410, a current meter 411, and a communication interface circuit 412.

The voltmeter 401 measures the voltage (i.e., DC voltage) output from the battery 40. The ammeter 402 measures the current (i.e., DC current) output from the battery 40. The first DC/DC converter 403 converts the first DC voltage (DC power) output from the battery 40 into a second DC voltage (DC power). The first control circuit 404 controls the first DC/DC converter 403 based on the measurements from the voltmeters 401 and 406 and the ammeter 402. The DC bus 405 supplies the second DC voltage output from the first DC/DC converter 403 to the first DC/AC converter 408.

Voltage gauge 406 measures the voltage of DC bus 405. Ammeter 407 measures the DC current output from the first DC/DC converter 403. The first DC/AC converter 408 converts the DC power output from the first DC/DC converter 403 into AC power. The second control circuit 409 controls the first DC/AC converter 408 based on the measurements from voltage gauges 406 and 410 and the measurements from ammeters 407 and 411. Voltage gauge 410 measures the voltage (i.e., AC voltage) output from the first DC/AC converter 408. Ammeter 411 measures the current (i.e., AC current) output from the first DC/AC converter 408. The communication interface circuit 412 enables communication between the battery power conversion device 41 and the CEMS31.

Furthermore, the first DC/DC conversion circuit 403 and the first DC/AC conversion circuit 408 can be configured using known DC/DC converters and inverters, respectively. In the configuration shown in Figure 5, the first DC/AC conversion circuit 408 corresponds to an embodiment of a "static inverter section." Furthermore, the second control circuit 409 corresponds to an embodiment of a "static inverter control section."

Figure 6 is a block diagram illustrating the structure of the first control circuit 404 of the first DC/DC conversion circuit 403 of the control battery power conversion device 41 shown in Figure 5.

Referring to Figure 6, the first control circuit 404 includes a charging control circuit 4041, a discharging control circuit 4042, a first switching circuit 4043, and a third control circuit 4044.

The charging control circuit 4041 generates control command values for the first DC/DC converter 403 during the charging control of the battery 40 based on the measured values of voltmeters 401 and 406 and the measured value of ammeter 402. The discharging control circuit 4042 generates control command values for the first DC/DC converter 403 during the discharging control of the battery 40 based on the measured values of voltmeters 401 and 406 and the measured value of ammeter 402.

The third control circuit 4044 outputs control parameters and target values (command values) to the charging control circuit 4041 and the discharging control circuit 4042, and manages the charging amount, charging current, and discharging power of the battery 40. Furthermore, the third control circuit 4044 outputs control signals to the first switching circuit 4043.

The first switching circuit 4043 selectively outputs one of the outputs of the charging control circuit 4041 and the discharging control circuit 4042 as the control command value for the first DC/DC converter 403, based on the control signal from the third control circuit 4044. The first switching circuit 4043 is controlled to output the control command value generated by the charging control circuit 4041 when the battery 40 is instructed to charge. The first switching circuit 4043 is also controlled to output the control command value generated by the discharging control circuit 4042 when the battery 40 is instructed to discharge.

Figure 7 is a block diagram illustrating the structure of the first DC/AC conversion circuit 408 and the second control circuit 409 of the control battery power conversion device 41 shown in Figure 5.

Referring to Figure 7, the second control circuit 409 includes an AC frequency detection circuit 4091, an effective power calculation circuit 4092, a virtual synchronous generator control circuit 4093, an inverter current control circuit 4094, an inverter voltage control circuit 4095, a second switching circuit 4096, and a fourth control circuit 4097.

The AC frequency detection circuit 4091 detects the phase and frequency from the AC voltage waveform measured by the voltmeter 410. In this embodiment 1, the AC frequency detection circuit 4091 detects zero-crossing points from the AC voltage waveform and detects the frequency from the time interval of the detected zero-crossing points. However, the AC voltage frequency detection method is not limited to using the detection results of zero-crossing points.

The effective power calculation circuit 4092 calculates the effective power from the AC voltage and AC current information measured by the voltmeter 410 and the ammeter 411. In this embodiment 1, the effective power calculation circuit 4092 calculates the effective power by accumulating the power of one cycle of the AC voltage waveform based on the zero-crossing detection information and AC frequency information output from the AC frequency detection circuit 4091. However, the method for calculating the effective power is not limited to the above. For example, when the AC system is three-phase, dq conversion or similar methods can also be used to calculate the effective power.

The virtual synchronous generator control circuit 4093 calculates the frequency information of the AC voltage output by the circuit 4092 and the AC effective power information from the AC frequency detection circuit 4091 and the effective power, so that the first DC/AC conversion circuit 408 (i.e., the static inverter) has the inertial force, synchronization force and braking force of a synchronous generator.

The following is a brief explanation of virtual synchronous generator control technology. As a representative of synchronous generators in thermal power plants, the functions of a virtual synchronous generator include: adjusting the output power according to frequency (i.e., speed governor function); maintaining angular velocity (i.e., inertial force); achieving synchronization with the AC system voltage (i.e., synchronization force); and regulating the base system voltage (i.e., AVR (Automatic Voltage Regulator)). The function includes a regulator (automatic voltage regulator) and the ability to continue operating even during a momentary drop in AC system voltage, such as in the event of a system failure. In virtual synchronous generator control technology, the transient response of a stationary inverter is controlled to simulate the functions of a synchronous generator. Specifically, this includes three functions: speed governor function, function of simulating a mass system model based on the rock equation (i.e., the dynamic characteristics of a rotating machine), and AVR function.

In this embodiment 1, the function of installing a speed governor and simulating a mass system model based on the oscillation equation will be explained in particular. Figure 42 shows a conceptual diagram illustrating the virtual synchronous generator control technology. Furthermore, the AVR function of the synchronous generator mainly involves control based on output voltage commands from the upper system (CEMS31 in embodiment 1) or invalid power command values; therefore, it is not installed in embodiment 1. The speed governor function and the function of simulating a mass system model based on the oscillation equation will be explained in detail below.

First, let's explain the function of the speed governor. The speed governor in a power plant controls the output of gas turbines or steam turbines in thermal or nuclear power generation, or the guide vanes of waterwheels in hydroelectric power generation, thereby controlling the generator's output power. In an AC power system, if demand exceeds supply, the frequency of the AC system voltage decreases. In thermal and hydroelectric generators capable of output control, the speed governor is controlled to have a droop characteristic, increasing power generation when the frequency decreases. Conversely, if supply exceeds demand, the frequency of the AC system voltage increases. Similarly, in this case, in thermal and hydroelectric generators capable of output control, the speed governor is controlled to have a droop characteristic, decreasing power generation when the frequency increases.

Figure 42 is a schematic diagram illustrating the function of the speed governor. As shown in Figure 42, if the angular velocity ω of the synchronous generator increases, the valve regulating the energy inflow moves to the right, and the energy supplied to the synchronous generator decreases. Conversely, if the angular velocity of the synchronous generator decreases, the valve regulating the energy inflow moves to the left, and the energy supplied to the synchronous generator increases. In this way, the energy output from the synchronous generator can be controlled independently by the frequency of the AC system voltage at its own end (i.e., the angular velocity of the synchronous generator). Since the above actions are also managed by the frequency of the AC system voltage when performed individually by the synchronous generators, load sharing between generators is possible. As for the model of the speed controller, the Institute of Electrical Engineers of Japan (IEEJ) has provided a model consisting of a one-time delay system as the standard model.

In this embodiment 1, the operation is described when approximating the speed regulator using a model constructed from the aforementioned primary delay system. The transmission coefficient of the speed regulator is represented by the following equation (1). In addition, -1/Kgd in equation (1) represents the proportional gain of the speed regulator (Kgd: speed regulation rate), and Tg represents the time constant of the primary delay system (Tg: speed regulator time constant).

... (1)

Next, the function of simulating the particle system model based on the oscillation equation will be explained. The synchronous generator is a generator rotor with a unit inertial constant M, as shown in Figure 42. For example, when the generated power of the MW-level solar photovoltaic system 26 decreases sharply due to rapid changes in solar radiation, the speed governor control mentioned above cannot supply the insufficient power instantaneously. The synchronous generator converts the rotational energy stored in the generator rotor into electricity and outputs it to the system. At this time, the angular velocity of the generator rotor (i.e., the number of rotations per unit time) decreases. If the angular velocity of the generator rotor decreases, the energy supplied by the speed governor control increases, supporting demand and supply. The following equation (2) shows the oscillation equation of the simulated particle system model (generator rotor). In equation (2) below, the energy P is divided by the angular velocity ω and converted into torque T. In addition, Dg in equation (2) represents the braking coefficient and M represents the inertial constant mentioned above.

... (2)

In this embodiment 1, it is explained that equations (1) and (2) are incorporated into the control of a stationary inverter (i.e., the first DC/AC conversion circuit 408) and the inertial force, synchronization force and braking force of a synchronous generator are simulated.

Referring back to Figure 7, the inverter current control circuit 4094 generates control command values for controlling the first DC/AC converter 408 using current control based on the outputs of the voltmeter 406, ammeter 411, and AC frequency detection circuit 4091. The inverter voltage control circuit 4095 generates control command values for controlling the first DC/AC converter 408 using voltage control (i.e., the control method of outputting AC system voltage from the first DC/AC converter 408) based on the outputs of the voltmeter 410 and AC frequency detection circuit 4091. The second switching circuit 4096 switches between the control command values from the inverter current control circuit 4094 and the control command values from the inverter voltage control circuit 4095 based on the output of the fourth control circuit 4097.

The fourth control circuit 4097 collects measurement results from voltmeter 406 and ammeter 407 regarding the DC bus 405, measurement results from voltmeter 410 and ammeter 411 regarding the AC system, and status information from the first DC/DC converter 403 output from the first control circuit 404, and notifies the CEMS 31 of the information via the communication interface circuit 412.

Furthermore, the fourth control circuit 4097 also notifies the CEMS 31, etc., of various control parameters of the aforementioned virtual synchronous generator control circuit 4093, inverter current control circuit 4094 (more specifically, the first PI control circuit 40942 and the second PI control circuit 40945), and inverter voltage control circuit 4095 (more specifically, the third PI control circuit 40953 and the first current limiting circuit 40955) via the communication interface circuit 412. Moreover, the fourth control circuit 4097 transmits information regarding the effective voltage of the AC system measured by the effective voltage measurement unit of the AC system (not shown), and the effective voltage of the AC system (not shown). The effective and ineffective power information measured by the ineffective power measurement unit is also notified to CEMS31 via communication interface circuit 412. Furthermore, the fourth control circuit 4097 also notifies the third control circuit 4044 of the measurement results of the effective voltage and effective power of the AC system mentioned above.

Figure 8 is a block diagram illustrating the structure of the AC frequency detection circuit 4091 shown in Figure 7. Referring to Figure 8, the AC frequency detection circuit 4091 includes a phase detection circuit 40910, a frequency detection circuit 40911, and a first sine wave generation circuit 40912.

Phase detection circuit 40910 detects zero-crossing points from the voltage waveform of the AC system output from voltmeter 410. Frequency detection circuit 40911 detects frequency based on the result of zero-crossing point detection by phase detection circuit 40910. However, the method for detecting phase in phase detection circuit 40910 is not limited to zero-crossing point detection. Externally, the zero-crossing detection in the actual machine is affected by errors caused by the zero-point detection error of the voltmeter 410 (mainly offset error), the amplitude detection error of the voltmeter 410 (mainly linearity error), and the sampling period error during the sampling of the system AC voltage waveform (e.g., the inconsistent time from carrier interruption to actual sampling when sampling is performed using a microcomputer). A phase detection circuit 40910 can also be configured to correct these errors and detect the zero-crossing point.

The first sine wave generating circuit 40912 generates a sine wave synchronized with the AC system voltage based on the results of zero-crossing detection in phase detection circuit 40910, frequency detection in frequency detection circuit 40911, and the amplitude of the system AC voltage output from CEMS31. The AC frequency detection circuit 4091 outputs the zero-crossing detection result (i.e., the zero-crossing detection time), the frequency detection result, and information about the sine wave (i.e., voltage, frequency, phase, and sine wave waveform).

Figure 9 is a block diagram illustrating the configuration of the inverter current control circuit 4094 shown in Figure 7. Referring to Figure 9, the inverter current control circuit 4094 includes a subtractor 40941, a first PI control circuit 40942, a multiplier 40943, a subtractor 40944, a second PI control circuit 40945, and a first PWM conversion circuit 40946.

The inverter current control circuit 4094 generates a control command value for controlling the first DC/AC conversion circuit 408 based on the DC voltage of the DC bus 405 output from the voltmeter 406. The DC voltage of the DC bus 405 output from the voltmeter 406 is subtracted from the target value of the DC bus voltage output from the fourth control circuit 4097 by the subtractor 40941, and the result is input to the first PI control circuit 40942. The first PI control circuit 40942 outputs a command value to make the DC voltage of the DC bus 405 reach a predetermined value based on the control parameters (i.e., proportional gain and integration time) output from the fourth control circuit 4097.

The command value output from the first PI control circuit 40942 is multiplied by multiplier 40943 and a sine wave synchronized with the AC voltage waveform (i.e., sine wave waveform) output from the first sine wave generator 40912. This generates the current command value. The current command value output from multiplier 40943 is subtracted by subtractor 40944 from the AC system current value measured by ammeter 411 and input into the second PI control circuit 40945. In the second PI control circuit 40945, the control command value is output to the first PWM converter 40946 based on the control parameters (i.e., proportional gain and integration time) output from the fourth control circuit 4097, so that the subtraction result output from subtractor 40944 becomes zero. The first PWM conversion circuit 40946 performs PWM modulation when a control command value is input from the second PI control circuit 40945, and outputs it as a command value to the first DC/AC conversion circuit 408.

Furthermore, as mentioned above, the control parameters of the first PI control circuit 40942 and the second PI control circuit 40945 are also notified from the fourth control circuit 4097.

Figure 10 is a block diagram illustrating the structure of the inverter voltage control circuit 4095 shown in Figure 7. Referring to Figure 10, the inverter voltage control circuit 4095 includes a second sine wave generation circuit 40951, a subtractor 40952, a third PI control circuit 40953, a first current limiting circuit 40955, and a second PWM conversion circuit 40954.

The inverter voltage control circuit 4095 outputs a control command value for controlling the first DC/AC converter circuit 408 based on the frequency and phase information output from the virtual synchronous generator control circuit 4093 (described in detail later) and the amplitude information of the AC system voltage output from the fourth control circuit 4097 (in this embodiment, it is input via the first sine wave generation circuit 40912).

The sine wave information (i.e., frequency, phase, and amplitude information) from the AC frequency detection circuit 4091 and the frequency and phase information from the virtual synchronous generator control circuit 4093 are input to the second sine wave generation circuit 40951. However, in this embodiment 1, QV control (ineffective power-voltage control) is not performed by the virtual synchronous generator control circuit 4093, so the amplitude is not controlled. The second sine wave generation circuit 40951 generates the target value of the AC system voltage output from the first DC/AC conversion circuit 408 based on the input frequency, phase, and amplitude information.

Subtractor 40952 subtracts the voltage measured by voltmeter 410 from the output of the second sine wave generator 40951, and outputs the subtraction result to the third PI control circuit 40953. The third PI control circuit 40953 generates a voltage command through PI control to make the input subtraction result zero, and outputs the generated voltage command to the first current limiting circuit 40955. In addition, the control parameters (i.e., control gain and integration time) of the third PI control circuit are output from the fourth control circuit 4097. The first current limiting circuit 40955 adds a limit to the command value output from the third PI control circuit 40953 based on the result measured by ammeter 411 input through the fourth control circuit 4097. The command value output from the first current limiting circuit 40955 is output to the first DC/AC conversion circuit 408 after being PWM modulated by the second PWM conversion circuit 40954.

Figure 11 is a block diagram illustrating the structure of the virtual synchronous generator control circuit 4093 shown in Figure 7. Referring to Figure 11, the virtual synchronous generator control circuit 4093 includes a subtractor 40932, a speed controller control circuit 40933, an adder 40935, a subtractor 40936, and a mass system calculation circuit 40937.

Subtractor 40932 subtracts the frequency command value (Fref) output from the fourth control circuit 4097 from the measured frequency result. The output of subtractor 40932 is input to the speed controller control circuit 40933. The detailed operation of the speed controller control circuit 40933 will be explained later. Adder 40935 adds the offset value added to the power target value (command value) output from the speed controller control circuit 40933 to the power command value (Pref) output from the fourth control circuit 4097, thereby generating the control power target value (command value) of the mass system calculation circuit 40937.

Subtractor 40936 subtracts the effective power output from effective power calculation circuit 4092 from the control power target value (command value) output from adder 40935. The output of subtractor 40936 is input to mass system calculation circuit 40937. Details will be explained later. Mass system calculation circuit 40937 calculates the frequency and phase of the AC system voltage output from battery power conversion device 41 to make the output of subtractor 40936 zero. In addition, the control parameters (speed adjustment rate Kgd, speed governor time constant Tg, inertia constant M, and braking coefficient Dg) of the speed governor control circuit 40933 and the mass system calculation circuit 40937 are notified by the fourth control circuit 4097 to the CEMS31.

Figure 12 is a block diagram illustrating the structure of the speed controller control circuit 40933 shown in Figure 11. Referring to Figure 12, the speed controller control circuit 40933 includes a multiplier 409331, a first-order delay system model (represented in the figure as 1/(1+s×Tg)) 409332, and a limiting circuit 409333.

Multiplier 409331 multiplies the output of subtractor 40932 by the proportional gain (represented as -1/Kgd in the figure) output from the fourth control circuit 4097. The output of multiplier 409331 is output to the primary delay system model 409332. In this embodiment 1, the explanation is based on the standard model of a primary delay system controlled by a speed controller as suggested by the Electrical Institute (IEEJ). Therefore, the primary delay system model 409332 is the model of the primary delay system installed as shown in Figure 12 (i.e., 1/(1+s×Tg)). The output of the primary delay system model 409332 is limited by the limiting circuit 409333 and then output.

Figure 13 is a block diagram illustrating the structure of the particle system calculation circuit 40937 shown in Figure 11. Referring to Figure 13, the particle system calculation circuit 40937 includes a subtractor 409371, an integrator (represented as 1/(M+s)) 409372, a multiplier 409373, a divider 409374, an adder 409375, and a phase calculation circuit 409376.

Subtractor 409371 subtracts the output of multiplier 409373 from the output of subtractor 40936 in Figure 11 (i.e., the subtraction result of the measured effective power and the power target value (command value)). The subtraction result is input to integrator 409372. Integrator 409372 integrates the output of subtractor 409371 by multiplying it by 1/M, thereby generating the difference (Δω) between the angular velocity of the generator rotor and the angular velocity command value of the generator rotor as shown in Figure 42. In this embodiment 1, the frequency command value is set to 60 Hz. Therefore, the angular velocity command value is 2 × π × 60 rad/s. The output of integrator 409372 is input to multiplier 409373, where it is multiplied by the braking coefficient Dg output from the fourth control circuit 4097. Subtractor 409371 subtracts the output of multiplier 409373 from the output of subtractor 40936, thereby simulating the braking force of a synchronous generator under the control of the first DC/AC converter 408.

The output (Δω) of integrator 409372 is divided by 2×π by divider 409374, thereby converting it into frequency difference information (Δf). The frequency difference information (Δf) is added to the frequency target value (60Hz) by adder 409375, thereby converting it into the frequency (rotation frequency) of the generator rotor. The output of adder 409375 is input to phase calculation circuit 409376, and the phase calculation circuit 409376 calculates the phase of the generator rotor based on information from the fourth control circuit 4097 (i.e., zero crossover detection information, frequency detection information, new input start indication, etc.).

Next, the transfer function of the oscillation equation part of the particle system calculation circuit 40937 will be explained. The transfer function of the oscillation equation part is shown in the following equation (3), which can be represented by a single-order delay system with a proportional gain of 1/Dg and a time constant of M/Dg. In addition, the speed regulator time constant (Tg) and the particle system calculation unit time constant (M/Dg) in the virtual synchronous generator control circuit 4093 are determined according to the response speed required by the system.

... (3)

Figure 43 is a block diagram for calculating the transfer function F(s) of the virtual synchronous generator control circuit 4093 shown in Figure 11. The transfer function F(s) (i.e. Δf/ΔP) of the block diagram shown in Figure 43 is represented by the following equation (4).

... (4)

Therefore, according to the theorem of final value, the following equation (5) holds. Equation (5) is equivalent to the tilt of the vertical characteristic of the virtual synchronous generator control unit (i.e., 1/(2×π×Dg+1/Kgd)).

... (5)

[Operational Overview of the Distributed Power Management Device] The operation overview of the distributed power management device of Embodiment 1 will now be explained with reference to Figures 14 to 19.

Figure 14 shows the area filled by the virtual synchronous generator control installed in the battery power conversion device 41. In Figure 14, the horizontal axis shows the response time, and the vertical axis shows the magnitude of demand variation. As shown in the figure, in the virtual synchronous generator control installed in the static inverter, small variations of tens of milliseconds to several minutes and short-cycle variations are filled. For control of several minutes or more, load frequency control (LFC) or economic load distribution control (EDC) is used. Therefore, in this embodiment 1, the response performance of the virtual synchronous generator control circuit 4093 is set to less than 1 second.

Figure 15 is a graph showing an example of the droop characteristics of the virtual synchronous generator control shown in Embodiment 1. The horizontal axis of Figure 15 is frequency, showing the frequency command value (Fref). In this disclosure, the difference between the measured frequency (Fmeasure) and the frequency command value is referred to as Δfrequency (Fmeasure-Fref). The vertical axis of Figure 15 is the difference (Δpower) between the power command value (Pref) and the measured effective power (Pmeasure). Equation (5) shows the tilt of the droop characteristics shown in Figure 15. In addition, this graph shows an example when the power command value (Pref) is set to "zero" for ease of explanation. In terms of droop characteristics, it is adjusted to obtain the power command value (Pref) from the frequency command value (Fref).

Next, we will briefly explain the droop characteristics of a power distribution system (i.e., the droop characteristics of the backbone system). Generally speaking, the upper and lower limits of the frequency of the AC system voltage in the backbone system are approximately 1 to 2% of the system frequency (i.e., the rated frequency). Therefore, when the system frequency is 60Hz, the upper limit frequency is approximately 61.2 to 60.6Hz, and the lower limit frequency is approximately 59.4 to 58.8Hz. Furthermore, the frequency of the power distribution system constantly changes within the above frequency range.

Figure 16 shows an example of the results after measuring the frequency of the power distribution system voltage over 25 hours with a 1-second cycle. As shown in the figure, it can be confirmed that the voltage fluctuates normally within ±0.2Hz around 60Hz.

Figure 17 is a diagram showing an example of the vertical characteristics of the battery power conversion device 41 in the power distribution system 1 of this embodiment 1. In the figure, the horizontal axis displays the frequency of the AC system voltage, and the vertical axis displays the power. Fmax on the horizontal axis displays the maximum frequency achievable by the battery power conversion device 41, and Fmin displays the minimum frequency achievable by the battery power conversion device 41. 60.1Hz displays the maximum frequency achievable by the power distribution system voltage, and 59.9Hz displays the minimum frequency achievable by the power distribution system voltage. Hereinafter, the frequency range achievable by the power distribution system voltage will also be referred to as the rated frequency range. Fref displays the frequency command value for virtual synchronous generator control, and Pref displays the power command value. Furthermore, in this embodiment 1, the upper and lower limits of the distribution system voltage frequency are set to ±0.1Hz. Additionally, for ease of explanation, in this embodiment 1, the battery power conversion device 41 is only described for discharging purposes. Moreover, the upper and lower limits of the distribution system voltage frequency are not limited to ±0.1Hz; for example, it could be ±0.2Hz as a target for large power companies, or the upper and lower limits of the frequency determined by the distribution system contractor of a microgrid (e.g., ±0.15Hz).

Here, when a stationary inverter controlled by a virtual synchronous generator (operating as a voltage source) is connected to the backbone system, or when multiple stationary inverters controlled by virtual synchronous generators (operating as voltage sources) are connected through an independent system, or when multiple main power sources (operating as voltage sources) are connected through an independent system such as a synchronous generator, the braking coefficient Dg needs to be increased to ensure stable operation of the stationary inverter controlled by the virtual synchronous generator (operating as a voltage source). If the braking coefficient Dg is increased, as shown in equation (5), the frequency range ΔF that can be filled by the droop characteristic controlled by the virtual synchronous generator will become narrower. Therefore, as shown in Figure 16, compared to the rated frequency range of the AC system voltage (59.9Hz to 60.1Hz in this embodiment 1), the frequency range (Fmin to Fmax) filled by the droop characteristic controlled by the virtual synchronous generator becomes narrower. Consequently, if the frequency of the system AC voltage becomes smaller than Fmin or larger than Fmax, the battery power conversion device 41 will be unable to maintain operation and will stop. For example, when Fmin is 59.95Hz and the frequency of the system AC voltage is 59.94Hz, the voltage phase will always be offset by the difference between the frequency of the AC system voltage that can be output by the battery power conversion device 41 and the frequency of the system AC voltage, so there will be a problem of protective shutdown of the battery power conversion device 41.

Figure 18 is a diagram illustrating the method for generating the frequency command value (Fref) in the distributed power management device of Embodiment 1. Details will be explained later, but in Embodiment 1, while the CEMS31 generates the frequency command value Fref for each battery power conversion device 41, the operation plan generation circuit 314 shown in Figure 2 generates the power command value Pref (i.e., operation plan power command value information) for each battery power conversion device 41. Once the power command value Pref is generated, the CEMS31, as shown in part A of Figure 18, assumes that the frequency command value Fref is equal to the rated frequency of the backbone system (e.g., 60Hz) and generates a drooping characteristic. Furthermore, compared to the measured frequency (Fmeasure) of the AC system voltage received by the AC frequency collection circuit 313, for example, when Fmeasure is lower than Fmin, given the current droop characteristics, as described above, the battery power conversion device 41 will stop. In this embodiment 1, the details of this situation will be explained later, but for example, CEMS 31 notifies the battery power conversion device 41 by setting the frequency command value Fref to the measured result (Fmeasure) as shown in part B of the figure. In this case, as shown in the figure, because the droop characteristics shift to the left, the battery power conversion device 41 can continue to operate.

Next, the effectiveness of the frequency command value generation method described above will be explained with reference to Figures 19A and 19B. Figure 19A is a graph showing the frequency command value when the comparative example droop characteristic is used. In this graph, it is shown that the load becomes lighter over time and the frequency of the AC system voltage increases in a ramp-like manner. As shown in the figure, when the frequency command value (Fref) is the rated frequency (60Hz) of the backbone system and is fixed, the area inside the thick dashed line becomes the frequency range (also known as the frequency management range) of the battery power conversion device 41 (inverter). As shown in the figure, if the frequency of the system voltage gradually increases, the frequency of the system voltage will escape the frequency range of the inverter that can be controlled by the battery power conversion device 41 (inverter) (NG area in the figure). Therefore, the virtual synchronous generator control (VSG control) will fail and the battery power conversion device 41 will stop.

On the other hand, Figure 19B is a graph showing the frequency command value when using the drooping characteristic of Embodiment 1. As shown in the figure, the frequency command value (Fref) is controlled based on the measured result of the frequency of the AC system voltage. Specifically, in Embodiment 1, details will be explained later, but the frequency of the AC system voltage is measured at 1-minute intervals, and the frequency command value (Fref) is controlled based on the measurement result. As shown in the figure, since the frequency command value (Fref) is appropriately controlled according to the frequency of the AC system voltage, even when the frequency of the system voltage gradually increases, the connected operation can continue without the measured system frequency falling outside the frequency management range of the battery power conversion device 41 (inverter).

In summary, when a power conversion device equipped with a stationary inverter featuring droop characteristics (e.g., virtual synchronous generator control) is connected to an AC system, a distributed power management device generates a frequency command value (Fref) for the droop characteristics based on the frequency of the AC system voltage. This allows the power conversion device to be controlled even when the backbone system frequency deviates from the rated frequency (e.g., 60Hz), while maintaining the frequency control range of the power conversion device with the stationary inverter featuring droop characteristics.

[Details of the Operation of the Distributed Power Management System (CEMS)] The operation of the distributed power management system (CEMS31) of Embodiment 1 will be explained in detail with reference to Figures 1 to 30. Referring again to Figure 1, the power distribution system to which the distributed power management system of Embodiment 1 is connected will be explained. In Embodiment 1, the power distribution system 1 has three SVR23s to control the power distribution system voltage output from the substation 20 to a predetermined voltage. These three SVR23s are connected in series to the distribution line 24m between the substation 20 and the MW-level solar photovoltaic system power conversion device 27 (or the battery power conversion device 41a, town D100d). Furthermore, a battery power conversion device 41a is disposed near the MW-level solar photovoltaic system power conversion device 27. In this embodiment 1, the battery power conversion device 41a operates as a voltage source, and the MW-level solar photovoltaic system power conversion device 27 operates as a current source. The MW-level solar photovoltaic system power conversion device 27 also adjusts the fluctuation of the generated power of the MW-level solar photovoltaic system 26 by activating the virtual synchronous generator control circuit 4093.

In addition, as loads, there are town A100a, town B100b, town C100c, town D100d, factory 101, building 102, and building 103. Power is supplied to these loads from substation 20, generated by the MW-level solar photovoltaic system 26, and from batteries 40a to 40c. Furthermore, a synchronous generator 30a is installed in factory 101 for emergency use, and a synchronous generator 30b is installed in building 102 for emergency use.

The following describes the operation of the power distribution system used to control the power supplied from substation 20, the power generated by MW-level solar photovoltaic system 26, and the power discharged from batteries 40a to 40c.

Figure 20 is a sequence diagram of the normal operation of the distributed power management system centered on the CEMS31 shown in Figure 1. As shown in the figure, the normal operation of the distributed power management system includes two processes: process P1, which is implemented in a 30-minute cycle, and process P2, which is implemented in a 1-minute cycle.

In the diagram, if P1 is processed in a 30-minute cycle, DSO21 will request the CEMS31 to output the measurement data to be collected via communication line 25 (F1). CEMS31 will then receive the request from DSO21, which is a request for the transmission of measurement data from the battery power conversion device 41, voltmeter 22, and various users (including the MW-level solar photovoltaic system power conversion device 27) (F2, F4), and collect the latest measurement information (F3, F5). Furthermore, CEMS31 combines the data collected in 30 sessions at 1-minute intervals to calculate the power consumption of each user, the power generation of the MW-level solar photovoltaic system 26, and the charging and discharging power of the battery 40 during the 30-minute period. This data, along with the SOC (State of Charge) information of the battery 40, is then transmitted to DSO21 (F6).

If the measurement results are received, DSO21 will generate a demand plan for a 30-minute cycle within a 24-hour period required for the operation plan of the battery 40 (that is, the total power supplied from the substation 20 to the distribution line 24 within 30 minutes), and will notify CEMS31 (F7) of the results. If CEMS31 receives the aforementioned information to be used in the operation plan for the battery, that is, based on previously collected SOC information, SOH (State of Health) information of the battery 40, power generation forecast information of the MW-level solar photovoltaic system 26 (details will be explained later), and user demand forecast information (details will be explained later), it will create an operation plan for the battery 40 and control parameters (i.e., power command value (Pref), frequency command value (Fref), etc.) (F8). Furthermore, the method for creating the operation plan and control parameters will be explained later. Once the operation plan and control parameters of the battery 40 are completed, the CEMS31 will transmit the operation plan and control parameters to each battery power conversion device 41 (F9) and end the 30-minute cycle processing P1.

Furthermore, CEMS31 collects measurement data from the power conversion devices 41 and voltmeter 22 of each battery in the processing P2, which is performed in 1-minute cycles (F10, F12). Moreover, CEMS31 verifies the difference between the collected results, the power command value (Pref), and the actual charging/discharging power, and further verifies the difference between the frequency command value Fref and the measured frequency (Fmeasure) of the distribution system voltage, and determines whether the operation plan and/or control parameters (Pref, Fref, etc.) need to be adjusted (F14). According to Embodiment 1, when the difference exceeds a pre-defined value, CEMS31 recalculates the operation plan and/or control parameters (Pref, Fref, etc.) (F15), and notifies each battery power conversion device 41 of the recalculation result (F16). The specific recalculation process will be explained later.

Next, the detailed operation of CEMS31 will be explained with reference to Figure 21. Figure 21 is a flowchart showing the control processing of CEMS31 shown in Figure 1. In the figure, when processing begins, CEMS31 checks in step S101 whether it has received a request to transmit measurement data from DSO21. When it receives an output request (YES in step S101), CEMS31, in the next step S102, sends output requests for transmitting measurement data to the battery power conversion device 41, voltmeter 22, and various users (including the power conversion device 27 for MW-level solar photovoltaic systems), thereby collecting the latest measurement information from these machines. Furthermore, CEMS31 uses measurement data collected 30 times at 1-minute intervals to calculate the power consumption of each user, the power generation of the MW-level solar photovoltaic system 26, and the charging and discharging power of the battery 40 over 30 minutes, and stores the calculated power in memory circuit 312. This data stored in memory circuit 312 is equivalent to the measurement data requested to be transmitted by DSO21 in step S101. In the next step S103, CEMS31 transmits the aforementioned measurement data stored in memory circuit 312, along with information such as the SOC of the battery 40, to DSO21 via communication circuit 311.

CEMS31 proceeds to step S104 after transmitting measurement data to DSO21 in step S103, or when no data transmission request is received from DSO21 in step S101 (No in step S101). In step S104, CEMS31 checks whether a demand plan notification has been received from DSO21. If a demand plan is received, CEMS31 performs operation plan creation in the next step S105. Furthermore, in this embodiment 1, DSO21 notifies CEMS31 of the demand plan for power supplied from the backbone system to distribution system 1 at 30-minute intervals for a 24-hour period. The following details the process of creating the operation plan, with reference to Figure 22.

Figure 22 is a flowchart showing the detailed actions of the operation plan creation process in step S105 of the flowchart shown in Figure 21. In Figure 22, if the creation of the operation plan begins, CEMS 31 first performs the power generation prediction of the MW-level solar photovoltaic system 26 in step S1051. Specifically, referring again to Figures 2 and 3, if the control circuit 318 in CEMS receives a notification of the demand plan (battery operation plan) from DSO 21, it instructs the management circuit 3146 in the operation plan creation circuit 314 to create the operation plan. Upon receiving the instruction, management circuit 3146, via battery operation planning circuit 3141, instructs power generation prediction circuit 3142 to predict the power generation of the MW-level solar photovoltaic system 26. Upon receiving the instruction, power generation prediction circuit 3142 obtains a 24-hour weather forecast from a weather forecast server configured on an unshown internet connection. Power generation prediction circuit 3142 uses the obtained weather forecast results and data from an unshown power generation prediction database managed by power generation prediction circuit 3142 to predict the 24-hour power generation. Furthermore, the database used for power generation forecasting, which is not shown in the figure, is constructed, for example, based on power generation data, weather data, and time information (year, month, day, and hour) collected from MW-level solar photovoltaic systems 26 at 30-minute intervals. Details of the database construction method are omitted as they are not relevant to the focus of this case.

If the power generation prediction of the MW-level solar photovoltaic system 26 in step S1051 above is completed, CEMS31 will predict the user's power consumption in step S1052 of Figure 22. Specifically, referring again to Figure 3, if the management circuit 3146 in the operation plan creation circuit 314 receives the power generation prediction result of the MW-level solar photovoltaic system 26 from the power generation prediction circuit 3142, it will issue an instruction to the power consumption prediction circuit 3143 to predict the user's power consumption through the battery operation plan creation circuit 3141. Upon receiving the instruction, the power consumption prediction circuit 3143 uses data from a power consumption prediction database (not shown) managed by the power consumption prediction circuit 3143 to predict the user's power consumption over a 24-hour period. Furthermore, the power consumption prediction database (not shown) is constructed, for example, from user power consumption data collected at 30-minute intervals, based on date, time, and weather information. Details of the database construction method are omitted as they are not relevant to the focus of this case. Additionally, steps S1051 and S1052 can be performed either first or simultaneously.

If the user's power consumption prediction in step S1052 above is completed, CEMS31 will begin the demand plan creation in step S1053 of Figure 22. Specifically, referring again to Figure 3, the battery operation plan creation circuit 3141 in the operation plan creation circuit 314 calculates the total charge and discharge power of batteries 40a to 40c for every 30 minutes based on the power generation prediction result of the MW-level solar photovoltaic system 26 in the power generation prediction circuit 3142, the user's power consumption prediction result in the power consumption prediction circuit 3143, and the demand plan notified from DSO21. In addition, as described above according to this embodiment 1, the demand plan notified from DSO21 is a 24-hour power supply plan (i.e., a power supply plan every 30 minutes) for the power distribution system 1 that is closer to the load side than substation 20.

If the demand plan is completed in step S1053 of Figure 22, CEMS31 will determine the charging and discharging power of batteries 40a to 40c in the next step S1054. Specifically, referring again to Figures 2 and 3, the operation plan generation circuit 314 determines (allocates) the charging and discharging power from each of the 30 batteries by using the SOC information of batteries 40a to 40c collected in the memory circuit 312 via the communication circuit 311 and the battery capacity of batteries 40a to 40c.

In Implementation 1, during the 24-hour battery operation plan, the operation plan circuit 314 is designed to ensure that the SOC of batteries 40a to 40c is almost simultaneously zero, or that they can be charged and discharged simultaneously after 24 hours. This is based on the following reasons. For example, imagine a cloud crossing a MW-level solar photovoltaic system 26 (e.g., 10MW) for about 5 minutes, resulting in a decrease in power generation (from 10MW to 4MW). Furthermore, the capacities of the static inverters of the battery power conversion devices 41a to 41c are assumed to be 8MW, 4MW, and 2MW, respectively. Here, assuming that battery 40a is in a stopped state with its SOC at zero, and is notified of a battery operation plan to discharge 1MW and 0.5MW from batteries 40b and 40c respectively. In this case, due to the rapid change in sunlight, the power discharged from batteries 40b and 40c can only be additionally output by 3MW and 1.5MW respectively through virtual synchronous generator control, which cannot make up for the shortfall of 6MW. On the other hand, when batteries 40a to 40c are operating, a maximum discharge of up to 14MW can be achieved, which is a wider range of power that can be supplemented by virtual synchronous generator control compared to the 6MW case in the previous example. Therefore, when using CEMS31 to make the operation plan for battery 40, the operation plan should be made so that batteries 40a to 40c are almost at zero SOC at the same time, or are fully charged.

If the setting of the charging and discharging power of batteries 40a to 40c is completed in step S1054 of Figure 22, in the next step S1055, the AC frequency collection circuit 313 in CEMS31 obtains the frequency of the power distribution system voltage and calculates the average value (Fmeasure) as a representative value. As described above in this embodiment 1, the frequency at each location is calculated from the measured AC system voltage by voltmeters 22a to 22x, and the average value of the frequency is calculated by the AC frequency collection circuit 313 and output.

If the collection of the power distribution system voltage frequency and the calculation of the representative value (Fmeasure) are completed in step S1055 of Figure 22, the control circuit 318 in the CEMS will check in the next step S1056 whether all control parameters (i.e., power command values and frequency command values) of the battery power conversion device 41 have been generated. If the result is No in step S1056, the control circuit 318 in the CEMS will generate the frequency command value (Fref) in the next step S1057. The generation process of the frequency command value (Fref) in step S1057 will be explained below with reference to Figure 23.

Figure 23 is a flowchart showing the frequency command value (Fref) generation process. In Figure 23, when the frequency command value (Fref) generation process begins, in the initial step S10571, the frequency command value generation circuit 315 shown in Figure 2 instructs the control circuit 318 in the CEMS to obtain the control parameters (i.e., droop characteristics) of the battery power conversion device 41 that should generate this frequency command value (Fref).

If the CEMS internal control circuit 318 receives the instruction from the frequency command value generation circuit 315, it obtains the droop characteristics from the distributed power supply droop characteristic management circuit 316. In this embodiment 1, the CEMS internal control circuit 318 obtains the speed adjustment rate (Kgd), speed governor time constant (Tg), inertia constant (M), braking coefficient (Dg), and the capacity (inverter capacity) of the first DC/AC conversion circuit 408 as control parameters. Furthermore, the droop characteristic information is not limited to the above. It can also be table data showing the relationship between the output ΔP (i.e., power command value (Pref) - Pmeasure (effective power measured value)) and the output ΔF (i.e., frequency command value (Fref) - AC system voltage measured value (Fmeasure)) of the first DC/AC conversion circuit 408, or data such as the tilt of the droop characteristic. In other words, the droop characteristic information can be the shape of the droop characteristic, or it can be a parameter that determines the shape of the droop characteristic.

If step S10571 is completed, the frequency command value generation circuit 315 will issue an instruction to the control circuit 318 within the CEMS in the next step S10572 to generate the upper and lower limits of the frequency of the AC system voltage defined by the droop characteristic. In this embodiment 1, the case of using virtual synchronous generator control as the droop characteristic is explained. In virtual synchronous generator control, ΔF can be obtained using the above equation (5). Therefore, in this embodiment 1, the upper limit value Fmax and the lower limit value Fmin of the frequency can be calculated by substituting the minimum and maximum values of the speed regulation rate Kgd, the braking coefficient Dg, and ΔP into equation (5). In this embodiment 1, the minimum value of ΔP is calculated by subtracting the maximum discharge power from the power command value (Pref). On the other hand, the maximum value of ΔP is calculated from the power command value (Pref) - 0, assuming that the first DC/AC converter 408 does not charge.

If the generation of the upper and lower limits of the AC system voltage frequency in the droop characteristic is completed in step S10572, the frequency command value generation circuit 315 will then confirm in the next step S10573 whether the frequency of the measured AC system voltage falls within the frequency reference range defined by the upper and lower limits of the droop characteristic (see Figure 24). The operation of step S10573 will be explained below with reference to Figure 24.

Figure 24 is a diagram showing an example of the droop characteristics of the battery power conversion device 41 in the distributed power management system of Embodiment 1. In the figure, the horizontal axis displays the frequency of the power distribution system voltage, and the vertical axis displays the discharge power output from the battery power conversion device 41. Furthermore, in Embodiment 1, for ease of explanation, it is assumed that the battery power conversion device 41 is not charging. Fmax and Fmin in the figure display the upper and lower limit frequencies of the droop characteristics. In addition, in Embodiment 1, the range falling inside the upper limit frequency Fmax and lower limit frequency Fmin by offsetting the frequency F_offset is defined as the frequency reference range determined by the upper and lower limit frequencies Fmax and Fmin. In addition, the frequency offset F_offset can of course take different values on the upper and lower limits, and can also be changed according to the value of the power command (Pref).

In Figure 24, the frequency command value generation circuit 315 selects NO in step S10573 when the representative value (Fmeasure) of the measured frequency output from the AC frequency collection circuit 313 falls outside the frequency reference range defined by the upper and lower limit frequencies (*1 in the figure), and selects YES when the representative value (Fmeasure) of the measured frequency is within the frequency reference range defined by the upper and lower limit frequencies (*2 in the figure).

When the value is YES in step S10573, in the next step S10575, the frequency command value generation circuit 315 sets the frequency command value (Fref) to the rated frequency of the power system (e.g., 60Hz) and ends the frequency command value (Fref) generation process. On the other hand, when the value is NO in S10573, the frequency command value generation circuit 315 generates the frequency command value (Fref) in the next step S10574. The operation of step S10574 will be explained below with reference to FIG25.

Figure 25 is a flowchart showing the frequency command value (Fref) generation procedure in step S10574 of Figure 23. In the initial step S10574 of Figure 25, the frequency command value generation circuit 315 generates the droop characteristic assuming Fref = Fmeasure, and calculates the upper and lower limit frequencies of the AC system voltage based on the generated droop characteristic. Specifically, the upper and lower limit frequencies can be calculated in the same way as in step S10572 of Figure 23. That is, the frequency command value generation circuit 315 substitutes the speed adjustment rate Kgd, the braking coefficient Dg, the minimum value of ΔP, and the maximum value of ΔP into equation (5) to calculate the upper limit value Fmax and the lower limit value Fmin of the frequency (corresponding to part B of Figure 26). Here, as mentioned above, the minimum value of ΔP in this embodiment 1 is calculated by subtracting the maximum discharge force from the power command value (Pref). The maximum value of ΔP in this embodiment 1 is equal to the power command value (Pref) assuming that the first DC/AC converter 408 is not charging.

If step S105741 ends, the frequency command value generation circuit 315 will confirm in the next step S105742 whether the upper and lower limit frequencies of the droop characteristic are within the upper and lower limit values of the AC system voltage frequency (i.e., whether they fall within the pre-defined rated frequency range). In this embodiment 1, the upper and lower limit values of the AC system voltage frequency are set to 60.1Hz to 59.9Hz. When the result in step S105742 is YES, the frequency command value generation circuit 315 will set the frequency command value (Fref) to Fmeasure and end the calculation procedure of the frequency command value (Fref). On the other hand, when NO is selected in step S105742, the frequency command value generation circuit 315 corrects the frequency command value (Fref) in the next step S105743. The operation of step S105743 will be explained below with reference to FIG26.

Figure 26 illustrates the correction procedure for the frequency command value. As shown in part A of Figure 26, when the frequency command value (Fref) is 60Hz, the representative value (Fmeasure) of the measured AC system voltage frequency is set to 59.915Hz. In this case, when the representative value (Fmeasure) of the measured frequency is set to the frequency command value (Fref) to generate the droop characteristic, as shown in part B of Figure 26, the lower limit frequency of the droop characteristic is lower than the lower limit value of the AC system voltage frequency (59.9Hz). Therefore, the frequency command value generation circuit 315 corrects the frequency command value (Fref) as shown in part C of Figure 26 so that the lower limit frequency of the droop characteristic is consistent with the lower limit value of the AC system voltage frequency, 59.9Hz. Specifically, in a vertical characteristic where the lower limit frequency of the vertical characteristic is consistent with the lower limit value of the frequency of the AC system voltage, the frequency at which the output power becomes the power command value (Pref) is set as the frequency command value (Fref).

Furthermore, the same applies when the upper frequency limit of the droop characteristic exceeds the upper frequency limit of the AC system voltage. In this case, the frequency command value generation circuit 315 corrects the frequency command value (Fref) so that the upper frequency limit of the droop characteristic matches the upper frequency limit of the AC system voltage. Specifically, in a droop characteristic corrected so that the upper frequency limit of the droop characteristic matches the upper frequency limit of the AC system voltage, the frequency of the output power becoming the power command value (Pref) is set as the frequency command value (Fref). If step S105743 in Figure 25 is completed, the control circuit 318 in the CEMS ends the calculation of the frequency command value (Fref) (step S10574 in Figure 23).

Returning to Figure 22, if step S1057 is completed, the control circuit 318 in the CEMS will process and return to step S1056. Then, step S1057 will be repeated until step S1056 becomes YES, that is, the calculation of the frequency command value Fref of all battery power conversion devices 41 is completed.

Referring back to Figure 21, if the operation plan created in step S105 is completed, the control circuit 318 within the CEMS notifies each battery power conversion device 41 of the created operation plan (i.e., the power command value Pref and the frequency command value Fref) in the next step S110. In the next step S111, the control circuit 318 within the CEMS determines whether to stop the operation of the CEMS 31. When step S111 is YES, the control circuit 318 within the CEMS stops the operation of the CEMS 31. On the other hand, when step S111 is NO, the control circuit 318 within the CEMS returns to step S101 and repeats the above process.

Next, we will explain the case where step S104 in Figure 21 is NO. In this case, the control circuit 318 within the CEMS checks in step S106 whether it is the start time of a 1-minute cycle. If step S106 is NO, the control circuit 318 within the CEMS will return the processing to step S101 and repeat the above process. On the other hand, if step S106 is YES, the control circuit 318 within the CEMS will advance the processing to the next step S107.

In step S107, the CEMS internal control circuit 318 collects measurement data from the voltmeter 22, the battery power conversion device 41, the MW-level solar photovoltaic system power conversion device 27, and user measurement data. Once the measurement data collection in step S107 is complete, the CEMS internal control circuit 318 determines in the next step S108 whether the operation plan needs to be revised. For example, in this embodiment 1, when the SoC notified by the battery power conversion device 41 deviates from the pre-defined range, the CEMS internal control circuit 318 determines whether the operation plan needs to be revised. For example, in this embodiment 1, when the SoC exceeds 0.9 during charging, or when the SoC is below 0.05 during discharging, the control circuit 318 within the CEMS determines that the operation plan needs to be corrected. Furthermore, the SoC is set to be fully charged at 1.0. As another example, the control circuit 318 within the CEMS determines that the operation plan needs to be corrected when the representative value (Fmeasure) of the frequency of the measured system voltage output from the AC frequency collection circuit 313 deviates from a predetermined range. Step S108 of Figure 21 will be explained in more detail below with reference to Figure 27.

Figure 27 is a flowchart showing the procedure for determining whether to modify the operation plan. If the procedure for determining whether to modify the operation plan begins, the control circuit 318 within the CEMS clears the modification flag for the operation plan in step S1081. If the modification flag for the operation plan has already been set, in step S108 of Figure 21, the control circuit 318 within the CEMS determines that the operation plan needs to be modified; if the modification flag for the operation plan has been cleared, it determines that the operation plan does not need to be modified. Furthermore, in this embodiment 1, the modification flag for the operation plan is prepared based on the battery power conversion device 41.

If step S1081 is completed, the control circuit 318 inside the CEMS will obtain the representative value Fmeasure of the frequency of the measured system voltage output from the AC frequency collection circuit 313 in the next step S1082.

In the next step S1083, charging and discharging power and SoC are obtained from each battery power conversion device 41. Furthermore, in step S1084, the control circuit 318 in the CEMS obtains the virtual synchronous generator control parameters (vertical characteristics) of each battery power conversion device 41 from the distributed power supply vertical characteristic management circuit 316.

In the next step S1085, the control circuit 318 in the CEMS calculates the upper and lower limit frequencies of the droop characteristics from the droop characteristics collected in step S1084, using the methods described in step S10572 of Figure 23 and step S105741 of Figure 25.

If step S1085 ends, the CEMS internal control circuit 318 will check in the next step S1086 whether the SoC is within the predefined range. When the SoC deviates from the predefined range, the CEMS internal control circuit 318 will cause the processing to proceed to step S1088, and set a correction flag for the operation plan in step S1088.

When the SoC is within the predefined range (step S1086 is YES), the CEMS control circuit 318 checks whether the representative value (Fmeasure) of the frequency of the measured power distribution system voltage in the next step S1087 falls within the frequency reference range defined by the upper and lower limits of the droop characteristics. Here, the frequency reference range is the same as that described in steps S10573 of Figure 23 and Figure 24. When the representative value (Fmeasure) of the measured system frequency is outside the frequency reference range defined by the droop characteristics (step S1087 is NO), the CEMS control circuit 318 causes the processing to proceed to step S1088, and sets a correction flag for the operation plan in step S1088.

If a correction flag for the operating plan has been set in step S1088, or if the measured system frequency (Fmeasure) has been confirmed to be within the frequency range defined by the droop characteristics in step S1087 (YES in step S1087), the process proceeds to step S1089. In step S1089, the control circuit 318 within the CEMS checks whether a correction flag needs to be set for all battery power conversion devices 41. When the setting of the correction flag for all battery power conversion devices 41 is completed (YES in step S1089), the process of determining whether to correct the operating plan ends. On the other hand, when NO is selected in step S1089, the control circuit 318 in the CEMS returns the processing to step S1083 and repeats the above procedure.

Referring back to Figure 21, when the CEMS control circuit 318 determines in step S108 that no modification to the operation plan is needed (i.e., when the modification flag for the operation plan of all battery power conversion devices 41 is "0") (NO in step S108), the CEMS control circuit 318 returns the process to the initial step S101 and repeats the above process. On the other hand, when the CEMS control circuit 318 determines in step S108 that the operation plan needs modification (i.e., even if one of the modification flags for the operation plan is "1") (YES in step S108), the operation plan is modified in the next step S109. The details of step S109 are explained below with reference to Figure 28.

Figure 28 is a flowchart showing the modification procedure of the operation plan. If the modification flag of the operation plan is activated, the control circuit 318 in the CEMS will check in step S1091 whether the modification flag of the operation plan has been set. As described above, in this embodiment 1, the modification flag of the operation plan is set according to the battery power conversion device 41, and the frequency command value (Fref) and/or power command value (Pref) are regenerated for those who need to modify the operation plan.

If no correction flag for the operation plan has been set (NO in step S1091), proceed to step S1098. The processing in step S1098 will be explained later. On the other hand, if a correction flag for the operation plan has been set (YES in step S1091), proceed to steps S1092 to S1094. In step S1092, the control circuit 318 of the CEMS obtains the data (charge and discharge power, SoC) measured by the battery power conversion device 41, and in step S1093 obtains the frequency command value (Fref) and power command value (Pref). Furthermore, in step S1094, it obtains the representative value (Fmeasure) of the frequency of the measured AC voltage output from the AC frequency collection circuit 313.

If steps S1092 to S1094 are completed, the control circuit 318 within the CEMS will confirm in the next step S1095 whether the SoC is within the predefined range. Furthermore, in this embodiment 1, as mentioned above, the case where the SoC deviates from the predefined range refers to the case where the SoC exceeds 0.9 during charging and the case where the SoC is below 0.05 during discharging. Here, the SoC is considered fully charged at 1.0. Moreover, the case where the SoC deviates from the predefined range is limited to this example. For example, when using a lead-acid battery, if over-discharge occurs, the battery deteriorates rapidly; therefore, the lower limit of the SoC during discharge is set, for example, to 0.3. Furthermore, in the case of lead-acid batteries, even overcharging will not cause rapid degradation, so the upper limit during charging can certainly be set to 1.0 or higher. Thus, it is acceptable to determine the upper and lower limits of the SoC based on the characteristics of the battery.

When the battery's SoC is not within the predefined range (NO in step S1095), the control circuit 318 within the CEMS changes the power command value (Pref) in the next step S1096. In this embodiment 1, a data sheet (not shown) that determines the power command value based on the SoC value is first stored in the CEMS 31, and the control circuit 318 within the CEMS determines the power command value (Pref) based on this information. Furthermore, the method for determining the power command value is not limited to the data sheet method. For example, it can also be based on the time up to the moment the demand plan notification from DSO21 is received, the SoC value, and the current power command value, and then, upon receiving the demand plan notification from DSO21, change the power command value to a value that will not cause over-discharge or over-charge.

When the battery's SoC is within the predefined range (YES in step S1095), or when the generation of the power command value (Pref) in step S1096 above is completed, processing proceeds to step S1097. In step S1097, the control circuit 318 within the CEMS confirms whether the representative value (Fmeasure) of the measured power distribution system voltage frequency falls within the frequency reference range defined by the upper and lower limits of the droop characteristics. Here, the frequency reference range is the same as that described in steps S10573 of Figure 23 and Figure 24.

When the representative value (Fmeasure) of the measured voltage frequency of the power distribution system does not fall within the frequency reference range (NO in step S1097), the control circuit 318 in the CEMS calculates the frequency command value (Fref) in the next step S10910. Step S10910 in Figure 28 is the same as step S10574 in Figure 23, and more specifically, it is the same as the flowchart in Figure 25, so it will not be explained again.

When no correction flag for the operation plan has been set (NO in step S1091), or when the calculation of the frequency command value (Fref) in step S10910 above has been completed, or when the representative value (Fmeasure) of the measured power distribution system voltage frequency is within the frequency reference range (YES in step S1097), the process proceeds to step S1098. In step S1098, the CEMS control circuit 318 confirms whether the control parameters (Pref, Fref) of all battery power conversion devices 41 that need to be corrected have been generated. When the generation of all control parameters has been completed (YES in step S1098), the CEMS control circuit 318 terminates the operation plan correction process. On the other hand, when the generation of control parameters for all the battery power conversion devices 41 that need to be corrected is not completed (NO in step S1098), the control circuit 318 in the CEMS returns to the original step S1091 and performs the above-mentioned processing again after changing the processing object to the next battery power conversion device 41 in step S1099.

Returning to Figure 21, when the modification of the operation plan in step S109 is completed, or when the creation of the operation plan in step S105 is completed, in the next step S110, the control circuit 318 within the CEMS notifies each battery power conversion device 41 of the created operation plan (power command value (Pref) and frequency command value (Fref)). Furthermore, in the next step S111, the control circuit 318 within the CEMS determines whether to terminate the operation of CEMS 31. When the operation of CEMS 31 is terminated (YES in step S111), CEMS 31 stops. On the other hand, when the action of CEMS31 is not terminated (NO in step S111), the processing returns to the initial step S101, and the above processing is executed again.

In summary, in this embodiment 1, when an operation plan (i.e., power command value (Pref) and frequency command value (Fref)) is made for the battery power conversion device 41, the frequency command value (Fref) is generated based on the vertical characteristics of the stationary inverter in the battery power conversion device 41, the power command value made, and the frequency (Fmeasure) of the measured AC system voltage. As a result, it has the ability to operate continuously without stopping distributed power supply, even when the power consumption of the load changes rapidly (rapidly) and/or the solar radiation changes rapidly, causing changes (rapidly) in the power generated from renewable energy machines to the power distribution system, and the frequency of the AC system voltage changes.

[Detailed Operation of the Battery Power Conversion Device] The operation of the battery power conversion device 41 will now be described in detail with reference to Figures 5 to 13, 29, and 30. In this embodiment 1, a virtual synchronous generator control is installed in the battery power conversion device 41, therefore the first DC/AC conversion circuit 408 operates as a voltage source (i.e., voltage control). Therefore, the first control circuit 404 controls the voltage of the DC bus 405 to a constant value. The operation of the first control circuit 404 will now be described with reference to Figure 6. The voltage of DC bus 405 is measured by voltmeter 406 and input to charging control circuit 4041, discharging control circuit 4042, and third control circuit 4044.

The charging control circuit 4041 controls the charging power to the battery 40 to be the target voltage when the voltage of the DC bus 405 is greater than the target voltage output from the third control circuit 4044. On the other hand, when the voltage of the DC bus 405 is less than the target voltage output from the third control circuit 4044, the discharging control circuit 4042 controls the discharging power to increase the discharging power of the battery 40. Furthermore, the switching between the output of the charging control circuit 4041 and the output of the discharging control circuit 4042 is implemented by a first switching circuit 4043. The switching control signal for the first switching circuit 4043 is output by the third control circuit 4044 based on the voltage value of the DC bus 405 measured by the voltmeter 406.

Next, the operation of the second control circuit 409 will be explained with reference to Figures 7 to 13, Figure 29, and Figure 30. Figure 29 is a flowchart mainly showing the operation of the second control circuit 409. In Figure 29, when the operation of the battery power conversion device 41 starts, in step S201, the second control circuit 409 initializes various control parameters to the predetermined initial values.

Once the initialization of various control parameters is complete, the fourth control circuit 4097 collects the measured voltages of voltmeters 401, 406, and 410, the measured currents of ammeters 402, 407, and 411, and the status information (e.g., SOC) of the battery 40 in the next step S202. Furthermore, since the result measured by voltmeter 410 is AC voltage, the fourth control circuit 4097 calculates its effective voltage and sets it as the measured voltage. Similarly, since the result measured by ammeter 411 is AC current, the fourth control circuit 4097 calculates its effective current and sets it as the measured current. Furthermore, in this embodiment 1, the charging and discharging power and charge/discharge force of the battery 40 are calculated based on the collected data using the charging and discharging power calculation circuit (not shown) in the third control circuit 4044 of Figure 6.

In step S203 of Figure 29, the AC voltage waveform of the distribution line 24 measured by the voltmeter 410 is input to the AC frequency detection circuit 4091 shown in Figures 7 and 8, and the zero-crossing point of the AC voltage is detected. Specifically, referring to the block diagram of the AC frequency detection circuit 4091 in Figure 8, the measurement result of the voltmeter 410 is input to the phase detection circuit 40910, and the zero-crossing point is detected. In addition, in this embodiment 1, the phase detection circuit 40910 detects the point and moment when the AC voltage waveform measured by the voltmeter 410 switches from negative to positive as zero-crossing point information. The zero-crossing information detected by the phase detection circuit 40910 is also input to the frequency detection circuit 40911. The frequency detection circuit 40911 calculates the period of the AC voltage from the timing information of the zero-crossing point previously detected by the phase detection circuit 40910 and the timing information of the zero-crossing point detected this time, and calculates the AC system frequency based on the result. The first sine wave generation circuit 40912 outputs the zero-crossing information detected by the phase detection circuit 40910 and the frequency information of the AC voltage detected by the frequency detection circuit 40911 as sine wave information. In addition, zero-crossing point detection information and frequency detection information are output to inverter current control circuit 4094, inverter voltage control circuit 4095, virtual synchronous generator control circuit 4093, and fourth control circuit 4097.

Referring back to Figure 29, the fourth control circuit 4097 establishes a zero-crossing detection flag in the next step S204 when a zero-crossing point is detected in step S203. When the flag establishment is completed in step S204, or when a zero-crossing point is not detected (NO in step S203), the third control circuit 4044 controls the first DC/DC converter circuit 403 in the next step S205. In this embodiment 1, as described above, the third control circuit 4044 controls the charging and discharging of the battery 40 to make the voltage of the DC bus 405 reach a predetermined value. If step S205 is completed, the fourth control circuit 4097 controls the first DC/AC converter circuit 408 in the next step S206.

Figure 30 is a flowchart showing the control program of the first DC/AC converter 408. Referring to Figures 7 and 30, if the control of the first DC/AC converter 408 starts, in step S2061 of Figure 30, the effective power calculation circuit 4092 calculates the power value based on the measurement information from the voltmeter 410 and the ammeter 411. In the next step S2062, the effective power calculation circuit 4092 integrates the measured power value using an integrator. Furthermore, when a zero-crossing detection flag has been set (YES in step S2063), the effective power calculation circuit 4092 calculates the effective power value of the AC voltage for one cycle. The effective power calculation circuit 4092 stores the calculated effective power value in a memory circuit (not shown) within the fourth control circuit 4097 (step S2064) and initializes the integrator to zero (step S2065). After the integrator initialization is completed in step S2065, or when no zero-crossing detection flag is set (NO in step S2063), in the next step S2066, the inverter voltage control circuit 4095 generates the command value for the first DC/AC conversion circuit 408.

The control of the first DC/AC conversion circuit 408 will be explained below with reference to Figures 7, 10, and 30. As mentioned above, the battery power conversion device 41 is equipped with a virtual synchronous generator control, therefore the first DC/AC conversion circuit 408 is controlled as a voltage source (i.e., voltage control). Therefore, when the power supplied to the distribution line 24 is insufficient, the power to be output is increased; when the power supplied is greater, the power to be output is decreased.

The operation of the inverter voltage control circuit 4095 will be explained below with reference to Figure 10. The inverter voltage control circuit 4095 outputs control command values for controlling the first DC/AC conversion circuit 408 based on the frequency and phase information output from the virtual synchronous generator control circuit 4093 and the amplitude information of the AC system voltage output from the fourth control circuit 4097 (in this embodiment 1, it is input via the first sine wave generation circuit 40912). The sine wave information (i.e., frequency, phase, and amplitude information) from the AC frequency detection circuit 4091 and the frequency and phase information calculated by the virtual synchronous generator control circuit 4093 are input to the second sine wave generation circuit 40951.

The second sine wave generating circuit 40951 generates the target value of the AC system voltage output from the first DC/AC converter circuit 408 based on the input information, namely the frequency and phase information calculated by the virtual synchronous generator control circuit 4093 and the amplitude information output from the fourth control circuit 407. The subtractor 40952 subtracts the voltage measured by the voltmeter 410 from the target AC voltage output from the second sine wave generating circuit 40951, and inputs the subtraction result into the third PI control circuit 40953. The third PI control circuit 40953 generates a voltage command using PI control to make the input subtraction result zero, and outputs the generated voltage command to the first current limiting circuit 40955.

The first current limiting circuit 40955 applies a limit to the command value output from the third PI control circuit 40953 based on the result measured by the ammeter 411 and input via the fourth control circuit 4097. Specifically, in this embodiment 1, current limiting is implemented when the current flows exceeding the current capacity of the first DC/AC converter 408, and the current flowing in the first DC/AC converter 408 is controlled to a predetermined current value (i.e., the current capacity of the first DC/AC converter 408). The first current limiting circuit 40955 monitors the current flowing in the first DC/AC converter 408 and controls (specifically limits) the current value so that the current does not exceed the current capacity of the first DC/AC converter 408. The output of the first current limiting circuit 40955 is input to the second PWM conversion circuit 40954. In addition, the control parameters (i.e., control gain and integration time) of the third PI control circuit 40953 and the first current limiting circuit 40955 are output from the fourth control circuit 4097.

The second PWM conversion circuit 40954 performs PWM modulation on the voltage command value output from the first current limiting circuit 40955, and outputs the PWM-modulated voltage command value to the second switching circuit 4096. The second switching circuit 4096 in Figure 7 selects one of the control command value of the inverter current control circuit 4094 and the control command value of the inverter voltage control circuit 4095 according to the control signal (i.e., the switching signal) output from the fourth control circuit, and outputs the selected control command value to the first DC/AC conversion circuit 408.

Additionally, although not used in this embodiment 1, the operation of the inverter current control circuit 4094 is also explained with reference to FIG9. The inverter current control circuit 4094 generates a control command value for controlling the first DC/AC conversion circuit 408 based on the DC voltage of the DC bus 205 output from the voltmeter 406. Specifically, the subtractor 40941 subtracts the target value of the DC bus voltage output from the fourth control circuit 4097 from the DC voltage of the DC bus 405 output from the voltmeter 406, and inputs the subtraction result into the first PI control circuit 40942. The first PI control circuit 40942 generates a command value to make the subtraction result zero using PI control, and outputs the generated command value to the multiplier 4094. The control parameters (proportional gain and integration time) of the first PI control circuit 40942 are output from the fourth control circuit 4097.

Next, multiplier 40943 multiplies the command value output from the first PI control circuit 40942 by a sine wave synchronized with the AC voltage waveform output from the first sine wave generation circuit 40912 within the AC frequency detection circuit 4091. This generates a current command value. Subtractor 40944 subtracts the AC system current value measured by ammeter 411 from the current command value output from multiplier 40943, and inputs the subtraction result into the second PI control circuit 40945. The second PI control circuit 40945 generates a control command value to make the subtraction result input from subtractor 40944 zero, and outputs the generated control command value to the first PWM conversion circuit 40946. The control parameters (proportional gain and integration time) of the second PI control circuit are input from the fourth control circuit 4097. The first PWM converter circuit 40946 performs PWM modulation on the control command value input from the second PI control circuit 40945 and outputs the PWM-modulated control command value to the first DC/AC converter circuit 408.

Returning to Figure 29, if the control of the first DC/AC conversion circuit 408 in step S206 (more specifically, the generation of the instruction value of the first DC/AC conversion circuit 408 in step S2066 of Figure 30) is completed, the fourth control circuit 4097 will confirm in the next step S207 whether a measurement information transmission request has been received from CEMS31. When a measurement information transmission request is received from CEMS31 (YES in step S207), in the next step S208, the fourth control circuit 4097 will notify CEMS31 of various measurement results stored in a memory not shown via the communication interface circuit 412.

When no measurement information transmission request is received from CEMS31 (NO in step S207), or when various measurement results have been notified in step S208, the fourth control circuit 4097 checks in the next step S209 whether control information has been received from CEMS31. When control information is received from CEMS31 (YES in step S209), the fourth control circuit 4097 establishes a reception flag in the next step S210. When no control information is received from CEMS31 (NO in step S209), or when the establishment of the reception flag in step S210 has been completed, the fourth control circuit 4097 checks in the next step S211 whether a detection flag with a zero-crossing point has been established. When no detection flag with zero crossover point is set (NO in step S211), the fourth control circuit 4097 returns the processing to step S202 and re-implements the processing after step S202.

On the other hand, when a zero-crossing detection flag has been established (YES in step S211), the fourth control circuit 4097, in the next step S212, acquires the representative value of the frequency and the detection result of the phase of the AC system voltage output from the AC frequency detection circuit 4091. If the acquisition of the AC frequency and phase detection results is completed in step S212, the fourth control circuit 4097 performs virtual synchronous generator control in the next step S213. In this embodiment 1, one cycle of the AC system voltage is set as the control cycle. Alternatively, the control cycle can be an integer multiple of the AC system voltage cycle, or a pre-defined cycle such as one second.

The control of the virtual synchronous generator in step S213 of Figure 29 will be explained below with reference to the block diagram of the second control circuit 409 shown in Figure 7, the block diagram of the virtual synchronous generator control circuit 4093 shown in Figure 11, the block diagram of the speed regulator control circuit 40933 shown in Figure 12, and the block diagram of the mass system calculation circuit 40937 shown in Figure 13. First, if the fourth control circuit 4097 in Figure 7 determines that the timing for executing the control of the virtual synchronous generator has been reached after the control cycle, it issues an instruction to the virtual synchronous generator control circuit 4093 to generate the frequency and phase information to be used for voltage control. In this embodiment 1, the second sine wave generation circuit 40951 within the inverter voltage control circuit 4095 updates the target values of the frequency and phase of the AC voltage based on the zero-crossing point. Therefore, in this embodiment 1, the control cycle becomes the cycle of the zero-crossing point detected by the AC frequency detection circuit 4091.

Referring to Figure 11, the subtractor 40932 subtracts the frequency (Fref, e.g., 60Hz) of the reference AC voltage output from the fourth control circuit 4097 from the representative value of the frequency of the measured AC system voltage output from the self-frequency detection circuit 40911, and inputs the subtraction result into the speed controller control circuit 40933.

Referring to Figure 12, the multiplier 409331 of the speed controller control circuit 40933 multiplies the output of the subtractor 40932 in Figure 11 with the control parameter (-1/Kgd) notified from the fourth control circuit 4097, and inputs the multiplication result into the first-order delay system model 409332. Furthermore, the speed adjustment rate Kgd and the speed controller time constant Tg used in the speed controller control circuit 40933 are used in a register (not shown) that is notified from the CEMS31 via the fourth control circuit 4097.

The primary delay system model 409332, as described above, uses the time constant Tg notified from the fourth control circuit 4097 to perform a calculation simulating the primary delay system (1/(1+s×Tg)), and inputs the calculation result into the limiting circuit 409333. The limiting circuit 409333 imposes a restriction on the data input from the primary delay system model 409332. Specifically, the limiting circuit 409333 restricts the output of the speed controller control circuit 40933 to not exceed the power capacity of the first DC/AC conversion circuit 408.

Referring back to Figure 11, adder 40935 adds the output of speed controller control circuit 40933 to the power command value (Pref) output from fourth control circuit 4097, and outputs the sum to subtractor 40936. Additionally, as mentioned above, the power command value is output from fourth control circuit 4097 from the receiver of CEMS31. Subtractor 40936 subtracts the measured effective power output from effective power calculation circuit 4092 from the output of adder 40935, and inputs the subtraction result to mass system calculation circuit 40937.

The operation of the particle system calculation circuit 40937 will be explained below with reference to Figure 13. The subtractor 409371 of the particle system calculation circuit 40937 subtracts the output of the multiplier 409373 from the output of the subtractor 40936 in Figure 11, and inputs the subtraction result into the integrator 409372. The integrator 409372 divides the subtraction result output from the subtractor 409371 by the inertial constant M output from the fourth control circuit 4097, and integrates the division result. The integration result of the integrator 409372 represents the difference Δω between the angular velocity (2×π×60Hz) and the AC system frequency. Integrator 409372 inputs the integration result to multiplier 409373 and divider 409374. Multiplier 409373 multiplies the output Δω of integrator 409372 with the braking coefficient Dg output from the fourth control circuit 4097, and outputs the multiplication result to the aforementioned subtractor 409371. Furthermore, divider 409374 divides the output Δω of integrator 409372 by 2×π, thereby converting Δω into a difference value Δf between it and the AC system frequency (60Hz). Adder 409375 adds the output Δf of divider 409374 to Fref, which is a frequency command value belonging to the AC system voltage. This generates the frequency used for voltage control by the inverter voltage control circuit 4095. Furthermore, the inertia constant M and braking coefficient Dg used in the mass system calculation circuit 40937, as described above, are those generated in the CEMS31 and notified to the user via the fourth control circuit 4097 and stored in a register not shown.

Furthermore, the frequency information output from adder 409375 is input to phase calculation circuit 409376. The operation of phase calculation circuit 409376 is explained below. In Embodiment 1, the frequency information output from adder 409375 is integrated by phase calculation circuit 409376 and output as phase information of the frequency of the power distribution system voltage when voltage control is performed by inverter voltage control circuit 4095. The phase and frequency information output from the mass system calculation circuit 40937 is transmitted through the first sine wave generation circuit 40912 in the AC frequency detection circuit 4091 of Figure 8 to the second sine wave generation circuit 40951 in the inverter voltage control circuit 4095 of Figure 10. The second sine wave generation circuit 40951 generates the target value of the AC system voltage output from the battery power conversion device 41 based on the input sine wave information.

Returning to Figure 29, if the control processing of the virtual synchronous generator is completed in step S213, the fourth control circuit 4097 resets the detection flag of the zero-crossing point in the next step S214, and confirms whether a receiving flag has been established in the next step S215. When no receiving flag has been established (NO in step S125), the fourth control circuit 4097 returns the processing to step S202 and executes the processing after step S202 again. On the other hand, when a reception flag has been set (YES in step S215), in the next step S216, the fourth control circuit 4097 sets the frequency command value (Fref) and power command value (Pref) notified from CEMS31 in a register (not shown) within the fourth control circuit 4097, and then resets the reception flag in the next step S217. Afterwards, the fourth control circuit 4097 returns the processing to step S202 and executes the subsequent processing again.

[Effects of Embodiment 1] The distributed power management device and distributed power management system of Embodiment 1 are configured as described above to generate a frequency command value (Fref) based on the vertical characteristics of the stationary inverter in the battery power conversion device 41, the generated power command value, and the measured frequency of the AC system voltage (Fmeasure) when making an operation plan (i.e., power command value (Pref) and frequency command value (Fref)) for the battery power conversion device 41. Therefore, even when the frequency of the AC system voltage changes due to fluctuations in load power consumption (rapid changes) or fluctuations in solar radiation due to rapid changes in the power supplied to the system from renewable energy generators (rapid changes), the AC system voltage frequency will not deviate from the frequency range managed by the stationary inverter equipped with virtual synchronous generator control characteristics (vertical characteristics). As a result, it provides the ability to continuously operate the stationary inverter without interrupting distributed power supply.

In this embodiment 1, the description pertains to a power conversion device connected to an AC system that has a droop characteristic, represented by virtual synchronous generator control. However, this disclosure is not limited to this case. Since the frequency command value (Fref) is generated based on the measured frequency of the AC system voltage (Fmeasure), the power command value (Pref), and the droop characteristic (i.e., the droop characteristic) of the static inverter, it has the effect of controlling the power conversion device with the droop characteristic (i.e., the droop characteristic) without deviating from its frequency management range, even when the frequency of the backbone system deviates from the rated frequency (e.g., 60Hz).

In Embodiment 1, although the description pertains to the case where a power conversion device with droop characteristics is connected to a connected system (i.e., the case where power is supplied from the backbone system), this disclosure is not limited to that case. If configured such that, in an independent system, a frequency command value (Fref) is generated based on the droop characteristics of the stationary inverter, the generated power command value, and the measured frequency (Fmeasure) of the measured AC system voltage, then the device can control the power conversion device with a stationary inverter equipped with droop characteristics (i.e., droop characteristics) even when the frequency of the independent system deviates from the rated frequency (e.g., 60Hz) as it does in connection, without deviating from the frequency management range of the power conversion device.

In this embodiment 1, although the situation where the battery power conversion device 41, as shown in Figures 18, 24, and 26, is in a discharging operation, resulting in increased load power consumption and a decrease in the frequency of the power distribution system voltage, has been explained, this disclosure is not limited to this situation. For example, when the load power consumption decreases and the frequency of the power distribution system voltage increases during discharging, or when load changes and the frequency of the power distribution system voltage increases or decreases during charging, the same effect can be achieved by controlling the frequency command value (Fref) based on the measured result (Fmeasure) of the power distribution system voltage frequency.

Embodiment 2 While Embodiment 1 explained the case where the frequency command value (Fref) is controlled based on the measured frequency of the AC system voltage (Fmeasure), Embodiment 2 explains the case where the power command value (Pref) is controlled (corrected) based on the measured frequency of the AC system voltage (Fmeasure). The following explanation focuses on the operations that differ from Embodiment 1.

[Composition of CEMS in Embodiment 2] Figure 31 is a block diagram of the CEMS 31 in Embodiment 2. As shown in Figure 31, the CEMS 31 of Embodiment 2 includes a communication circuit 311, a memory circuit 312, an AC frequency collection circuit 313, an operation plan generation circuit 314, a power command value correction circuit 320, a distributed power supply vertical characteristic management circuit 316, a data transmission generation circuit 317, and a second CEMS internal control circuit 321. That is, the CEMS 31 of Embodiment 2 has a power command value correction circuit 320 to replace the frequency command value generation circuit 315, and a second CEMS internal control circuit 321 to replace the CEMS internal control circuit 318, which is different from the CEMS 31 of Embodiment 1 shown in Figure 2. The following mainly explains the above-described structure that differs from Embodiment 1.

[Operational Overview of the Distributed Power Management Device] Figures 32A and 32B illustrate the method for generating the power command value in the CEMS31 of Embodiment 2. Figure 32A shows the droop characteristics of the power command value (Pref) before correction, and Figure 32B shows the droop characteristics of the power command value (Pref) after correction. The operating principle of the CEMS31 of Embodiment 2 will be explained below with reference to Figures 32A and 32B.

In this embodiment 2, CEMS 31 generates the power command values (Pref) of each battery power conversion device 41 in two stages. Specifically, when CEMS 31 starts generating the power command values (Pref), the operation plan creation circuit 314 shown in FIG. 31, as in embodiment 1, creates a demand plan based on the expected power generation results of the MW-level solar photovoltaic system 26 and the predicted power consumption results of users. Furthermore, CEMS 31 creates the power command values (Pref) of each battery power conversion device 41 before modification based on the created demand plan, that is, the operation plan power command value information.

CEMS31 assumes that the frequency command value (Pref) before modification is completed, and assumes that the frequency command value Fref is equal to the rated frequency of the backbone system (e.g., 60Hz), thus creating a droop characteristic (see Figure 32A). Furthermore, compared to the measured result (Fmeasure) of the frequency of the AC system voltage received by the AC frequency collection circuit 313, for example, when it is lower than Fmin, similarly to the case of Embodiment 1, with the current droop characteristic, as mentioned above, there is a possibility that the battery power conversion device 41 will stop when load changes or sudden changes in power generation occur. In the CEMS31 of this embodiment 2, details will be explained later, but for example, as shown in FIG32B, in order to output the power of the power command value (Pref) before correction mentioned above in the measured value (Fmeasure) of the frequency of the AC system voltage, a power command value (Pref’) is generated and output to the battery power conversion device 41. In the example of FIG32B, the droop characteristic (solid line in the figure) before correction of the power command value is changed to the droop characteristic after being horizontally shifted to the left (a dotted chain in the figure). The same change of droop characteristic is implemented in the case of embodiment 1 by setting the measured system frequency (Fmeasure) to the frequency command value (Fref) and outputting it to the battery power conversion device 41. In Embodiment 2, the change in droop characteristics is implemented by modifying the power command value (Pref). Specifically, in the example shown in Figure 32B, the droop characteristics are shifted to the left by reducing the power command value (Pref) generated by the operation plan circuit 314. As a result, as shown in Figure 32B, even if the measured value (Fmeasure) of the frequency of the power distribution system voltage deviates from the frequency range filled by the original droop characteristic of the battery power conversion device 41, the CEMS31 can still transmit the corrected power command value (Pref’) to each battery power conversion device 41, thereby shifting the droop characteristic to the left as shown in Figure 32B, so that the battery power conversion device 41 can continue to operate.

Next, the effectiveness of the above-mentioned method for generating power command values will be explained with reference to Figures 33A and 33B. Figure 33A is a graph showing the frequency range of the inverter using the comparative example of droop characteristics. In Figure 33A, the horizontal axis displays time, and the vertical axis displays the frequency of the AC system voltage. This graph shows that as the load decreases over time, the frequency of the AC system voltage increases in a slope-like manner. As shown in the figure, when the frequency command value (Fref) is fixed at the rated frequency (60Hz) and the power command value (Pref) is a fixed value generated by the operation plan circuit 314, the area inside the thick dashed line becomes the frequency range (also known as the frequency management range) of the battery power conversion device 41 (inverter). As shown in the figure, if the frequency of the system voltage gradually increases, the frequency of the system voltage will escape the frequency range of the inverter that the battery power conversion device 41 (inverter) can control (NG area in the figure), thus the virtual synchronous generator control (VSG control) will be compromised, and the battery power conversion device 41 will stop.

On the other hand, Figure 33B is a graph showing the power command value and inverter frequency when using the drooping characteristics of Embodiment 2. As shown in the figure, the power command value (Pref'), after being corrected based on the measured frequency of the AC system voltage, is output to the battery power conversion device 41. Specifically, in Embodiment 2, the frequency of the AC system voltage is measured at 1-minute intervals, similar to Embodiment 1. Furthermore, the power command value (Pref') is controlled based on the measured frequency of the AC system voltage. In Figure 33B, the horizontal axis displays time, and the vertical axis displays the power command value (Pref’) and the frequency of the power distribution system voltage of the battery power conversion device 41. As shown in the figure, since the power command value (Pref’) is appropriately controlled according to the frequency of the AC system voltage, even when the frequency of the system voltage gradually increases, the frequency range (also known as the frequency management range) that can be controlled by the battery power conversion device 41 (inverter) based on the virtual synchronous generator control (vertical characteristic) can be appropriately controlled. As a result, the connected operation can continue without the frequency of the power distribution system voltage deviating from the frequency management range of the battery power conversion device 41 (inverter).

In summary, the distributed power management device is configured to generate a power command value (Pref) based on the measured frequency of the AC system voltage, the power command value (Pref) generated by the operation planning circuit 314, and the droop characteristic when a power conversion device equipped with a static inverter featuring a droop characteristic is connected to an AC system. This allows the device to control the power conversion device without exceeding the frequency management range of the static inverter with the droop characteristic, even when the frequency of the backbone system deviates from the rated frequency (e.g., 60Hz).

[Detailed Explanation of the Operation of the Distributed Power Management System (CEMS)] The operation of the distributed power management system (CEMS31) of Embodiment 2 will be explained in detail with reference to Figures 31 to 38. In the following explanation, only the operations of the parts that differ from those of Embodiment 1 will be described. The power distribution system to which the CEMS31 is connected is the same as in Embodiment 1, and will not be repeated. Furthermore, the configuration and operation of the battery power conversion device 41 managed by the CEMS31 are also the same as in Embodiment 1, and will not be repeated. Furthermore, in Embodiment 2, the CEMS 31 notifies the battery power conversion device 41 of the revised power command value (Pref’) and frequency command value (specifically, the reference value of the frequency of the power distribution system voltage (i.e., the rated frequency), for example, 60Hz).

Similar to Embodiment 1, the power supplied from substation 20, the power generated by MW-level solar photovoltaic system 26 (where the power conversion device 27 of the MW-level solar photovoltaic system operates as a current source), and the discharge power output from batteries 40a to 40c are supplied to the load of distribution system 1. Here, the normal operating sequence of the distributed power management system centered on CEMS31 is the same as in Embodiment 1, consisting of a 30-minute cycle processing and a 1-minute cycle processing, as shown in Figure 20. The processing content of the distributed power management device is also basically the same, only the methods for generating power command values and frequency command values differ.

The detailed operation of CEMS31 will be explained below with reference to the block diagram of CEMS31 in Figure 31 and Figures 21, 34 to 39. When processing begins in CEMS31, the control circuit 321 within the second CEMS basically performs processing according to the flow shown in Figure 21. Furthermore, the flowchart shown in Figure 21 is basically the same as in Embodiment 1; therefore, steps common to Embodiment 1 will only be briefly explained without repeating detailed descriptions.

In Figure 21, if processing begins, CEMS31 checks in step S101 whether it has received a data transmission request from DSO21. When a transmission request is received (YES in step S101), CEMS31 collects the latest measurement information from the battery power conversion device 41, voltmeter 22, and each user (including the MW-level solar photovoltaic system power conversion device 27) in the next step S102. Furthermore, CEMS31 uses the measurement data collected at 30 times per 1-minute intervals to calculate the power consumption of each user, the power generation of the MW-level solar photovoltaic system 26, and the charging and discharging power of the battery 40 over 30 minutes. CEMS31 transmits the calculated electrical power and SOC information of battery 40 to DSO21 via communication circuit 311 (S103). When the data transmission in step S103 is completed, or if no data transmission request is received from DSO21 (NO in step S101), CEMS31 checks in the next step S104 whether a demand plan notification has been received from DSO21. When a demand plan notification is received (YES in step S104), CEMS31 performs the operation plan creation in the next step S105. In addition, in this embodiment 2, similar to the case of embodiment 1, the demand plan for the power supplied from the backbone system to the distribution line 24 is notified to the CEMS31 at 30-minute intervals for 24 hours.

Figure 34 is a flowchart showing the detailed operations of the operation plan creation process in step S105 of Figure 21 in this embodiment 2. In Figure 34, if the creation of the operation plan begins, CEMS 31 first performs the power generation prediction of the MW-level solar photovoltaic system 26 in step S1051. Specifically, referring again to Figures 31 and 3, if the control circuit 321 in the second CEMS receives a notification of the demand plan (specifically the battery operation plan) from DSO 21, it instructs the management circuit 3146 in the operation plan creation circuit 314 to create the operation plan. Upon receiving the instruction, management circuit 3146, via battery operation planning circuit 3141, instructs power generation prediction circuit 3142 to predict the power generation of the MW-level solar photovoltaic system 26. Upon receiving the instruction, power generation prediction circuit 3142 obtains a 24-hour weather forecast from a weather forecast server configured on an internet network (not shown). Power generation prediction circuit 3142 uses the obtained weather forecast results and data from a power generation prediction database (not shown) managed by power generation prediction circuit 3142 to predict the 24-hour power generation. An example of the database is illustrated in the flowchart of Figure 22 and will not be repeated here.

If the power generation prediction in step S1051 of Figure 34 above is completed, CEMS31 will predict the user's power consumption in the next step S1052. Specifically, referring again to Figure 3, if the management circuit 3146 in the operation plan creation circuit 314 receives the power generation prediction result of the MW-level solar photovoltaic system 26 from the power generation prediction circuit 3142, it will instruct the power consumption prediction circuit 3141 to predict the user's power consumption. If the power consumption prediction circuit 3143 receives the instruction, it will use data from the power consumption prediction database (not shown) managed by the power consumption prediction circuit 3143 to predict the user's power consumption over a 24-hour period. In addition, an example of a database is illustrated in the flowchart in Figure 22, so it will not be repeated here.

If the user's power consumption ends in step S1052 of Figure 34, CEMS31 will begin the demand plan creation in step S1053 of Figure 34. Specifically, referring again to Figure 3, the battery operation plan creation circuit 3141 in the operation plan creation circuit 314 calculates the total charge and discharge power of batteries 40a to 40c every 30 minutes based on the power generation prediction result of the MW-level solar photovoltaic system 26 in the power generation prediction circuit 3142, the power consumption prediction result of the user in the power consumption prediction circuit 3143, and the demand plan notified from DSO21. In addition, when the above is the case of this embodiment 2, the demand plan notified from DSO21 is the power supply plan for the distribution system 1 that is closer to the load side than substation 20 during the 24-hour period (i.e., the power supply plan every 30 minutes).

If the demand plan is completed in step S1053 of Figure 34, CEMS31 will determine the charging and discharging power of batteries 40a to 40c in the next step S1054. Specifically, referring again to Figures 31 and 3, the operation plan creation circuit 314 determines (allocates) the charging and discharging power from each of the 30 batteries by collecting the SOC information of batteries 40a to 40c from the communication circuit 311 to the memory circuit 312, and the battery capacity of batteries 40a to 40c. In Embodiment 2, similar to Embodiment 1, the operation plan is designed such that when the battery is scheduled to operate for 24 hours, the SOC of the batteries 40a to 40c is almost zero at the same time, or they are in a rechargeable state after 24 hours.

If the charging and discharging power of batteries 40a to 40c is completed in step S1054 of Figure 34, the AC frequency collection circuit 313 in CEMS31 will obtain the frequency of the power distribution system voltage in the next step S1055. As described above, in this embodiment 2, similarly to the case of embodiment 1, the voltmeters 22a to 22x measure the frequency at each location from the measured AC system voltage, and the AC frequency collection circuit 313 calculates the average frequency as a representative value (Fmeasure) and outputs it.

If the collection of the frequency of the power distribution system voltage and the calculation of the representative value (Fmeasure) are completed in step S1055 of Figure 34, the control circuit 321 in the second CEMS will check in the next step S1056 whether the control parameters (i.e., power command values and power command values (Pref’)) of all battery power conversion devices 41 have been generated. If NO is selected in step S1056, the control circuit 321 in the second CEMS will perform power command value (Pref’) generation in the next step S1060. The power command value (Pref’) generation process in step S1060 will be explained below with reference to Figure 35.

Figure 35 is a flowchart showing the process of generating the power command value (Pref’). In Figure 35, when the generation of the power command value (Pref’) begins, in the initial step S10571, the power command value correction circuit 320 shown in Figure 31 issues an instruction to the control circuit 321 in the second CEMS to obtain the control parameters (i.e., droop characteristics) of the virtual synchronous generator control circuit 4093 of the battery power conversion device 41 that generated this power command value (Pref’) (i.e., the object to which the power command value (Pref) is corrected).

If the second CEMS internal control circuit 321 receives the instruction from the power command value correction circuit 320, it obtains the droop characteristics from the distributed power supply droop characteristic management circuit 316. In this embodiment 2, the second CEMS internal control circuit 321 obtains the speed regulation rate (Kgd), speed governor time constant (Tg), inertia constant (M), braking coefficient (Dg), and the capacity (inverter capacity) of the first DC/AC conversion circuit 408 as control parameters, just as in embodiment 1. In addition, the droop characteristic is not limited to the above. It can also be a data sheet showing the relationship between the output ΔP (i.e., power command value (Pref) - effective power measured value (Pmeasure)) and the output ΔF (i.e., frequency command value (Fref) - AC system voltage frequency measured value (Fmeasure)) of the first DC/AC conversion circuit 408, or data such as the tilt of the droop characteristic.

If step S10571 is completed, the power command value correction circuit 320 will issue an instruction to the control circuit 321 within the second CEMS in the next step S10572 to generate an upper and lower limit value of the frequency of the AC system voltage defined by the droop characteristic. In this embodiment 2, the explanation is similar to that of embodiment 1, focusing on the case where virtual synchronous generator control is used as the droop characteristic. In virtual synchronous generator control, ΔF can be obtained using the above equation (5). Specifically, in this embodiment 2, the upper limit value Fmax and the lower limit value Fmin of the frequency can be calculated by substituting the minimum and maximum values of the speed regulation rate Kgd, the braking coefficient Dg, and ΔP into equation (5). In this embodiment 2, the minimum value of ΔP is calculated by subtracting the maximum discharge power from the power command value (Pref). On the other hand, the maximum value of ΔP is calculated by subtracting 0 from the power command value (Pref) assuming that the first DC/AC converter 408 is not charging.

Once the generation of the upper and lower limits of the AC system voltage frequency in step S10572's droop characteristic is complete, the power command value correction circuit 320 will, in the next step S10573, confirm whether the frequency of the measured AC system voltage falls within the frequency reference range defined by the upper and lower limits of the droop characteristic (see Figure 36). The operation of S10573 will be explained below with reference to Figure 36.

Figure 36 is a diagram showing an example of the droop characteristics of the battery power conversion device 41 in the distributed power management system of Embodiment 2. In the figure, the horizontal axis shows the frequency of the power distribution system voltage, and the vertical axis shows the discharge power output from the battery power conversion device 41. Furthermore, in Embodiment 2, similar to Embodiment 1, for ease of explanation, it is assumed that the battery power conversion device 41 is not charging. Fmax and Fmin in the figure show the upper and lower limit frequencies of the droop characteristics. Furthermore, in this embodiment 2, similarly to embodiment 1, the range falling within the upper limit frequency Fmax and lower limit frequency Fmin by offsetting the frequency F_offset is set as the frequency reference range defined by the upper and lower limit frequencies. Additionally, the frequency offset F_offset can, of course, take different values on the upper and lower limit sides, or it can be changed according to the power command value (Pref) generated by the operation plan circuit 314.

In Figure 36, the power command value correction circuit 320 selects NO in step S10573 when the representative value (Fmeasure) of the measured frequency output from the AC frequency collection circuit 313 falls outside the frequency reference range defined by the upper and lower limit frequencies (*1 in the figure), and selects YES in step S10573 when the measured frequency (Fmeasure) is within the frequency reference range defined by the upper and lower limit frequencies (*2 in the figure).

If the condition is YES in step S10573, in the next step S10581, the power command value correction circuit 320 will notify the operation plan creation circuit 314 to set the power command value (Pref) for the operation plan as the power command value (Pref’) output to the battery power conversion device 41 (step S10581) and end the power command value (Pref’) generation process. On the other hand, if the condition is NO in step S10573, in the next step S10580, the power command value correction circuit 320 will calculate the power command value (Pref’). The operation of step S10580 will be explained below with reference to FIG37.

Figure 37 is a flowchart showing the process of generating the power command value (Pref’) in step S10580 of Figure 35. In the initial step S105750 of Figure 37, the power command value correction circuit 320, as in Embodiment 1, assumes Fref = Fmeasure to generate the droop characteristic and calculates the upper and lower frequency limits of the AC system voltage based on the generated droop characteristic. Specifically, the upper and lower frequency limits can be calculated in the same way as in step S10572 of Figure 35. That is, the power command value correction circuit 320 calculates the upper limit value Fmax and the lower limit value Fmin of the frequency by substituting the speed adjustment rate Kgd, the braking coefficient Dg, the minimum value of ΔP and the maximum value of ΔP into equation (5) (see part B of Figure 38).

Furthermore, in step S105750, the power command value correction circuit 320 sets the power value in the current frequency command value Fref (e.g., 60Hz in Figure 38) to a temporary power command value Pref based on the generated droop characteristics.

If step S105750 ends, the power command value correction circuit 320 will confirm in the next step S105751 whether the upper and lower limit frequencies of the droop characteristic are within the upper and lower limit values of the AC system voltage frequency. In this embodiment 2, similar to the case of embodiment 1, the upper and lower limit values of the AC system voltage frequency are set to 60.1Hz to 59.9Hz. Furthermore, the power command value correction circuit 320 confirms whether the temporary power command value "Pref" is within the range of the power capacity of the battery power conversion device 41, that is, whether the absolute value of the temporary power command value "Pref" is below the maximum discharge power and below the maximum charging power.

When the condition is YES in step S105751, the power command value correction circuit 320 terminates the process by using the temporary power command value (Pref) as the final power command value (Pref'). On the other hand, when the condition is NO in step S105751, the power command value correction circuit 320 corrects the temporary power command value (Pref) in the next step S105752, thereby finalizing the power command value (Pref'). The operation of step S105752 will be explained below with reference to Figure 38.

Figure 38 is a diagram illustrating the correction procedure for the power command value. As shown in part A of Figure 38, it is assumed that when the frequency command value (Fref) is 60Hz, the representative value (Fmeasure) of the measured AC system voltage frequency is 59.915Hz. In this case, as shown in part B of Figure 38, the power command value correction circuit 320 calculates a temporary power command value (Pref) within the frequency command value (Fref=60Hz) so that the output power of the battery power conversion device 41 when the frequency of the distribution system voltage is set to Fmeasure becomes the power command value (Pref) generated by the operation plan generation circuit 314. However, in this example, as shown in part B of Figure 38, the lower limit frequency of the droop characteristic (i.e., the frequency in the maximum discharge power) is lower than the lower limit value of the AC system voltage frequency (59.9Hz). In addition, in the case of Figure 38, the temporary power command value (Pref) is within the range of the power capacity of the battery power conversion device 41. Therefore, the power command value correction circuit 320, as shown in part C of Figure 38, determines the power command value (Pref’) by correcting the temporary power command value (Pref) in the frequency command value (Fref=60Hz) so that the lower limit frequency of the droop characteristic is consistent with the lower limit frequency of the AC system voltage.

On the other hand, when the power command value (Pref) in the frequency command value (Fref=60Hz) is calculated so that the output power of the battery power conversion device 41 when the frequency of the power distribution system voltage is set to Fmeasure becomes the power command value (Pref) made by the operation plan making circuit 314, when the lower limit frequency Fmin and upper limit frequency Fmax of the droop characteristic are within the rated frequency range of the AC system (59.9Hz to 60.1Hz), the power command value correction circuit 320 outputs the temporary power command value (Pref) as the final power command value (Pref’) to the battery power conversion device 41.

The same applies when the upper limit frequency of the droop characteristic exceeds the upper limit frequency of the AC system voltage. In this case, the power command value correction circuit 320 generates a power command value (Pref’) in the frequency command value (Fref=60Hz) to make the upper limit frequency of the droop characteristic consistent with the upper limit frequency of the AC system voltage.

When the temporary power command value (Pref) in the frequency command value (Fref=60Hz) is outside the range of the power capacity of the battery power conversion device 41, a power command value (Pref’) is generated to be within the range of the power capacity. A specific example of this situation will be explained later with reference to Figure 41A. If step S105752 in Figure 37 is completed, the control circuit 321 in the second CEMS will end the calculation of the power command value (Pref’) (S10580 in Figure 35).

Returning to Figure 34, if step S1060 ends, the control circuit 321 in the second CEMS will process and return to step S1056. Then, step S1060 will be repeated until step S1056 becomes YES, that is, the calculation of the power command value (Pref’) of all battery power conversion devices 41 is completed.

Returning to Figure 21, if the operation plan in step S105 is completed, i.e., in the next step S110, the second CEMS internal control circuit 321 notifies each battery power conversion device 41 of the completed operation plan (power command value Pref' and frequency command value Fref (60Hz)). In the next step S111, the second CEMS internal control circuit 321 determines whether to stop CEMS 31. If step S111 is YES, the second CEMS internal control circuit 321 stops CEMS 31. On the other hand, if S111 is NO, the second CEMS internal control circuit 321 returns to step S101 and repeats the above process.

Next, we will explain the case where step S104 in Figure 21 is NO. In this case, the second CEMS internal control circuit 321 checks in step S106 whether it is the start time of a 1-minute cycle processing. If step S106 is NO, the second CEMS internal control circuit 321 returns the processing to step S101 and repeats the above process. On the other hand, if step S106 is YES, the second CEMS internal control circuit 321 advances the processing to the next step S107.

The second CEMS internal control circuit 321 collects measurement data from the voltmeter 22, the battery power conversion device 41, the MW-level solar photovoltaic system power conversion device 27, and user measurement data in step S107. If the measurement data collection in step S107 is completed, the second CEMS internal control circuit 321 determines in the next step S108 whether the operation plan needs to be modified. In this embodiment 2, similar to the case of embodiment 1, modification is determined when the SoC notified by the battery power conversion device 41 deviates from the predetermined range, or when the output (Fmeasure) of the AC frequency collection circuit 313 deviates from the predetermined range. Furthermore, the action in step S108 when determining whether to modify the operation plan is the same as the flowchart shown in Figure 27 of Implementation Form 1, so a detailed explanation will not be repeated.

When the second CEMS internal control circuit 321 determines in step S108 that no modification to the operation plan is required (i.e., when the modification flag for the operation plan of all battery power conversion devices 41 is "0") (NO in step S108), the second CEMS internal control circuit 321 returns the process to the initial step S101 and repeats the above process. On the other hand, when the second CEMS internal control circuit 321 determines in step S108 that modification to the operation plan is required (i.e., even if one of the modification flags for the operation plan is "1") (YES in step S108), the second CEMS internal control circuit 321 performs modification to the operation plan in the next step S109. The details of step S109 are explained below with reference to Figure 39.

Figure 39 is a flowchart showing the modification procedure of the operation plan in the distributed power management device of Embodiment 2. If the modification procedure of the operation plan is started, the control circuit 321 in the second CEMS checks in step S1091 whether a modification flag for the operation plan has been set. As described above, in this Embodiment 2, the modification flag for the operation plan is set according to the battery power conversion device 41, just as in Embodiment 1, and the power command value (Pref or Pref') is regenerated for those who need to modify the operation plan.

When no correction flag for the operation plan has been set (NO in step S1091), the process proceeds to step S1098. The processing in step S1098 will be explained later. On the other hand, when a correction flag for the operation plan has been set (YES in step S1091), the process proceeds to steps S1092 to S1094. In step S1092, the control circuit 321 of the second CEMS obtains the data (charge and discharge power, SoC) measured by the battery power conversion device 41, and in step S1093 obtains the frequency command value (Fref) and power command value (Pref), and then in step S1094 obtains the representative value (Fmeasure) of the frequency of the measured AC voltage output from the AC frequency collection circuit 313.

If steps S1092 to S1094 are completed, the control circuit 321 within the second CEMS will confirm in the next step S1095 whether the SoC is within the predefined range. Furthermore, in this embodiment 2, similar to the case of embodiment 1, the case where the SoC deviates from the predefined range refers to the case where the SoC exceeds 0.9 during charging and the case where the SoC is below 0.05 during discharging. Here, the SoC is fully charged at 1.0. However, the case where the SoC deviates from the predefined range is not limited to this example, as is the case in embodiment 1.

When the battery's SoC is not within the predefined range (NO in step S1095), the control circuit 321 within the second CEMS changes the power command value (Pref) in the next step S1096. In this embodiment 2, a data sheet (not shown) that determines the power command value based on the SoC value is first stored in the CEMS 31, and the control circuit 321 within the second CEMS determines the power command value (Pref) based on this information. Furthermore, as explained in Embodiment 1 with reference to FIG. 28, the method for determining the power command value is not limited to the data sheet method.

When the battery's SoC is within the predefined range (YES in step S1095), or when the generation of the power command value (Pref) in step S1096 above is completed, processing proceeds to step S1097. In step S1097, the control circuit 321 within the second CEMS confirms whether the representative value (Fmeasure) of the measured power distribution system voltage frequency falls within the frequency reference range. Here, the frequency reference range is the same as that described in steps S10573 of Figure 35 and Figure 36.

When the representative value (Fmeasure) of the frequency of the measured power distribution system voltage does not fall within the frequency reference range (NO in step S1097), the control circuit 321 in the second CEMS calculates the power command value (Pref’) in the next step S10911. Step S10911 in Figure 39 is the same as step S10580 in Figure 35, and more specifically, it is the same as the flowchart in Figure 37, so it will not be explained again.

When no correction flag for the operation plan is set (NO in step S1091), or when the calculation of the power command value (Pref’) is completed in step S10911 above, or when the representative value (Fmeasure) of the frequency of the measured distribution system voltage is within the frequency reference range (YES in step S1097), the process proceeds to step S1098. In step S1098, the control circuit 321 within the second CEMS confirms whether the control parameters (Pref, Pref’) of all battery power conversion devices 41 that need to be corrected have been generated. The control circuit 321 within the second CEMS terminates the operation plan correction process when the generation of all control parameters is completed (YES in step S1098). On the other hand, when the generation of control parameters for all the battery power conversion devices 41 that need to be corrected is not completed (NO in step S1098), the control circuit 321 in the second CEMS changes the processing object to the next battery power conversion device 41 in step S1099, and then returns to the original step S1091 to perform the above processing again.

Returning to Figure 21, when the modification of the operation plan in step S109 is completed, or when the creation of the operation plan in step S105 is completed, in the next step S110, the control circuit 321 within the second CEMS notifies each battery power conversion device 41 of the created operation plan (power command value (Pref or Pref') and frequency command value (Fref: 60Hz). Furthermore, in the next step S111, the second CEMS... The internal control circuit 321 determines whether to terminate the operation of CEMS31. When the operation of CEMS31 is terminated (YES in step S111), CEMS31 stops. On the other hand, when the operation of CEMS31 is not terminated (NO in step S111), the process returns to the initial step S101 and the above process is executed again. In addition, the operation of the battery power conversion device 41 is the same as that in Embodiment 1, so it will not be described again.

[Effects of Embodiment 2] In summary, the distributed power management device (CEMS31) of Embodiment 2 is configured such that, when an operation plan (including a power command value (Pref’)) is made for the battery power conversion device 41, a correction is added to the power command value (Pref) made by the operation plan making circuit 314 based on the vertical characteristics of the stationary inverter in the battery power conversion device 41, the power command value (Pref) made by the operation plan making circuit 314, and the frequency (Fmeasure) of the measured AC system voltage, thereby calculating the power command value (Pref’). Therefore, even when the frequency of the AC system voltage changes drastically due to variations in load power consumption or sudden changes in the power supplied to the system from renewable energy generators due to sudden changes in sunlight, the inverter equipped with virtual synchronous generator control characteristics (i.e., droop characteristics) will not deviate from the frequency range managed by the stationary inverter, thus enabling continuous operation without interrupting the distributed power supply.

[Examples of Other Droop Characteristics] In Embodiments 1 and 2, examples of droop characteristics for the battery power conversion device 41 have been described, illustrating the use of the droop characteristics of the virtual synchronous generators shown in Figures 15 and 17. However, the droop characteristics are not limited to those of virtual synchronous generators. Furthermore, in Embodiments 1 and 2, for ease of explanation, the description focuses on the case where the battery power conversion device 41 only performs a discharging operation. However, the operation of the battery power conversion device 41 is not limited to discharging only; it can also perform charging only, or both charging and discharging. Hereinafter, examples of other vertical characteristics applied to the distributed power management device of Embodiment 1 will be described with reference to Figures 40A to 40G, and examples of other vertical characteristics applied to the distributed power management device of Embodiment 2 will be described with reference to Figures 41A to 41D.

Figure 40A is a diagram showing an example of the linear vertical characteristic when the power conversion device 41 for the storage battery is charging and discharging. As shown in Figure 40A, in the case of implementation mode 1, the frequency command value Fref is changed from the initial value (60Hz) to a representative value (Fmeasure) of the frequency of the measured system voltage (e.g., average value).

Figure 40B is a diagram showing an example of a straight, drooping characteristic without inductance when the battery power conversion device 41 is charging and discharging. As shown in Figure 40B, in the case of Embodiment 1, the frequency command value Fref is changed from the initial value (60Hz) to the representative value Fmeasure of the frequency of the measured system voltage.

Figure 40C is a diagram showing an example of the curved drooping characteristics of the battery power conversion device 41 during charging and discharging. As shown in Figure 40C, in the case of Embodiment 1, the frequency command value Fref changes from the initial value (60Hz) to the representative value Fmeasure of the frequency of the measured system voltage.

Figure 40D is a diagram showing an example of a battery power conversion device 41 having a non-inductive straight-line drooping characteristic when only discharging. As shown in Figure 40D, in the case of Embodiment 1, the frequency command value Fref is changed from the initial value (60Hz) to the representative value Fmeasure of the frequency of the measured system voltage.

Figure 40E is a diagram showing an example of the curved drooping characteristic of the battery power conversion device 41 when it is only discharging. As shown in Figure 40E, in the case of embodiment 1, the frequency command value Fref is changed from the initial value (60Hz) to the representative value Fmeasure of the frequency of the measured system voltage.

Figure 40F is a diagram showing an example of a non-inductive straight-line drooping characteristic of the battery power conversion device 41 when it is only charging. As shown in Figure 40F, in the case of Embodiment 1, the frequency command value Fref is changed from the initial value (60Hz) to the representative value Fmeasure of the frequency of the measured system voltage.

Figure 40G is a diagram showing an example of the curved drooping characteristics of the battery power conversion device 41 when it is only charging. As shown in Figure 40G, in the case of Embodiment 1, the frequency command value Fref is changed from the initial value (60Hz) to the representative value Fmeasure of the frequency of the measured system voltage.

Figure 41A is a diagram showing an example of the linear vertical characteristic of the power conversion device 41 for the battery during charging and discharging. As shown in Figure 41A, in Embodiment 2, a temporary power command value Pref” in the frequency command value Fref (60Hz) is temporarily specified to obtain the power command value Pref obtained by the operation plan in the measured system frequency Fmeasure. However, in this case, since the temporary power command value Pref” exceeds the DC/AC converter capacity, the final power command value Pref’ is specified to be consistent with the maximum charging power of the DC/AC converter.

Figure 41B is a diagram showing an example of the linear vertical characteristic of the battery power conversion device 41 when it is only charging. As shown in Figure 41B, in the case of Embodiment 2, the temporary power command value Pref' in the frequency command value Fref (60Hz) is temporarily specified to obtain the power command value Pref obtained through the operation plan in the measured system frequency Fmeasure. However, in this case, the lower limit frequency of the droop characteristic (i.e., the frequency in the maximum discharge power) is lower than the lower limit of the AC system voltage frequency (59.9Hz). Therefore, the power command value Pref' in the frequency command value Fref (60Hz) is finally specified to make the lower limit frequency of the droop characteristic consistent with the lower limit of the AC system voltage frequency.

Figure 41C is a diagram showing an example of a battery power conversion device 41 having a non-inductive straight-line drooping characteristic when only discharging. As shown in Figure 41C, in the case of Embodiment 2, the power command value Pref” in the frequency command value Fref (60Hz) is specified to obtain the power command value Pref obtained by the operation plan in the measured system frequency Fmeasure.

Figure 41D is a diagram showing an example of a straight, drooping characteristic without induction when the battery power conversion device 41 is only being charged. As shown in Figure 41D, in the case of Embodiment 2, the power command value Pref” in the frequency command value Fref (60Hz) is specified to obtain the power command value Pref obtained by the operation plan in the measured system frequency Fmeasure.

[Variations] Variations of embodiments 1 and 2 are described below. It is also possible to control the generation of droop characteristics (specifically, frequency command values Fref) so that the maximum and minimum frequencies of the droop characteristics of these multiple stationary inverters are substantially the same when controlled by a distributed power management device (i.e., CEMS31 (host EMS)). In this way, the frequency range is controlled so that even when load changes or sudden changes in the power generation of energy-generating machines occur, all stationary inverters equipped with droop characteristics can operate in accordance with the frequency of the power distribution system voltage. Therefore, the frequency of the AC system voltage does not deviate from the frequency range managed by the droop characteristics, enabling continuous operation without stopping the distributed power supply. Furthermore, considering errors from voltage sensors, etc., a frequency deviation (i.e., the difference between the maximum frequency and the frequency command value Fref, or the difference between the minimum frequency and the frequency command value Fref) of 5% to 10% can be used to substantially match the maximum and minimum frequencies of the droop characteristics of multiple stationary inverters.

In embodiments 1 and 2, although the case in which a virtual synchronous generator control is installed in the battery power conversion device 41 has been described, the object of installing the virtual synchronous generator control is not limited to this. For example, the virtual synchronous generator control and the above-mentioned vertical characteristics can also be installed in energy-generating machines such as wind turbines, energy-generating machines such as fuel cells, and power conversion devices that charge and discharge electricity in the batteries of electric vehicles and fuel cell vehicles. In this case, as long as the distributed power management device (CEMS31) controls the droop characteristics of each distributed power source based on the measured frequency (Fmeasure) of the distribution system voltage, the frequency range is controlled so that even if the frequency of the distribution system voltage deviates from the rated frequency (e.g., 60Hz), the stationary inverter equipped with droop characteristics such as virtual synchronous generator control characteristics can follow the frequency of the distribution system voltage. Therefore, the frequency of the AC system voltage will not escape the frequency range managed by the droop characteristics, and continuous operation can be achieved without stopping the distributed power sources.

In addition, since wind turbines use propellers to drive motors, there is inertial force on the generator side, so the same effect can be achieved.

In embodiments 1 and 2, although the case of a power distribution system with a static inverter (battery power conversion device 41) having droop characteristics connected to the backbone system has been explained, it is not limited to this, and of course, a self-contained system can also achieve the same effect. In this case, in addition to distributed power sources such as batteries, wind turbines, solar power systems, and fuel cells with static inverters installed in the self-contained system, a system with emergency generators (synchronous generators) can also be provided. In this self-contained system, as long as the vertices of the stationary inverter equipped with vertices are controlled according to the frequency (Fmeasure) of the AC system voltage as shown in forms 1 and 2, the frequency range of the stationary inverter is controlled to operate in accordance with the frequency of the distribution system voltage. Therefore, the frequency of the AC system voltage will not deviate from the frequency range managed by the vertices, and continuous operation can be achieved without stopping the distributed power supply.

In embodiments 1 and 2, the rated frequency range of the AC system is set to the rated frequency range of the backbone system (e.g., refer to Figure 17: 59.9Hz to 60.1Hz), but is not limited to this frequency range. When connected to the backbone system, it can be set to the rated frequency range that can be specified by the television distribution operator of the backbone system (e.g., ±0.2Hz). In addition, in the case of an independent system, it can be set to the frequency range specified by the operator of the independent system (e.g., ±0.15Hz), or the frequency range defined by the vertical characteristics of the synchronous generator whose vertical characteristics cannot be changed from CEMS31, or the frequency range obtainable by the vertical characteristics of the largest capacity stationary inverter in the independent system. If this frequency range is set, even in a self-contained system, the frequency range of a stationary inverter equipped with vertices such as virtual synchronous generator control characteristics is controlled to follow the frequency of the distribution system voltage. Therefore, the frequency of the AC system voltage does not deviate from the frequency range managed by the vertices, allowing for continuous operation without stopping distributed power supplies. This is particularly useful when a synchronous generator with vertices that cannot be changed from the CEMS31 is installed; however, controlling the vertices of other distributed power supplies within the frequency range achievable by the synchronous generator effectively stabilizes the frequency of the self-contained system.

In Embodiments 1 and 2, although the power distribution system is described as a three-phase AC system, it is not limited to this. For example, the power distribution system can also be a single-phase system (including a single-phase three-wire system) or a power distribution system with more than three phases. Furthermore, when a battery power conversion device (three-phase AC) is mixed with a household battery system (single-phase AC), the same effect can be obtained by generating a power command value (Pref’) or frequency command value (Fref) with drooping characteristics for a stationary inverter, just as in Embodiments 1 and 2.

In embodiments 1 and 2, although the measured frequency of the AC system voltage measured by voltmeters 22a to 22x is measured at various locations when determining the frequency of the power distribution system voltage, and the average value calculated by the AC frequency collection circuit 313 is used as a representative value to average the measurement error of the voltmeter 22, it is not limited to this, as mentioned above. Of course, the measurement result at a representative point or the average value of the measurement results in each battery power conversion device 41 can also be used. Furthermore, although the noise component contained in the output of the averaging circuit 3131 is removed by a primary IIR filter, a filter may not be specifically provided. Furthermore, the filter is not limited to a primary IIR filter; it can also be a higher-order IIR filter or an FIR filter.

In embodiments 1 and 2, as examples of the droop characteristics of the battery power conversion device 41, although the droop characteristics used in the virtual synchronous generator control shown in Figures 15 and 17, or the droop characteristics shown in Figures 40 and 41, are illustrated, the embodiments are not limited to these. Furthermore, the droop characteristics are not limited to those possessed by the virtual synchronous generator control. Moreover, the definition of the droop characteristics is not particularly limited. For example, the data could also be a data sheet showing the relationship between the output ΔP (i.e., power command value (Pref) - Pmeasure (effective power measured value)) and the output ΔF (i.e., frequency command value (Fref) - AC system voltage measured value (Fmeasure)), or data such as the tilt of the droop characteristic, or the coordinate information of the start point, end point, and vertices of the line in the characteristic shown in Figure 40B. Furthermore, while embodiments 1 and 2 describe the case where the droop characteristics of each battery power conversion device 41 are managed by the CEMS31, the description is not limited to this. The same effect can be achieved by having the CEMS31 obtain the droop characteristics pre-existing in the battery power conversion device 41 and manage them within the distributed power supply droop characteristic management circuit 316. Additionally, the distributed power supply droop characteristic management circuit 316 can also be configured to obtain control parameters (i.e., droop characteristics) from the virtual synchronous generator control circuit 4093 of the battery power conversion device 41 for management.

In embodiments 1 and 2, as explained with reference to Figures 24 and 36, although the frequency reference range used when determining whether to generate a frequency command value (Fref) or a power command value (Pref’) falls within the range of the upper limit frequency Fmax and lower limit frequency Fmin determined by the droop characteristics, it is not limited to this, as mentioned above. For example, the upper limit frequency offset F_offset_up and the lower limit frequency offset F_offset_down can also be different values. In addition, this value can also be changed by the value of the power command value (Pref) generated by the operation plan generating circuit 314 or the measured result (Fmeasure) of the frequency of the distribution system voltage. For example, the value of frequency offset F_offset can be reduced as the power command value approaches the inverter capacity.

In embodiments 1 and 2, the speed controller circuit 40933, which controls the virtual synchronous generator installed in the battery power conversion device 41, uses a model based on the primary delay system shown in Figure 12, but is not limited to it. For example, it can also be a secondary delay system model, or other models recommended by the Institute of Electrical Engineering (IEEJ), etc. Furthermore, the mass system calculation circuit 40937 uses a model based on the oscillation equation shown in Figure 13, but is not limited to it; for example, it can also be modeled using a primary delay system, a secondary delay system, an LPF, etc. Furthermore, in embodiments 1 and 2, although VQ control, which is often implemented in virtual synchronous generator control, is not mentioned, the same effect can certainly be obtained by using the method disclosed herein in a power conversion device equipped with VQ control as virtual synchronous generator control.

In embodiments 1 and 2, the communication cycle of DSO21 and CEMS31 is set to 30 minutes, but as mentioned above, it is not limited to this. The communication cycle can also be set to, for example, a 15-minute cycle or a 1-hour cycle. Furthermore, regarding the communication cycle with voltmeter 22 and battery power conversion device 41, as mentioned above, it is not limited to 1 minute. The communication cycle can also be, for example, a 1-second cycle, a 10-second cycle, a 30-second cycle, a 2-minute cycle, etc.

In embodiments 1 and 2, when detecting the phase from the AC voltage waveform measured by the voltmeter 410, zero-crossing points are detected from the AC voltage waveform, and the frequency is detected from the time interval of the detected zero-crossing points. However, the method for detecting the frequency of AC voltage is not limited to using the detection results of zero-crossing points. For example, in the case of three-phase AC, the frequency of the power distribution system voltage can also be calculated by using dq conversion, etc.

In embodiments 1 and 2, when the SoC deviates from the predetermined range and the power command value needs to be changed, a data sheet (not shown) determining the power command value based on the SoC's value is first stored in CEMS31, and the power command value (Pref) is determined based on that information. However, as mentioned above, the method for determining the power command value is not limited to the data sheet. For example, the power command value can be changed to a value that does not cause over-discharge or over-charge during the period from the time the demand plan is received from DSO21 to the time the demand plan is received from DSO21, based on the time up to the time the demand plan is received from DSO21, the SoC's value, and the current power command value.

In embodiments 1 and 2, although the case of connecting several power conversion devices used in large-capacity batteries, such as the battery 40 used in the power distribution system, to the power distribution system has been described, it is also possible to install virtual synchronous generator control on power conversion devices for household batteries and electric vehicles, and implement the same control as CEMS31. In this case, the number of power conversion devices connected to the power distribution line 24 will reach several hundred. Furthermore, large-capacity batteries, such as the battery 40 used in the power distribution system (e.g., hundreds of kW to several MW), and small-capacity batteries, such as household batteries (several kW), can achieve the same effect when connected to the same power distribution system.

In embodiments 1 and 2, although the power conversion device 41 for batteries has been described, it is not limited to this. Regarding the case where a virtual synchronous generator control is installed on a system that uses a static inverter as a voltage source to supply power from sources such as solar cells (not limited to MW-level solar photovoltaic systems, but also residential solar cells), wind turbines, or fuel cells, the same effect can be obtained if the control parameters of the virtual synchronous generator control unit are configured in the same way as in embodiments 1 and 2 described above. Furthermore, onboard batteries from electric vehicles (EVs), plug-in hybrid electric vehicles (PHEVs), or fuel cell vehicles (FCVs) can also be used.

In embodiments 1 and 2, for ease of explanation, the control circuit of the battery power conversion device 41 is shown in Figures 5 to 13, and the configuration of the CEMS 31 is shown in Figures 2 to 4. The explanation focuses on the case where each functional block is constructed using hardware (H/W), but is not limited to this. The same control function can also be achieved by implementing the function of at least some of the functional blocks using software (S/W) installed on the CPU (Central Processing Unit). Alternatively, the same control function can also be achieved by separating the functions of at least some of the functional blocks into software and hardware functionalities.

[Summary of the Effects of Embodiments 1 and 2] In summary, the distributed power management device disclosed herein is configured to generate a frequency command value (Fref) or a power command value (Pref’) of the droop characteristic (i.e., the characteristic of vertical droop) based on the measured result (Fmeasure) of the AC system voltage frequency when a power conversion device equipped with a static inverter with a droop characteristic is connected to an AC system. Therefore, it has the effect of controlling the power conversion device with the droop characteristic even when the frequency of the backbone system deviates from the rated frequency (e.g., 60Hz), without falling outside the frequency management range of the power conversion device equipped with the static inverter.

The embodiments disclosed herein should be understood as illustrative only and should not be construed as limiting the invention. The scope of this disclosure is defined by the scope of the patent application, not by the foregoing description, and includes all variations within the same meaning and scope as the scope of the patent application.

20: Substation 21: Distribution Automated System (DSO) 22: Voltmeter 23: Automatic Voltage Regulator (SVR) 24: Distribution System 25: Communication Line 26: MW-level Solar Photovoltaic System 27: Power Conversion Device for MW-level Solar Photovoltaic System 28: Switch 30: Synchronous Generator 31: CEMS 40: Battery 41: Power Conversion Device for Battery 100: Town 101: Factory 102: Building 103: Tower 311: Communication Circuit 312: Memory Circuit 313: AC Frequency Collection Circuit 314: Operation plan generation circuit 315: Frequency command value generation circuit 316: Distributed power supply vertical characteristic management circuit 317: Data transmission generation circuit 318: CEMS internal control circuit 320: Power command value correction circuit 321: Second CEMS internal control circuit 401, 406, 410: Voltmeters 402, 407, 411: Ammeters 403: First DC/DC conversion circuit 404: First control circuit 405: DC bus 408: First DC/AC conversion circuit 409: Second control circuit 412: Communication interface circuit 3131: Averaging circuit 3132, 3134, 40943, 409331, 409373: Multipliers 3133, 40935, 409375: Adders 3135: Registers 3141: Battery Operation Plan Creation Circuit 3142: Power Generation Prediction Circuit 3143: Power Consumption Prediction Circuit 3144: Battery Operation Plan Correction Circuit 3145: Power Command Value Memory Transmission Circuit 3146: Management Circuit 4041: Charging Control Circuit 4042: Discharge Control Circuit 4043: First Switching Circuit 4044: Third Control Circuit 4091: AC Frequency Detection Circuit 4092: Effective Power Calculation Circuit 4093: Virtual Synchronous Generator Control Circuit 4094: Inverter Current Control Circuit 4095: Inverter Voltage Control Circuit 4096: Second Switching Circuit 4097: Fourth Control Circuit 40910: Phase Detection Circuit 40911: Frequency Detection Circuit 40912: First Sine Wave Generation Circuit 40932, 40936, 40941, 40944, 40952, 409371: Subtractors 40933: Speed Regulator Control Circuit 40937: Mass System Calculation Circuit 40942: First PI Control Circuit 40945: Second PI Control Circuit 40946: First PWM Conversion Circuit 40951: Second Sine Wave Generation Circuit 40953: Third PI Control Circuit 40954: Second PWM Conversion Circuit 40955: First Current Limiting Circuit 409332: First Delay System Model 409333: Limiting Circuit 409372: Integrator 409374: Divider 409376: Phase Calculation Circuit

Figure 1 is a block diagram showing the distributed power management device of Embodiment 1 and the power distribution system having a plurality of distributed power sources controlled by the distributed power management device. Figure 2 is a block diagram of the CEMS shown in Figure 1. Figure 3 is a block diagram of the operation planning circuit within the CEMS shown in Figure 2. Figure 4 is a block diagram of the AC frequency collection circuit within the CEMS shown in Figure 2. Figure 5 is a block diagram of the battery power conversion device shown in Figure 1. Figure 6 is a block diagram illustrating the structure of the first control circuit of the first DC/DC conversion circuit controlling the battery power conversion device shown in Figure 5. Figure 7 is a block diagram illustrating the structure of the second control circuit of the first DC/AC conversion circuit in the battery power conversion device shown in Figure 5. Figure 8 is a block diagram illustrating the structure of the AC frequency detection circuit shown in Figure 7. Figure 9 is a block diagram illustrating the structure of the inverter current control circuit shown in Figure 7. Figure 10 is a block diagram illustrating the structure of the inverter current control circuit shown in Figure 7. Figure 11 is a block diagram illustrating the structure of the virtual synchronous generator control circuit shown in Figure 7. Figure 12 is a block diagram illustrating the structure of the governor control circuit shown in Figure 11. Figure 13 is a block diagram illustrating the structure of the mass system calculation circuit shown in Figure 11. Figure 14 shows the area filled by the virtual synchronous generator control installed in the battery power conversion device. Figure 15 shows an example of the droop characteristics of the virtual synchronous generator control shown in Embodiment 1. Figure 16 shows an example of the results of measuring the frequency of the distribution system voltage over 25 hours with a 1-second cycle. Figure 17 shows an example of the droop characteristics of the battery power conversion device in the distribution system of Embodiment 1. Figure 18 is a diagram illustrating the method of generating the frequency command value in the distributed power management device of Embodiment 1. Figure 19A shows the frequency command value when using the droop characteristics of the comparative example. Figure 19B is a diagram showing the frequency command value when using the droop characteristics of Embodiment 1. Figure 20 is a sequence diagram of the normal operation of the distributed power management system centered on the CEMS shown in Figure 1. Figure 21 is a flowchart showing the control processing of the CEMS shown in Figure 1. Figure 22 is a flowchart showing the detailed operations of the operation plan creation process in step S105 of the flowchart shown in Figure 21. Figure 23 is a flowchart showing the frequency command value generation procedure. Figure 24 is a diagram showing an example of the droop characteristics of the battery power conversion device in the distributed power management system of Embodiment 1. Figure 25 is a flowchart showing the frequency command value generation procedure in step S10574 of Figure 23. Figure 26 illustrates the procedure for correcting the frequency command value. Figure 27 is a flowchart showing the procedure for determining whether to correct the operation plan. Figure 28 is a flowchart showing the procedure for correcting the operation plan. Figure 29 is a flowchart mainly showing the operation of the second control circuit. Figure 30 is a flowchart showing the control procedure of the first DC/AC conversion circuit. Figure 31 is a block diagram of the CEMS in Embodiment 2. Figure 32A illustrates the method for generating the power command value in the CEMS of Embodiment 2 (before power command value correction). Figure 32B illustrates the method for generating the power command value in the CEMS of Embodiment 2 (after power command value correction). Figure 33A is a diagram showing the frequency range of the inverter when using the comparative example's droop characteristics. Figure 33B is a diagram showing the power command value and inverter frequency when using the droop characteristics of Embodiment 2. Figure 34 is a flowchart showing the detailed operations of the operation plan creation process in step S105 of Figure 21 in Embodiment 2. Figure 35 is a flowchart showing the power command value generation procedure. Figure 36 is a diagram showing an example of the droop characteristics of a battery power conversion device in the distributed power management system of Embodiment 2. Figure 37 is a flowchart showing the power command value generation procedure in step S10580 of Figure 35. Figure 38 is a diagram illustrating the power command value correction procedure. Figure 39 is a flowchart showing the revised operation plan in the distributed power management device of Embodiment 2. Figure 40A is a diagram showing an example of a linear drooping characteristic when the battery power conversion device is charging and discharging. Figure 40B is a diagram showing an example of a linear drooping characteristic without inductance when the battery power conversion device is charging and discharging. Figure 40C is a diagram showing an example of a curved drooping characteristic when the battery power conversion device is charging and discharging. Figure 40D is a diagram showing an example of a linear drooping characteristic without inductance when the battery power conversion device is only discharging. Figure 40E is a diagram showing an example of a curved drooping characteristic when the battery power conversion device is only discharging. Figure 40F shows an example of a straight, non-inductive downward characteristic when the battery power conversion device is only charging. Figure 40G shows an example of a curved, downward characteristic when the battery power conversion device is only charging. Figure 41A shows an example of a straight, downward characteristic when the battery power conversion device is charging and discharging. Figure 41B shows an example of a straight, downward characteristic when the battery power conversion device is only charging. Figure 41C shows an example of a straight, non-inductive downward characteristic when the battery power conversion device is only discharging. Figure 41D shows an example of a straight, non-inductive drooping characteristic when the battery is only being charged by the power conversion device. Figure 42 is a schematic diagram illustrating the function of the speed controller. Figure 43 is a block diagram showing the calculation of the transfer function F(s) of the virtual synchronous generator control circuit 4093 shown in Figure 11.

25: Communication Line 31: CEMS 311: Communication Circuit 312: Memory Circuit 313: AC Frequency Collection Circuit 314: Operation Plan Creation Circuit 315: Frequency Command Value Generation Circuit 316: Vertical Characteristic Management Circuit 317: Data Transmission Generation Circuit 318: CEMS Internal Control Circuit

Claims (16)

A distributed power supply management device manages one or more distributed power supplies; Each of the aforementioned one or more distributed power supplies is connected to a power system and operates as a voltage source; The frequency-power relationship of each of the aforementioned one or more distributed power supplies has a vertical characteristic and is adjusted so that frequency command values correspond to power command values; The aforementioned distributed power supply management device comprises: An AC frequency collection unit that collects AC frequency information of the aforementioned power system and determines a representative value of the AC frequency based on the collected AC frequency information; and A frequency command value generation unit that generates the aforementioned frequency command value for each of the aforementioned one or more distributed power supplies based on the aforementioned representative value of the AC frequency. As in claim 1, the distributed power management device further includes a vertical characteristic management unit that manages the shape of the vertical characteristic corresponding to each of the aforementioned one or more distributed power supplies, or parameters determining the shape of the vertical characteristic, as vertical characteristic information; The frequency command value generation unit generates the aforementioned frequency command value for each of the aforementioned one or more distributed power supplies based not only on the representative value of the aforementioned AC frequency but also on the aforementioned corresponding vertical characteristic information managed by the aforementioned vertical characteristic management unit. As in claim 2, the distributed power management device further includes an operation plan generation unit that generates operation plans for each of the aforementioned one or more distributed power supplies and generates power command values for each of the aforementioned one or more distributed power supplies based on the corresponding operation plans; The frequency command value generation unit generates the aforementioned frequency command values for each of the aforementioned one or more distributed power supplies based on the representative value of the aforementioned AC frequency and the corresponding vertical characteristic information stored in the aforementioned vertical characteristic management unit, as well as based on the corresponding power command values generated by the aforementioned operation plan generation unit. As in the distributed power management device of claim 3, the aforementioned frequency command value generation unit determines the maximum and minimum frequencies achievable by each of the aforementioned distributed power sources based on the corresponding power capacity of each of the aforementioned distributed power sources; When the frequency command value generation unit does not include a representative value of the aforementioned AC frequency at the current time within the frequency reference range of the aforementioned maximum and minimum frequencies, it modifies the aforementioned frequency command value to a value based on the representative value of the aforementioned AC frequency at the current time. As in the distributed power management device of claim 4, the frequency command value generation unit, when changing the frequency command value of the first distributed power supply among the aforementioned one or more distributed power supplies, (i) assuming that the frequency command value of the first distributed power supply is set to be equal to the representative value of the AC frequency at the current time, calculates the maximum and minimum frequencies achievable by the first distributed power supply, and when the calculated maximum and minimum frequencies satisfy the first condition that they fall within the predetermined rated frequency range according to the rated frequency of the aforementioned power system, sets the frequency command value to be actually equal to the representative value of the AC frequency at the current time. (ii) If the first condition is not met, the aforementioned frequency command value shall be set to a value offset from the representative value of the aforementioned AC frequency at the current time to satisfy the first condition. If the distributed power management device described in any of claims 3 to 5 is configured such that a plurality of distributed power sources are connected in the aforementioned power system as one or more distributed power sources; the aforementioned frequency command value generation unit generates the aforementioned frequency command value for each of the plurality of distributed power sources so that the maximum and minimum frequencies achievable by each of the plurality of distributed power sources are substantially the same. A distributed power supply management device manages one or more distributed power supplies; Each of the aforementioned one or more distributed power supplies is connected to a power system and operates as a voltage source; The frequency-power relationship of each of the aforementioned one or more distributed power supplies has a vertical characteristic and is adjusted so that frequency command values and power command values correspond to each other; The aforementioned distributed power supply management device comprises: An AC frequency collection unit that collects AC frequency information of the aforementioned power system and determines a representative value of the AC frequency based on the collected AC frequency information; and A power command value correction unit that corrects the aforementioned power command value of each of the aforementioned one or more distributed power supplies based on the aforementioned representative value of the AC frequency. As in claim 7, the distributed power management device further includes a vertical characteristic management unit that manages the shape of the vertical characteristic corresponding to each of the aforementioned one or more distributed power supplies, or parameters determining the shape of the vertical characteristic, as vertical characteristic information; The power command value correction unit corrects the power command value of each of the aforementioned one or more distributed power supplies based not only on the representative value of the AC frequency but also on the vertical characteristic information managed by the vertical characteristic management unit. As in claim 8, the distributed power management device further includes an operation plan generation unit that generates operation plans for each of the aforementioned one or more distributed power supplies, and generates power command values for each of the aforementioned one or more distributed power supplies based on the corresponding operation plans; The power command value correction unit corrects the power command values generated by the operation plan generation unit based on the representative value of the aforementioned AC frequency and the corresponding vertical characteristic information stored in the aforementioned vertical characteristic management unit. As in the distributed power management device of claim 9, the aforementioned power command value correction unit determines the maximum and minimum frequencies achievable by each of the aforementioned distributed power sources based on the power capacity corresponding to each of the aforementioned distributed power sources; The aforementioned power command value correction unit corrects the aforementioned power command value to a value based on the representative value of the aforementioned AC frequency at the current time when the frequency reference range of the aforementioned maximum and minimum frequencies does not include the representative value of the aforementioned AC frequency at the current time. As in the distributed power management device of claim 10, the aforementioned power command value correction unit corrects the power command value of the first distributed power source among the aforementioned one or more distributed power sources, (i) Under the assumption that the power command value corresponding to the aforementioned frequency command value is corrected to a first value so that the power value in the representative value of the aforementioned AC frequency at the current time is equal to the aforementioned power command value generated by the aforementioned operation plan generation unit, the maximum and minimum frequencies achievable by the aforementioned first distributed power supply are calculated. When the calculated maximum and minimum frequencies satisfy the first condition that they fall within the predetermined rated frequency range according to the rated frequency of the aforementioned power system and the aforementioned first value is within the power capacity of the aforementioned first distributed power supply, the aforementioned power command value corresponding to the aforementioned frequency command value is actually corrected to the aforementioned first value. (ii) When the first condition is not met, the power command value corresponding to the frequency command value is corrected to a value offset from the first value to satisfy the first condition. If the distributed power management device described in any of claims 9 to 11 is configured such that a plurality of distributed power sources are connected in the aforementioned power system as one or more distributed power sources; the aforementioned power command value correction unit corrects the aforementioned power command value of each of the plurality of distributed power sources so that the maximum and minimum frequencies achievable by each of the plurality of distributed power sources are substantially consistent with each other. For example, in any of the distributed power management devices described in claims 2 to 5 and 8 to 11, each of the aforementioned one or more distributed power sources performs virtual synchronous generator control, simulating the operation of a synchronous generator; The aforementioned vertical characteristic management unit remembers the speed governor time constant, speed regulation rate, inertia constant, and braking coefficient as the aforementioned vertical characteristic information during the execution of the aforementioned virtual synchronous generator control. The distributed power management device according to any of claims 3 to 5 and 9 to 11, wherein a plurality of distributed power sources are connected in the aforementioned power system as one or more distributed power sources; each of the plurality of distributed power sources calculates an AC frequency based on the voltage of the aforementioned power system; the aforementioned AC frequency collection unit collects the calculated AC frequency value from at least one of the plurality of distributed power sources as the aforementioned AC frequency information. For example, in the distributed power management device of claim 14, the aforementioned power system is an independent system; The representative value of the aforementioned AC frequency is a calculated value collected from the distributed power source with the largest power capacity among the aforementioned plurality of distributed power sources, or from the distributed power source corresponding to the largest power command value among the power command values generated by the aforementioned operation plan generation unit. A power distribution system includes a distributed power management device comprising any one of claims 1 to 15. The distributed power management device comprises one or more distributed power sources, each operating as a voltage source. The frequency-power relationship of each of the one or more distributed power sources exhibits a vertical characteristic and is adjusted such that frequency command values and power command values correspond to each other. Furthermore, the distributed power management device manages the one or more distributed power sources.