JP2018081621A - Power control apparatus and power control method thereof - Google Patents

Abstract

Provided is a technique capable of causing generated power to follow a power demand even when there is a sudden change in the power demand during independent operation. A power control device that performs power tracking control of a solar cell string includes a power generation control unit. The power generation control unit controls the generated power of the solar cell string by changing the power point of the solar cell string, and makes the change rate of the power point during the independent operation faster than during the interconnection operation with the system power supply. [Selection] Figure 4

Description

  The present invention relates to a power control apparatus and a power control method thereof.

  In recent years, a photovoltaic power generation system that is connected to a system power supply is being introduced into a home for general households or an industrial facility. The power conditioner of the solar power generation system is required to efficiently extract the electric power generated by the solar cell string during the interconnection operation. Therefore, the power conditioner causes the power point of the solar cell string to follow the maximum power point so that the generated power becomes maximum by the maximum power point tracking control (MPPT control). In such maximum power point tracking control, the power point of the solar cell string is frequently adjusted in order to accurately control the actual generated power. However, the adjustment accuracy of the power point is in a trade-off relationship with the tracking speed of the power point. That is, if priority is given to the adjustment accuracy of the power point, the tracking speed of the power point becomes slow.

  Therefore, in the maximum power control method of Patent Document 1, when the power point of the solar cell is made to follow the maximum power point, the amount of change in the power point (operating voltage) of the solar cell is proportional to the amount of change in the output power of the power conditioner. I am letting. By controlling the power point in this way, the follow-up speed of the power point away from the maximum power point is increased, and the amount of change in the operating voltage near the maximum power point is reduced to increase the accuracy of the maximum power point tracking control. ing.

  By the way, at the time of a power failure of the system power supply, the power conditioner operates independently without being connected to the system power supply, and only supplies power to a dedicated load connected to a dedicated energization path during the independent operation. In this case, the power conditioner suppresses the generated power of the solar cell string according to the power required by the dedicated load.

Japanese Patent Laid-Open No. 06-83465

  However, if there is a sudden change in the power required for the dedicated load during autonomous operation, the change in the generated power of the solar cell string cannot follow the power demand and the operation of the dedicated load may not be maintained due to insufficient power. . For example, when a device such as a microwave oven is used during a self-sustained operation, the electric power consumed at the start of use increases instantaneously, resulting in a rapid increase in power demand. In this case, it is not possible to increase the generated power corresponding to the power consumed by the device by making the change rate of the generated power follow the increasing rate of the power demand, and the device may stop due to power shortage. Patent Document 1 makes no mention of such a problem during independent operation.

  The present invention has been made in view of such a situation, and provides a technique capable of causing generated power to follow the power demand even when there is a sudden change in the power demand during the autonomous operation. For the purpose.

  In order to achieve the above object, a power control apparatus according to an aspect of the present invention is a power control apparatus that performs power tracking control of a solar cell string, and changes the power point of the solar cell string to change the power point of the solar cell string. A power generation control unit that controls the generated power is provided, and the power generation control unit has a configuration (first configuration) that makes the change rate of the power point during the self-sustained operation faster than during the interconnection operation with the system power supply.

  In the power control device of the first configuration, the power generation control unit controls the generated power by changing the operating voltage of the solar cell string, and when the operating voltage is changed, the amount of change in the operating voltage during the independent operation It is good also as a structure (2nd structure) made larger than at the time of interconnection operation. In this configuration, the amount of change is an amount by which the operating voltage is changed when the above control is performed once. The operating voltage at the time when the generated power is detected in the control, and then the generated power This is the difference from the operating voltage at the most recent time point at which the current is detected.

  In the power control device having the first or second configuration, the power control device supplies power to a predetermined load during the independent operation, and the power generation control unit changes the operating voltage as a mode for controlling the generated power. A first mode that changes with a first change amount, and a second mode that changes with a second change amount that is larger than the first change amount when changing the operating voltage. The first mode is a mode for controlling the generated power when the control unit is larger than the amount of change in the operating voltage that is changed during the interconnected operation and the power difference of the generated power with respect to the demand power of the load is greater than or equal to a predetermined value during the independent operation. It is good also as a structure (3rd structure) switched from to 2nd mode. In this configuration, the first change amount is an amount by which the operating voltage is changed when the control in the first mode is performed once. The second change amount is an amount by which the operating voltage is changed when the second mode control is performed once.

  The power control device having the first configuration further includes a power conversion unit that converts the generated power by switching the switching element, and the power generation control unit changes one of a switching duty and a switching frequency of the switching element. The generated power may be controlled by the above, and the one change amount during the self-sustained operation may be larger than that during the interconnected operation (fourth configuration). In this configuration, the amount of change is an amount by which one of the switching duty and the switching frequency is changed when the control of the generated power is performed once, and the generated power is changed in the control. This is a difference between the one set value at the time of detection and the one set value at the most recent time when the generated power is detected next.

  The power control apparatus of the fourth configuration may have a configuration (fifth configuration) in which one of the switching duty and the switching frequency has a set value during the self-sustained operation that is larger than that during the interconnected operation.

  In the power control device having the fourth or fifth configuration, the power control device supplies power to a predetermined load during the independent operation, and the power generation control unit changes the one as a mode for controlling the generated power. A third mode that changes with a third change amount, and a fourth mode that changes with a fourth change amount that is larger than the third change amount when changing one of the above, the third change amount When the control unit is larger than the one change amount that is changed at the time of the interconnection operation and the power difference of the generated power with respect to the demand power of the load at the time of the independent operation is a predetermined value or more, the mode for controlling the generated power is the third mode. To the fourth mode (sixth configuration). In this configuration, the third change amount is an amount that changes one of the switching duty and the switching frequency when the control in the third mode is performed once. Further, the fourth change amount is an amount by which one of the above changes is changed when the control in the fourth mode is performed once.

  In order to achieve the above object, a power control method according to an aspect of the present invention is a power control method for a power control device that performs power tracking control of a solar cell string, and changes the power point of the solar cell string. A step of controlling the generated power of the solar cell string, and in the step of controlling the generated power, the power point change rate during the self-sustaining operation is made faster than that during the interconnected operation with the system power supply (seventh Configuration).

  ADVANTAGE OF THE INVENTION According to this invention, even if there exists a sudden change in the electric power demand at the time of a self-sustained operation, the technique which can make a generated electric power follow the electric power demand favorably can be provided.

It is a block diagram which shows the structural example of the solar energy power generation system which concerns on 1st Embodiment. It is a table | surface which shows the combination of the driving | running state of PCS, a control method, and control mode. It is a figure which shows the example of control of the generated electric power in normal mode. It is a figure which shows an example of the example of control of the generated electric power in the 1st following speed priority mode and the 2nd following speed priority mode. It is a figure which shows the example of a relationship between the electric power supply-and-demand balance at the time of the independent operation in a comparative example, and the change of bus voltage. It is a figure which shows the example of a relationship between the electric power supply-and-demand balance at the time of the independent operation in 1st Example, and the change of a bus voltage. It is a figure which shows the example of a relationship between the electric power supply-and-demand balance at the time of the independent operation in 2nd Example, and the change of a bus voltage. It is a figure which shows the example of a relationship between the electric power supply-and-demand balance at the time of the independent operation in the modification of 2nd Example, and the change of an output voltage. It is a block diagram which shows the structural example of the solar energy power generation system which concerns on 2nd Embodiment. It is a block diagram which shows the structural example of the solar energy power generation system which concerns on 3rd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment>
FIG. 1 is a block diagram illustrating a configuration example of a photovoltaic power generation system 100 according to the first embodiment. The photovoltaic power generation system 100 is electrically connected to the commercial power system CS via, for example, a single-phase three-wire current path Pa, and can be connected to the commercial power system (system power source) CS. Moreover, the solar power generation system 100 cut | disconnects the electrical connection with the commercial power grid | system CS at the time of the power failure of the commercial power grid | system CS, etc., and carries out an independent operation.

  During the grid connection operation, the solar power generation system 100 converts the generated power of the solar cell string PV from direct current to alternating current, and transmits the power from the solar power generation system 100 to the commercial power system CS via the current path Pa (that is, reverse) The power can be sold to a power company or the like. It is also possible to receive power from the commercial power system CS to the power supply path Pa and purchase the power from an electric power company or the like. Hereinafter, power that is reversely flowed (sold) into the commercial power system CS is referred to as reverse power, and power that is supplied (purchased) from the commercial power system CS to the power path Pa is referred to as forward power. In addition, a power load (not shown) such as household appliances or factory equipment is connected to the current path Pa. Electric power is supplied to the electric power load through the energization path Pa.

  Next, the configuration of the solar power generation system 100 will be described. As shown in FIG. 1, the photovoltaic power generation system 100 includes a watt-hour meter M, a solar cell string PV, a power conditioner 1, and a controller 3. Hereinafter, the power conditioner 1 is referred to as a PCS (Power Conditioning System) 1.

  The watt-hour meter M is provided at a power receiving point (not shown) on the energization path Pa. The watt-hour meter M is a power detector that detects the direction in which the power Wr flows at the power receiving point, the power value ([W]), and the power amount ([Wh]). The detection information indicating the detection result is sent to the controller 3. Output to. Hereinafter, the power Wr detected by the watt-hour meter M is referred to as a power receiving point power Wr. In FIG. 1, the power value of the receiving point power Wr (forward power flow) flowing in the direction away from the commercial power system CS is shown as a positive value, and the receiving point power Wr (reverse power flow) flowing in the direction toward the commercial power system CS is shown. The electric power value is indicated by a negative value.

  The solar cell string PV is a power generation device including one or a plurality of solar cell modules connected in series, and is connected to the PCS 1. The solar cell string PV generates power by receiving sunlight, and outputs the generated DC power WG to the PCS 1. Hereinafter, the DC power WG is referred to as generated power WG.

  The PCS 1 is a power control device that controls the solar cell string PV, and can be connected to the commercial power system CS. The PCS 1 is provided between the current path Pa and the solar cell string PV, and is electrically connected to both, and is further connected to the commercial power system CS via the current path Pa. The PCS 1 outputs the output power Wo obtained by converting the generated power WG to the energization path Pa during the interconnection operation.

  Further, the PCS 1 is connected to the dedicated load L through the energization path Pb. The PCS 1 supplies power WL to the dedicated load L through the dedicated outlet 18 and the energization path Pb of the PCS 1 during the interconnecting operation and the independent operation. Hereinafter, this power WL is referred to as supply power WL. Further, the power Wd required for the dedicated load L is referred to as demand power Wd. This dedicated load L is, for example, household appliances, factory equipment and the like. Alternatively, an energy storage device such as a storage battery may be used. Moreover, it is not limited to this embodiment, The exclusive outlet 18 may supply the supply electric power WL to the exclusive load L only at the time of a self-sustained operation.

  Further, the PCS 1 performs MPPT (Maximum Power Point Tracking) control or power tracking control on the solar cell string PV. The MPPT control is a control method of the solar cell string PV that varies the power point E aiming at the maximum power point Emax at which the generated power WG becomes the maximum generated power Wmax. The power tracking control is a method of controlling the solar cell string PV while performing other control such as MPPT control and input suppression control of the generated power WG. In addition, although a hill-climbing method etc. can be used for MPPT control and electric power follow-up control, for example, it is not limited to this.

  Next, a specific configuration of the PCS 1 will be described. The PCS 1 includes a power conversion unit 11, an inverter 12, a smoothing capacitor 13, a communication unit 15, a memory 16, and an IC 17. In addition, the PCS 1 also includes a current detection unit (not shown) that detects the output current I of the solar cell string PV and a voltage detection unit (not shown) that detects the operating voltage V of the solar cell string PV. The detection results of the output current I and the operating voltage V are output to the IC 17.

  The power conversion unit 11 is a DC / DC converter, for example, and is controlled by the IC 17. The power conversion unit 11 is provided between the solar cell string PV and the bus line BL. It is connected to the solar cell string PV and connected to the inverter 12 via the bus line BL. The power conversion unit 11 has a conversion circuit (not shown) composed of a plurality of switching elements, converts the generated power WG to DC power of a predetermined voltage by switching of the switching elements, and converts the DC power into the bus line BL. Output to. The power conversion in the power conversion unit 11 is controlled by the IC 17. Moreover, the power converter 11 prevents a reverse current from flowing through the solar cell string PV.

  The inverter 12 is a power conversion unit controlled by the IC 17 and is provided between the bus line BL and the energization path Pa and the energization path Pb. The inverter 12 converts the DC power input from the bus line BL according to a predetermined power standard such as the commercial power system CS and / or the dedicated load L by PWM (Pulse Width Modulation) control or PAM (Pulse Amplitude Modulation) control. DC / AC conversion into alternating current power having an alternating frequency can be output to at least one of the energization path Pa and the energization path Pb.

  The smoothing capacitor 13 is connected to the bus line BL and removes or reduces a change in the bus voltage VB of the power flowing through the bus line BL.

  The communication unit 15 is a communication interface that performs wireless communication or wired communication with the controller 3. For example, the communication unit 15 transmits the operation states (particularly, the power conversion amount, the rated power, etc.) of the power conversion unit 11 and the inverter 12 to the controller 3. Further, the communication unit 15 receives control information for managing the power control of the PCS 1 from the controller 3.

  The memory 16 is a non-volatile storage medium that holds stored information non-temporarily without supplying power. The memory 16 stores setting information, control information, a program, and the like used in each component (particularly, the IC 17) of the PCS 1.

  The IC 17 is a control unit that controls each component of the PCS 1 using information and programs stored in the memory 16, control information output from the controller 3, and the like. For example, the IC 17 controls the power conversion unit 11 and the inverter 12, and particularly controls their power conversion.

  The IC 17 includes a power generation control unit 171 as a functional component. The power generation control unit 171 controls power generation of the solar cell string PV. The power generation control unit 171 controls the power generated by the solar cell string PV, for example, by changing the power point E (particularly the operating voltage V) of the solar cell string PV. Such control can be performed, for example, by changing one of the switching duty and the switching frequency of the switching element of the power conversion unit 11.

  The power generation control unit 171 has a normal mode, a first tracking speed priority mode, and a second tracking speed priority mode as control modes of the generated power WG during MPPT control and power tracking control. The normal mode is a mode in which priority is given to the adjustment accuracy of the power point E. The first follow-up speed priority mode and the second follow-up speed priority mode are modes in which the change speed ΔWG / Δt of the generated power WG (that is, the change amount ΔWG per unit time Δt) is controlled with priority. In the first follow-up speed priority mode and the second follow-up speed priority mode, the changing speed of the power point E is faster than that in the normal mode during the interconnection operation. The processing in the normal mode, the first following speed priority mode, and the second following speed priority mode will be described in detail later.

  FIG. 2 is a table showing combinations of operating states, control methods, and control modes of the PCS 1. In FIG. 2, “◯” indicates that the mode can be used, and “X” indicates that the mode cannot be used. In addition, “(◯ / ×)” indicates that the availability can be switched by an operation input or the like.

  As shown in FIG. 2, the generated power WG is controlled in the normal mode in the MPPT control and the power follow-up control during the interconnection operation.

  In the MPPT control and the power follow-up control during the autonomous operation, when the second follow-up speed priority mode is disabled (“×”), the generated power WG is controlled in the first follow-up speed priority mode. In this case, the generated power WG is controlled in the normal mode during the interconnected operation, and the generated power WG is controlled in the first follow-up speed priority mode during the independent operation. If it carries out like this, the change speed of the electric power point E at the time of a self-sustained operation can be made faster than at the time of a self-sustained operation, triggered by the change from a grid operation to an independent operation. Such control can be realized by, for example, increasing the amount of change in one of the switching duty and switching frequency of the switching element of the power conversion unit 11 during the self-sustained operation compared to during the interconnected operation. Therefore, the generated power WG during the independent operation can be changed faster than during the grid operation. Therefore, even if the power demand changes suddenly during the self-sustained operation, the generated power WG can be made to follow the power demand satisfactorily.

  Further, in the MPPT control and the power follow-up control during the autonomous operation, when the second follow-up speed priority mode is set to be usable (“◯”), the generated power WG is set to the first follow-up speed priority mode or the second follow-up speed. Controlled in priority mode. In this case, the control mode of the generated power WG is switched according to, for example, a power difference | Wd−WG | between the generated power WG and the demand power Wd. For example, when the power difference | Wd−WG | is less than a predetermined value ΔWs, the generated power WG is controlled in the first follow-up speed priority mode. On the other hand, when the power difference | Wd−WG | is equal to or greater than the predetermined value ΔWs, the generated power WG is controlled in the second follow-up speed priority mode in which the change speed of the generated power WG is faster than the first follow-up speed priority mode. In this way, the control mode of the generated power WG can be switched using the power difference | Wd−WG | as a trigger. Therefore, further increase in the power difference | Wd−WG | can be suppressed or prevented, and the generated power WG can be made to follow the power demand at the load L by reducing the power difference | Wd−WG |. it can.

  Further, the power generation control unit 171 monitors the generated power WG, the output power Wo, and the supplied power WL. The power generation control unit 171 also monitors the bus voltage VB and the output voltage Vo of the supplied power WL. When the supply / demand balance between the supplied power WL and the demand power Wd is lost during the self-sustained operation of the PCS 1, the bus voltage VB (especially its instantaneous value and effective value) changes. For example, during the self-sustained operation, the bus voltage VB decreases when WL <Wd and increases when WL> Wd. Based on the bus voltage VB, the power generation control unit 171 determines whether or not the supply power WL is balanced with respect to the demand power Wd during the self-sustained operation, and the supply power WL and the demand power Wd when the supply-demand balance is lost. Detect the difference between

  When the bus voltage VB changes during the self-sustained operation, the output voltage Vo (particularly the instantaneous value and effective value) of the supplied power WL also changes. For example, the output voltage Vo of the supply power WL decreases when the bus voltage VB decreases and increases when the bus voltage VB increases. Therefore, the power generation control unit 171 determines whether or not the supply power WL is balanced with respect to the demand power Wd during the self-sustained operation based on the output voltage Vo, and the supply power WL and the demand power when the supply-demand balance is lost. You may detect the difference with Wd.

  Next, the controller 3 will be described. The controller 3 is a power management device that manages the PCS 1. As illustrated in FIG. 1, the controller 3 includes a display unit 31, an input unit 32, a communication unit 33, a memory 35, and a CPU 36.

  The display unit 31 displays information on the photovoltaic power generation system 100 on a display (not shown). The input unit 32 receives an operation input and outputs input information corresponding to the operation input to the CPU 36. The communication unit 33 is a communication interface that performs wireless communication or wired communication with the PCS 1. For example, the communication unit 33 receives information related to power conversion of the PCS 1 and outputs the information to the CPU 36, and transmits control information output from the CPU 36 to the PCS 1. Moreover, the communication part 33 receives the information regarding the power conversion of PCS1, etc., for example.

  The memory 35 is a storage medium that holds stored information non-temporarily without supplying power. The memory 35 stores various information used by each component (particularly the CPU 36) of the controller 3 and a software program.

  The CPU 36 controls each component of the controller 3 using control information and programs stored in the memory 35. Further, the CPU 36 has a power monitoring function for monitoring the power of the solar power generation system 100. For example, the CPU 36 detects the power receiving point power Wr and the flow direction thereof based on the detection result of the watt-hour meter M.

  Next, each control mode of the generated power WG will be described.

(Normal mode)
FIG. 3 is a diagram illustrating a control example of the generated power WG in the normal mode. In the normal mode, the power generation control unit 171 changes the power point E by changing the operating voltage V of the solar cell string PV step by step by a constant change amount ΔVn, for example, using a hill-climbing method. Are changed toward predetermined power (for example, maximum generated power Wmax, demand power Wd). Here, a case where the generated power WG is changed toward the maximum generated power Wmax will be described as an example.

  The power generation control unit 171 changes the operating voltage V in a direction to increase (or decrease) by a constant change amount ΔVn, and detects the generated power WG after the change. When the power difference | Wmax−WG | between the generated power WG and the maximum generated power Wmax becomes smaller, the power generation control unit 171 further detects the generated power WG by changing the operating voltage V in the same direction by the change amount ΔVn. To do. On the other hand, when the power difference | Wmax−WG | between the generated power WG and the maximum generated power Wmax increases, the power generation control unit 171 further changes the operating voltage V by the change amount ΔVn in the reverse direction to further increase the generated power WG. To detect. By repeatedly performing such a control step, the power point E of the solar cell string PV is brought close to the power point Emax where the maximum generated power Wmax is output.

  In the case of FIG. 3, when the power point E of the solar cell string PV is changed from the power point Ea1 of the operating voltage Va1 to the power point Ea2 of the operating voltage Va2 (= Va1-ΔVn), the output current I of the solar cell string PV is The current value Ia1 increases from the current value Ia2 to the current value Ia2, the generated power WG also increases from the power value Wa1 to the power value Wa2 (> Wa1), and the power difference | Wmax−WG | decreases. In this case, the PCS 1 changes the power point E from the power point Ea2 to the power point Ea3 of the operating voltage Va3 (= Va2−ΔVn) in order to make the generated power WG closer to the maximum generated power Wmax. By frequently repeating these control steps, the generated power WG is brought close to the maximum generated power Wmax.

  When the generated power WG exceeds the maximum generated power Wmax, the power generation control unit 171 changes the generated power WG toward the maximum generated power Wmax again by changing the power point E in the reverse direction. That is, in FIG. 3, when the generated power WG exceeds the maximum generated power Wmax by reducing the operating voltage V by the change amount ΔVn, the operating voltage V is increased by the change amount ΔVn. When the generated power WG exceeds the maximum generated power Wmax by increasing the operating voltage V by the change amount ΔVn, the operating voltage V is decreased by the change amount ΔVn.

  The change amount ΔVn for each control step of the operating voltage V in the normal mode is smaller than the change amount ΔVs1 in the first follow-up speed priority mode and the change amount ΔVs2 in the second follow-up speed priority mode described below. .

(First and second following speed priority mode)
FIG. 4 is a diagram illustrating a control example of the generated power WG in the first follow-up speed priority mode and the second follow-up speed priority mode. In FIG. 4, the change amount ΔVs1 in the first follow-up speed priority mode and the change amount ΔVs2 in the second follow-up speed priority mode are collectively referred to as a change amount ΔVs. Hereinafter, the change amounts ΔVs1 and ΔVs2 may be collectively referred to as a change amount ΔVs.

  In the first follow-up speed priority mode and the second follow-up speed priority mode, the power generation control unit 171 changes the operating voltage V of the solar cell string PV step by step by a constant change amount ΔVs (> ΔVn), for example, using a hill-climbing method. By changing the power point E, the generated power WG is changed toward a predetermined power (for example, maximum generated power Wmax, demand power Wd). In FIG. 4, the change amount ΔVs of the operating voltage V for each control step is set larger than the change amount ΔVn in the normal mode (for example, ΔVs1 = 1.5ΔVn, ΔVs2 = 2ΔVn). Here, a case where the generated power WG is changed toward the maximum generated power Wmax when the predetermined power is the maximum generated power Wmax, that is, when WG << Wd will be described as an example. In the case of WG >> Wd, the predetermined power is the demand power Wd, and the generated power WG is changed toward the demand power Wd.

  In the case of FIG. 4, when the power point E of the solar cell string PV is changed from the power point E1 of the operating voltage V1 to the power point E2 of the operating voltage V2 (= V1−ΔVs), the output current I of the solar cell string PV is The current value I1 increases from the current value I2 to the current value I2, and the generated power WG also increases from the power value W1 to the power value W2 (> W1), and the power difference | Wmax−WG | decreases. In this case, the PCS 1 changes the power point E from the power point E2 to the power point E3 of the operating voltage V3 (= V2−ΔVs) in order to make the generated power WG closer to the maximum generated power Wmax. By repeating these control steps, the power point E is brought close to the power point Emax corresponding to the power demand in a stepwise manner.

  When the generated power WG exceeds the maximum generated power Wmax, the power generation control unit 171 changes the generated power WG toward the maximum generated power Wmax again by changing the power point E in the reverse direction. That is, in FIG. 4, when the generated power WG exceeds the maximum generated power Wmax by reducing the operating voltage V by the change amount ΔVs, the operating voltage V is increased by the change amount ΔVs. When the generated power WG exceeds the maximum generated power Wmax by increasing the operating voltage V by the change amount ΔVs, the operating voltage V is reduced by the change amount ΔVs. Alternatively, in these cases, when the generated power WG exceeds the maximum generated power Wmax, the power generation control unit 171 may switch to the normal mode and set the change amount for each control of the operating voltage V to ΔVn (<ΔVs).

  In the first follow-up speed priority mode and the second follow-up speed priority mode, the generated power WG of the solar cell string PV is set to a predetermined power (maximum generated power Wmax, Demand power Wd, etc.) can be approached and reached. Accordingly, the generated power WG can be satisfactorily followed with respect to changes in power demand.

  Note that the change amount ΔVs1 for each control step of the operating voltage V in the first follow-up speed priority mode only needs to be larger than the change amount ΔVn in the normal mode. Further, the change amount ΔVs2 for each control step of the operating voltage V in the second follow-up speed priority mode may be larger than the change amount ΔVs1 in the first follow-up speed priority mode. Further, the change amount ΔVs1 and the change amount ΔVs2 may be the same or different between the MPPT control and the power follow-up control.

  Next, control of the generated power WG during the self-sustaining operation will be described with reference to a comparative example, a first example, and a second example. In the comparative example, the generated power WG is controlled only in the normal mode. On the other hand, in the first embodiment, the generated power WG is controlled in the first follow-up speed priority mode. In the second embodiment, the generated power WG is controlled by selectively using the first follow-up speed priority mode and the second follow-up speed priority mode.

(Comparative example)
First, a comparative example will be described. FIG. 5 is a diagram illustrating a relationship example between the power supply / demand balance and the change in the bus voltage VB during the independent operation in the comparative example. The upper graph in FIG. 5 shows the supply-demand balance of the generated power WG and the demand power Wd when the control in the normal mode is continued without stopping the operation of the PCS 1. Further, the lower graph of FIG. 5 shows a change with time of the bus voltage VB in the PCS 1 when the control in the normal mode is continued without stopping the operation of the PCS 1.

  When the power source of the dedicated load L is turned on at time tr1, the solar cell string PV starts power generation. In the period (tr1 ≦ tr ≦ tb), the demand power Wd increases rapidly, and the generated power WG increases due to the control in the normal mode. Here, if the generated power WG cannot be increased following the rapidly increasing demand power Wd and remains below the demand power Wd, the bus voltage VB in the PCS 1 is changed from the generated power WG to the demand power Wd at time tr2. It keeps decreasing until it reaches.

  Actually, at time ts (tr1 <ts ≦ tr2), when the instantaneous average value or effective value of the bus voltage VB reaches the stop voltage threshold Ve1 for low voltage protection, the PCS1 controls the low voltage protection of the IC 17. Will stop and will not be able to maintain operation. When the PCS 1 is stopped, the output of the supplied power WL is also stopped and is not supplied to the dedicated load L, so that the dedicated load L is also stopped.

  FIG. 5 illustrates the case where the state of WG <Wd is continued during the independent operation. However, even when the state of WG> Wd is continued during the autonomous operation, the PCS 1 is similarly controlled by the overvoltage protection control of the IC 17. Stop. That is, if the state of WG> Wd continues during the self-sustained operation, the bus voltage VB continues to rise. When the time average value of the instantaneous value or the effective value of the bus voltage VB reaches the stop voltage threshold Ve2 for overvoltage protection, the PCS1 is stopped by the protection control of the IC 17, and the dedicated load L is also stopped.

  Thus, in the normal mode, when the power point E is changed, the operating voltage V is frequently changed by a relatively small constant change amount ΔVn. Therefore, the number of control steps increases, and the time until the power point E corresponding to the power demand is reached tends to be relatively long. Therefore, for example, when the power demand changes suddenly due to an instantaneous increase / decrease in the demand power Wd at the dedicated load L, the generated power WG may not be able to follow the power demand.

(First embodiment)
Next, a first embodiment will be described. FIG. 6 is a diagram illustrating a relationship example between the power supply / demand balance and the change in the bus voltage VB during the self-sustaining operation in the first embodiment. The upper graph of FIG. 6 shows the rate of change of the change rate of the power point E, and the amount of increase ΔWG per unit time Δt of the generated power WG that changes toward the demand power Wd (that is, the follow-up speed ΔWG / Δt). The rate of change [%] is shown on the basis of the tracking speed (ΔWG / Δt) of the generated power WG in the normal mode during the grid operation. The middle graph in FIG. 6 shows the supply and demand balance between the generated power WG and the demand power Wd. The lower graph of FIG. 6 shows the change with time of the bus voltage VB.

  When the PCS 1 switches from the grid operation to the independent operation at time t0, the power generation control unit 171 switches the mode for controlling the generated power WG to the first following speed priority mode. That is, the change amount ΔVs1 of the operating voltage V for each control step is set to be larger than the change amount ΔVn in the normal mode during the interconnection operation, for example, 1.5 times the change amount ΔVn in each control step in the normal mode. Is done.

  At time t1, the dedicated load L is turned on. Here, in FIG. 6, the state of WG≈Wd continues after time t1. That is, the supply and demand balance between the generated power WG and the demand power Wd is balanced. In this case, the power generation control unit 171 continues to control the generated power WG in the first follow-up speed priority mode.

  At time te, when the PCS 1 switches from the independent operation to the grid operation, the power generation control unit 171 switches to the normal mode and controls the generated power WG.

  As described above, in the first embodiment, when the grid operation is switched to the independent operation, the power generation control unit 171 switches the mode for controlling the generated power WG from the normal mode to the first follow-up speed priority mode. The power generation control unit 171 maintains the first follow-up speed priority mode when the supply and demand balance between the generated power WG and the demand power Wd is balanced.

(Second embodiment)
Next, a second embodiment will be described. FIG. 7 is a diagram illustrating a relationship example between the power supply / demand balance and the change in the bus voltage VB during the independent operation in the second embodiment. The upper graph in FIG. 7 shows the rate of change of the change rate of the power point E, and the amount of increase ΔWG per unit time Δt of the generated power WG that changes toward the demand power Wd (that is, the follow-up speed ΔWG / Δt). The rate of change [%] is shown on the basis of the tracking speed (ΔWG / Δt) of the generated power WG in the normal mode during the grid operation. The middle graph in FIG. 7 shows the supply and demand balance between the generated power WG and the demand power Wd. The lower graph of FIG. 7 shows the change with time of the bus voltage VB.

  When the PCS 1 switches from the grid operation to the independent operation at time t0, the power generation control unit 171 switches the mode for controlling the generated power WG to the first following speed priority mode. That is, the change amount ΔVs1 of the operating voltage V for each control step is made larger than the change amount ΔVn in the normal mode during the grid operation.

  When the power source of the dedicated load L is turned on at time t1, the solar cell string PV starts power generation in the first follow-up speed priority mode. Here, when the state of WG <Wd continues, the bus voltage VB in the PCS 1 continues to decrease.

  When the time average value of the instantaneous value or effective value of the bus voltage VB becomes equal to or lower than the voltage drop threshold VL at time t2, the power generation control unit 171 switches the mode for controlling the generated power WG to the second follow-up speed priority mode. That is, the change amount ΔVs2 of the operating voltage V for each control step is made larger than the change amount ΔVs1 in the first follow-up speed priority mode, for example, twice the change amount ΔVn in each control step in the normal mode. The solar cell string PV generates power in the second follow-up speed priority mode. The voltage drop threshold VL corresponds to the instantaneous value or the time average value of the effective value of the bus voltage VB when the power difference (WG−Wd) is a predetermined value (−ΔWs). By this switching, as shown in the upper diagram of FIG. 7, the changing speed of the power point E is improved, and the follow-up speed (ΔWG / Δt) of the generated power WG with respect to the demand power Wd is increased. Then, as shown in the lower diagram of FIG. 7, the decrease of the bus voltage VB is suppressed, and the decrease amount ΔVB per unit time Δt (in other words, the decrease rate ΔVB / Δt <0) is reduced. Therefore, the generated power WG can reach the demand power Wd before the instantaneous or effective time average value of the bus voltage VB reaches the stop voltage threshold Ve1. By doing so, it is possible to prevent the instantaneous value or effective time average value of the bus voltage VB from reaching the stop voltage threshold Ve1, and therefore it is possible to avoid the operation stop of the PCS 1 due to the decrease in the bus voltage VB. Accordingly, since the supplied power WL can be continuously supplied to the dedicated load L, the dedicated load L can also maintain its operation.

  When the generated power WG exceeds the demand power Wd after the time t3, the mode is switched to the first follow-up speed priority mode, and the generated power WG is suppressed until the generated power WG becomes the same as the demand power Wd at the time t4. By this control, the bus voltage VB changes toward the steady value VB0. However, it is not limited to the illustration of FIG. 7, and the control of the generated power WG in the period (t3 ≦ t <t4) may be performed in the second follow-up speed priority mode.

  At time te, when the PCS 1 switches from the independent operation to the grid operation, the power generation control unit 171 switches to the normal mode and controls the generated power WG.

  Here, FIG. 7 illustrates the case where the state of WG <Wd is continued during the autonomous operation, but the bus voltage VB continues to increase even when the state of WG> Wd is continued during the autonomous operation. PCS1 may stop. Therefore, the control of the generated power WG with WG> Wd is switched to the second follow-up speed priority mode when the instantaneous or effective time average value of the bus voltage VB is equal to or higher than the voltage increase threshold VH, and the bus voltage VB Rise is suppressed. The voltage increase threshold VH corresponds to the instantaneous value or the time average value of the effective value of the bus voltage VB when the power difference (WG−Wd) is a predetermined value (+ ΔWs). Therefore, the generated power WG can follow the demand power Wd before the time average value of the instantaneous value or the effective value of the bus voltage VB reaches the stop voltage threshold Ve2. By doing so, it is possible to prevent the instantaneous value or effective time average value of the bus voltage VB from reaching the stop voltage threshold Ve2, and therefore it is possible to avoid the stop of the PCS1 due to the rise of the bus voltage VB. Accordingly, since the supplied power WL can be continuously supplied to the dedicated load L, the dedicated load L can also maintain its operation.

  As described above, in the second embodiment, when the power difference | Wd−WG | of the generated power WG with respect to the demand power Wd is equal to or greater than the predetermined value ΔWs during the self-sustained operation, the power generation control unit 171 controls the generated power WG. The mode is switched from the first following speed priority mode to the second following speed priority mode.

  Note that the timing at which the generated power WG is controlled in the second follow-up speed priority mode is not limited to the illustration in FIG. For example, in the control of the generated power WG in the second follow-up speed priority mode during the autonomous operation, the change amount ΔVB (change speed ΔVB / Δt) per unit time Δt of the bus voltage VB is set to the upper or lower change speed threshold. It may be performed at a timing exceeding. That is, it may be performed at a timing when the amount of decrease ΔVB (that is, the decrease rate ΔVB / Δt <0) per unit time Δt of the bus voltage VB exceeds the decrease rate threshold during the independent operation. Further, it may be performed at a timing when the increase amount ΔVB (that is, the increase rate ΔVB / Δt> 0) of the bus voltage VB per unit time Δt exceeds the increase rate threshold value that is larger than the decrease rate threshold value during the independent operation.

  Further, when the generated power WG cannot follow the demand power Wd when the PCS 1 is operating independently, the output voltage Vo of the power output from the PCS 1 (for example, the supplied power WL) also changes. Therefore, the control of the generated power WG in the second follow-up speed priority mode during the self-sustaining operation is performed by the voltage change threshold VoL having the lower limit of the instantaneous value or effective time average value of the output voltage Vo of the supplied power WL or the upper limit voltage. You may implement at the timing which exceeds change value VoH (refer FIG. 8). Alternatively, the change amount ΔVo per unit time Δt of the output voltage Vo (that is, the change speed ΔVo / Δt) may be performed at a timing at which the upper limit or the lower limit change speed threshold is exceeded.

  Further, the control of the generated power WG in the second follow-up speed priority mode during the independent operation may be performed immediately when the demand power Wd exceeds the generated power WG.

  Further, the phenomenon that the generated power WG cannot follow the demand power Wd is likely to occur when the PCS 1 is operating independently. Therefore, it may be possible to set whether or not the control of the generated power WG in the second follow-up speed priority mode is to be performed immediately at the time of the autonomous operation.

  Further, the variation amounts ΔVs1 and ΔVs2 of the operating voltage V for each control step in the control of the generated power WG in the first follow-up speed priority mode and the second follow-up speed priority mode are respectively constant in the present embodiment. It is not limited to this example and may be variable. For example, the power generation control unit 171 causes the change amounts ΔVs1 and ΔVs2 in the first follow-up speed priority mode and the second follow-up speed priority mode to be different from the reference bus voltage VB (for example, the steady value VB0). It may be set to a value that is linearly or non-linearly proportional to | ΔVB | or the magnitude of the change speed | ΔVB / Δt |. Alternatively, the power generation control unit 171 causes the change amounts ΔVs1 and ΔVs2 in the first follow-up speed priority mode and the second follow-up speed priority mode to be the magnitude | ΔVo | of the change amount of the output voltage Vo or the magnitude of the change speed, respectively. It may be set to a value that is linearly or non-linearly proportional to | ΔVo / Δt |.

  According to this embodiment described above, the power control device 1 is a power control device 1 that performs power follow-up control of the solar cell string PV, and changes the power point E of the solar cell string PV. A power generation control unit 171 that controls the generated power WG of the string PV is provided, and the power generation control unit 171 is configured to make the change speed of the power point E during the self-sustaining operation faster than during the interconnection operation with the system power supply CS. The

  The power control method of the power control device 1 is a power control method of the power control device 1 that performs power follow-up control of the solar cell string PV, and the solar cell string PV is changed by changing the power point of the solar cell string PV. The step of controlling the generated power WG is configured such that in the step of controlling the generated power WG, the rate of change of the power point E during the self-sustained operation is faster than that during the interconnection operation with the system power supply CS.

  According to these structures, the change speed of the electric power point E is accelerated by switching from the grid operation to the independent operation as a trigger. Therefore, the generated power WG at the time of the independent operation can be changed faster than at the time of the interconnection operation. Therefore, even if the power demand changes suddenly during the independent operation, the generated power WG can be made to follow the power demand satisfactorily.

  In the power control device 1 configured as described above, the power generation control unit 171 controls the generated power WG by changing the operating voltage V of the solar cell string PV, and when the operating voltage V is changed, the operating voltage at the time of the independent operation is changed. The amount of change in V is set to be larger than that in the connected operation. In this configuration, the amount of change is an amount by which the operating voltage V is changed when the above control is performed once, and the operating voltage V1 when the generated power WG is detected in the control, The difference (V1−V2) from the operating voltage V2 at the most recent time point at which the generated power WG is detected.

  According to this configuration, the change speed of the operating voltage V of the solar cell string PV is increased by using the switching from the grid operation to the independent operation as a trigger. Therefore, the operating voltage V during the independent operation can be changed faster than during the interconnected operation. Therefore, the changing speed of the generated power WG during the independent operation can be made faster than that during the interconnection operation.

  In addition, for example, when the generated power WG is controlled by a stepwise change in the operating voltage V (see FIG. 7 and the like), the above-described control required until the generated power WG can follow the power demand during the self-sustaining operation. The number of times can be reduced as compared to the time of interconnection operation. Therefore, even if the power demand (for example, the demand power Wd required by the dedicated load L) changes suddenly (particularly rapidly) during the autonomous operation, the generated power WG can be made to follow the power demand satisfactorily.

  Further, the power control device 1 configured as described above supplies power WL to a predetermined load L when the power control device 1 is operating independently, and the power generation control unit 171 changes the operating voltage V as a mode for controlling the generated power WG. A first change mode (first follow-up speed priority mode) that changes with the first change amount ΔVs1 when changing, and a second change amount with a second change amount ΔVs2 that is larger than the first change amount ΔVs1 when changing the operating voltage V. Mode (second follow-up speed priority mode), and when the power difference | Wd−WG | of the generated power WG with respect to the demand power Wd of the load L is equal to or greater than a predetermined value ΔWs during the independent operation, the generated power WG is The mode to be controlled is switched from the first mode to the second mode. In this configuration, the first change amount ΔVs1 is an amount by which the operating voltage V is changed when the control in the first mode is performed once. The second change amount ΔVs2 is an amount by which the operating voltage V is changed when the control in the second mode is performed once.

  According to this configuration, it is possible to switch the mode for controlling the generated power WG using the power difference | Wd−WG | of the generated power WG with respect to the demand power Wd of the load L as a trigger during the independent operation. For example, if the power difference | Wd−WG | is equal to or greater than a predetermined value ΔWs, the mode is switched to the second mode in which the change rate of the generated power WG is faster than that in the first mode. Therefore, further increase in the power difference | Wd−WG | can be suppressed or prevented, and the generated power WG can be made to follow the power demand at the load L by reducing the power difference | Wd−WG |. it can.

  Alternatively, the power control device 1 configured as described above further includes a power conversion unit 11 that converts the generated power WG by switching the switching element, and the power generation control unit 171 has one of the switching duty and the switching frequency of the switching element. The generated power WG is controlled by changing, and the third change amount during the one self-sustaining operation is larger than that during the interconnection operation. In this configuration, the amount of change is an amount by which one of the switching duty and the switching frequency is changed when the control of the generated power WG is performed once. This is a difference between the one set value at the time when WG is detected and the one set value at the most recent time point at which the generated power WG is detected next.

  Furthermore, the power control device 1 having the above configuration is configured such that one of the switching duty and the switching frequency of the switching element has a larger set value during the self-sustained operation than during the interconnected operation.

  According to these configurations, by using one of the switching duty and the switching frequency of the switching element as a trigger triggered by the switching from the grid operation to the independent operation, the solar cell string PV in the independent operation is accelerated. The operating voltage V can be changed faster than in the grid operation. Therefore, the changing speed of the generated power WG during the independent operation can be made faster than that during the interconnection operation.

  In the power control device 1 configured as described above, the power control device 1 supplies the power WL to the predetermined load L during the independent operation, and the power generation control unit 171 changes one of the modes as a mode for controlling the generated power WG. A third mode (first follow-up speed priority mode) that changes with a third change amount, and a fourth mode (second follow-up mode) that changes with a fourth change amount that is larger than the third change amount when changing one of the above. Speed priority mode), and the third change amount is larger than the one change amount that the power generation control unit changes during the grid operation, and the generated power WG with respect to the demand power Wd of the load L during the independent operation When the power difference | Wd−WG | is equal to or greater than the predetermined value ΔWs, the mode for controlling the generated power WG may be switched from the third mode to the fourth mode. In this configuration, the third change amount is an amount that changes one of the switching duty and the switching frequency when the control in the third mode is performed once. Further, the fourth change amount is an amount by which one of the above changes is changed when the control in the fourth mode is performed once.

  According to this configuration, it is possible to switch the mode for controlling the generated power WG using the power difference | Wd−WG | of the generated power WG with respect to the demand power Wd of the load L as a trigger during the independent operation. For example, if the power difference | Wd−WG | is equal to or greater than a predetermined value ΔWs, the mode is switched to the fourth mode in which the change rate of the generated power WG is faster than that in the third mode. Therefore, further increase in the power difference | Wd−WG | can be suppressed or prevented, and the generated power WG can be made to follow the power demand at the load L by reducing the power difference | Wd−WG |. it can.

Second Embodiment
Next, a second embodiment will be described. In the second embodiment, the solar cell string PV includes three solar cell strings PVa to PVc. Hereinafter, a configuration different from the first embodiment will be described. Moreover, the same code | symbol is attached | subjected to the component similar to 1st Embodiment, and the description may be abbreviate | omitted.

  FIG. 9 is a block diagram illustrating another configuration example of the solar power generation system 100 according to the second embodiment. As shown in FIG. 9, three solar cell strings PVa to PVc are connected to PCS1. Each of the solar cell strings PVa to PVc is a power generation device including one or a plurality of solar cell modules connected in series, and generates DC power (generated power WGa, WGb, WGc) generated by receiving sunlight to generate PCS1. Respectively.

  The PCS 1 includes three power conversion units 11a to 11c. Each of the power conversion units 11a to 11c is connected to the inverter 12 via the bus line BL. In addition, since the structure of each power conversion part 11a-11c is the same as that of the power conversion part 11 of FIG. 1, these description is abbreviate | omitted.

  Hereinafter, the generated power WGa, WGb, and WGc are collectively referred to as the generated power WG. In addition, the number of solar cell strings PV connected to PCS1 and the number of power conversion units 11 included in PCS1 are not limited to the example of FIG. 9 and may be other than three.

  The power generation control unit 171 controls power generation of the solar cell strings PVa to PVc. In addition, the power generation control unit 171 monitors the generated power WGa to WGc of each of the solar cell strings PVa to PVc, and detects the solar cell string PV that is particularly generating power.

  Further, when the generated power WG is controlled in the first follow-up speed priority mode or the second follow-up speed priority mode during the self-sustained operation, the power generation control unit 171 includes the number of solar cell strings PV outputting the generated power WG. The control step of the operating voltage V of each solar cell string PVa-PVc further according to at least one of the power generation capacity of each solar cell string PVa-PVc and the open circuit voltage Vf of each solar cell string PVa-PVc Each change amount ΔVs (ΔVs1, ΔVs2) is set.

  For example, consider a case where two solar cell strings PVa and PVc are generating power and the solar cell string PVc cannot generate power (or the generated power WGc is very small). In this case, the amount of change ΔVs (ΔVs1, ΔVs2) for each control step of the operating voltage V of the two solar cell strings PVa and PVc is larger than that when the three solar cell strings PVa to PVc are generating power. Is set.

  Further, when the power generation capacity of the solar cell string PV is sufficiently large with respect to the power demand during the self-sustained operation, the generated power can be generated even if the follow-up speed of the generated power WG with respect to the power demand (for example, the demand power Wd) is not changed significantly. The WG can follow the power demand. On the other hand, when the power generation capacity of the solar cell string PV is small with respect to the power demand during the self-sustained operation, the generated power WG follows the power demand (for example, the demand power Wd). Needs to be changed relatively large. Therefore, the change amount ΔVs for each control step in the solar cell string PV having a relatively large power generation capacity may be set smaller than that of the solar cell string PV having a relatively small power generation capacity. For example, with respect to the demand power Wd = 1000 [W], the change amount ΔVs of the operating voltage V during the independent operation set when the power generation capacities of the solar cell strings PVa to PVc are all 1000 [W]. May be set to a smaller value than when the power generation capacities of the solar cell strings PVa to PVc are all 500 [W].

  Further, the change amount ΔVs (ΔVs1, ΔVs2) for each control step in the solar cell string PV having a relatively large open circuit voltage Vf may be set larger than that of the solar cell string PV having a relatively small open circuit voltage Vf. .

  According to the present embodiment, the power generation control unit 171 includes the number of solar cell strings PV outputting the generated power WG, the power generation capacity of each solar cell string PV, and the open-circuit voltage value of each solar cell string PV. The change amount ΔVs (ΔVs1, ΔVs2) is set to a value further corresponding to at least one of the above. In this case, at least one of the number of the solar cell strings PV outputting the generated power WG, the power generation capacity of each solar cell string PV, and the open circuit voltage Vf of each solar cell string PV is further considered. Thus, it is possible to set the change amount ΔVs (ΔVs1, ΔVs2) for each stage during the independent operation. For example, as the number of solar cell strings PV outputting the generated power WG increases, each generated power WG easily follows the demand power Wd. Therefore, it is possible to suppress a decrease in the adjustment accuracy of the power point E of the solar cell string PV that is generating power while making the generated power WG follow the demand power Wd satisfactorily.

<Third Embodiment>
Next, a third embodiment will be described. In the third embodiment, the controller 3 is provided integrally with the PCS 1 (for example, in the same apparatus). Hereinafter, a configuration different from the first and second embodiments will be described. Moreover, the same code | symbol is attached | subjected to the component similar to 1st and 2nd embodiment, and the description may be abbreviate | omitted.

  FIG. 10 is a block diagram illustrating another configuration example of the solar power generation system 100 according to the third embodiment. In the photovoltaic power generation system 100 of FIG. 10, the PCS 1 has a built-in controller 3 (see, for example, FIG. 1), in addition to the power conversion unit 11, the inverter 12, the smoothing capacitor 13, the memory 16, the IC 17, and the dedicated outlet 18. In addition, a display unit 31 and an input unit 32 are provided. The IC 17 has a power monitoring function of the CPU 36 in FIG. In this way, it is not necessary to provide the PCS 1 and the controller 3 separately. Therefore, the configuration of the power system 100 can be simplified.

  The embodiment of the present invention has been described above. The above-described embodiment is an exemplification, and various modifications can be made to the combination of each component and each process, and it will be understood by those skilled in the art that it is within the scope of the present invention.

  For example, in the first to third embodiments described above, some or all of the functional components 171 of the IC 17 and the functions of the CPU 36 are physical components (eg, electric circuits, elements, devices, etc.). It may be realized.

  In the first and second embodiments described above, at least a part of the functions of the IC 17 may be realized by the CPU 36. For example, the CPU 36 may include a functional component 171 of the IC 17, and the IC 17 may control the power conversion unit 11 and the inverter 12 based on a command from the CPU 36.

100 Solar power generation system 1 PCS (Power conditioner)
11, 11a-11c Power conversion unit 12 Inverter 13 Smoothing capacitor 15 Communication unit 16 Memory 17 IC
171 Power generation control unit 18 Dedicated outlet 3 Controller 31 Display unit 32 Input unit 33 Communication unit 35 Memory 36 CPU
CS Commercial power system L Electric power load M Electricity meter BL Bus line PV, PVa-PVc Solar cell string Pa, Pb Current path

Claims (7)

A power control device that performs power tracking control of a solar cell string,
A power generation control unit for controlling the power generated by the solar cell string by changing the power point of the solar cell string;
The power generation control unit is a power control device that makes a change speed of the power point at the time of independent operation faster than that at the time of interconnection operation with a system power source. The power generation control unit
Controlling the generated power by changing the operating voltage of the solar cell string;
The power control device according to claim 1, wherein, when the operating voltage is changed, a change amount of the operating voltage during the independent operation is set larger than that during the interconnection operation. The power control device supplies power to a predetermined load during the independent operation,
The power generation control unit is configured to control the generated power as a mode for changing the operating voltage by a first change amount when changing the operating voltage, and for changing the operating voltage than the first change amount. A second mode that changes with a large second change amount,
The first change amount is larger than a change amount of the operating voltage that the power generation control unit changes during the grid operation,
The mode for controlling the generated power is switched from the first mode to the second mode when the power difference of the generated power with respect to the demand power of the load is greater than or equal to a predetermined value during the independent operation. 2. The power control apparatus according to 2. A power conversion unit that converts the generated power by switching a switching element;
The power generation control unit controls the generated power by changing one of a switching duty and a switching frequency of the switching element,
The power control apparatus according to claim 1, wherein the amount of change in one of the independent operations is larger than that in the interconnection operation.   The power control device according to claim 4, wherein a setting value of the one of the switching duty and the switching frequency at the time of the independent operation is larger than that at the time of the interconnection operation. The power control device supplies power to a predetermined load during the independent operation,
The power generation control unit, as a mode for controlling the generated power, a third mode that changes with a third change amount when changing the one, and a third mode that is larger than the third change amount when changing the one. A fourth mode for changing by four change amounts,
The third change amount is larger than the one change amount that the power generation control unit changes during the grid operation,
The mode for controlling the generated power is switched from the third mode to the fourth mode when the power difference of the generated power with respect to the demand power of the load is greater than or equal to a predetermined value during the independent operation. 5. The power control apparatus according to 5. A power control method for a power control device that performs power tracking control of a solar cell string,
Controlling the generated power of the solar cell string by changing the power point of the solar cell string,
In the step of controlling the generated power, the power control method of the power control device, wherein the change speed of the power point during the independent operation is faster than during the interconnection operation with the system power supply.

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