JP2006280178A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow only a power generation output corresponding to a power generated by a solar cell to be reversely flowed in a system in which an output of an engine generator and a solar cell is combined and connected to a system.
A system power calculation unit calculates power supplied from a system to a load. The inverter drive control circuit 22 drives the high-voltage inverter circuit 11 to generate an output to the power supply device when the system power becomes equal to or higher than the output control set value CPV. The output control set value CPV is set to forward power (buy side) in the operation of only the engine generator 3. When the output power of the solar cell 1 is linked, the output control set value CPV is changed to reverse power (sell side) according to the output power of the solar cell 1. When the output power of the solar cell 1 is large, the reverse flow to the grid 4 is allowed by changing the set value CPV. If the reverse power flow exceeds the limit value RPLMT, the power supply device stops output for protection.
[Selection] Figure 1

Description

  The present invention relates to a power supply device, and more particularly, to a power supply device in which a power supply such as an engine-driven generator and a solar cell can be combined to extract the power generation output.

  Small-scale power generators such as engine-driven generators are widely used for various purposes as portable power supplies and emergency power supplies. When this type of power supply device is used as a small-scale power generation device such as a home cogeneration device, it is possible to effectively use energy comprehensively by connecting it to a commercial power supply or by installing a solar cell. It becomes possible to plan.

For example, Japanese Patent Laid-Open No. 8-186927 discloses a connection between an output of a commercial power source (system), an output of a solar power generation device (solar cell), and an output of a power generation device (generator) that uses fuel. A power supply system is disclosed.
JP-A-8-186927

  In the power supply system described in the above-mentioned patent document, since the solar cell output and the generator output or the solar cell output and the system output are connected to each other, the output voltage of the solar cell must be set higher. . However, there is a problem that it is difficult to fully utilize the power generated by the solar cell because a small-scale solar cell power generation for home use cannot obtain a high voltage output in cloudy weather.

  In addition, from the viewpoint of effective use of energy, it is important to reversely flow the power generated by the power supply device to the system. However, the output power of a generator driven by an engine that uses fuel, such as an engine or a gas turbine, and the output power of solar power generation differ in the purchase price by the commercial power supplier, and the latter is expensive. Therefore, when constructing a composite power supply apparatus that incorporates solar power generation, dealing with this price difference is a major practical issue for promoting diffusion in consideration of profitability costs.

  An object of the present invention is to provide a power supply device that improves the profitability in consideration of the price difference of the generated power and promotes more effective energy use by promoting the spread of a composite system using solar power generation. It is in.

  The present invention includes a generator as a first power source, a rectifier circuit that rectifies the output of the generator, an inverter that converts the output of the rectifier circuit into AC power of a predetermined frequency, and outputs the inverter. In a power supply device having a grid connection control device for connecting outputs to the grid connection, the grid connection control device controls the output of the inverter so that the value of reverse power flow during a grid operation is a predetermined value or less. An inverter control unit that includes a solar cell as a second power source, and a solar cell output control unit that supplies the output of the solar cell to the input side of the inverter. In the inverter control unit, The first point is that the value corresponding to the generated power value of the solar cell detected by the solar cell output control unit is added to the predetermined value for determining the value of the reverse power flow. Characteristic A.

  The present invention also provides a battery that is charged using the output of the solar cell, a step-down converter that steps down the output of the solar cell and supplies it to the battery, and boosts the voltage of the battery to the input side of the inverter. There is a second feature in that the step-down inverter is configured to use a power value passing through the step-up converter as a generated power value of the solar cell. There is a third feature in that the power value passing through is used as the generated power value of the solar cell.

  According to the present invention having the first feature, since the amount corresponding to the solar cell output is added to the predetermined value for determining the magnitude of the reverse power flow, the portion of the reverse power flow exceeding the predetermined value among the generated reverse power flow It becomes clear that everything is the power output of the solar cell. Therefore, it is possible to sell the reverse power flow exceeding the predetermined value at the selling price of solar power generation. Therefore, since the profitability of the introduction of facilities such as a cogeneration device equipped with this type of power supply device is enhanced for the user of the power supply device of the present invention, it has a great effect on the spread of a system in which a solar cell is combined with the power supply device. be able to.

  According to the second feature, the generated power of the solar cell once charged in the battery can also be detected as the power supplied to the input side of the inverter.

  According to the 3rd characteristic, since electric power is detected in the part with little circuit loss near the output part of a solar cell, the electric power generation output of a solar cell can be detected to small electric power.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 is a block diagram showing a configuration of a power supply device in which the output of the solar battery and the output of the engine generator are linked to the commercial power system. The power supply device shown in FIG. 2 includes a solar cell 1, a battery 2, and an engine generator 3 as power sources. The battery 2 can be charged with the output of the solar cell 1. The engine generator 3 is a three-phase multipolar magnet generator driven by a gas internal combustion engine using city gas as fuel. The outputs of the solar cell 1, the battery 2, and the engine generator 3 are linked to the system power supply 4 in a combined state. The drive source of the engine generator 3 is not limited to a gas internal combustion engine, but may be an engine of a type using other fuel such as gasoline.

  The power supply apparatus includes elements that constitute the low voltage region 100 and elements that constitute the high voltage region 200. The low voltage region 100 includes a solar cell 1, a battery 2, a DC-DC converter 5, and a low voltage inverter circuit 6. On the other hand, the high voltage region 200 includes the engine generator 3, the DC smoothing circuits 8 and 9, the boost converter 10, and the high voltage inverter circuit 11. The high voltage inverter circuit 11 can include an LC filter circuit. The output of the high voltage inverter circuit 11 is connected to the system power supply 4.

  The low voltage region 100 and the high voltage region 200 are coupled by an insulating transformer booster circuit 7 provided between the low voltage inverter circuit 6 and the DC smoothing circuit 8.

  The DC-DC converter 5 is composed of a non-isolated step-down chopper, and the boost converter 10 is composed of a non-isolated step-up chopper. The DC-DC converter 5 steps down and outputs the input voltage by controlling the duty (on-time ratio) of a switching element such as an FET constituting the chopper. Boost converter 10 boosts and outputs an input voltage by controlling the duty of a switching element such as an FET constituting a chopper. The low-voltage inverter circuit 6 forms a bridge with switching elements such as FETs, and inputs rectangular wave alternating current to the insulating transformer booster circuit 7. The high-voltage inverter circuit 11 is a circuit that converts an input into a three-phase alternating current that is suitable for system interconnection, and is formed by bridge-connecting switching elements such as FETs. A well-known FET drive circuit for controlling the duty of the FET can be used.

  The output voltage V1 of the solar cell 1 is stepped down by the DC-DC converter 5 to become the voltage V5, and is applied to the battery 2 via the diode D1. The stepped down voltage V5 of the solar cell 1 and the voltage V2 of the battery 2 are input to the low-voltage inverter circuit 6 in a state of approximately V5 = V2 when the voltage V2 is a sufficient predetermined charging voltage, and the rectangular wave AC Is converted to This rectangular wave alternating current is further boosted by the insulating transformer boosting circuit 7 to become a high-voltage rectangular wave alternating current, and is input to the direct current smoothing circuit 8. The low voltage inverter circuit 6 and the insulating transformer booster circuit 7 form a battery voltage booster circuit. The DC smoothing circuit 8 rectifies and smoothes the input high-voltage rectangular wave AC and outputs a DC voltage.

  The three-phase alternating current output from the engine generator 3 is rectified and smoothed by the direct current smoothing circuit 9. The power P3 output from the DC smoothing circuit 9 is combined with the power (P1 + P2) output from the DC smoothing circuit 8, and the voltage (generator DC voltage) V8 is input to the boost converter 10. The voltage (linked DC voltage) V8 boosted by the boost converter 10 is input to the high-voltage inverter circuit 11 and converted into a three-phase AC, noise is removed by the LC filter circuit, and the output voltage Vout is supplied to the load. It is connected to the system power supply 4.

  Boost converter 10 is controlled in duty so that the input-side voltage of high-voltage inverter circuit 11 can be maintained at a predetermined value regardless of fluctuations in the output current of high-voltage inverter circuit 11. The high-voltage inverter circuit 11 forms an AC output of the same quality (with respect to voltage, frequency, noise, etc.) as the system power supply 4 and has a system interconnection function for linking in synchronization with the phase of the system power supply 4. That is, the high voltage inverter circuit 11 constitutes a system interconnection control unit. An example of an apparatus having a grid interconnection function is disclosed in Japanese Patent Publication No. 4-10302.

  FIG. 1 is a block diagram showing a cogeneration system including the power supply device, and the same reference numerals as those in FIG. 2 denote the same parts. Control power is supplied to the switchboard 12 to a main switch 13, a switch 14 dedicated to the cogeneration device, a switch 16 dedicated to the household electrical load 15, and a hot water storage tank 17 that uses the exhaust heat of the engine 3 A that drives the generator 3. A switch 18 is provided. The main switch 13, the cogeneration device dedicated switch 14, and the switches 16 and 18 each have an overcurrent breaker function.

  A disconnect switch 19 is provided between the output side of the high-voltage inverter circuit 11 and the switchboard 12 for system interconnection protection.

  In the system power calculation unit 20, the power (system power PCN and the power supplied from the system) by the current CT flowing through the main switch 13 and the system voltage VT measured between the disconnection switch 19 and the switch 14 dedicated to the cogeneration apparatus. Called) is calculated. If this system power PCN is negative, that is, if reverse power is supplied, it is in a reverse power flow state.

  The inverter drive control circuit 22 performs duty control on the high-voltage inverter circuit 11 in a range where the grid power PCN calculated by the grid power calculation unit 20 does not interrupt the selling side, that is, in a range where no reverse power flow occurs. The household load is covered by the power generated by the engine generator 3. When a household load exceeding the maximum output power of the engine generator 3 is generated, a shortage of power is supplied from the system power PCN.

  The solar cell power calculation unit 21 calculates the power passing through the battery voltage boost converters 6 and 7 including the low voltage inverter circuit 6 and the insulating transformer boost circuit 7 based on the input power from the solar cell 1. When the solar battery 1 is operated together with the engine generator 3, the power flow calculated by the solar battery power calculation unit 21 can be reversed. When the power of the reverse power flow becomes equal to or higher than a preset reverse power flow limit value RPLMT, the reverse power protection function operates and the inverter drive control circuit 22 stops the output of the high-voltage inverter circuit 11.

  The control function of the power supply apparatus will be described with reference to FIGS. FIG. 3 is a diagram showing a control function when only the engine generator 3 is operated. The power display on the plus (positive) side indicates the power on the buying side of power from the grid 4 to the home (forward power), and the power display on the minus (negative) side indicates the power on the selling side from the home to the grid 4 (reverse power). ).

  In FIG. 3, assuming that the total power consumption of the home is equal to or higher than the output control set value CPV, the high-voltage inverter circuit 11 is operated in a forward power state equal to or higher than the output control set value CPV (here, 100 watts). However, the maximum output Poutmax of the high-voltage inverter circuit 11 is, for example, 1 kilowatt, and when the household power consumption is 1 kilowatt or more, the shortage is compensated by the power from the system power supply 4 side. On the other hand, when the household power consumption is reduced to less than 1 kilowatt, the output Pout of the high-voltage inverter circuit 11 is controlled so that a reverse power flow due to surplus power does not occur.

  When the system power PCN calculated by the system power calculation unit 20 becomes a reverse power equal to or greater than the reverse power flow limit value RPLMT, that is, when the reverse power flow abnormally increases, the inverter drive control circuit 22 Set the output to zero and stop the power generation output of the power supply. The reverse power flow limit value RPLMT is determined according to the output power of the power supply device. For example, it is set to -50 watts for a maximum output power of 1 kilowatt.

  FIG. 4 is a diagram showing an outline of control in the case where the generated power of the solar battery 1 is connected to the system and supplied to the load in addition to the generated power of the engine generator 3. As in the case of operating only the engine generator 3, the power supply device is operated such that the output Pout of the high-voltage inverter circuit 11 is in a forward power state equal to or higher than the output control set value CPV. However, when the solar cell 1 is operated, the high voltage inverter circuit 11 is controlled by changing the output control set value CPV to the reverse power direction, that is, the selling side by the amount of the generated power of the solar cell 1.

  In association with the generated power of the solar cell 1, not only the output control set value CPV but also the reverse power flow limit value RPLMT is changed to the selling side. For example, when the output power of the insulating transformer booster circuit 7 is calculated as 300 watts based on the output voltage of the solar cell 1, the output control set value CPV is changed to the reverse power 200 watts (100-300 = -200). . This allows reverse power flow within 200 watts on the selling side. That is, 200 watts of the generated electric power of the solar cell 1 is a portion capable of reverse flow. As the maximum output power becomes 1.3 kilowatts, the reverse flow limit value RPLMT for protection against reverse flow is set to −350 watts (−50−300 = −350). Thereby, the presence or absence of reverse power flow for reverse power protection is determined by whether or not the grid power PCN has interrupted the selling side to 350 watts or more.

  When 300 watts of generated power for the solar cell 1 is added, the maximum output Poutmax of the high-voltage inverter circuit 11 is 1.3 kilowatts, so when the household power consumption exceeds 1.3 kilowatts, the shortage is Supplemented with power from the 4th side. On the other hand, when the household power consumption is reduced to less than 1.3 kilowatts, the output Pout of the high voltage inverter circuit 11 is controlled so that the reverse power flow does not occur more than 200 watts.

  FIG. 5 is a flowchart showing the main part control operation of the power supply device, and shows an example in the case where only the engine generator 3 is operated. In step S1 of FIG. 5, it is determined whether or not the system power PCN is less than or equal to the reverse power limit value RPLMT (eg, −50 watts), that is, whether or not the system power PCN is interrupting the reverse power side equal to or greater than the reverse power limit value RPLMT. To do. If the determination in step S1 is affirmative, the process proceeds to step S2 to determine whether or not the reverse power state is maintained for a predetermined time or more. In this way, it is determined whether the reverse power flow is instantaneous. If the determination in step S2 is affirmative, it is determined that the output control of the high voltage inverter circuit 11 is abnormal, the process proceeds to step S3, and the output of the high voltage inverter circuit 11 is stopped.

  If the determination in step S1 is negative, the process proceeds to step S4 to determine whether or not the system power PCN is equal to or greater than the output control set value CPV (for example, 100 watts). If the determination in step S4 is affirmative, the process proceeds to step S5 to determine whether or not the output power Pout of the high-voltage inverter circuit 11 is less than the maximum power value Poutmax (1 kilowatt when only the generator 3 is operating). If the determination in step S5 is affirmative, it is determined that there is still room for increasing the output, so the process proceeds to step S6 and the output of the high-voltage inverter circuit 11 is increased by a predetermined power. If the determination in step S5 is negative, that is, if the maximum power value Poutmax is output, the process proceeds to step S7, where the output power of the high-voltage inverter circuit 11 is switched with the duty at which the value at that time, that is, 1 kilowatt is obtained. Control.

  If the determination in step S2 or step S4 is negative, the process proceeds to step S8. In step S8, the output power Pout of the high-voltage inverter circuit 11 is decreased to reduce the reverse power flow or eliminate the reverse power flow.

  FIG. 6 is a flowchart showing the main part control operation of the power supply device, and shows an example in the case of operating the engine generator 3 and the solar cell 1. In step S10 of FIG. 6, the presence or absence of output power from the solar cell 1 is determined based on whether or not the value calculated by the solar cell power calculation unit 21 is equal to or greater than a predetermined value. When there is no output power from the solar cell 1, it progresses to step S11 and sets "0" to the variable SOL showing a solar cell output power value. When the output power of the solar cell 1 is present, the process proceeds to step S12, and the value calculated by the solar cell power calculation unit 19 is set in the variable SOL.

  In step S13, the reverse power flow limit value RPLMT is updated by subtracting only the power value SOL.

  In step S14, it is determined whether or not the system power PCN is less than or equal to the reverse power flow limit value RPLMT, that is, whether or not the system power PCN generates reverse power that is greater than or equal to the reverse power flow limit value RPLMT. If the value calculated by the solar cell power calculator 19 is 300 watts, the reverse power flow limit value RPLMT is subtracted from -50 watts to 300 watts in step S13, so that the system power PCN is -350 watts or more. It is determined whether the power generation state is present.

  If the determination in step S14 is affirmative, the process proceeds to step S15 to determine whether or not the reverse power state is maintained for a predetermined time or more. If the determination in step S15 is affirmative, it is determined that the output control of the high-voltage inverter circuit 11 is abnormal, so the process proceeds to step S16 and the output of the high-voltage inverter circuit 11 is stopped.

  If the determination in step S14 is negative, the process proceeds to step S17 to determine whether or not the system power PCN is equal to or higher than the output control set value CPV obtained by adding the generated power of the solar cell 1. If the determination in step S17 is affirmative, the process proceeds to step S18 to determine whether or not the output power of the high-voltage inverter circuit 11 is less than the maximum power value (1 kilowatt + SOL because the output of the solar cell 1 is added to the output of the generator 3). To do. If the determination in step S18 is affirmative, the process proceeds to step S19 to increase the output of the high-voltage inverter circuit 11 by a predetermined power. If the determination in step S18 is negative, that is, if the maximum power value is output, the process proceeds to step S20, and the high-voltage inverter circuit 11 is switched with the duty at which the output power of the high-voltage inverter circuit 11 is obtained, that is, 1 kilowatt + SOL. Control.

  If the determination in step S15 or step S17 is negative, the process proceeds to step S21. In step S21, the output power Pout of the high-voltage inverter circuit 11 is decreased to reduce the reverse power flow or to eliminate the reverse power flow.

  FIG. 7 is a diagram showing the relationship between the output power of the power supply device and the household power consumption when only the engine generator 2 is operated. As shown in this figure, the high-voltage inverter circuit 11 is configured so that the inverter output power Pout is excessive with respect to the power consumption Pc in the household load 15 and the hot water storage tank 16 and the like, and reverse power flow does not occur (operating with poor profitability). To be controlled). That is, in the region where the output power Pout of the high-voltage inverter circuit 11 is less than 1 kilowatt, a constant power difference (100 watts here) is always generated on the buying side.

  On the other hand, the relationship between the output power of the power supply device when the engine generator 2 and the solar battery 1 are operated and the power consumption in the home is as shown in FIG. As shown in FIG. 8, since the output power Pout of the high-voltage inverter circuit 11 is added to the generated power of the solar cell 1, the output power Pout of the high-voltage inverter circuit 11 exceeds the domestic power consumption Pc. When the output power Pout is less than 1 kilowatt, there is always a constant power surplus (200 watts here). This surplus will flow back into the grid.

  Therefore, there is no need to perform operation control that prevents reverse-flow power operation that is not profitable. If the amount of power actually back-flowed is less than or equal to the amount of power generated by solar cells, It can be determined that

  In this embodiment, the output power of the solar cell 1 is calculated by the power passing through the boost converter composed of the low-voltage inverter circuit 6 and the insulating transformer booster circuit 7. However, the output power of the solar cell 1 is calculated at this position. It is not limited. You may make it calculate with the electric power which passes DC-DC converter 5, ie, the step-down converter which steps down the output of a solar cell.

1 is a block diagram of a cogeneration system including a power supply device according to an embodiment of the present invention. It is a principal part block diagram of the power supply device which concerns on one Embodiment of this invention. It is a schematic diagram which shows operation | movement of the power supply device which concerns on one Embodiment of this invention (at the time of an engine generator only driving | operation). It is a schematic diagram which shows operation | movement of the power supply device which concerns on one Embodiment of this invention (at the time of an engine generator and a solar cell driving | operation). It is a flowchart of electric power control (at the time of an engine generator only operation). It is a flowchart of electric power control (at the time of engine generator and a solar cell driving | operation). It is a figure which shows the relationship between the output electric power of the power supply device which concerns on one Embodiment of this invention, and power consumption (only when an engine generator is drive | operating). It is a figure which shows the relationship between the output electric power of the power supply device which concerns on one Embodiment of this invention, and power consumption (at the time of an engine generator and a solar cell driving | operation).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Solar cell, 2 ... Battery, 3 ... Generator, 4 ... System power supply, 5 ... DC-DC converter, 6 ... Low voltage inverter circuit, 7 ... Insulation transformer booster circuit, 10 ... Boost converter, 11 ... High voltage inverter circuit, 20 ... grid power calculation unit, 21 ... solar cell power calculation unit, 22 ... inverter drive control circuit

Claims (3)

A generator as a first power source, a rectifier circuit that rectifies the output of the generator, an inverter that converts the output of the rectifier circuit into AC power having a predetermined frequency, and an output of the inverter. In a power supply device having a grid interconnection control device for system connection,
The grid interconnection control device includes an inverter control unit that controls the output of the inverter so that the value of the reverse power flow during the interconnection operation is equal to or less than a predetermined value,
A solar cell as a second power source;
A solar cell output controller for supplying the output of the solar cell to the input side of the inverter;
The inverter control unit is configured to control a value corresponding to the generated power value of the solar cell detected by the solar cell output control unit by adding it to the predetermined value for determining the value of the reverse power flow. A power supply device characterized by that. A battery that is charged using the output of the solar cell;
A step-down converter for stepping down the output of the solar cell and supplying it to the battery;
A boost converter that boosts the battery voltage and supplies the boosted voltage to the input side of the inverter;
The power supply device according to claim 1, wherein the inverter control unit is configured to use a power value passing through the boost converter as a generated power value of the solar cell. A battery that is charged using the output of the solar cell;
A step-down converter for stepping down the output of the solar cell and supplying it to the battery;
A boost converter that boosts the battery voltage and supplies the boosted voltage to the input side of the inverter;
The power supply apparatus according to claim 1, wherein the inverter control unit is configured to use a power value passing through the step-down inverter as a generated power value of the solar cell.

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