JP7779175B2 - Distributed Power Systems - Google Patents

Description

The present invention relates to a distributed power generation system equipped with multiple inverters.

There is a distributed power supply system that includes a battery storage power conditioner that operates by connecting a storage battery unit to the power grid, and a PV (photovoltaic power generation) power conditioner that operates by connecting a PV unit to the power grid (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2021-145538

When solar panels generate more power due to increased sunlight, the output of the PV power conditioner may become excessive. If the output of the PV power conditioner becomes excessive, the current flowing through components such as terminal blocks and relays may exceed their capacity, causing damage to the components.

The present invention was made in consideration of the above-mentioned circumstances, and its purpose is to provide technology that can prevent the output of a power conditioner from becoming excessive.

To solve the above problems, the present invention provides a distributed power system that includes multiple power conditioners that convert input DC power into AC power and supply it to a load, with at least one of the multiple power conditioners receiving DC power from a solar cell. The system is characterized in that the upper limit of the output command value is determined so that the total value of the upper limit of the output command values of the multiple power conditioners is equal to or less than a predetermined limit value during stand-alone operation, and AC power is supplied to the load so that the output values of the multiple power conditioners are equal to or less than the upper limit of the output command value during stand-alone operation.

In this invention, AC power is supplied to the load so that the output values of multiple power conditioners are kept below the upper limit of the output command value. Because the output of multiple power conditioners is limited, the total output of the multiple power conditioners is prevented from becoming excessive even if the amount of power generated by the solar cells becomes excessive. This prevents the current flowing through components such as terminal blocks and relays from exceeding their capacity, preventing damage to the components.

Furthermore, in the present invention, the upper limit of the output command value may be determined individually for each of the multiple power conditioners. By determining the upper limit of the output command value individually for each of the multiple power conditioners, the upper limit of the output command value for the multiple power conditioners can be appropriately set in accordance with the output performance of the multiple power conditioners.

In the present invention, each of the upper limit values of the output command values of the plurality of power conditioners may be determined based on a ratio to the predetermined limit value set for the plurality of power conditioners. By determining each of the upper limit values of the output command values of the plurality of power conditioners based on a ratio to the predetermined limit value set for the plurality of power conditioners, it is possible to appropriately maintain the efficiency of power supply to the load while preventing the total output of the plurality of power conditioners from becoming excessive.

Furthermore, in the present invention, each of the multiple power conditioners may have a single-phase inverter, and AC power generated by a three-phase voltage may be supplied to a three-phase load by combining single-phase voltages of different phases from the single-phase inverters of each of the multiple power conditioners. In this way, a three-phase voltage can be generated by combining single-phase voltages of different phases from the single-phase inverters of each of the multiple power conditioners, and AC power generated by the three-phase voltage can be supplied to a three-phase load.

Furthermore, in the present invention, the output command value may be an apparent current command value, and the output value may be an apparent current value. In the present invention, AC power is supplied to the load so that the apparent current values of the multiple power conditioners are equal to or less than the upper limit of the apparent current command value. Therefore, even if the amount of power generated by the solar cell becomes excessive, the total output of the multiple power conditioners is prevented from becoming excessive.

Furthermore, in the present invention, the apparent current command value may include an active current command value and a reactive current command value, and the upper limit of the active current command value may be determined based on the upper limit of the apparent current command value and the reactive current command value. In the present invention, the upper limit of the active current command value can be determined based on the upper limit of the apparent current command value and the reactive current command value.

Furthermore, in the present invention, the apparent current command value may include an active current command value and a reactive current command value, and the upper limit of the reactive current command value may be determined based on the upper limit of the apparent current command value and the active current command value. In the present invention, the upper limit of the reactive current command value can be determined based on the upper limit of the apparent current command value and the active current command value.

Furthermore, in the present invention, the output command value may be an apparent power command value, and the output value may be an apparent power value. In the present invention, AC power is supplied to the load so that the apparent power values of the multiple power conditioners are equal to or less than the upper limit of the apparent power command value. Therefore, even if the amount of power generated by the solar cells becomes excessive, the total output of the multiple power conditioners is prevented from becoming excessive.

Furthermore, in the present invention, the apparent power command value may include an active power command value and a reactive power command value, and the upper limit of the active power command value may be determined based on the upper limit of the apparent power command value and the reactive power command value. In the present invention, the upper limit of the active power command value can be determined based on the upper limit of the apparent power command value and the reactive power command value.

Furthermore, in the present invention, the apparent power command value may include an active power command value and a reactive power command value, and the upper limit of the reactive power command value may be determined based on the upper limit of the apparent power command value and the active power command value. In the present invention, the upper limit of the reactive power command value can be determined based on the upper limit of the apparent power command value and the active power command value.

This invention makes it possible to prevent the power conditioner's output from becoming excessive.

FIG. 1 is a diagram showing a schematic configuration of a distributed power supply system. FIG. 2 is a diagram showing the configuration of a distributed power supply system including a controller. 3(1) to 3(3) are diagrams showing an example of changes in the output value of a power conditioner. 4(1) to 4(3) are diagrams showing an example of changes in the output value of a power conditioner. FIG. 5 is a diagram showing functional blocks related to a process for generating an apparent current command value (instantaneous value) of the power conditioner.

[Application example]
An application example of the present invention will be described below with reference to the drawings. As shown in Fig. 1 , a distributed power system 1 according to this application example includes four single-phase power conditioners 20A, 20B, 20C, and 20D. The power conditioners 20A and 20B are power conditioners for storage batteries, with the power conditioner 20A including a single-phase inverter 10A and the power conditioner 20B including a single-phase inverter 10B. DC power from storage batteries 7A and 7B is input to the single-phase inverters 10A and 10B. The power conditioners 20C and 20D are power conditioners for solar cells, with the power conditioner 20C including a single-phase inverter 10C and the power conditioner 20D including a single-phase inverter 10D. DC power generated by solar cells 7C and 7D is input to the single-phase inverters 10C and 10D. The power conditioners 20A to 20D convert the input DC power into AC power and supply it to the load.

The outputs of the single-phase inverters 10A-10D are connected to a single-phase system 1A and single-phase consumer loads 2 and 3. The single-phase system 1A is, for example, a single-phase commercial power system. The outputs of the single-phase inverters 10A-10D are connected to a three-phase isolated load 8. The three-phase isolated load 8 is an example of a three-phase load. During grid-connected operation, the single-phase inverters 10A-10D are connected in parallel, and AC power generated by the single-phase output voltage of the single-phase inverters 10A-10D is supplied to the single-phase consumer loads 2 and 3. During grid-connected operation, AC power generated by a three-phase voltage from the three-phase system 1B is supplied to the three-phase isolated load 8. The three-phase system 1B is, for example, a three-phase commercial power system. During isolated operation, AC power generated by the output voltage of the single-phase inverters 10A-10D is supplied to the isolated load 8. During this stand-alone operation, a three-phase voltage is generated based on the output voltage of single-phase inverters 10A-10D.

The upper limit of the output command values of power conditioners 20A to 20D is determined so that the sum of the upper limit of the output command values of power conditioners 20A to 20D is equal to or less than a predetermined limit (threshold). AC power is supplied from power conditioners 20A to 20D to at least one of single-phase consumer loads 2 and 3 and isolated operation load 8 so that the output values of power conditioners 20A to 20D are equal to or less than the upper limit of the output command value. Because the output of power conditioners 20A to 20D is limited so that the sum of the upper limit of the output command values of power conditioners 20A to 20D is equal to or less than the predetermined limit, the output of power conditioners 20C and 20D can be prevented from becoming excessive. This prevents the current flowing through components such as terminal blocks and relays from exceeding their capacity, preventing damage to the components.

In FIG. 1, the distributed power system 1 is shown equipped with two power conditioners 20A and 20B for storage batteries, but the number of power conditioners for storage batteries can be increased or decreased. The number of power conditioners for storage batteries may be one, or three or more. In FIG. 1, the distributed power system 1 is shown equipped with two power conditioners 20C and 20D for solar cells, but the number of power conditioners for solar cells can be increased or decreased. The number of power conditioners for solar cells may be one, or three or more. In addition, the number of power conditioners for storage batteries may be zero, and the number of power conditioners for solar cells may be two or more.

<Embodiment>
Next, an embodiment of the present invention will be described in detail with reference to the drawings. A distributed power system 1 in this embodiment includes two single-phase power conditioners 20A and 20B connected to two storage batteries 7A and 7B, respectively, which are examples of power supply devices. The power conditioner 20A includes a single-phase inverter 10A and a control unit 11A. The control unit 11A controls the entire power conditioner 20A and the single-phase inverter 10A. The control unit 11A may be configured, for example, by a computer including a processor such as a CPU, RAM, and non-volatile storage devices (e.g., ROM, flash memory, etc.). The output of the single-phase inverter 10A is connected to a single-phase grid 1A and single-phase consumer loads 2 and 3 at output terminals 17, 18, and 19 via relays 5A and 5B. The output of the single-phase inverter 10A is also connected to a three-phase isolated load 8 serving as a second load via relays 5C and 5D and relay switches 6A and 6B. The power conditioner 20B includes a single-phase inverter 10B and a control unit 11B. The control unit 11B controls the entire power conditioner 20B and the single-phase inverter 10B. The control unit 11B may be configured, for example, by a computer including a processor such as a CPU, RAM, and a non-volatile storage device (e.g., ROM, flash memory, etc.). The output of the single-phase inverter 10B is connected to the single-phase grid 1A and single-phase consumer loads 2 and 3 at output terminals 17, 18, and 19 via relays 5E and 5F. The output of the single-phase inverter 10B is also connected to the three-phase isolated load 8 via relays 5G and 5H and relays SW6B and 6C.

When relays 5A, 5B and relays 5E, 5F are connected, power generated by the single-phase voltage of single-phase inverters 10A, 10B is supplied to single-phase consumer loads 2, 3. When relays SW6A, 6B, 6C are connected to the grid side, the output of three-phase grid 1B is connected to three-phase isolated load 8. On the other hand, when relays SW6A, 6B, 6C are connected to the power conditioner side, the output of single-phase inverters 10A, 10B is connected to three-phase isolated load 8.

The distributed power system 1 also includes two single-phase power conditioners 20C and 20D, each connected to two solar cells 7C and 7D, which are examples of power supply devices. The power conditioner 20C includes a single-phase inverter 10C and a control unit 11C. The control unit 11C controls the entire power conditioner 20C and the single-phase inverter 10C. The control unit 11C may be configured, for example, by a computer including a processor such as a CPU, RAM, and non-volatile storage devices (e.g., ROM, flash memory, etc.). The output of the single-phase inverter 10C is connected at output terminals 17, 18, and 19 to the single-phase grid 1A and single-phase consumer loads 2 and 3 via relays 5I and 5J and relays SW9A, 9B, and 9C. The output of the single-phase inverter 10C is connected to a three-phase isolated load 8 via relays 5I and 5J, relays SW9A and 9C, and relays SW6A and 6C.

The power conditioner 20D includes a single-phase inverter 10D and a control unit 11D. The control unit 11D controls the entire power conditioner 20D and the single-phase inverter 10D. The control unit 11D may be configured, for example, by a computer including a processor such as a CPU, RAM, and a non-volatile storage device (e.g., ROM, flash memory, etc.). The output of the single-phase inverter 10D is connected to a single-phase grid 1A and single-phase consumer loads 2 and 3 at output terminals 17, 18, and 19 via relays 5K and 5L and relays SW9D, 9E, and 9F. The output of the single-phase inverter 10D is also connected to a three-phase isolated load 8 via relays 5K and 5L, relays SW9D and 9F, and relays SW6A and 6C. The relays 5I, 5J, 5K, 5L, relays SW9A, 9B, 9C, and relays SW9D, 9E, 9F are connected to the single-phase inverters 10C, 10
The power from the single-phase voltage of D is supplied to single-phase consumer loads 2 and 3 .

The following describes grid-connected operation with single-phase grid 1A. With relays 5A, 5B and 5E, 5F connected and relays 5C, 5D and 5G, 5H disconnected, power generated by the single-phase voltage of single-phase inverters 10A, 10B is supplied to single-phase consumer loads 2, 3. With relays 5I, 5J connected and relays SW9A, 9B, 9C connected to the grid, power generated by the single-phase voltage of single-phase inverter 10C is supplied to single-phase consumer loads 2, 3. With relays 5K, 5L connected and relays SW9D, 9E, 9F connected to the grid, power generated by the single-phase voltage of single-phase inverter 10D is supplied to single-phase consumer loads 2, 3. As a result, single-phase inverters 10A-10D are connected in parallel, and power generated by each single-phase voltage is supplied to single-phase consumer loads 2, 3.

Power is supplied from the single-phase system 1A to the single-phase consumer loads 2 and 3 at a single-phase voltage. Furthermore, by connecting relays SW6A, 6B, and 6C to the system side, AC power (three-phase power) at a three-phase voltage is supplied from the three-phase system 1B to the three-phase isolated operation load 8. In addition to directly connecting the single-phase consumer loads 2 and 3 and the three-phase isolated operation load 8 to the single-phase inverters 10A-10D, they can also be connected via a transformer.

The following describes the operation during stand-alone operation. Relays 5A, 5B, 5E, and 5F are disconnected, relays 5C, 5D, 5G, and 5H, relays 5I, 5J, and 5K and 5L are connected, and relays SW9A, 9C, and 9D and 9F are connected to the non-grid side. Relays SW9B and 9E are connected to GND. Relays SW6A, 6B, and 6C are connected to the non-grid side. Power conditioner 20A then transmits a synchronization signal to power conditioners 20B, 20C, and 20D. Control unit 11A may also transmit a synchronization signal to control units 11B, 11C, and 11D. The synchronization signal is input to single-phase inverters 10B, 10C, and 10D via control units 11B, 11C, and 11D.

Single-phase inverter 10A outputs a single-phase voltage. Single-phase inverter 10B outputs a single-phase voltage that is delayed by 120 degrees from the single-phase voltage output from single-phase inverter 10A. As a result, a three-phase voltage is generated by combining the out-of-phase single-phase voltages of single-phase inverters 10A and 10B, and the voltage of the phase to which the outputs of single-phase inverters 10C and 10D are connected becomes a single-phase voltage that is delayed by 240 degrees from the single-phase voltage output from single-phase inverter 10A. Single-phase inverters 10C and 10D output currents synchronized with the voltages of the phases to which they are connected, and AC power generated by the three-phase voltage is supplied to the three-phase independent operation load 8. During independent operation, AC power generated by the three-phase voltage may be supplied to the three-phase independent operation load 8. Single-phase inverter 10B may output a single-phase voltage that is delayed by 240 degrees from the single-phase voltage output from single-phase inverter 10A. Alternatively, a three-phase voltage may be generated by combining the single-phase voltages output from the single-phase inverters of multiple solar cell power conditioners, and AC power generated by the three-phase voltage may be supplied to a three-phase independent operation load 8.

During stand-alone operation, the connection between single-phase grid 1A and single-phase consumer loads 2, 3 may be cut off, and power generated by the single-phase voltage of single-phase inverters 10A-10D may be supplied to single-phase consumer loads 2, 3. During grid-connected operation with single-phase grid 1A and stand-alone operation, at least one of storage batteries 7A and 7B may be charged. At least one of storage batteries 7A and 7B may be charged using at least one of DC power generated by solar cell 7C and DC power generated by solar cell 7D. At least one of storage batteries 7A and 7B may be charged using power supplied from single-phase grid 1A.

1 shows a configuration in which power conditioner 20A transmits a synchronization signal to power conditioners 20B, 20C, and 20D, but this embodiment is not limited to the configuration shown in Fig. 1. As shown in Fig. 2, distributed power supply system 1 may include a controller 21, and the controller 21 may transmit synchronization signals to power conditioners 20A to 20D. The controller 21 may be configured by, for example, a computer having a processor such as a CPU, RAM, a non-volatile storage device (e.g., ROM, flash memory, etc.), etc.

When the amount of sunlight increases and the amount of power generated by solar cells 7C and 7D increases, the output values of power conditioners 20C and 20D increase. The output values of power conditioners 20C and 20D are the values of power or current output from power conditioners 20C and 20D. If the output values of power conditioners 20C and 20D become excessive and the total output value of power conditioners 20C and 20D exceeds a threshold, the current flowing from power conditioners 20C and 20D to components such as terminal blocks and relays may exceed their tolerances, resulting in damage to the components. Furthermore, if the output values of power conditioners 20C and 20D become excessive while charging storage battery 7A and the total output value of power conditioners 20C and 20D exceeds a threshold, the charging current on the power conditioner 20A side may become excessive, causing distributed power system 1 to detect an abnormality and shut down. If the sum of the output values of power conditioners 20C and 20D exceeds the threshold value while storage battery 7B is being charged, the charging current on the power conditioner 20B side may become excessive, causing distributed power system 1 to detect an abnormality and shut down.

In the distributed power supply system 1, the upper limit of the output command values of the power conditioners 20C and 20D is determined so that the sum of the upper limit of the output command values of the power conditioners 20C and 20D is equal to or less than a predetermined limit value. The power conditioner 20C or 20D may determine the sum of the upper limit of the output command values of the power conditioners 20C and 20D, and determine the upper limit of the output command values of the power conditioners 20C and 20D based on the sum of the upper limit of the output command values of the power conditioners 20C and 20D. Alternatively, the controller 21 may determine the sum of the upper limit of the output command values of the power conditioners 20C and 20D, and determine the upper limit of the output command values of the power conditioners 20C and 20D based on the upper limit of the sum of the output command values of the power conditioners 20C and 20D.

In the distributed power system 1, AC power is supplied from the power conditioners 20C and 20D to the isolated operation load 8 while the output values of the power conditioners 20C and 20D are kept below the upper limit of the output command value of the power conditioners 20C and 20D. Alternatively, AC power may be supplied from the power conditioners 20C and 20D to at least one of the single-phase consumer loads 2 and 3 and the isolated operation load 8 while the output values of the power conditioners 20C and 20D are kept below the upper limit of the output command value of the power conditioners 20C and 20D. Because the output of the power conditioners 20C and 20D is limited, excessive output from the power conditioners 20C and 20D can be prevented even if the power generation amount of the solar cells 7C and 7D becomes excessive. This prevents the current flowing from the power conditioners 20C and 20D to components such as terminal blocks and relays from exceeding their capacity, thereby preventing damage to the components. The predetermined limit value may be determined based on the component tolerances of the terminal block and relay, or may be determined through experiments, simulations, etc.

When storage battery 7A is being charged, the output of power conditioners 20C and 20D is limited, preventing the charging current on the power conditioner 20A side from becoming excessive even if the amount of power generated by solar cells 7C and 7D becomes excessive. Furthermore, when storage battery 7B is being charged, the output of power conditioners 20C and 20D is limited, preventing the charging current on the power conditioner 20B side from becoming excessive even if the amount of power generated by solar cells 7C and 7D becomes excessive. This makes it possible to avoid shutdowns due to the detection of an abnormality in distributed power system 1.

Furthermore, during isolated operation, the output of power conditioners 20C and 20D may be limited to supply AC power from power conditioners 20C and 20D to isolated operation load 8. During isolated operation, the output of power conditioners 20C and 20D may be limited to supply AC power from power conditioners 20C and 20D to at least one of single-phase consumer loads 2 and 3 and isolated operation load 8. For cost reduction purposes, the component tolerances of terminal blocks and relays used during isolated operation may be inferior to the component tolerances of terminal blocks and relays used during grid-connected operation. Therefore, limiting the output of power conditioners 20C and 20D during isolated operation can prevent damage to terminal blocks and relays used during isolated operation.

Figures 3(1) to 3(3) are diagrams showing an example of changes in the output value of a power conditioner. The vertical axis of Figures 3(1) to 3(3) represents the output value, and the horizontal axis of Figures 3(1) to 3(3) represents time. Figure 3(1) shows changes in the total output value of power conditioners 20C and 20D. Figure 3(2) shows changes in the output value of power conditioner 20C. Figure 3(3) shows changes in the output value of power conditioner 20D. As the amount of sunlight increases after time t1, the output values of power conditioners 20C and 20D increase, and the total output value of power conditioners 20C and 20D also increases.

As shown in Figure 3 (2), by setting the upper limit of the output command value of power conditioner 20C below the limit value, the output value of power conditioner 20C is prevented from exceeding the individual limit value even when the amount of sunlight increases. Also, as shown in Figure 3 (3), by setting the upper limit of the output command value of power conditioner 20D below the individual limit value, the output value of power conditioner 20D is prevented from exceeding the individual limit value even when the amount of sunlight increases. The individual limit values of power conditioners 20C and 20D are, for example, the rated output values of power conditioners 20C and 20D, and the output command values of power conditioners 20C and 20D are smaller than the rated output values of power conditioners 20C and 20D. By preventing the output values of power conditioners 20C and 20D from exceeding the individual limit values, the total output value of power conditioners 20C and 20D is kept below the predetermined limit value, as shown in Figure 3 (1). Therefore, even if the total output value of power conditioners 20C and 20D increases due to an increase in the amount of sunlight, the total output value of power conditioners 20C and 20D is limited to a predetermined limit value or less.

Figures 4 (1) to 4 (3) are diagrams showing an example of changes in the output value of a power conditioner. The vertical axis of Figures 4 (1) to 4 (3) represents the output value, and the horizontal axis of Figures 4 (1) to 4 (3) represents time. Figure 4 (1) shows changes in the total output value of power conditioners 20C and 20D. Figure 4 (2) shows changes in the output value of power conditioner 20C. Figure 4 (3) shows changes in the output value of power conditioner 20D. As the amount of sunlight increases after time t1, the output values of power conditioners 20C and 20D increase, and the total output value of power conditioners 20C and 20D also increases.

As shown in Figures 4(1) to 4(3), when it is detected that the total output value of power conditioners 20C and 20D has exceeded a predetermined limit and a limit is set on the upper limit of the output command value of power conditioners 20C and 20D, it takes time for the total output value of power conditioners 20C and 20D to fall below the predetermined limit. Therefore, when the control shown in Figures 4(1) to 4(3) is used, the amount by which the total output value of power conditioners 20C and 20D exceeds the predetermined limit becomes larger. In this embodiment, by using the control shown in Figures 3(1) to 3(3), it is possible to reduce the amount by which the total output value of power conditioners 20C and 20D exceeds the predetermined limit more than when the control shown in Figures 4(1) to 4(3) is used.

The upper limit of the output command value for power conditioners 20C and 20D may be the same value. Alternatively, the upper limit of the output command value for power conditioners 20C and 20D may be determined individually for each power conditioner 20C and 20D. This allows the upper limit of the output command value for power conditioners 20C and 20D to be appropriately set according to the output performance of power conditioners 20C and 20D. Therefore, it is possible to prevent the output of power conditioners 20C and 20D from becoming excessive while appropriately maintaining the power supply efficiency for at least one of single-phase consumer loads 2 and 3 and isolated operation load 8.

The upper limit values of the output command values of power conditioners 20C and 20D may each be determined based on a ratio to a predetermined limit value set for power conditioners 20C and 20D. The ratio to a predetermined limit value may be set for power conditioners 20C and 20D based on the output performance of power conditioners 20C and 20D. The ratio to a predetermined limit value may also be set for power conditioners 20C and 20D based on various factors such as the usage status of power conditioners 20C and 20D, the time elapsed since the start of use, their installation location, and their state of deterioration. By determining the upper limit values of the output command values of power conditioners 20C and 20D based on a ratio to a predetermined limit value set for power conditioners 20C and 20D, it is possible to appropriately maintain the efficiency of power supply to at least one of single-phase consumer loads 2 and 3 and isolated operation load 8 while preventing the output of power conditioners 20C and 20D from becoming excessive.

The ratio of the predetermined limit value set for power conditioners 20C and 20D can be changed as appropriate. By changing the ratio of the predetermined limit value set for power conditioners 20C and 20D, it is possible to individually change the upper limit values of the output command values for power conditioners 20C and 20D. The ratio of the predetermined limit value set for power conditioners 20C and 20D may be changed based on various factors such as the usage status of power conditioners 20C and 20D, the time elapsed since the start of use, the installation location, and the state of deterioration.

The output command value of power conditioners 20C, 20D may be the apparent current command value of power conditioners 20C, 20D, and the output value of power conditioners 20C, 20D may be the apparent current value of power conditioners 20C, 20D. The apparent current value of power conditioners 20C, 20D is the value of the apparent current output from power conditioners 20C, 20D. In distributed power supply system 1, AC power is supplied from power conditioners 20C, 20D to isolated operation load 8 so that the apparent current value of power conditioners 20C, 20D is equal to or less than the upper limit of the apparent current command value of power conditioners 20C, 20D. Furthermore, AC power may be supplied from power conditioners 20C, 20D to at least one of single-phase consumer loads 2, 3 and isolated operation load 8 by ensuring that the apparent current values of power conditioners 20C, 20D are equal to or less than the upper limit of the apparent current command value of power conditioners 20C, 20D. Because the apparent current output from power conditioners 20C, 20D is limited, even if the amount of power generated by solar cells 7C, 7D becomes excessive, the apparent current output from power conditioners 20C, 20D can be prevented from becoming excessive. This prevents the current flowing from power conditioners 20C, 20D to terminal blocks and relays from exceeding the component tolerances, thereby preventing damage to components and equipment.

The output command values of the power conditioners 20C and 20D may be apparent power command values of the power conditioners 20C and 20D, and the output values of the power conditioners 20C and 20D may be apparent power values of the power conditioners 20C and 20D. The apparent power values of the power conditioners 20C and 20D are values of apparent power output from the power conditioners 20C and 20D. In the distributed power supply system 1,
The power conditioners 20C and 20D supply AC power to the isolated operation load 8 while ensuring that the apparent power values of the power conditioners 20C and 20D are equal to or less than the upper limit of the apparent power command values of the power conditioners 20C and 20D. The power conditioners 20C and 20D may supply AC power to at least one of the single-phase consumer loads 2 and 3 and the isolated operation load 8 while ensuring that the apparent power values of the power conditioners 20C and 20D are equal to or less than the upper limit of the apparent power command values of the power conditioners 20C and 20D. Because the apparent power output from the power conditioners 20C and 20D is limited, the apparent power output from the power conditioners 20C and 20D can be prevented from becoming excessive even when the amount of power generated by the solar cells 7C and 7D becomes excessive. This prevents the current flowing from the power conditioners 20C and 20D to the terminal blocks and relays from exceeding the component tolerances, thereby preventing damage to components and equipment.

Figure 5 is a diagram showing functional blocks related to the process of generating an apparent current command value (instantaneous value) for power conditioner 20C. Control unit 11C may execute the process of generating an apparent current command value (instantaneous value). Alternatively, a processing unit different from control unit 11C may execute the process of generating an apparent current command value (instantaneous value). Note that the process of generating an apparent current command value (instantaneous value) performed by power conditioner 20C can also be applied to the process of generating an apparent current command value (instantaneous value) for power conditioner 20D.

The generator 31 generates a reactive current command value (effective value) based on the active current command value (effective value) and various parameters. The parameters may include the active power values of the power conditioners 20A and 20B and the SOC (State of Charge) of the storage batteries 7A and 7B. The multiplier 32 calculates an upper limit for the apparent current command value of the power conditioner 20C based on the sum of the upper limits for the apparent current command values of the power conditioners 20C and 20D and the ratio of the sum to a predetermined limit value set for the power conditioners 20C and 20D. The determiner 33 determines an upper limit for the active current command value of the power conditioner 20C based on the reactive current command value (effective value) and the upper limit for the apparent current command value of the power conditioner 20C.

The limiting unit 34, which functions as a limiter, limits the active current command value (effective value) using the upper limit of the active current command value of the power conditioner 20C. That is, the limiting unit 34 generates an active current command value (effective value) limited by the upper limit of the active current command value of the power conditioner 20C. The multiplier 35 multiplies the active current command value (effective value) by sinθ to generate an active current command value (instantaneous value). The multiplier 36 multiplies the reactive current command value (effective value) by cosθ to generate a reactive current command value (instantaneous value). The adder 37 adds the active current command value (instantaneous value) and the reactive current command value (instantaneous value) and multiplies the result by √2 to generate an apparent current command value (instantaneous value). That is, the adder 37 generates an apparent current command value (instantaneous value) including the active current command value (instantaneous value) and the reactive current command value (instantaneous value). The control unit 11C may control the apparent current output from the power conditioner 20C based on the apparent current command value (instantaneous value).

Next, we will explain the process of generating an apparent current command value (instantaneous value) for power conditioner 20C by limiting the reactive current command value (effective value) using the upper limit value of the reactive current command value for power conditioner 20C. Control unit 11C may execute the process of generating the apparent current command value (instantaneous value). Alternatively, a processing unit different from control unit 11C may execute the process of generating the apparent current command value (instantaneous value). Note that, similarly to the above, the process of generating an apparent current command value (instantaneous value) performed by power conditioner 20C can also be applied to the process of generating an apparent current command value (instantaneous value) for power conditioner 20D.

The generator 31 generates an active current command value (effective value) based on the reactive current command value (effective value) and various parameters. The multiplier 32 calculates an upper limit value of the apparent current command value of the power conditioner 20C based on the sum of the upper limit values of the apparent current command values of the power conditioners 20C and 20D and the ratio of the sum to a predetermined limit value set for the power conditioners 20C and 20D. The determiner 33 determines an upper limit value of the reactive current command value of the power conditioner 20C based on the active current command value (effective value) and the upper limit value of the apparent current command value of the power conditioner 20C.

The limiting unit 34 limits the reactive current command value (effective value) using the upper limit value of the reactive current command value of the power conditioner 20C. That is, the limiting unit 34 generates a reactive current command value (effective value) limited by the upper limit value of the reactive current command value of the power conditioner 20C. The multiplier 35 multiplies the reactive current command value (effective value) by cosθ to generate a reactive current command value (instantaneous value). The multiplier 36 multiplies the active current command value (effective value) by sinθ to generate an active current command value (instantaneous value). The adder 37 adds the active current command value (instantaneous value) and the reactive current command value (instantaneous value) to generate an apparent current command value (instantaneous value). That is, the adder 37 generates an apparent current command value (instantaneous value) including the active current command value (instantaneous value) and the reactive current command value (instantaneous value). The control unit 11C may control the apparent current output from the power conditioner 20C based on the apparent current command value (instantaneous value).

Next, we will explain the process of generating an apparent power command value (instantaneous value) for power conditioner 20C by limiting the active power command value (effective value) using the upper limit value of the active power command value for power conditioner 20C. The control unit 11C may execute the process of generating the apparent power command value (instantaneous value). Alternatively, a processing unit different from control unit 11C may execute the process of generating the apparent power command value (instantaneous value). Note that, similarly to the above, the process of generating the apparent power command value (instantaneous value) performed by power conditioner 20C can also be applied to the process of generating the apparent power command value (instantaneous value) for power conditioner 20D.

The generation unit 31 generates a reactive power command value (effective value) based on the active power command value (effective value) and various parameters. The multiplier 32 calculates the upper limit of the apparent power command value for power conditioner 20C based on the sum of the upper limit values of the apparent power command values for power conditioners 20C and 20D and the ratio to a predetermined limit value set for power conditioners 20C and 20D. The determination unit 33 determines the upper limit of the active power command value for power conditioner 20C based on the reactive power command value (effective value) and the upper limit of the apparent power command value for power conditioner 20C.

The limiting unit 34 limits the active power command value (effective value) using the upper limit of the active power command value of the power conditioner 20C. That is, the limiting unit 34 generates an active power command value (effective value) limited by the upper limit of the active power command value of the power conditioner 20C. The multiplier 35 generates an active current command value (instantaneous value) based on the active power command value (effective value). The multiplier 36 generates a reactive power command value (instantaneous value) based on the reactive power command value (effective value). The adder 37 adds the active power command value (instantaneous value) and the reactive power command value (instantaneous value) to generate an apparent power command value (instantaneous value). That is, the adder 37 generates an apparent power command value (instantaneous value) including the active power command value (instantaneous value) and the reactive power command value (instantaneous value). The control unit 11C may control the apparent power output from the power conditioner 20C based on the apparent power command value (instantaneous value).

Next, a process of generating an apparent power command value (instantaneous value) for the power conditioner 20C by limiting the reactive power command value (effective value) using an upper limit value of the reactive power command value for the power conditioner 20C will be described. The control unit 11C may execute the process of generating the apparent power command value (instantaneous value). Alternatively, a processing unit different from the control unit 11C may execute the process of generating the apparent power command value (instantaneous value). Note that, similarly to the above, the process of generating the apparent power command value (instantaneous value) performed by the power conditioner 20C can also be applied to the process of generating the apparent power command value (instantaneous value) for the power conditioner 20D.

The generation unit 31 generates an active power command value (effective value) based on the reactive power command value (effective value) and various parameters. The multiplier 32 calculates the upper limit of the apparent power command value for power conditioner 20C based on the sum of the upper limit values of the apparent power command values for power conditioners 20C and 20D and the ratio to a predetermined limit value set for power conditioners 20C and 20D. The determination unit 33 determines the upper limit of the reactive power command value for power conditioner 20C based on the active power command value (effective value) and the upper limit of the apparent power command value for power conditioner 20C.

The limiting unit 34 limits the reactive power command value (effective value) using the upper limit of the reactive power command value of the power conditioner 20C. That is, the limiting unit 34 generates a reactive power command value (effective value) limited by the upper limit of the reactive power command value of the power conditioner 20C. The multiplier 35 generates a reactive current command value (instantaneous value) based on the reactive power command value (effective value). The multiplier 36 generates an active power command value (instantaneous value) based on the active power command value (effective value). The adder 37 adds the active power command value (instantaneous value) and the reactive power command value (instantaneous value) to generate an apparent power command value (instantaneous value). That is, the adder 37 generates an apparent power command value (instantaneous value) including the active power command value (instantaneous value) and the reactive power command value (instantaneous value). The control unit 11C may control the apparent power output from the power conditioner 20C based on the apparent power command value (instantaneous value).

<Modification>
A modified example will be described. In the distributed power supply system 1, the upper limit of the output command values of the power conditioners 20A to 20D may be determined so that the sum of the upper limit of the output command values of the power conditioners 20A to 20D is equal to or less than a predetermined limit value. One of the power conditioners 20A to 20D may determine the sum of the upper limit of the output command values of the power conditioners 20A to 20D, and the controller 21 may determine the upper limit of the output command value of the power conditioners 20A to 20D based on the sum of the upper limit of the output command values of the power conditioners 20A to 20D. Alternatively, the controller 21 may determine the sum of the upper limit of the output command values of the power conditioners 20A to 20D, and the controller 21 may determine the upper limit of the output command value of the power conditioners 20A to 20D based on the upper limit of the sum of the output command values of the power conditioners 20A to 20D. The process of generating the apparent current command value (instantaneous value) and the process of generating the apparent power command value (instantaneous value) shown in FIG. 5 may be applied to the power conditioners 20A and 20B.

In the distributed power supply system 1, AC power is supplied from the power conditioners 20A to 20D to the isolated operation load 8 while the output values of the power conditioners 20A to 20D are kept below the upper limit of the output command value of the power conditioners 20A to 20D. AC power may be supplied from the power conditioners 20A to 20D to at least one of the single-phase consumer loads 2, 3 and the isolated operation load 8 while the output values of the power conditioners 20A to 20D are kept below the upper limit of the output command value of the power conditioners 20A to 20D. Because the output of the power conditioners 20A to 20D is limited, the output of the power conditioners 20C, 20D can be prevented from becoming excessive even if the amount of power generated by the solar cells 7C, 7D becomes excessive.

During islanded operation, the output of the power conditioners 20A to 20D may be limited to supply AC power from the power conditioners 20A to 20D to the islanded operation load 8. During islanded operation, the output of the power conditioners 20A to 20D may be limited to supply AC power from the power conditioners 20A to 20D to at least one of the single-phase consumer loads 2 and 3 and the islanded operation load 8. By limiting the output of the power conditioners 20A to 20D during islanded operation, damage to terminal blocks and relays used during islanded operation can be prevented.

Furthermore, each of the processes described above may be considered as a control method for the distributed power supply system 1. Each of the processes described above may be considered as a method executed by a computer. A program for causing a computer to execute each of the processes described above may be provided to the computer via a network or from a computer-readable recording medium that non-temporarily stores data. Note that the above means and processes may be combined with each other to the greatest extent possible to constitute the present invention.

<Additional Notes>
A distributed power system (1) including a plurality of power conditioners (20A-20D) that convert input DC power into AC power and supply the AC power to loads (2, 3, 8), at least one of the plurality of power conditioners receiving DC power from solar cells (7A, 7B),
an upper limit value of the output command value is determined so that a total value of the upper limit values of the output command values of the plurality of power conditioners is equal to or less than a predetermined limit value during stand-alone operation;
A distributed power system, characterized in that AC power is supplied to the load so that output values of the plurality of power conditioners are equal to or less than an upper limit value of the output command value during the independent operation.

DESCRIPTION OF SYMBOLS 1... Distributed power system 1A... Single-phase system 1B... Three-phase system 2, 3... Single-phase consumer load 7A, 7B... Storage battery 7C, 7D... Solar cell 8... Three-phase independent operation load 10A, 10B, 10C, 10D... Single-phase inverter 20A, 20B, 20C, 20D... Power conditioner 21... Controller

Claims (10)

A distributed power supply system including a plurality of power conditioners that convert input DC power into AC power and supply the AC power to a load, wherein at least one of the plurality of power conditioners receives DC power from a solar cell,
an upper limit value of the output command value is determined so that a total value of the upper limit values of the output command values of the plurality of power conditioners is equal to or less than a predetermined limit value during stand-alone operation;
A distributed power system, characterized in that AC power is supplied to the load so that output values of the plurality of power conditioners are equal to or less than an upper limit value of the output command value during the independent operation. The distributed power system of claim 1, wherein the upper limit of the output command value is determined individually for each of the multiple power conditioners. The distributed power system of claim 2, wherein each of the upper limit values of the output command values of the multiple power conditioners is determined based on a ratio to the predetermined limit value set for the multiple power conditioners. Each of the plurality of power conditioners has a single-phase inverter,
4. The distributed power system according to claim 1, wherein AC power based on a three-phase voltage is supplied to a three-phase load by combining single-phase voltages of different phases of the single-phase inverters of each of the plurality of power conditioners. the output command value is an apparent current command value,
5. The distributed power system according to claim 1, wherein the output value is an apparent current value. the apparent current command value includes an active current command value and a reactive current command value,
6. The distributed power generation system according to claim 5, wherein the upper limit of the active current command value is determined based on the upper limit of the apparent current command value and the reactive current command value. the apparent current command value includes an active current command value and a reactive current command value,
6. The distributed power generation system according to claim 5, wherein the upper limit of the reactive current command value is determined based on the upper limit of the apparent current command value and the active current command value. the output command value is an apparent power command value,
5. The distributed power system according to claim 1, wherein the output value is an apparent power value. the apparent power command value includes an active power command value and a reactive power command value;
9. The distributed power system according to claim 8, wherein the upper limit of the active power command value is determined based on the upper limit of the apparent power command value and the reactive power command value. the apparent power command value includes an active power command value and a reactive power command value;
9. The distributed power system according to claim 8, wherein the upper limit value of the reactive power command value is determined based on the upper limit value of the apparent power command value and the active power command value.