Distributed power systems

Abstract

To suppress output of a power conditioner from becoming excessive.SOLUTION: A distributed power supply system includes a plurality of power conditioners that converts DC power inputted from a solar cell for generating DC power into AC power and supply it to loads. On the basis of ratios to a predetermined value that is set on a plurality of power conditioners, output of the plurality of power conditioners is performed, and the ratios are adjusted so that a sum of output values of the plurality of power conditioners maintains the predetermined value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a distributed power system including a plurality of inverters.

Background Art

[0002] There is a distributed power system including a battery power conditioner that operates by connecting a battery unit to a power grid, and a PV (photovoltaic power generation) power conditioner that operates by connecting a PV unit to a power grid (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0007] In the present invention, the predetermined value may be a limit value for the total sum of the output values ​​of the multiple power conditioners. In addition, in the present invention, the upper limit value of the output command value of the multiple power conditioners may be determined based on the ratio. In addition, in the present invention, the ratio of the multiple power conditioners is adjusted so that the total sum of the output values ​​of the multiple power conditioners maintains a predetermined value. By adjusting the ratio of the multiple power conditioners so that the total sum of the output values ​​of the multiple power conditioners maintains a predetermined value, it is prevented from exceeding the predetermined value. Since it is prevented from exceeding the predetermined value, it is possible to prevent the output of the multiple power conditioners from becoming excessive. In this way, by adjusting the ratio of the multiple power conditioners, the output of the multiple power conditioners is adjusted, and it is prevented from becoming excessive. Since excessive output from multiple power conditioners is prevented, the current flowing through components such as terminal blocks and relays is prevented from exceeding the component's capacity, thus preventing component damage.

[0008] Furthermore, in the present invention, adjusting the ratio may include increasing the ratio and decreasing the ratio. The ratio of multiple power conditioners can be adjusted by increasing the ratio or decreasing the ratio of multiple power conditioners.

[0009] Furthermore, in the present invention, if the number of power conditioners is n (where n is an integer of 3 or more), and the ratio is adjusted so that the sum of the ratios of n-1 power conditioners out of the n power conditioners is 100%, and the ratio of the power conditioners other than n-1 out of the n power conditioners is 0%, then the sum of the output values ​​of the n-1 power conditioners maintains the predetermined value, and the output of the power conditioners other than n-1 may be stopped. In the present invention, the sum of the output values ​​of the n-1 power conditioners is prevented from exceeding the predetermined value, and the output of the power conditioners other than n-1 can be stopped. By stopping the output of the power conditioners other than n-1, the number of power conditioners in operation can be reduced. Therefore, within the range where the sum of the output values ​​of the n-1 power conditioners does not exceed the predetermined value, the number of power conditioners in operation can be minimized while maximizing the output of the multiple power conditioners.

[0010] Furthermore, in the present invention, if the number of power conditioners is 2, and the ratio is adjusted so that the ratio of one of the two power conditioners becomes 100% and the ratio of the other of the two power conditioners becomes 0%, and the output value of one of the two power conditioners remains at the predetermined value, the output of the other power conditioner may be stopped. In the present invention, it is possible to suppress the output value of one of the two power conditioners from exceeding the predetermined value, and to stop the output of the other power conditioner. By stopping the output of the other power conditioner, the number of power conditioners in operation can be reduced. Therefore, within the range in which the output value of one of the two power conditioners does not exceed the predetermined value, it is possible to maximize the output of one of the two power conditioners while minimizing the number of power conditioners in operation.

[0011] Furthermore, in the present invention, the plurality of power conditioners may perform maximum power point tracking control to produce output. By performing maximum power point tracking control, the plurality of power conditioners can output AC power corresponding to the maximum DC power that the solar cell can supply. [Effects of the Invention]

[0012] According to the present invention, it is possible to prevent the output of the power conditioner from becoming excessive. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 shows a schematic configuration of a distributed power supply system. [Figure 2] Figure 2 shows the configuration of a distributed power supply system equipped with a controller. [Figure 3] Figure 3 is a flowchart showing the processing flow according to this embodiment. [Figure 4] Figures 4(A) to 4(D) show an example of the process of adjusting the power conditioner ratio. [Modes for carrying out the invention]

[0014] [Examples of application] The following describes an example of the application of the present invention with reference to the drawings. As shown in Figure 1, the distributed power supply system 1 according to this example is equipped with four single-phase power conditioners 20A, 20B, 20C, and 20D. Power conditioners 20A and 20B are power conditioners for storage batteries, and power conditioner 20A has a single-phase inverter 10A. Power conditioner 20B has a single-phase inverter 10B. DC power from batteries 7A and 7B is input to single-phase inverters 10A and 10B. Power conditioners 20C and 20D are power conditioners for solar panels. Power conditioner 20C has a single-phase inverter 10C, and power conditioner 20D has a single-phase inverter 10D. DC power generated by solar panels 7C and 7D is input to single-phase inverters 10C and 10D. Power conditioners 20A to 20D convert the input DC power into AC power and supply it to the load.

[0015] The outputs of single-phase inverters 10A to 10D are connected to single-phase grid 1A and single-phase consumer loads 2 and 3. Single-phase grid 1A is, for example, a single-phase commercial power grid. The outputs of single-phase inverters 10A to 10D are also connected to a three-phase independent operation load 8. Three-phase independent operation load 8 is an example of a three-phase load. When operating in grid-connected mode, single-phase inverters 10A to 10D are connected in parallel, and the AC power from the single-phase output voltages of single-phase inverters 10A to 10D is supplied to single-phase consumer loads 2 and 3. Also, when operating in grid-connected mode, three-phase AC power from three-phase grid 1B is supplied to the three-phase independent operation load 8. Three-phase grid 1B is, for example, a three-phase commercial power grid. On the other hand, when operating independently, the AC power from the output voltages of single-phase inverters 10A to 10D is supplied to the independent operation load 8. During this independent operation, a three-phase voltage is generated based on the output voltage of the single-phase inverters 10A to 10D.

[0016] Based on the ratio of a predetermined value set for power conditioners 20C and 20D, the upper limit of the output command value for power conditioners 20C and 20D is determined, and output is performed. The ratio of power conditioners 20C and 20D is adjusted so that the sum of the output values ​​of power conditioners 20C and 20D remains at a predetermined value. By adjusting the ratio of power conditioners 20C and 20D so that the sum of the output values ​​of power conditioners 20C and 20D remains at a predetermined value, it is prevented that the sum of the output values ​​of power conditioners 20C and 20D will exceed the predetermined value. Since it is prevented that the sum of the output values ​​of power conditioners 20C and 20D will exceed the predetermined value, it is possible to prevent the output of power conditioners 20C and 20D from becoming excessive. This prevents the current flowing through components such as terminal blocks and relays from exceeding the component's capacity, and thus prevents component damage. The predetermined value may be determined based on the component capacity of terminal blocks and relays, or it may be determined by experimentation or simulation. The predetermined value may also be the required value (power value or current value) required by at least one of the single-phase consumer loads 2 and 3 and the standalone operation load 8 for power conditioners 20C and 20D.

[0017] In Figure 1, the distributed power system 1 is equipped with two power conditioners 20A and 20B for batteries, but the number of battery power conditioners can be increased or decreased. The number of battery power conditioners may be one or three or more. In Figure 1, the distributed power system 1 is equipped with two power conditioners 20C and 20D for solar cells, but the number of solar power conditioners (hereinafter referred to as PV power conditioners) can be changed. The number of PV power conditioners may be three or more. Also, the number of battery power conditioners may be zero, and the number of PV power conditioners may be two or more. The configuration of the battery power conditioners is the same as the configuration of power conditioners 20A and 20B. The configuration of the PV power conditioners is the same as the configuration of power conditioners 20C and 20D. Multiple PV power conditioners may include power conditioners 20C and 20D. Alternatively, a PV power conditioner may be any one of the multiple PV power conditioners that include power conditioners 20C and 20D.

[0018] <Embodiment> Next, embodiments of the present invention will be described in detail with reference to the drawings. The distributed power system 1 in the embodiment includes two single-phase power conditioners 20A and 20B respectively connected to two storage batteries 7A and 7B which are examples of power supply devices. The power conditioner 20A has 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 constituted by a computer having a processor such as a CPU, a RAM, and a non-volatile storage device (for example, a ROM, a flash memory, etc.). The output of the single-phase inverter 10A is connected to the single-phase system 1A and the single-phase consumer loads 2 and 3 at output terminals 17, 18, and 19 via relays 5A, 5B. Also, the output of the single-phase inverter 10A is connected to the three-phase self-operating load 8 as a second load via relays 5C, 5D and relays SW6A, 6B. The power conditioner 20B has 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 constituted by a computer having a processor such as a CPU, a RAM, and a non-volatile storage device (for example, a ROM, a flash memory, etc.). The output of the single-phase inverter 10B is connected to the single-phase system 1A and the single-phase consumer loads 2 and 3 at output terminals 17, 18, and 19 via relays 5E, 5F. Also, the output of the single-phase inverter 10B is connected to the three-phase self-operating load 8 via relays 5G, 5H and relays SW6B, 6C.

[0019] Then, by connecting the relays 5A, 5B and the relays 5E, 5F, the power generated by the single-phase voltages of the single-phase inverters 10A, 10B is supplied to the single-phase consumer loads 2, 3. Also, by connecting the relays SW6A, 6B, 6C to the system side, the output of the three-phase system 1B is connected to the three-phase self-operating load 8. On the other hand, by connecting the relays SW6A, 6B, 6C to the power conditioner side, the outputs of the single-phase inverters 10A, 10B are connected to the three-phase self-operating load 8.

[0020] Further, the distributed power system 1 includes two single-phase power conditioners 20C and 20D respectively connected to two solar cells 7C and 7D which are examples of power supply devices. The power conditioner 20C has a single-phase inverter 10C and a control unit 11C. The control unit 11C performs overall control of the power conditioner 20C and control of the single-phase inverter 10C. The control unit 11C may be constituted by a computer having a processor such as a CPU, a RAM, a non-volatile storage device (such as a ROM, a flash memory, etc.). The output of the single-phase inverter 10C is connected to the single-phase grid 1A and the single-phase customer loads 2 and 3 at output terminals 17, 18, and 19 via relays 5I, 5J and relays SW9A, 9B, 9C. Also, the output of the single-phase inverter 10C is connected to the three-phase self-operating load 8 via relays 5I, 5J, relays SW9A, 9C and relays SW6A, 6C.

[0021] The power conditioner 20D has a single-phase inverter 10D and a control unit 11D. The control unit 11D performs overall control of the power conditioner 20D and control of the single-phase inverter 10D. The control unit 11D may be constituted by a computer having a processor such as a CPU, a RAM, a non-volatile storage device (such as a ROM, a flash memory, etc.). The output of the single-phase inverter 10D is connected to the single-phase grid 1A and the single-phase customer loads 2 and 3 at output terminals 17, 18, and 19 via relays 5K, 5L and relays SW9D, 9E, 9F. Also, the output of the single-phase inverter 10D is connected to the three-phase self-operating load 8 via relays 5K, 5L, relays SW9D, 9F and relays SW6A, 6C. And, by connecting relays 5I, 5J, relays 5K, 5L, relays SW9A, 9B, 9C and relays SW9D, 9E, 9F, the power by the single-phase voltages of the single-phase inverters 10C and 10D is supplied to the single-phase customer loads 2 and 3.

[0022] This section describes the operation when connected to a single-phase grid 1A. When relays 5A, 5B and 5E, 5F are connected, and relays 5C, 5D and 5G, 5H are disconnected, the single-phase voltage power from single-phase inverters 10A and 10B is supplied to single-phase consumer loads 2 and 3. When relays 5I and 5J are connected, and relays SW9A, 9B, and 9C are connected to the grid side, the single-phase voltage power from single-phase inverter 10C is supplied to single-phase consumer loads 2 and 3. When relays 5K and 5L are connected, and relays SW9D, 9E, and 9F are connected to the grid side, the single-phase voltage power from single-phase inverter 10D is supplied to single-phase consumer loads 2 and 3. As a result, single-phase inverters 10A to 10D are connected in parallel, and the single-phase voltage power from each is supplied to single-phase consumer loads 2 and 3.

[0023] Single-phase power is supplied to single-phase consumer loads 2 and 3 from single-phase grid 1A at single-phase voltage. Furthermore, by connecting relays SW6A, 6B, and 6C to the grid side, three-phase AC power (three-phase power) at three-phase voltage is supplied to the three-phase independent operation load 8 from three-phase grid 1B. In addition to directly connecting the single-phase consumer loads 2 and 3 and the three-phase independent operation load 8 to the single-phase inverters 10A to 10D, it is also possible to connect them via transformers.

[0024] The following describes the operation during independent operation. Relays 5A, 5B, 5E, and 5F are disconnected, relays 5C, 5D, 5G, 5H, 5I, 5J, 5K, and 5L are connected, and relays SW9A, 9C, SW9D, 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 send 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.

[0025] Single-phase inverter 10A outputs a single-phase voltage. Single-phase inverter 10B outputs a single-phase voltage that is 120 degrees behind the single-phase voltage output from single-phase inverter 10A. By combining the single-phase voltages with different phases from single-phase inverters 10A and 10B, a three-phase voltage is generated, 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 240 degrees behind the single-phase voltage output from single-phase inverter 10A. Single-phase inverters 10C and 10D output a current synchronized with the voltage of the connected phase, and AC power due to the three-phase voltage is supplied to the three-phase independent operation load 8. During independent operation, AC power due to 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 240 degrees behind 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 using this three-phase voltage may be supplied to a three-phase independent operation load 8.

[0026] During standalone operation, the connection between single-phase grid 1A and single-phase consumer loads 2 and 3 may be disconnected, and power from single-phase inverters 10A to 10D may be supplied to single-phase consumer loads 2 and 3. During grid-connected operation with single-phase grid 1A and during standalone operation, at least one of batteries 7A and 7B may be charged. At least one of batteries 7A and 7B may be charged using at least one of the DC power generated by solar cell 7C and the DC power generated by solar cell 7D. At least one of batteries 7A and 7B may be charged using power supplied from single-phase grid 1A.

[0027] Figure 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 Figure 1. As shown in Figure 2, the distributed power supply system 1 may include a controller 21, and the controller 21 may transmit a synchronization signal to power conditioners 20A to 20D. The system 21 may be composed of a computer having, for example, a processor such as a CPU, RAM, and a non-volatile storage device (such as ROM or flash memory).

[0028] Power conditioners 20C and 20D are capable of performing Maximum Power Point Tracking (MPPT) control, which maximizes the power generated by solar cells 7C and 7D. By performing Maximum Power Point Tracking control, power conditioners 20C and 20D can output AC power corresponding to the maximum DC power that solar cells 7C and 7D can supply.

[0029] As solar radiation increases and the power generation of solar cells 7C and 7D increases, the output values ​​of power conditioners 20C and 20D also increase. The output values ​​of power conditioners 20C and 20D are the power or current values ​​output from power conditioners 20C and 20D. If the output values ​​of power conditioners 20C and 20D become excessive and the sum of their output values ​​exceeds a predetermined value, the current flowing from power conditioners 20C and 20D to components such as terminal blocks and relays may exceed the component's capacity, potentially causing component damage. Furthermore, if the output values ​​of power conditioners 20C and 20D become excessive during charging of battery 7A and the sum of their output values ​​exceeds a predetermined value, the charging current on the power conditioner 20A side may become excessive, potentially causing the distributed power system 1 to detect an abnormality and shut down. If the combined output value of power conditioners 20C and 20D exceeds a predetermined value while battery 7B is being charged, the charging current on the power conditioner 20B side may become excessive, potentially causing the distributed power system 1 to detect an abnormality and shut down.

[0030] This section describes the process of supplying AC power from at least one of the power conditioners 20C and 20D to at least one of the single-phase consumer loads 2 and 3 and the standalone operation load 8. Based on the ratio to a predetermined value set for power conditioners 20C and 20D, the upper limit of the output command value for power conditioners 20C and 20D is determined, and output is performed. Power conditioner 20C may be set as the master unit and power conditioner 20D as the slave unit. In this case, power conditioner 20C may send a signal to power conditioner 20D indicating the start of output (output start signal), a signal indicating the stop of output (output stop signal), and various instruction signals. Power conditioner 20C may set a ratio (balance ratio) to a predetermined value for power conditioners 20C and 20D. The ratio may be a percentage (%) or a decimal. Power conditioner 20C may collect various information and set and adjust the ratio of power conditioners 20C and 20D. This information includes output values, such as power or current values, from power conditioners 20C and 20D.

[0031] Power conditioner 20C may be set as a slave unit and power conditioner 20D as a master unit. In this case, power conditioner 20D may send output start signals, output stop signals, and various instruction signals to power conditioner 20C. Power conditioner 20D may set ratios to predetermined values ​​for power conditioners 20C and 20D. Power conditioner 20D may collect various information and set and adjust the ratios of power conditioners 20C and 20D. Controller 21 may set ratios to predetermined values ​​for power conditioners 20C and 20D. Controller 21 may collect various information and set and adjust the ratios of power conditioners 20C and 20D. Controller 21 may send output start signals, output stop signals, and various instruction signals to power conditioners 20C and 20D. The controller 21 may determine the upper limit of the output command value of the power conditioners 20C and 20D based on a ratio to a predetermined value set for the power conditioners 20C and 20D.

[0032] This section describes an example of the process when power conditioner 20C is set as the master unit and power conditioner 20D is set as the slave unit. Figure 3 is a flowchart showing the process flow when power conditioner 20C is set as the master unit and power conditioner 20D is set as the slave unit. At startup (start of independent operation), when power conditioners 20C and 20D are ready for grid connection, one of the power conditioners 20C or 20D is started. Here, the operation of the first power conditioner 20C is started (S1). Power conditioner 20C sets the ratio of power conditioners 20C and 20D so that the sum of the ratio of power conditioner 20C and the ratio of power conditioner 20D is 100%. For example, power conditioner 20C sets the ratio of power conditioner 20C to 100% and the ratio of power conditioner 20D to 0%.

[0033] Power conditioner 20C determines whether the sum of the output values ​​of power conditioner 20C and power conditioner 20D maintains a predetermined value. Power conditioner 20C calculates the upper limit of the output command value of power conditioner 20C based on the ratio of power conditioner 20C, and calculates the upper limit of the output command value of power conditioner 20D based on the ratio of power conditioner 20D. Specifically, the upper limit of the output command value of power conditioner 20C is calculated based on the following formula (1), and the upper limit of the output command value of power conditioner 20D is calculated based on the following formula (2). The predetermined value may be the limit value of the sum of the output values ​​of power conditioner 20C and power conditioner 20D. The upper limit of the output command value for power conditioner 20C = predetermined value × ratio of power conditioner 20C (%) ... (1) The upper limit of the output command value for power conditioner 20D = predetermined value × ratio of power conditioner 20D (%) ... (2)

[0034] If the predetermined value is less than or equal to the rated output of power conditioner 20C, and the ratio of power conditioner 20C is 100%, then the upper limit of the output command value of power conditioner 20C will be predetermined value × 100%. The maximum output value of power conditioner 20C is the value of current or power that can be output from power conditioner 20C according to the amount of power generated by solar cell 7C. The maximum output value of power conditioner 20C may also be the value of current or power that can be output from power conditioner 20C when power conditioner 20C performs maximum power point tracking control.

[0035] When the ratio of power conditioner 20D is 0%, the upper limit of the output command value of power conditioner 20D is a predetermined value × 0%. The maximum output value of power conditioner 20D is the value of current or power that can be output from power conditioner 20D according to the amount of power generated by solar cell 7D. The maximum output value of power conditioner 20D may also be the value of current or power that can be output from power conditioner 20D when power conditioner 20D performs maximum power point tracking control.

[0036] Power conditioner 20C adjusts the ratio of power conditioners 20C and 20D if the sum of the output values ​​of power conditioner 20C and power conditioner 20D does not maintain a predetermined value. Figures 4(A) to 4(D) show an example of the process of adjusting the ratio of power conditioners 20C and 20D. In Figures 4(A) to 4(D), PCS (Power Conditioning System) 1 refers to the first power conditioner. PCS2 refers to the second power conditioner. In the following, power conditioner 20C corresponds to PCS1, and power conditioner 20D corresponds to PCS2. The upper limit of the output (upper limit of the output command value) in Figures 4(A) to 4(D) is a predetermined value multiplied by a ratio. The upper limit of the output of power conditioner 20C is calculated by multiplying a predetermined value by the ratio of power conditioner 20C, and the upper limit of the output of power conditioner 20D is calculated by multiplying a predetermined value by the ratio of power conditioner 20D.

[0037] Figure 4(A) shows the output value of power conditioner 20C when operation of power conditioner 20C is started. The power generation of solar cell 7C is small, and the maximum output value of power conditioner 20C is smaller than the upper limit of power conditioner 20C's output. Therefore, when the ratio of power conditioner 20C is adjusted to 100%, as shown in Figure 4(A), the output value of power conditioner 20C does not reach the upper limit of power conditioner 20C's output. When the ratio of power conditioner 20D is adjusted to 0%, the output value of power conditioner 20D is zero.

[0038] Figure 4(A) shows the case where the output value of power conditioner 20C has not reached the upper limit of power conditioner 20C. If the output value of power conditioner 20C has not reached the upper limit of power conditioner 20C, the operation of the second power conditioner 20D is started (S2). However, if the power generation of solar cell 7C is sufficiently large and the output value of power conditioner 20C has reached the upper limit of power conditioner 20C, power conditioner 20D will not be operated (output). The same applies when three or more PV power conditioners are used. If the predetermined value is less than or equal to the rated output of the first PV power conditioner, at startup, the ratio of the first PV power conditioner is set to 100%, and the ratio of the second and subsequent PV power conditioners is set to 0%. If the output value of the first PV power conditioner reaches its upper output limit, the operation (output) of subsequent PV power conditioners will not be performed.

[0039] The ratio of the first power conditioner 20C and the ratio of the second power conditioner 20D are adjusted (S3). Figure 4(B) shows the output values ​​of power conditioners 20C and 20D when they are in operation. In Figure 4(B), the ratio of power conditioners 20C and 20D is adjusted by decreasing the ratio of power conditioner 20C and increasing the ratio of power conditioner 20D. As shown in Figure 4(B), the upper limit of the output of power conditioner 20C decreases in accordance with the power generation of solar cell 7C, so the output value of power conditioner 20C reaches the upper limit of the output of power conditioner 20C, and the upper limit of the output of power conditioner 20D increases, so the output value of power conditioner 20D reaches the upper limit of the output of power conditioner 20D with the surplus power generation of solar cell 7D. Therefore, in Figure 4(B), the sum of the output values ​​of power conditioner 20C and power conditioner 20D maintains a predetermined value (= upper limit of power conditioner 20C's output + upper limit of power conditioner 20D's output).

[0040] The ratio of power conditioners 20C and 20D is adjusted so that the sum of their output values ​​remains at a predetermined value, in accordance with the maximum power that solar cells 7C and 7D can generate, which fluctuates depending on the amount of solar radiation. By adjusting the ratio of power conditioners 20C and 20D so that the sum of their output values ​​remains at a predetermined value, the sum of their output values ​​is maximized within a range that does not exceed the predetermined value, while also preventing it from exceeding the predetermined value. Since the sum of their output values ​​is prevented from exceeding the predetermined value, it is possible to prevent the output of power conditioners 20C and 20D from becoming excessive. In this way, by adjusting the ratio of power conditioners 20C and 20D, the output of power conditioners 20C and 20D is adjusted, and the output of power conditioners 20C and 20D is prevented from becoming excessive. Power conditioner 20C, 2 Since the output of 0D is prevented from becoming excessive, the current flowing through components such as terminal blocks and relays can be prevented from exceeding the component's capacity, thus preventing component damage.

[0041] The process described with reference to Figure 4(B) is also applicable when using three or more PV power conditioners. If the sum of the output values ​​of the first and second PV power conditioners remains at a predetermined value, the operation (output) of the third and subsequent PV power conditioners will not be performed. If the sum of the output values ​​of the first and second PV power conditioners does not reach a predetermined value, the ratio of the first, second, and third PV power conditioners will be adjusted. The ratio of the multiple PV power conditioners will be adjusted until the sum of the output values ​​of the multiple PV power conditioners remains at a predetermined value.

[0042] Figure 4(C) shows the output values ​​of power conditioners 20C and 20D when they are in operation. As shown in Figure 4(C), the output value of power conditioner 20C has reached its upper limit, and the output value of power conditioner 20D has reached its upper limit. Power conditioner 20C slightly increases the ratio of either power conditioner 20C or power conditioner 20D. For example, if the ratio of power conditioner 20D is greater than the ratio of power conditioner 20C, power conditioner 20C increases the ratio of power conditioner 20D. Power conditioner 20C slightly decreases the ratio of the other power conditioner. For example, if the ratio of power conditioner 20C is smaller than the ratio of power conditioner 20D, power conditioner 20C will reduce the ratio of power conditioner 20C.

[0043] If increasing the ratio of power conditioner 20D increases the output value of power conditioner 20D, there is surplus power generation capacity for solar cell 7D. Power conditioner 20C gradually increases the ratio of power conditioner 20D until the increase in the output value of power conditioner 20D stops. Power conditioner 20C gradually decreases the ratio of power conditioner 20C. Figure 4(D) shows the output value of power conditioner 20D when the ratio of power conditioner 20D is gradually increased until the increase in the output value of power conditioner 20D stops. In Figure 4(D), the ratio of power conditioner 20C is adjusted to 0%, and the output value of power conditioner 20C is zero. Also in Figure 4(D), the ratio of power conditioner 20D is adjusted to 100%. In Figure 4(D), the sum of the output values ​​of power conditioner 20C and power conditioner 20D maintains a predetermined value (= limit value for the sum of the output values ​​of power conditioners 20C and 20D).

[0044] Since the output value of power conditioner 20C is zero, power conditioner 20C does not provide any output. In other words, the output of power conditioner 20C is stopped (S4). In Figure 4(D), the ratio of power conditioners 20C and 20D is adjusted so that the sum of the output values ​​of power conditioners 20C and 20D maintains a predetermined value. In other words, the ratio of power conditioners 20C and 20D is adjusted so that the output value of power conditioner 20D maintains a predetermined value. This prevents the output value of power conditioner 20D from exceeding the predetermined value and allows the output of power conditioner 20C to be stopped. By stopping the output of power conditioner 20C, the number of PV power conditioners in operation can be reduced. Therefore, within the range where the output value of power conditioner 20D does not exceed the predetermined value, the output of power conditioner 20D can be maximized while minimizing the number of PV power conditioners in operation.

[0045] When there are n PV power conditioners (where n is an integer greater than or equal to 3), the ratio of the n PV power conditioners is adjusted so that the sum of the ratios of n-1 PV power conditioners is 100%, and the ratio of the other PV power conditioners is 0%. If the sum of the output values ​​of the n-1 PV power conditioners remains at a predetermined value, the output of the other PV power conditioners is stopped. This prevents the sum of the output values ​​of the n-1 PV power conditioners from exceeding the predetermined value, and also allows for the stopping of the output of the other PV power conditioners. By stopping the output of the other PV power conditioners, the number of PV power conditioners in operation can be reduced. Therefore, within the range where the sum of the output values ​​of n-1 PV power conditioners does not exceed a predetermined value, it is possible to maximize the output of n-1 PV power conditioners while minimizing the number of PV power conditioners in operation.

[0046] When there are two PV power conditioners, if a predetermined value is less than or equal to the rated output of one PV power conditioner, the ratio of the two PV power conditioners is adjusted so that the ratio of one PV power conditioner becomes 100% and the ratio of the other PV power conditioner becomes 0%. If the output value of one of the two PV power conditioners remains at a predetermined value (the limit value of the total output value of the two PV power conditioners), the output of the other PV power conditioner is stopped. This prevents the output value of one of the two PV power conditioners from exceeding the predetermined value, and also allows the output of the other PV power conditioner to be stopped. By stopping the output of the other PV power conditioner, the number of PV power conditioners in operation can be reduced. Therefore, within the range where the output value of one of the two PV power conditioners does not exceed the predetermined value, the output of one of the two PV power conditioners can be maximized while minimizing the number of PV power conditioners in operation.

[0047] A known mounting method called "oversizing" involves mounting solar cells capable of outputting more than the rated capacity of a PV power conditioner onto the PV power conditioner to improve power generation during periods of low solar radiation. When solar radiation increases sharply, the input power to the PV power conditioner increases instantaneously, causing the PV power conditioner's output to temporarily exceed the output command value. In the case of oversizing, the more PV power conditioners are in operation, the greater the increase in input power to the PV power conditioner tends to be. Therefore, it is expected that the amount by which the PV power conditioner's output temporarily exceeds a predetermined value will increase due to the excessive output of the PV power conditioner. In this embodiment, it is possible to maximize the total output of multiple PV power conditioners while minimizing the number of PV power conditioners in operation, within the range where the total output value of multiple PV power conditioners does not exceed a predetermined value. Therefore, even in the case of overloading, by minimizing the number of operating PV power conditioners, it is possible to suppress the increase in the amount of power input to the PV power conditioners, and to suppress the amount by which the total output value of the PV power conditioners exceeds a predetermined value.

[0048] Furthermore, each of the processes described above may be considered as a control method for the distributed power system 1, etc. Each of the processes described above may also be considered as a method to be executed by a computer. A program to cause the 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 holds data non-temporarily. Note that each of the above means and processes can be combined with each other as much as possible to constitute the present invention.

[0049] <Note> A distributed power supply system (1) comprising multiple power conditioners (10C, 10D) that convert DC power input from solar cells (7C, 7D) that generate DC power into AC power and supply it to loads (2, 3, 8), Based on the ratio to a predetermined value set for each of the aforementioned power conditioners, the output of the aforementioned power conditioners is performed. A distributed power supply system characterized by adjusting the ratio such that the sum of the output values ​​of the plurality of power conditioners maintains the predetermined value. [Explanation of Symbols]

[0050] 1. Distributed power systems 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 conditioners 21.. Controller

Claims

1. A distributed power supply system comprising multiple power conditioners that convert DC power input from solar cells that generate DC power into AC power and supply it to a load, Based on the ratio to a predetermined value set for each of the aforementioned power conditioners, the output of the aforementioned power conditioners is performed. Based on the aforementioned ratio, the upper limit of the output command value for each of the multiple power conditioners is determined. A distributed power supply system characterized by adjusting the ratio such that the sum of the output values ​​of the plurality of power conditioners maintains the predetermined value.

2. The distributed power supply system according to claim 1, characterized in that the predetermined value is a limit value for the total sum of the output values ​​of the plurality of power conditioners.

3. The distributed power supply system according to claim 1 or 2, characterized in that the output value is a power value or a current value.

4. The distributed power supply system according to any one of claims 1 to 3, characterized in that adjusting the ratio includes increasing the ratio and decreasing the ratio.

5. The number of the aforementioned power conditioners is n (where n is an integer of 3 or more), A distributed power supply system according to any one of claims 1 to 4, characterized in that when the ratios are adjusted so that the sum of the ratios of n-1 power conditioners out of n units is 100%, and the ratio of the power conditioners other than the n-1 unit out of n units is 0%, the total output value of the n-1 power conditioners remains at the predetermined value, the output of the power conditioners other than the n-1 unit is stopped.

6. The number of the aforementioned power conditioners is 2, When the ratio is adjusted so that the ratio of one of the two power conditioners becomes 100% and the ratio of the other of the two power conditioners becomes 0%, the output value of one of the two power conditioners maintains the predetermined value. A distributed power supply system according to any one of claims 1 to 4, characterized in that the output of the other of the two power conditioners is stopped.

7. The distributed power supply system according to any one of claims 1 to 6, characterized in that the plurality of power conditioners perform maximum power point tracking control to produce an output.

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