Photovoltaic power generation system and control device

Abstract

Provided is a photovoltaic power generation system (2) comprising: a plurality of solar battery panels (4); a plurality of power conversion devices (6) that convert DC power supplied from the plurality of solar battery panels (4) into AC power adapted to a power system (PS); and a control device (10) that controls operation of the plurality of power conversion devices (6). The control device (10) includes a total output value computation unit (20) for computing a total effective power value representing the magnitude of effective power that can be currently output from all of the plurality of power conversion devices (6), a difference computation unit (22) for computing a first difference between an upper-limit total command value and the total effective power value, and an upper-limit command value computation unit (24) for computing, on the basis of the first difference and the effective power value of each of the plurality of power conversion devices (6), an individual upper-limit command value representing the upper limit of effective power output individually from each of the plurality of power conversion devices (6). Through the above, provided are the photovoltaic power generation system (2) and control device (10) that are capable of suppressing excessive lowering of the total value of the effective power of AC power to be supplied from the plurality of power conversion devices (6) to the power system (PS).

Description

Photovoltaic power generation system and control device

[0001] FIELD An embodiment of the present invention relates to a solar power generation system and a control device.

[0002] A known photovoltaic power generation system includes multiple solar cell panels, multiple power conversion devices, and a control device. The multiple power conversion devices are provided corresponding to the multiple solar cell panels, respectively. Each power conversion device is connected to a corresponding solar cell panel and also to a power grid. Each power conversion device converts DC power supplied from the corresponding solar cell panel into AC power compatible with the power grid and supplies the converted AC power to the power grid. The control device controls the power conversion operations of the multiple power conversion devices.

[0003] In a solar power generation system, an upper limit of the active power that can be output to the power grid is determined in advance to suppress fluctuations in the frequency and voltage of the power grid. The control device controls the operation of the multiple power conversion devices so that the total value of the active power of the AC power output from the multiple power conversion devices does not exceed the upper limit.

[0004] The control device calculates individual upper limits for each of the power conversion devices by dividing the upper limit for the active power of the entire system by the number of the power conversion devices, and sets the active power of the AC power of each of the power conversion devices to be equal to or less than the individual upper limit, thereby making it possible to set the total value of the active power of the AC power output from the power conversion devices to be equal to or less than the upper limit for the active power of the entire system.

[0005] However, when individual upper limit values ​​are set for each of the multiple power conversion devices as described above, for example, if an upper limit value lower than the rated output of the system is set and there is a bias in the solar radiation of the multiple solar cell panels, the total value of the active power of the AC power supplied from the multiple power conversion devices to the power grid may be suppressed more than necessary.

[0006] For example, suppose there are two power conversion devices and the upper limit of the active power of the entire system is 10 kW. In this case, in the above calculation method, the individual upper limit is set to 5 kW. If the output active power of one power conversion device is 6 kW and the output active power of the other power conversion device is 4 kW, even though the entire system is capable of outputting 10 kW of active power, the active power of one power conversion device is limited from 6 kW to 5 kW by its individual upper limit, so that only a total of 9 kW of active power is output to the power grid.

[0007] In this way, when individual upper limits are calculated as described above, the total value of the active power of AC power supplied from multiple power conversion devices to the power grid may be suppressed more than necessary. For example, generated power may be wasted. Furthermore, for solar power generation system operators, this may lead to a decrease in revenue from selling electricity.

[0008] For this reason, it is desirable that a solar power generation system and a control device used therein be able to prevent the total value of the active power of the AC power supplied from multiple power conversion devices to the power grid from being reduced more than necessary.

[0009] Japanese Patent Application Laid-Open No. 2013-207862

[0010] An embodiment of the present invention provides a photovoltaic power generation system and a control device that can prevent the total value of active power of AC power supplied from a plurality of power conversion devices to a power grid from being suppressed more than necessary.

[0011] According to an embodiment of the present invention, a power conversion system includes a plurality of solar cell panels, a plurality of power conversion devices provided corresponding to the plurality of solar cell panels, each converting DC power supplied from the plurality of solar cell panels into AC power compatible with a power grid and supplying the converted AC power to the power grid, and a control device controlling power conversion operations of the plurality of power conversion devices, wherein the control device includes an output total value calculation unit that receives an input of an active power value representing the magnitude of active power that can currently be output from each of the plurality of power conversion devices and adds up the active power values ​​of the plurality of power conversion devices to calculate a total active power value representing the magnitude of active power that can currently be output from all of the plurality of power conversion devices, and a total upper limit command value that receives an input of the active power total value and also receives an input of a total upper limit command value representing the upper limit of active power to be output from all of the plurality of power conversion devices, and calculates a total upper limit command value and a total active power total value. and an upper limit command value calculation unit that receives an input of the first difference and also receives an input of the active power value of each of the plurality of power conversion devices, and calculates an individual upper limit command value that represents an upper limit of active power to be individually output from each of the plurality of power conversion devices, based on the active power value of each of the plurality of power conversion devices and the first difference, wherein the upper limit command value calculation unit calculates a second difference by dividing the first difference by the number of power conversion devices for which a difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than a first reference value, and calculates new individual upper limit command values ​​for the power conversion devices that are equal to or less than the first reference value, by adding the calculated second difference to the current individual upper limit command values ​​for the power conversion devices for which a difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than the first reference value.

[0012] According to an embodiment of the present invention, a solar power generation system and a control device are provided that can prevent the total value of active power of AC power supplied from multiple power conversion devices to a power grid from being reduced more than necessary.

[0013] 1 is a block diagram schematically showing a solar power generation system according to an embodiment; FIG. 2 is a block diagram schematically showing a control device according to an embodiment; FIG. 3 is a flowchart schematically showing an example of the operation of the control device according to an embodiment; FIG. 4 is a graph schematically showing an example of the operation of a reference control device;

[0014] Each embodiment will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc., are not necessarily the same as those in reality. Even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0015] Fig. 1 is a block diagram schematically illustrating a solar power generation system according to an embodiment. As illustrated in Fig. 1, the solar power generation system 2 includes a plurality of solar cell panels 4, a plurality of power conversion devices 6, and a control device 10. The plurality of solar cell panels 4 convert light energy into electrical energy by photoelectric conversion, thereby supplying DC power.

[0016] The multiple power conversion devices 6 are provided corresponding to the multiple solar cell panels 4, respectively. The number of the multiple power conversion devices 6 is, for example, the same as the number of the multiple solar cell panels 4. The multiple power conversion devices 6 are connected to the multiple solar cell panels 4, respectively. However, multiple solar cell panels 4 may be connected to one power conversion device 6. The number of the multiple power conversion devices 6 does not necessarily have to be the same as the number of the multiple solar cell panels 4.

[0017] The solar power generation system 2 further includes, for example, a plurality of transformers 12 and a transformer 14. The plurality of transformers 12 are provided corresponding to the plurality of power conversion devices 6, respectively. The plurality of power conversion devices 6 are connected to the primary sides of the plurality of transformers 12. The secondary sides of the plurality of transformers 12 are connected to the primary side of the transformer 14. The secondary side of the transformer 14 is connected to the power system PS. The plurality of power conversion devices 6 are connected to the power system PS via the transformers 12, 14, etc. A circuit breaker, more transformers, etc. may be provided between the power conversion devices 6 and the power system PS. The configuration between the power conversion devices 6 and the power system PS may be any configuration that allows the power conversion devices 6 to be connected to the power system PS.

[0018] The power of the power system PS is AC power. The power of the power system PS is, for example, three-phase AC power. However, the power of the power system PS may be single-phase AC power or the like.

[0019] The plurality of power conversion devices 6 converts DC power supplied from the plurality of solar cell panels 4 into AC power compatible with the power grid PS, and supplies the converted AC power to the power grid PS. The plurality of power conversion devices 6 each have, for example, a plurality of switching elements, and perform power conversion by switching the plurality of switching elements.

[0020] The control device 10 controls the power conversion operations of the multiple power conversion devices 6. In this way, the photovoltaic power generation system 2 supplies the power generated by the multiple solar cell panels 4 to the power grid PS. The control device 10 may also be called, for example, a PPC (Power Plant Controller).

[0021] The photovoltaic power generation system 2 further includes, for example, a measuring device 16. The measuring device 16 detects, for example, active power values, reactive power values, and voltage values ​​at interconnection points between the plurality of power conversion devices 6 and the power grid PS, and inputs the detected active power values, reactive power values, and voltage values ​​to the control device 10.

[0022] 2 is a block diagram illustrating a control device according to an embodiment. As illustrated in FIG. 2, the control device 10 includes an output sum calculation unit 20, a difference calculation unit 22, and an upper limit command value calculation unit 24.

[0023] The output total value calculation unit 20 receives an input of an active power value B2 representing the magnitude of active power that can currently be output from each of the multiple power electronics devices 6. The control device 10 receives the input of the active power value B2 from each of the multiple power electronics devices 6, for example, by communicating with each of the multiple power electronics devices 6. The multiple active power values ​​B2 of each of the multiple power electronics devices 6 may be input to the control device 10 from, for example, a higher-level controller. The method of inputting the multiple active power values ​​B2 to the control device 10 is not limited to the above, and any method that can appropriately input the multiple active power values ​​B2 to the control device 10 may be used.

[0024] The output total value calculation unit 20 calculates the total active power value B1 representing the magnitude of the active power that can currently be output from all of the multiple power conversion devices 6 by adding up the active power values ​​B2 of each of the multiple power conversion devices 6.

[0025] More specifically, when the number of the plurality of power electronics devices 6 is N, the active power value B2 of the first power electronics device 6 is B2a, the active power value B2 of the second power electronics device 6 is B2b, and the active power value B2 of the Nth power electronics device 6 is B2n, the total output value calculation unit 20 calculates the total active power value B1 by the formula B1 = B2a + B2b + ... + B2n. In other words, the total active power value B1 is the sum of the active power values ​​B2 of the plurality of power electronics devices 6. The total output value calculation unit 20 inputs the calculated total active power value B1 to the difference calculation unit 22.

[0026] The difference calculation unit 22 receives an input of the active power total value B1 from the output total value calculation unit 20, and also receives an input of a total upper limit command value A1 that represents the upper limit of the active power output from all of the multiple power conversion devices 6. In other words, the total upper limit command value A1 is a command value that represents the upper limit of the active power supplied from the photovoltaic power generation system 2 to the power grid PS. The total upper limit command value A1 is input to the control device 10 from, for example, a higher-level controller. The total upper limit command value A1 may be input to the control device 10 based on the operation of, for example, an administrator of the photovoltaic power generation system 2. The total upper limit command value A1 may be, for example, a predetermined constant value. The method of inputting the total upper limit command value A1 to the control device 10 is not limited to the above, and any method that can appropriately input the total upper limit command value A1 to the control device 10 may be used.

[0027] The difference calculation unit 22 calculates a first difference C1 between the total upper limit command value A1 and the total active power value B1 by subtracting the total active power value B1 from the input total upper limit command value A1. That is, the difference calculation unit 22 calculates the first difference C1 using the formula C1=A1-B1. The difference calculation unit 22 inputs the calculated first difference C1 to the upper limit command value calculation unit 24.

[0028] The upper limit command value calculation unit 24 receives an input of the second difference C2 from the difference calculation unit 22, and also receives an input of the active power values ​​B2 of each of the plurality of power electronics devices 6. Similar to the case of the total output value calculation unit 20, the plurality of active power values ​​B2 are input to the upper limit command value calculation unit 24 from the plurality of power electronics devices 6, etc. The upper limit command value calculation unit 24 calculates an individual upper limit command value A2 representing the upper limit of the active power to be individually output from each of the plurality of power electronics devices 6, based on the input second difference C2 and each active power value B2.

[0029] The control device 10 calculates a plurality of individual upper limit command values ​​A2 corresponding to the plurality of power electronics devices 6, respectively, and then controls the operation of each of the plurality of power electronics devices 6 so that the active power output from each of the plurality of power electronics devices 6 does not exceed the corresponding individual upper limit command value A2. This allows the photovoltaic power generation system 2 to supply an appropriate amount of active power according to the total upper limit command value A1 to the power grid PS.

[0030] The control device 10 controls the operation of each of the multiple power conversion devices 6, for example, by inputting each of the multiple calculated individual upper limit command values ​​A2 to each of the multiple corresponding power conversion devices 6, so that the active power output from each of the multiple power conversion devices 6 does not exceed the corresponding individual upper limit command value A2.

[0031] Without being limited to this, the control device 10 may, for example, generate a control signal according to the individual upper limit command value A2 and input the control signal to the power electronics device 6, thereby controlling the operation of each of the multiple power electronics devices 6 so that the active power output from each of the multiple power electronics devices 6 does not exceed the corresponding individual upper limit command value A2. The control device 10 may input the individual upper limit command value A2 directly to the power electronics device 6, or may input another control signal according to the individual upper limit command value A2 to the power electronics device 6.

[0032] Fig. 3 is a flowchart schematically illustrating an example of the operation of the control device according to the embodiment. Fig. 4 is a graph schematically illustrating an example of the operation of the control device according to the embodiment. Fig. 3 schematically illustrates an example of the operation of the upper limit command value calculation unit 24 to calculate a plurality of individual upper limit command values ​​A2. Fig. 4 is a bar graph illustrating the active power value B2 of the first power electronics device 6 (PCS1), the active power value B2 of the second power electronics device 6 (PCS2), and the active power value B2 of the third power electronics device 6 (PCS3).

[0033] When calculating multiple individual upper limit command values ​​A2, the upper limit command value calculation unit 24 first calculates a second difference C2 by dividing the first difference C1 by the number of power conversion devices 6 for which the difference obtained by subtracting the current active power value B2 from the current individual upper limit command value A2 is less than or equal to the first reference value (step S101 in Figure 3).

[0034] The first reference value is set to zero, for example. In this case, a power electronics device 6 for which the difference obtained by subtracting the current active power value B2 from the individual upper limit command value A2 is equal to or less than the first reference value is a power electronics device 6 for which the current active power value B2 is equal to or greater than the individual upper limit command value A2. For example, in the example shown in Fig. 4, PCS1 and PCS2 correspond to the power electronics devices 6 for which the difference is equal to or less than the first reference value. In this case, the upper limit command value calculation unit 24 calculates the second difference C2 by dividing the first difference C1 by "2", which corresponds to the number of PCS1 and PCS2.

[0035] 4 illustrates a state in which the initial value of the individual upper limit command value A2 is set as the current individual upper limit command value A2. The initial values ​​of the multiple individual upper limit command values ​​A2 are set, for example, to a value obtained by dividing the total upper limit command value A1 by the number of the multiple power electronics devices 6. The initial value of the individual upper limit command value A2 is set, for example, when the photovoltaic power generation system 2 starts operating or when a predetermined setting operation is performed.

[0036] The first reference value is not limited to zero and may be any value. For example, the first reference value may be set to a positive value so that it is possible to detect that the current active power value B2 is slightly smaller than the current individual upper limit command value A2, or may be set to a negative value so that it is possible to detect that the current active power value B2 is larger than the current individual upper limit command value A2. However, it is more preferable to set the first reference value so that it is possible to detect that the current active power value B2 is equal to or larger than the current individual upper limit command value A2.

[0037] After calculating the second difference C2, the upper limit command value calculation unit 24 calculates a new individual upper limit command value A2 for the power conversion device 6 whose difference, obtained by subtracting the current active power value B2 from the current individual upper limit command value A2, is equal to or less than the first reference value by adding the calculated second difference C2 to the current individual upper limit command value A2 for the power conversion device 6 whose difference is equal to or less than the first reference value (step S102 in Figure 3).

[0038] For example, in the example shown in Figure 4, the upper limit command value calculation unit 24 calculates new individual upper limit command values ​​A2 for PCS1 and PCS2 by adding the second difference C2 to the current individual upper limit command values ​​A2 for PCS1 and PCS2.

[0039] The upper limit command value calculation unit 24 calculates a new individual upper limit command value A2 for the power conversion device 6 whose difference is less than or equal to the first reference value, and then calculates the total active power value B3 for the power conversion device 6 whose difference, obtained by subtracting the current active power value B2 from the current individual upper limit command value A2, is greater than the first reference value (step S103 in Figure 3).

[0040] 4, only PCS3 corresponds to the power electronics device 6 whose difference is larger than the first reference value. In this case, the total active power value B3 is the same as the current active power value B2 of PCS3. In other words, the power electronics device 6 whose difference is larger than the first reference value is the power electronics device 6 whose current active power value B2 is smaller than the current individual upper limit command value A2.

[0041] After calculating the total active power value B3, the upper limit command value calculation unit 24 does not change the individual upper limit command value A2 for any power electronics device 6 for which the difference obtained by subtracting the current active power value B2 from the current individual upper limit command value A2 is greater than the first reference value and for which the difference obtained by subtracting the current active power value B2 from the total active power value B3 is equal to or less than the second reference value (step S104 in FIG. 3). For example, the upper limit command value calculation unit 24 does not change the individual upper limit command value A2 for PCS3.

[0042] On the other hand, for the power conversion devices 6 for which the difference obtained by subtracting the current active power value B2 from the current individual upper limit command value A2 is greater than the first reference value, and for which the difference obtained by subtracting the current active power value B2 from the total active power value B3 is greater than the second reference value, the upper limit command value calculation unit 24 sets the individual upper limit command value A2 as the output command value of the interconnection point (step S105 in Figure 3).

[0043] The output command value at the interconnection point is, for example, a value obtained by dividing the total upper limit command value A1 by the number of the plurality of power electronics devices 6. In other words, the output command value at the interconnection point is the initial value of the individual upper limit command value A2. For example, when the current active power value B2 is smaller than the total active power value B3 by equal to or greater than the second reference value, the upper limit command value calculation unit 24 returns the individual upper limit command value A2 to its initial value. This makes it possible to prevent, for example, an excessively high individual upper limit command value A2 from being set for a power electronics device 6 with a small current active power value B2.

[0044] For example, the control device 10 acquires the active power values ​​B2 of the multiple power electronics devices 6, acquires the total upper limit command value A1, and calculates the first difference C1 for each predetermined control period. Then, the upper limit command value calculation unit 24 performs the processes of steps S101 to S105 for each predetermined control period, thereby calculating multiple individual upper limit command values ​​A2 for each predetermined control period. This allows the total active power value B1 to approach the total upper limit command value A1.

[0045] Note that steps S104 and S105 can be interchanged. That is, step S104 may be performed after step S105. Also, steps S101 and S102 may be performed after steps S103 to S105.

[0046] Fig. 5 is a graph schematically illustrating an example of the operation of the reference control device. Similar to Fig. 4, Fig. 5 is a bar graph illustrating the active power value B2 of the first power electronics device 6 (PCS1), the active power value B2 of the second power electronics device 6 (PCS2), and the active power value B2 of the third power electronics device 6 (PCS3).

[0047] Figure 5 shows a schematic example of the operation of a reference control device when a common upper limit command value A0 is set for multiple power conversion devices 6 by dividing the total upper limit command value A1 by the number N of multiple power conversion devices 6.

[0048] In the example shown in Fig. 5, the output of PCS1 is limited to the upper limit command value A0. On the other hand, in the example shown in Fig. 5, the output of PCS3 is lower than the upper limit command value A0. Therefore, in the example shown in Fig. 5, for example, the output of the entire system becomes lower than the total upper limit command value A1 by the amount of the difference between the upper limit command value A0 and the active power value B2 of PCS3. In the example shown in Fig. 5, even though there is a margin in the output of PCS1, the output of the entire system becomes lower than the total upper limit command value A1.

[0049] In this way, when a common upper limit command value A0 is set for multiple power conversion devices 6, a total upper limit command value A1 that is lower than the rated output (maximum active power that can be output) of the solar power generation system 2 is set, and if there is a bias in the solar radiation of the multiple solar cell panels 4, the total value of the active power of the AC power supplied from the multiple power conversion devices 6 to the power system PS may be suppressed more than necessary.

[0050] In contrast, the control device 10 of the solar power generation system 2 according to this embodiment calculates the second difference C2 by dividing the first difference C1 by the number of power conversion devices 6 for which the difference obtained by subtracting the current active power value B2 from the current individual upper limit command value A2 is less than or equal to the first reference value, and calculates a new individual upper limit command value A2 by adding the calculated second difference C2 to the current individual upper limit command value A2 of the power conversion devices 6 for which the difference obtained by subtracting the current active power value B2 from the current individual upper limit command value A2 is less than or equal to the first reference value.

[0051] 4 , even when there is a bias in the active power values ​​B2 of the plurality of power electronics devices 6, it is possible to set an individual upper limit command value A2 of an appropriate magnitude according to each active power value B2 for each of the plurality of power electronics devices 6. In other words, it is possible to appropriately allocate the total upper limit command value A1 to each of the plurality of power electronics devices 6.

[0052] Therefore, even when a total upper limit command value A1 lower than the rated output of the solar power generation system 2 is set and there is a bias in the solar radiation of the multiple solar cell panels 4, the total value of the active power of the AC power supplied from the multiple power conversion devices 6 to the power system PS can be prevented from being suppressed more than necessary.

[0053] For example, compared to when a common upper limit command value A0 is set for multiple power electronics devices 6, the total active power value (total active power value B1) of the AC power supplied from multiple power electronics devices 6 to the power grid PS can be brought closer to the total upper limit command value A1. This makes it possible to, for example, reduce wasted power generation. Furthermore, for example, for the operator of the solar power generation system 2, it is possible to prevent a decrease in revenue from selling electricity.

[0054] In the above embodiment, among the power conversion devices 6 for which the difference obtained by subtracting the current active power value B2 from the current individual upper limit command value A2 is greater than the first reference value, the individual upper limit command value A2 is not changed for the power conversion devices 6 for which the difference obtained by subtracting the current active power value B2 from the total active power value B3 is equal to or less than the second reference value, and the individual upper limit command value A2 is set as the output command value of the interconnection point for the power conversion devices 6 for which the difference obtained by subtracting the current active power value B2 from the total active power value B3 is greater than the second reference value.

[0055] Without being limited to this, for example, for a power conversion device 6 where the difference obtained by subtracting the current active power value B2 from the current individual upper limit command value A2 is greater than the first reference value, it is possible not to change all of the individual upper limit command values ​​A2 of the corresponding power conversion device 6.

[0056] This embodiment includes the following aspects: (Supplementary Note 1) A power conversion system includes: a plurality of solar cell panels; a plurality of power conversion devices provided corresponding to the plurality of solar cell panels, each converting DC power supplied from the plurality of solar cell panels into AC power compatible with a power grid and supplying the converted AC power to the power grid; and a control device controlling the power conversion operations of the plurality of power conversion devices, wherein the control device comprises: an output total value calculation unit that receives an input of an active power value representing the magnitude of active power that can currently be output from each of the plurality of power conversion devices and calculates a total active power value representing the magnitude of active power that can currently be output from all of the plurality of power conversion devices by adding up the active power values ​​of each of the plurality of power conversion devices; a difference calculation unit that receives an input of the active power total value and also receives an input of a total upper limit command value representing an upper limit of active power to be output from all of the plurality of power conversion devices and calculates a first difference between the total upper limit command value and the total active power value; an upper limit command value calculation unit that receives an input of the first difference and an input of the active power value of each of the plurality of power electronics devices, and calculates an individual upper limit command value that represents an upper limit of active power to be individually output from each of the plurality of power electronics devices, based on the active power value of each of the plurality of power electronics devices and the first difference, wherein the upper limit command value calculation unit calculates a second difference by dividing the first difference by the number of power electronics devices for which a difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than a first reference value, and calculates new individual upper limit command values ​​for the power electronics devices that are equal to or less than the first reference value, by adding the calculated second difference to the current individual upper limit command values ​​for the power electronics devices for which a difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than the first reference value.

[0057] (Supplementary Note 2) In the solar power generation system according to Supplementary Note 1, the upper limit command value calculation unit calculates a total active power value of the power electronics devices for which the difference obtained by subtracting the current active power value from the current individual upper limit command value is greater than the first reference value, and does not change the individual upper limit command value for the power electronics devices for which the difference obtained by subtracting the current active power value from the total active power value is equal to or less than a second reference value, among the power electronics devices for which the difference is greater than the first reference value.

[0058] (Supplementary Note 3) In the photovoltaic power generation system according to Supplementary Note 2, the upper limit command value calculation unit sets the individual upper limit command value as the output command value of the interconnection point for a power conversion device whose difference obtained by subtracting the current active power value from the total active power value is greater than the second reference value, among the power conversion devices whose active power value is greater than the first reference value.

[0059] (Supplementary Note 4) A control device for controlling power conversion operations of a plurality of power conversion devices provided corresponding to a plurality of solar cell panels, the control device converting DC power supplied from the plurality of solar cell panels into AC power compatible with a power grid and supplying the converted AC power to the power grid, the control device comprising: an output total value calculation unit that receives an input of an active power value representing a magnitude of active power that can currently be output from each of the plurality of power conversion devices, and calculates a total active power value representing the magnitude of active power that can currently be output from all of the plurality of power conversion devices by adding up the active power values ​​of each of the plurality of power conversion devices; a difference calculation unit that receives an input of the active power total value and a total upper limit command value representing an upper limit of active power to be output from all of the plurality of power conversion devices, and calculates a first difference between the total upper limit command value and the active power total value; and an upper limit command value calculation unit that receives an input of the first difference and an active power value of each of the plurality of power conversion devices, and calculates an individual upper limit command value representing an upper limit of active power to be individually output from each of the plurality of power conversion devices, based on the active power value of each of the plurality of power conversion devices and the first difference, The upper limit command value calculation unit calculates a second difference by dividing the first difference by the number of power electronics devices for which the difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than a first reference value, and calculates new individual upper limit command values ​​for the power electronics devices for which the difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than the first reference value by adding the calculated second difference to the current individual upper limit command values ​​for the power electronics devices for which the difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than the first reference value.

[0060] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0061] 2... Photovoltaic power generation system, 4... Solar cell panel, 6... Power conversion device, 10... Control device, 12, 14... Transformer, 20... Output total value calculation unit, 22... Difference calculation unit, 24... Upper limit command value calculation unit

Claims

1. A power supply system comprising: a plurality of solar panels; a plurality of power conversion devices provided corresponding to the plurality of solar panels, converting DC power supplied from the plurality of solar panels into AC power compatible with a power grid and supplying the converted AC power to the power grid; and a control device controlling power conversion operations of the plurality of power conversion devices, wherein the control device comprises: an output total value calculation unit that receives an input of an active power value representing the magnitude of active power that can currently be output from each of the plurality of power conversion devices, and calculates an active power total value representing the magnitude of active power that can currently be output from all of the plurality of power conversion devices by adding up the active power values ​​of the plurality of power conversion devices; a difference calculation unit that receives an input of the active power total value and also receives an input of a total upper limit command value representing an upper limit of active power to be output from all of the plurality of power conversion devices, and calculates a first difference between the total upper limit command value and the active power total value; and an upper limit command value calculation unit that receives an input of the first difference and an input of the active power value of each of the multiple power conversion devices, and calculates an individual upper limit command value that represents an upper limit of active power to be individually output from each of the multiple power conversion devices based on the active power value of each of the multiple power conversion devices and the first difference, wherein the upper limit command value calculation unit calculates a second difference by dividing the first difference by the number of the power conversion devices for which a difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than a first reference value, and calculates new individual upper limit command values ​​for the power conversion devices that are equal to or less than the first reference value by adding the calculated second difference to the current individual upper limit command values ​​of the power conversion devices for which a difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than the first reference value.

2. The upper limit command value calculation unit calculates the total active power value of the power conversion devices for which the difference obtained by subtracting the current active power value from the current individual upper limit command value is greater than the first reference value, and for the power conversion devices for which the difference obtained by subtracting the current active power value from the total active power value is equal to or less than a second reference value, among the power conversion devices for which the difference is greater than the first reference value, the individual upper limit command value is not changed.

3. A photovoltaic power generation system as described in claim 2, wherein the upper limit command value calculation unit sets the individual upper limit command value as the output command value of the interconnection point for the power conversion devices whose difference, obtained by subtracting the current active power value from the total active power value, is greater than the second reference value, among the power conversion devices whose difference is greater than the first reference value.

4. A control device for controlling power conversion operations of a plurality of power conversion devices provided corresponding to each of a plurality of solar panels, converting DC power supplied from the plurality of solar panels into AC power corresponding to a power grid and supplying the converted AC power to the power grid, comprising: an output total value calculation unit that receives an active power value representing a magnitude of active power that can currently be output from each of the plurality of power conversion devices and calculates an active power total value representing the magnitude of active power that can currently be output from all of the plurality of power conversion devices by adding up the active power values ​​of each of the plurality of power conversion devices; a difference calculation unit that receives an active power total value and a total upper limit command value representing an upper limit of active power to be output from all of the plurality of power conversion devices and calculates a first difference between the total upper limit command value and the active power total value; and an upper limit command value calculation unit that receives an input of the first difference and receives an active power value of each of the plurality of power conversion devices and calculates an individual upper limit command value representing an upper limit of active power to be individually output from each of the plurality of power conversion devices based on the active power value of each of the plurality of power conversion devices and the first difference, The upper limit command value calculation unit calculates a second difference by dividing the first difference by the number of power electronics devices for which the difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than a first reference value, and calculates new individual upper limit command values ​​for the power electronics devices that are equal to or less than the first reference value by adding the calculated second difference to the current individual upper limit command values ​​of the power electronics devices for which the difference obtained by subtracting the current active power value from the current individual upper limit command value is equal to or less than the first reference value.

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