Control device for a power generation system, method for controlling a power generation system, and program

Abstract

To provide a power generation system control device capable of suppressing occurrence of a reverse power flow while improving the usage rate of renewable energy generation.SOLUTION: A power generation system control device including a power generation device and a power storage device, includes a power line to which the power generation device and the power storage device are connected, a power measuring unit that measures a reception point power which is delivered at a reception point for a power grid, a charge rate acquisition unit that acquires the charge rate of the power storage device, and a charging / discharging control unit that controls charging and discharging of the power storage device on the basis of the reception point power and the charge rate. In a case where the reception point power is lower than a prescribed first threshold, the charging / discharging control unit increases power for charging the storage device when the charge rate is lower than a control start threshold which represents a charge rate lower than the upper limit charge rate of the storage device, and the charging / discharging control unit restricts the charging power to be equal to or lower than a charging restriction value corresponding to the charge rate when the charge rate is equal to or greater than the control start threshold.SELECTED DRAWING: Figure 2

Description

Technical Field

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[0001] The present disclosure relates to a control device for a power generation system, a control method for a power generation system, and a program.

Background Art

[0002] In recent years, the introduction of renewable energy power generation has been progressing. Hereinafter, taking solar power generation (also referred to as photovoltaics; PV) as an example of renewable energy power generation, it will be described. When surplus power is generated by PV, in order to avoid reverse power flow to the power grid, output control such as stopping the output of PV is performed. As a result, although reverse power flow to the power grid is avoided, the utilization rate of PV decreases. Therefore, it has been considered to improve the utilization rate of PV by installing a power storage system using a storage battery (also referred to as a Battery Energy Storage System; BESS) and charging the surplus power of PV into the BESS and then discharging from the BESS to the load later. For example, in Patent Document 1, when the PV output (generated power) is larger than the power consumption of the load, if the charge rate of the BESS (State of Charge; hereinafter, also referred to as BESS-SOC or simply SOC) is below the upper threshold value, the surplus power of PV is charged into the storage battery, and when the BESS-SOC exceeds the upper threshold value, a method of performing output control of PV is described.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In conventional technology, PV output control is performed only after detecting that the BESS-SOC has reached its upper limit, that is, after the supply of surplus PV power to the BESS (charging) has stopped. As a result, there is a time lag between the cessation of the supply of surplus PV power to the BESS and the execution of PV output control, and during this period, there is a possibility that surplus PV power may temporarily flow back into the power grid.

[0005] The purpose of this disclosure is to provide a control device for a power generation system, a control method for a power generation system, and a program that can suppress the occurrence of reverse power flow while improving the utilization rate of renewable energy generation. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, the control device is a control device for a power generation system comprising a power generation device and an energy storage device, comprising: a power measurement unit that measures power received at a point of power reception with a power line to which the power generation device and the energy storage device are connected; a power rate acquisition unit that acquires the charge rate of the energy storage device; and a charge / discharge control unit that controls the charging and discharging of the energy storage device based on the power received at point of power and the charge rate, wherein the charge / discharge control unit increases the charging power to the energy storage device when the power received at point of power falls below a predetermined first threshold and the charge rate is below a control start threshold that indicates a charge rate lower than the upper limit of the charge rate of the energy storage device, and limits the charging power to a charge limit value corresponding to the charge rate when the charge rate is equal to or greater than the control start threshold.

[0007] According to one aspect of the present disclosure, a control method is a control method for a power generation system comprising a power generation device and a power storage device, comprising the steps of: measuring the power at which the power generation device and the power storage device are connected at a point of power reception between a power line and a power grid; acquiring the charge rate of the power storage device; and controlling the charging and discharging of the power storage device based on the power at which the power generation device and the power storage device are connected, wherein the charging and discharging step increases the charging power to the power storage device when the power at which the power generation device falls below a predetermined first threshold and the charge rate is below a control start threshold that indicates a charge rate lower than the upper limit of the charge rate of the power storage device, and limits the charging power to a charge limit value corresponding to the charge rate when the charge rate is equal to or greater than the control start threshold.

[0008] According to one aspect of the present disclosure, the program causes a control device of a power generation system comprising a power generator and a power storage device to perform the steps of: measuring the power at the point of power reception between the power line to which the power generator and the power storage device are connected and the power grid; acquiring the charge rate of the power storage device; and controlling the charging and discharging of the power storage device based on the power at the point of power reception and the charge rate, wherein the step of controlling the charging and discharging increases the charging power to the power storage device when the power at the point of power reception falls below a predetermined first threshold and the charge rate is below a control start threshold that indicates a charge rate lower than the upper limit of the charge rate of the power storage device; and limits the charging power to a charge limit value corresponding to the charge rate when the charge rate is equal to or greater than the control start threshold. [Effects of the Invention]

[0009] According to the above embodiment, it is possible to improve the utilization rate of renewable energy generation while suppressing the occurrence of reverse power flow. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing the overall configuration of a power generation system according to one embodiment. [Figure 2] This is a block diagram showing the functional configuration of a control device according to one embodiment. [Figure 3] This flowchart shows an example of processing by a control device according to one embodiment. [Figure 4] This figure shows a first example of the power at the point of power reception and the State of Charge (SOC) according to one embodiment. [Figure 5] This is a diagram illustrating the function of a limiter according to one embodiment. [Figure 6] This figure shows a second example of the power at the point of reception and the State of Charge (SOC) according to one embodiment. [Figure 7] This is the first figure illustrating the operation of a reverse power flow suppression process according to one embodiment. [Figure 8] This is a second figure illustrating the operation of a reverse power flow suppression process according to one embodiment. [Modes for carrying out the invention]

[0011] (Overall configuration of the power generation system) The embodiments will be described in detail below with reference to the drawings. Figure 1 is a schematic diagram showing the overall configuration of a power generation system according to one embodiment. As shown in Figure 1, the power generation system 1 comprises a control device 10, a PV20, a BESS30, and a load 40. The PV20, BESS30, and load 40 are connected via a power line L1. The power line L1 is connected to the power grid via a transformer. In addition, the control device 10, PV20, and BESS30 are connected to each other via a communication line L2 so that they can communicate with one another.

[0012] PV20 is one embodiment of the power generation device (renewable energy power generation device) in this embodiment, and is a power generation device that utilizes photovoltaic (PV) power generation. In other embodiments, the power generation system 1 may include other renewable energy power generation devices such as wind power generation devices instead of PV20.

[0013] PV20 outputs generated power to power line L1 via PCS (Power Conditioning System; power conditioner) 22 and PCS controller 23.

[0014] PCS22 converts the DC power generated by PV20 into AC power and outputs it to the power line L1 according to the control of the PCS controller 23.

[0015] The PCS controller 23 controls the power output from PV20 to the power line L1 according to the output command received from the control device 10 via the communication line L2.

[0016] BESS30 is a power storage device using the storage battery 31. BESS30 includes the storage battery 31, the PCS32, the PCS controller 33, and the BMS (Battery Management System) 34. It is assumed that the power generation system 1 according to the present embodiment has only one BESS30 for easy explanation. In other embodiments, the power generation system 1 may include a plurality of BESS30s.

[0017] PCS32 switches the charge and discharge of the storage battery 31 according to the control of the PCS controller 33. When charging, PCS32 converts the AC power supplied via the power line L1 into DC power and inputs it to the storage battery 31. When discharging, PCS32 converts the DC power discharged from the storage battery 31 into AC power and outputs it to the power line L1.

[0018] The PCS controller 33 controls PCS32 so that the power corresponding to the power command value received from the control device 10 via the communication line L2 is charged into the storage battery 31 or discharged from the storage battery 31.

[0019] BMS34 monitors the SOC (State of Charge [%]) of the storage battery 31 and transmits it to the control device 10.

[0020] The load 40 is electrical equipment etc., of the facility where PV20 and BESS30 are provided. The load 40 is supplied with the power purchased from the power grid, the power generated by PV20, or the power discharged by BESS30 through the power line L1.

[0021] The control device 10 controls the output of the PV20 and the charging and discharging of the BESS30.

[0022] (Functional configuration of the control unit) Figure 2 is a block diagram showing the functional configuration of a control device according to one embodiment. As shown in Figure 2, the control device 10 includes a processor 11, memory 12, storage 13, and a communication interface 14.

[0023] The processor 11 performs the functions of an instruction acquisition unit 110, a power measurement unit 111, a charge rate acquisition unit 112, and a control unit 113 by operating according to a predetermined program.

[0024] The instruction acquisition unit 110 acquires an output control instruction that instructs the limiting of the output of generated power to the power grid. The output control instruction is notified by the power company that manages the power grid. When the control device 10 acquires an output control instruction, it performs a "reverse power flow suppression process" to suppress the reverse power flow of surplus PV power for the period specified in the output control instruction. In addition, during periods when no output control instruction is given, the control device 10 may perform a "normal process" within the scope of the contract with the power company, such as selling surplus power from PV20 or purchasing power to supply to BESS30 and load 40. In this embodiment, the details of the reverse power flow suppression process will be mainly described.

[0025] The power measurement unit 111 measures the power at the point where power is transferred between the power line L1 and the power system (hereinafter also referred to as the power at the point of power transfer). As shown in the example in Figure 1, a power meter 2 is provided at the point of power transfer, and the power measurement unit 111 measures the power at the point of power transfer through the power meter 2.

[0026] The charge rate acquisition unit 112 acquires the State of Charge (SOC) of the BESS30 (storage battery 31) from the BMS34 of the BESS30 via the communication line L2.

[0027] The control unit 113 controls the output of the PV20 and the charging and discharging of the BESS30. The control unit 113 includes a charge / discharge control unit 1131 and an output control unit 1132.

[0028] The charge / discharge control unit 1131 controls the charging and discharging of the BESS 30 (storage battery 31) based on the power at the point of charge and the State of Charge (SOC). At this time, the charge / discharge control unit 1131 calculates a BESS power command value that instructs the charging power or discharging power of the BESS and transmits it to the PCS controller 33 of the BESS 30. The PCS controller 33 controls the charging and discharging of the storage battery 31 based on the BESS power command value.

[0029] The output control unit 1132 controls the output of PV20 based on the SOC and the power at the point of power reception. At this time, the output control unit 1132 sets an upper limit for PV output and transmits it to the PCS controller 23. The PCS controller 23 controls the output of PV20 so that it is less than or equal to the upper limit for PV output.

[0030] Memory 12 has a memory area necessary for the operation of the processor 11.

[0031] Storage 13 is a so-called auxiliary storage device, such as an HDD (Hard Disk Drive) or SSD (Solid State Drive).

[0032] The communication interface 14 is an interface for sending and receiving various types of information with external devices (such as PCS controllers 23, 33, and BMS 34).

[0033] The predetermined program executed by the processor 11 of the control device 10 is stored on a computer-readable recording medium. A computer-readable recording medium refers to a magnetic disk, magneto-optical disk, CD-ROM, DVD-ROM, semiconductor memory, etc. Alternatively, this computer program may be distributed to a computer via a communication line, and the computer that receives the distribution may execute the program. Furthermore, this program may be intended to implement only a part of the functions described above. Moreover, it may be a program that can implement the above functions in combination with a program already recorded in the computer system, a so-called differential file (differential program).

[0034] (Processing flow of the control unit) Figure 3 is a flowchart showing an example of the processing of a control device according to one embodiment. The following will explain in detail the flow of the reverse power flow suppression process of the control device 10, with reference to Figure 3.

[0035] First, the power measurement unit 111 measures the power PS at the point of power reception. Then, the charge rate acquisition unit 112 acquires the SOC of BESS30 (step S1).

[0036] Figure 4 shows a first example of the power at the point of power reception and the State of Charge (SOC) according to one embodiment. The graph shown in Figure 4 represents an example of the time series of the power supply point PS and the State of Charge (SOC) of BESS30.

[0037] The power at the point of power reception (PS) is defined as follows: a positive value (PS > 0) indicates that power is being supplied from the power grid (purchased power), while a negative value (PS < 0) indicates that reverse power flow to the power grid is occurring.

[0038] Furthermore, the State of Charge (SOC) fluctuates between the lower limit of the charge level V2 and the upper limit of the charge level V1. The BESS30 stops charging when the SOC rises to the upper limit of the charge level V1 and stops discharging when it falls to the lower limit of the charge level V2. The upper limit of the charge level V1 may be 100% and the lower limit of the charge level V2 may be 0%, or they may be values ​​with a margin (for example, upper limit of charge level V1 = 95% and lower limit of charge level V2 = 5%).

[0039] The control unit 113 determines whether there is a possibility of reverse power flow (PS < 0) based on the measured power at the point of reception PS. Specifically, the control unit 113 determines whether the power at the point of reception PS is less than the first threshold E (step S2). The first threshold E is pre-set to a value greater than 0 by a predetermined margin X (0 + X kW) in order to prevent reverse power flow (PS < 0).

[0040] If the power at the point of power PS is less than the first threshold E (step S2; YES), the control unit 113 further determines whether the SOC is less than the control start threshold V3 (step S3). The control start threshold V3 is a threshold used to determine whether it is possible for the BESS 30 to consume (charge) the surplus PV power or whether output control (output suppression) of the PV 20 is necessary in order to suppress reverse power flow of surplus PV power, and is set to a value lower than the upper limit of the charge rate V1 (for example, 90%).

[0041] If the SOC is less than the control start threshold V3 (step S4; YES), the control unit 113 performs the processing for mode No. 1 (step S4). Mode No. 1 is a mode in which surplus PV power is used to charge the BESS 30 to suppress reverse power flow, while the output control of PV20 is not performed (no limit is placed on the PV output power). Details of mode No. 1 will be described later.

[0042] Furthermore, if the SOC becomes equal to or greater than the control start threshold V3 (step S3; NO), the control unit 113 further determines whether the SOC is less than the upper limit of the charge level V1 (step S5).

[0043] If the State of Charge (SOC) is less than the upper limit of the charge level V1 (step S5; YES), the control unit 113 performs the processing of mode No. 2 (step S6). Mode No. 2 is a mode in which the output control of PV20 is started while gradually reducing the power charged to BESS30. Details of mode No. 2 will be described later.

[0044] On the other hand, when the State of Charge (SOC) reaches full charge (SOC = upper limit of charge rate V1) (step S5; NO), the control unit 113 performs the processing of mode No. 3 (step S7). The processing of mode No. 3 is a mode in which only the output control of PV20 is performed because charging of surplus PV power stops when BESS30 is fully charged. Details of mode No. 3 will be described later.

[0045] Returning to step S2, if the power at the point of power reception PS is greater than or equal to the first threshold E (step S2; NO), the control unit 113 determines whether the power at the point of power reception PS exceeds the second threshold F (step S8). The second threshold F is a threshold used to determine whether the power at the point of power reception is large enough to eliminate the risk of reverse power flow, and is set in advance to a value (X+YkW) that is larger than the first threshold E (XkW) by a predetermined margin Y.

[0046] If the power at the point of power reception does not exceed the second threshold F (step S8; NO), the control unit 113 continues processing in the current mode (step S9).

[0047] On the other hand, if the power at the point of power reception is greater than or equal to the second threshold F (step S8; YES), the control unit 113 further determines whether the PV output upper limit is less than the rated output power of PV20 (step S10).

[0048] If the PV output limit is less than the rated output power of PV20, that is, if the output of PV20 is suppressed (step S10; YES), the control unit 113 performs processing in mode No. 4 (step S11). Mode No. 4 is a mode that improves the utilization rate of PV20 because the risk of reverse power flow has been eliminated. Details of mode No. 4 will be described later.

[0049] Furthermore, if the PV output upper limit is the rated output power of PV20 (step S10; NO), the control unit 113 determines whether the SOC exceeds the lower limit of the charge rate V2 (step S12).

[0050] If the State of Charge (SOC) exceeds the lower limit of the charge level V2 (step S12; YES), the control unit 113 performs the processing for mode No. 5 (step S13). Mode No. 5 is a mode in which power is supplied (discharged) from BESS 30 to the load 40 to compensate for the decrease in PV power generation power. Details of mode No. 5 will be described later.

[0051] If the State of Charge (SOC) is less than or equal to the lower limit of the charge level V2 (step S12; NO), the control unit 113 performs the processing of mode No. 6 (step S14). Mode No. 6 is a mode in which the power supply (discharge) from BESS 30 to load 40 is stopped. Details of mode No. 6 will be described later.

[0052] (For details on each mode) The following provides details about modes No. 1 to No. 6 mentioned above.

[0053] (1) Mode No. 1 Mode No. 1 is a mode in which there is a possibility of reverse power flow, and the surplus PV power is used to charge BESS30, increasing the power at the point of reception PS, while the output of PV20 is not controlled.

[0054] For example, as shown in Figure 4, suppose that the PV power generation increases during the day, and in conjunction with this, the power at the point of reception PS (purchased power) gradually decreases. At time t1, the power at the point of reception falls below the first threshold E (step S2; YES), and the SOC at this time is below the control start threshold V3 (step S3; YES). In this case, the control unit 113 performs the processing of mode No. 1 (step S4). Specifically, the charge / discharge control unit 1131 of the control unit 113 calculates the BESS power command value new [kW] that specifies the charge / discharge power of BESS 30 using the following formula (1) and transmits it to BESS 30.

[0055] BESS power command value new = BESS power command value old - β···(1)

[0056] The BESS power command value old[kW] is the previous command value. β[kW] is a preset value. If the BESS power command value is negative, it becomes a charge command value; if it is positive, it becomes a discharge command value. Note that if the BESS power command value is 0, no charging or discharging is performed. In other words, the charge / discharge control unit 1131 calculates a BESS power command value that increases the power to charge BESS30 using the above equation (1). At this time, the charge / discharge control unit 1131 adjusts the BESS power command value using a limiter (Figure 5), which will be described later, so that the charge command value does not exceed the rated input power of BESS30.

[0057] The BESS30 (PCS controller 33 and PCS32) controls the charging of the storage battery 31 to power corresponding to the BESS power command value new received from the control device 10.

[0058] Furthermore, the output control unit 1132 does not perform PV output control at this time. In other words, the PV output upper limit remains at its initial value. The initial value is, for example, the rated output power of PV20.

[0059] In this way, in Mode No. 1, by increasing the power supplied to BESS30, the utilization rate of PV20 can be maximized while suppressing reverse power flow.

[0060] For example, as shown in Figure 4, suppose that at time t2 the power at the point of power PS falls below the first threshold E again, and the SOC at this time is below the control start threshold V3 (step S2; YES, step S3; YES). In this case, the control unit 113 performs the mode No. 1 process again (step S4). That is, the charge / discharge control unit 1131 further reduces the BESS power command value by βkW (increases the charge command value by βkW) according to equation (1) above. In this way, as shown in Figure 4, during periods when the power generated by PV20 gradually increases, such as during the daytime, the charge command value can be increased in stages as long as there is sufficient margin in the SOC of BESS30, thereby consuming the surplus PV power by charging BESS30 and suppressing reverse power flow.

[0061] (2) Mode No. 2 Mode No. 2 is a mode in which, as BESS30 approaches the upper charge level value V1, the power being charged is gradually reduced, and the upper output value of PV20 is lowered accordingly as needed.

[0062] For example, suppose that after time t1 in Figure 4, the power at the point of power PS temporarily increased due to the execution of Mode No. 1 described above, but the PV power generation power increased further (the power at the point of power PS decreased). In the example in Figure 4, at time t3, the power at the point of power PS is less than the first threshold E (step S2; YES), and the SOC is greater than or equal to the control start threshold V3 (step S3; NO) and less than the upper limit of the charge rate V1 (step S5; YES). In this case, the control unit 113 performs the processing of Mode No. 2 (step S6). Specifically, the charge / discharge control unit 1131 and the output control unit 1132 of the control unit 113 perform the processing described below.

[0063] First, the charge / discharge control unit 1131 calculates a BESS power command value new[kW] that specifies the charge / discharge power of BESS30 using the following formula (2) and transmits it to BESS30.

[0064] BESS power command value new = BESS power command value old...(2)

[0065] According to equation (2), the charge / discharge control unit 1131 maintains the current BESS power command value. However, the charge / discharge control unit 1131 inputs the calculated BESS power command value new and SOC to the limiter (Figure 5) and adjusts the BESS power command value new so that the charge command value decreases in proportion to the increase in SOC.

[0066] Figure 5 is a diagram illustrating the function of a limiter according to one embodiment. As shown in Figure 5, the limiter imposes a restriction that reduces the charge command value [kW] as the SOC increases. When the SOC is less than the control start threshold V3, the limiter sets the upper limit of the charge command value (hereinafter also referred to as the charge limit value) to the rated input power of the BESS. Furthermore, when the SOC is in the range from the control start threshold V3 to the charge rate upper limit V1, the limiter gradually reduces the charge limit value so that the charge limit value becomes 0 [kW] when the charge rate upper limit V1 is reached.

[0067] For example, suppose the BESS power command value new is -10kW. If the charge limit value corresponding to the SOC is -10kW, the limiter will output the BESS power command value new(-10kW) as is, because the charge command value ≤ charge limit value. On the other hand, if the charge limit value corresponding to the SOC is -8kW, the charge command value > charge limit value, so the limiter will output the BESS power command value new(-8kW) which has been rewritten to the charge limit value.

[0068] In Mode No. 2, the charge / discharge control unit 1131 continuously monitors the State of Charge (SOC) and updates the BESS power command value using the limiter. As a result, during the period when the SOC is above the control start threshold V3 and below the charge rate upper limit V1, the power charged to the BESS 30 gradually decreases in proportion to the increase in SOC.

[0069] Furthermore, as the charging power of BESS30 gradually decreases, the power at the charging point PS also decreases slowly. Accordingly, the output control unit 1132 performs PV output control to suppress reverse power flow.

[0070] PV output control is a control mechanism that reduces the PV output upper limit when the power at the point of reception PS falls below a first threshold E, and increases the PV output upper limit when the power at the point of reception PS exceeds a second threshold F. In other embodiments, different threshold values ​​for PV output control may be set instead of the first threshold E and the second threshold F.

[0071] In mode No. 2, the output control unit 1132 lowers the PV output upper limit because the power at the point of reception PS falls below the first threshold E at time t3. As a result, the PV generated power decreases and the power at the point of reception PS increases.

[0072] (3) Mode No. 3 Mode No. 3 is a mode in which the BESS30 is fully charged and unable to continue charging, and the PV20's output control suppresses reverse power flow.

[0073] For example, at time t4 in Figure 4, the State of Charge (SOC) of BESS30 reaches the upper limit of the charge level V1 (Step S5; NO). In this case, the control unit 113 performs the processing of Mode No. 3 (Step S7).

[0074] Specifically, the charge / discharge control unit 1131 of the control unit 113 sets the BESS power command value new to "0".

[0075] Furthermore, the output control unit 1132 of the control unit 113 controls the output of PV20 in the same way as in mode No. 2. That is, the output control unit 1132 further reduces the upper limit of the PV output.

[0076] (4) Mode No. 4 Mode No. 4 processing is a mode that improves the utilization rate of PV20 because the power at the point of reception PS increases and the risk of reverse power flow is eliminated.

[0077] Figure 6 shows a second example of the power at the point of reception and the State of Charge (SOC) according to one embodiment. For example, as shown in Figure 6, suppose the power at the point of reception PS (purchased power) gradually increases due to a decrease in the power generated by PV20 or an increase in the power consumption of load 40. At time t5, the power at the point of reception exceeds the second threshold F (step S8; YES), and the PV output upper limit is less than the rated output power (step S10; YES). In this case, the control unit 113 performs the processing of mode No. 4 (step S11). Specifically, the output control unit 1132 of the control unit 113 increases the PV output upper limit and releases the output control of PV20. At this time, the output control unit 1132 may also gradually increase the PV output upper limit by αkW each time the power at the point of reception PS exceeds the second threshold F, thereby easing the PV output control. This makes it possible to improve the utilization rate of the power generated by PV20 while suppressing reverse power flow.

[0078] Furthermore, in Mode No. 4, the charge / discharge control unit 1131 of the control unit 113 keeps the BESS power command value at 0 (no charge / discharge).

[0079] (5) Mode No. 5 Mode No. 5 is a mode in which power is supplied (discharged) from BESS30 to load 40 when the PV power generation power decreases.

[0080] For example, at time t6 in Figure 6, the power at the point of power reception exceeds the second threshold F (step S8; YES), and the PV output upper limit has already reached the rated output power (step S10; NO). Furthermore, if the SOC is greater than the charge rate lower limit V2, the control unit 113 performs the processing of mode No. 5 (step S13). Specifically, the charge / discharge control unit 1131 of the control unit 113 calculates the BESS power command value new [kW] using the following formula (3) and transmits it to the BESS 30.

[0081] BESS power command value new = BESS power command value old + β···(3)

[0082] As described above, when the BESS power command value is a positive value, it becomes a discharge command value. The BESS 30 (PCS controller 33 and PCS 32) controls the power to be discharged from the battery 31 (supplied to the load 40) according to the BESS power command value new received from the control device 10.

[0083] For example, as shown in Figure 6, suppose that at time t7 the power at the point of power PS exceeds the second threshold F again, and the SOC at this time is greater than the lower limit of the charge rate V2 (step S8; YES, step S10; YES). In this case, the control unit 113 performs the processing of mode No. 5 again (step S13). That is, the charge / discharge control unit 1131 further increases the BESS power command value by βkW (increases the discharge command value by βkW) according to equation (3) above. In this way, as shown in Figure 6, if the power consumption of the load 40 increases further, the amount of electricity purchased can be reduced by gradually increasing the discharge command value as long as there is sufficient margin in the SOC of BESS 30.

[0084] (6) Mode No. 6 Mode No. 6 is a mode in which power supply (discharge) from BESS30 to load 40 is stopped because BESS30 has completely discharged.

[0085] For example, at time t8 in Figure 6, the BESS's SOC reaches the lower limit of the charge level V2 (step S12; NO). At this point, the control unit 113 performs the processing of mode No. 6.

[0086] Specifically, the charge / discharge control unit 1131 of the control unit 113 sets the BESS power command value new to "0". This stops the discharge of BESS 30.

[0087] (Regarding the operation of the control device) Figure 7 is a first diagram illustrating the operation of a reverse power flow suppression process according to one embodiment. Figure 8 is a second diagram illustrating the operation of a reverse power flow suppression process according to one embodiment. The operation of the reverse power flow suppression process performed by the control device 10 of this embodiment will be explained with reference to Figures 7 and 8. Figure 7 shows the changes in the power receiving point power PS [kW], BESS power PB [kW], PV output upper limit value UL [kW], and SOC [%] due to the reverse power flow suppression process of the conventional technology. Figure 8 shows the changes in the power receiving point power PS [kW], BESS power PB [kW], PV output upper limit value UL [kW], and SOC [%] due to the reverse power flow suppression process of this embodiment. BESS power PB is the power input and output to BESS 30 based on the BESS power command value, where a positive value represents discharge power and a negative value represents charging power.

[0088] First, let's explain an example of reverse power flow suppression processing in conventional technology. In conventional technology, when the power reception point power PS falls below the first threshold E at time t11 in Figure 7, a charging command value is transmitted to charge the BESS with surplus PV power. As a result, BESS power PB corresponding to the charging command value is supplied to (charged) the BESS. Furthermore, the charging command value is increased in stages each time the power reception point power PS falls below the first threshold E. Also, PV output control is not performed until the BESS is fully charged, and the PV output upper limit value UL is not changed.

[0089] Furthermore, when the BESS reaches full charge at time t12 in Figure 7, the supply of surplus PV power to the BESS stops, and the BESS power PB (PB_s1) that was supplied to the BESS until immediately before decreases rapidly to 0. As a result, the power equivalent to PB_s1 that was supplied to the BESS becomes surplus, and the power at the point of power reception PS decreases rapidly by that amount.

[0090] Furthermore, as shown in Figure 7, in the conventional technology, the power at the point of power supply PS could be increased by charging the BESS until it was fully charged, so PV output control was not performed. Subsequently, at time t12, when the BESS was fully charged and it was detected that the power at the point of power supply PS had fallen below the first threshold E, the process of lowering the PV output upper limit UL was performed. However, as shown in Figure 7, a time lag occurs between the time the power at the point of power supply PS falls to the first threshold E and the time when PV output control (lowering the PV output upper limit UL) is executed. In the conventional technology, due to this time lag, it was not possible to keep up with the rapid change in the power at the point of power supply PS and there was a possibility that the occurrence of reverse power flow could not be suppressed, as in the example in Figure 7.

[0091] Next, an example of the reverse power flow suppression process according to this embodiment will be explained with reference to Figure 8. First, the operation of modes No. 1 to No. 3 will be explained.

[0092] At time t22 in Figure 8, when the power at the point of power PS falls below the first threshold E and the SOC falls below the control start threshold V3, the control unit 113 performs the processing of mode No. 1. That is, the charge / discharge control unit 1131 of the control unit 113 decreases the BESS power command value by βkW (increases the charge command value by βkW) and transmits it to the BESS 30. As a result, the BESS 30 is supplied with BESS power PB corresponding to the charge command value moment by moment. Subsequently, the control unit 113 increases the charge command value in steps each time the power at the point of power PS falls below the first threshold E.

[0093] Furthermore, at time t23 in Figure 8, when the SOC becomes equal to or greater than the control start threshold V3, the control unit 113 performs the Mode No. 2 process. That is, the charge / discharge control unit 1131 of the control unit 113 uses a limiter (Figure 5) to reduce the charge command value in proportion to the increase in SOC. In other words, as the SOC approaches the upper charge rate limit V1, the BESS power PB gradually decreases, so just before the SOC reaches the upper charge rate limit V1, the BESS power PB_s2 is a very small value compared to the conventional BESS power PB_s1 (Figure 7). Therefore, when the BESS 30 is fully charged at time t25 in Figure 8 and the power supply to the BESS 30 stops, the impact (decrease) on the power receiving point power PS is also small. Therefore, unlike the conventional technology, it is possible to suppress the sharp decrease in power receiving point power PS and the occurrence of reverse power flow when the BESS power PB becomes 0.

[0094] Furthermore, in conventional technology, as described above, PV output control was performed only after the BESS was fully charged and the power reception point PS fell below the first threshold E. As a result, there was a possibility that reverse power flow would occur because the PV output control could not keep up. In contrast, in the processing of mode No. 2, the control unit 113 according to this embodiment starts PV output control in parallel with charging the BESS 30 with surplus PV power. That is, before the BESS 30 is fully charged (in the example in Figure 8, at the timing when it is detected that the power reception point PS has fallen below the first threshold E at time t24), the control unit 113 performs a process to lower the upper limit value UL of the PV output. As a result, the control unit 113 can suppress reverse power flow more reliably without being affected by time lags, etc.

[0095] Furthermore, after BESS30 is fully charged at time t25 in Figure 8, the control unit 113 performs processing in mode No. 3. At this time, if the power reception point power PS falls below the first threshold E, the output control unit 1132 of the control unit 113 gradually reduces the PV output upper limit value UL.

[0096] Next, the operation of modes No. 4 to No. 6 will be explained. At time t26 in Figure 8, when the power at the point of reception PS exceeds the second threshold F, the control unit 113 performs the processing of mode No. 4. At this time, the output control unit 1132 of the control unit 113 increases the PV output upper limit value UL, thereby easing (or releasing) the PV output control, because there is no risk of reverse power flow. As a result, the control unit 113 can improve the utilization rate of PV20 during periods when there is no risk of reverse power flow.

[0097] Furthermore, during the period up to time t21 in Figure 8, the power at the point of power PS exceeds the second threshold F, and the SOC is greater than the lower limit of the charge rate V2, so the control unit 113 performs processing in mode No. 5. That is, the charge / discharge control unit 1131 of the control unit 113 increases the BESS power command value by βkW (increases the discharge command value by βkW) and transmits it to the BESS 30. As a result, BESS power PB corresponding to the discharge command value is discharged from the BESS 30 moment by moment and supplied to the load 40, thereby reducing the amount of electricity purchased. In other words, the surplus PV power stored in the BESS 30 can be effectively utilized. After that, the control unit 113 may also gradually increase the discharge command value each time the power at the point of power PS falls below the second threshold F.

[0098] Subsequently, at time t21 in Figure 8, the SOC reaches the lower limit of the charge level, V2. At this point, the control unit 113 performs the processing of mode No. 6. Here, the charge / discharge control unit 1131 of the control unit 113 sets the BESS power command value to 0. This stops the discharge from the BESS 30, thereby suppressing over-discharge.

[0099] (effect) As described above, the control device 10 of the power generation system 1 according to this embodiment includes a power line L1 to which the PV20 and BESS30 are connected, a power measurement unit 111 that measures the power at the point of power reception PS that is exchanged with the power grid, a charge rate acquisition unit 112 that acquires the State of Charge (SOC) of BESS30, and a charge / discharge control unit 1131 that controls the charging and discharging of BESS based on the power at the point of power reception PS and SOC. When the power at the point of power reception PS falls below a first threshold E, the charge / discharge control unit 1131 increases the charging power to BESS30 when the SOC is below the control start threshold V3, and limits the charging power to a charge limit value corresponding to the SOC when the SOC is equal to or greater than the control start threshold V3.

[0100] In this way, the control device 10 can charge the BESS 30 with surplus PV power when there is sufficient margin in the SOC, thereby suppressing the occurrence of reverse power flow and a decrease in the utilization rate of PV 20. Furthermore, when the SOC approaches the upper limit of the charge rate V1, the control device 10 can gradually reduce the charging power, thereby suppressing the occurrence of reverse power flow when the power receiving point PS changes (decreases) abruptly when the BESS 30 is fully charged and charging stops.

[0101] Furthermore, the control device 10 includes an output control unit 1132 that controls the output of the PV20 based on the SOC and the power receiving point power PS.

[0102] In this way, if the power receiving point power PS still decreases even after the BESS 30 is charged with surplus PV power, the control device 10 can perform PV output control to suppress the occurrence of reverse power flow.

[0103] Furthermore, the output control unit 1132 reduces the PV output upper limit value UL when the SOC is greater than or equal to the control start threshold V3 and the power at the point of power PS is less than the first threshold E.

[0104] In this way, the control device 10 can reduce the output of PV20 before BESS30 is fully charged, thereby more reliably suppressing the occurrence of reverse power flow. Furthermore, since the control device 10 does not perform PV output control when SOC is below the control start threshold V3 (mode No. 1), the utilization rate of PV20 can be maximized during the period when BESS30 can be sufficiently charged.

[0105] Furthermore, the output control unit 1132 increases the PV output upper limit when the power at the point of power reception PS exceeds the second threshold F.

[0106] In this way, the control device 10 can release (relax) the PV output control when the power at the point of power PS increases, for example, due to an increase in the power consumption of the load 40. This allows the control device 10 to improve the utilization rate of PV 20.

[0107] Furthermore, the charge / discharge control unit 1131 increases the discharge power from BESS 30 when the power at the charging point PS exceeds the second threshold F and the PV output upper limit reaches the rated output power of PV20.

[0108] In this way, the control device 10 can reduce the amount of electricity purchased by discharging from the BESS 30 when the power at the point of power PS increases due to, for example, an increase in the power consumption of the load 40 or a decrease in the power generation of the PV 20. As a result, the control device 10 can effectively utilize the surplus PV power stored in the BESS 30.

[0109] Furthermore, the charge / discharge control unit 1131 stops discharging from the BESS 30 when the SOC reaches the lower limit of the charge level V2.

[0110] In this way, the control device 10 can suppress over-discharge of the BESS 30 and prevent deterioration of the BESS 30.

[0111] As described above, several embodiments relating to this disclosure have been explained, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be carried out 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 variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0112] <Note> The control device, control method, and program for the power generation system described in the above-described embodiment can be understood, for example, as follows.

[0113] (1) According to a first aspect of the present disclosure, the control device 10 is a control device 10 for a power generation system 1 comprising a power generation device 20 and a power storage device 30, comprising: a power measurement unit 111 that measures the power receiving point power transferred at the point of power reception with the power grid, a power line L1 to which the power generation device 20 and the power storage device 30 are connected, a power rate acquisition unit 112 that acquires the charge rate of the power storage device 30, and a charge / discharge control unit 1131 that controls the charging and discharging of the power storage device 30 based on the power receiving point power and the charge rate, wherein when the power receiving point power falls below a predetermined first threshold E, the charge / discharge control unit 1131 increases the charging power to the power storage device 30 when the charge rate is below a control start threshold V3 which indicates a charge rate lower than the upper limit value V1 of the charge rate of the power storage device 30, and limits the charging power to a charge limit value corresponding to the charge rate when the charge rate is equal to or greater than the control start threshold V3.

[0114] In this way, the control device 10 can charge the BESS 30 with surplus PV power when there is sufficient margin in the SOC, thereby suppressing the occurrence of reverse power flow and a decrease in the utilization rate of PV 20. Furthermore, when the SOC approaches the upper limit of the charge rate V1, the control device 10 can gradually reduce the charging power, thereby suppressing the occurrence of reverse power flow when the power receiving point PS changes (decreases) abruptly when the BESS 30 is fully charged and charging stops.

[0115] (2) According to a second aspect of the present disclosure, the control device 10 according to the first aspect further comprises an output control unit 1132 that controls the output of the power generator 20 based on the charge level and the power at the point of charging.

[0116] In this way, if the power receiving point power PS still decreases even after the BESS 30 is charged with surplus PV power, the control device 10 can perform PV output control to suppress the occurrence of reverse power flow.

[0117] (3) According to a third aspect of the present disclosure, in the control device 10 according to the second aspect, the output control unit 1132 reduces the upper limit of the output of the power generator 20 when the charge rate is equal to or greater than the control start threshold V3 and the power at the point of power reception is less than the first threshold E.

[0118] In this way, the control device 10 can reduce the output of PV20 before BESS30 is fully charged, thereby more reliably suppressing the occurrence of reverse power flow. Furthermore, since the control device 10 does not perform PV output control when SOC is below the control start threshold V3, the utilization rate of PV20 can be maximized during the period when BESS30 can be sufficiently charged.

[0119] (4) According to a fourth aspect of the present disclosure, in a control device 10 according to a second or third aspect, the output control unit 1132 increases the upper limit of the output of the power generator 20 when the power at the point of power reception exceeds a predetermined second threshold F.

[0120] In this way, the control device 10 can release (relax) the PV output control when the power at the point of power PS increases, for example, due to an increase in the power consumption of the load 40. This allows the control device 10 to improve the utilization rate of PV 20.

[0121] (5) According to a fifth aspect of the present disclosure, in a control device 10 according to a third or fourth aspect, the charge / discharge control unit 1131 increases the discharge power from the energy storage device 30 when the power at the point of power reception exceeds a predetermined second threshold F and the output upper limit reaches the rated output power of the power generation device 20.

[0122] In this way, the control device 10 can reduce the amount of electricity purchased by discharging from the BESS 30 when the power at the point of power PS increases due to, for example, an increase in the power consumption of the load 40 or a decrease in the power generation of the PV 20. As a result, the control device 10 can effectively utilize the surplus PV power stored in the BESS 30.

[0123] (6) According to a sixth aspect of the present disclosure, in the control device 10 according to the fifth aspect, the charge / discharge control unit 1131 stops discharging from the energy storage device 30 when the charge rate reaches the lower limit of the charge rate V2.

[0124] In this way, the control device 10 can suppress over-discharge of the BESS 30 and prevent deterioration of the BESS 30.

[0125] (7) According to a seventh aspect of the present disclosure, a control method is a control method for a power generation system 1 comprising a power generation device 20 and a power storage device 30, comprising the steps of: measuring the power at the point of reception between the power line L1 to which the power generation device 20 and the power storage device 30 are connected and the power grid; acquiring the charge rate of the power storage device 30; and controlling the charging and discharging of the power storage device 30 based on the power at the point of reception and the charge rate, wherein the charging and discharging step increases the charging power to the power storage device 30 when the power at the point of reception falls below a predetermined first threshold E, and when the charge rate is below a control start threshold V3 which indicates a charge rate lower than the upper limit value V1 of the charge rate of the power storage device 30, and limits the charging power to a charge limit value corresponding to the charge rate when the charge rate is equal to or greater than the control start threshold V3.

[0126] (8) According to the eighth aspect of the present disclosure, the program causes a control device 10 of a power generation system 1 comprising a power generator 20 and a power storage device 30 to perform the steps of: measuring the power at the point of power reception between the power line L1 to which the power generator 20 and the power storage device 30 are connected and the power grid; acquiring the charge rate of the power storage device 30; and controlling the charging and discharging of the power storage device 30 based on the power at the point of power reception and the charge rate, wherein the step of controlling the charging and discharging increases the charging power to the power storage device 30 when the power at the point of power reception falls below a predetermined first threshold E, and when the charge rate is below a control start threshold V3 which indicates a charge rate lower than the upper limit value V1 of the charge rate of the power storage device 30, and limits the charging power to a charge limit value corresponding to the charge rate when the charge rate is equal to or greater than the control start threshold V3. [Explanation of Symbols]

[0127] 1. Power generation system 2 wattmeter 10 Control device 11 processors 110 Instruction acquisition part 111 Power Measurement Unit 112 Charge rate acquisition section 113 Control Unit 1131 Charge / Discharge Control Unit 1132 Output Control Unit 12 memory 13 Storage 14. Communication Interface 20 PV (Power Generation Equipment) 23 PCS Controllers 30 BESS (power storage device) 31 Storage Battery 33 PCS Controllers 40 load

Claims

1. A control device for a power generation system comprising a power generation device and an energy storage device, A power line to which the power generation device and the energy storage device are connected, and a power measurement unit that measures the power at the point of power reception with the power grid, A charge rate acquisition unit that acquires the charge rate of the aforementioned energy storage device, A charge / discharge control unit that controls the charging and discharging of the energy storage device based on the power at the point of power reception and the charge level, Equipped with, The charge / discharge control unit, when the power at the receiving point falls below a predetermined first threshold, When the charge level is below a control start threshold that indicates a charge level lower than the upper limit of the charge level of the energy storage device, the charging power to the energy storage device is increased to a second charging power that is greater than the first charging power before the power at the receiving point falls below the first threshold. When the charge level is equal to or greater than the control start threshold, the charging power is limited to a charge limit value corresponding to the charge level. The charge / discharge control unit increases the charging power to the energy storage device to the second charging power, and then, if the power at the charging point falls below the first threshold and the charging rate falls below the control start threshold, it increases the charging power to the energy storage device to a third charging power greater than the second charging power. Control device for a power generation system.

2. The system further includes an output control unit that controls the output of the power generation device based on the charge rate and the power at the charging point. A control device for a power generation system according to claim 1.

3. The output control unit reduces the upper limit of the output of the power generator when the charge level is equal to or greater than the control start threshold and the power at the receiving point is less than the first threshold. A control device for a power generation system according to claim 2.

4. The output control unit increases the upper limit of the output of the power generation device when the power at the power receiving point exceeds a predetermined second threshold. A control device for a power generation system according to claim 2.

5. The charge / discharge control unit increases the discharge power from the energy storage device when the power at the receiving point exceeds a predetermined second threshold and the output upper limit reaches the rated output power of the power generation device. A control device for a power generation system according to claim 3 or 4.

6. The charge / discharge control unit stops discharging from the energy storage device when the charge rate reaches the lower limit of the charge rate. The control device for the power generation system according to claim 5.

7. A control method for a power generation system comprising a power generation device and an energy storage device, A step of measuring the power at the point of power reception between the power line to which the power generation device and the energy storage device are connected and the power grid, The steps include obtaining the charge level of the energy storage device, A step of controlling the charging and discharging of the energy storage device based on the power at the point of power reception and the charge rate, It has, The step of controlling the charging and discharging is performed when the power at the receiving point falls below a predetermined first threshold. When the charge level is below a control start threshold that indicates a charge level lower than the upper limit of the charge level of the energy storage device, the charging power to the energy storage device is increased to a second charging power that is greater than the first charging power before the power at the receiving point falls below the first threshold. When the charge level is equal to or greater than the control start threshold, the charging power is limited to a charge limit value corresponding to the charge level. The step of controlling the charging and discharging involves increasing the charging power to the energy storage device to the second charging power, and then, if the power at the charging point falls below the first threshold and the charging rate is below the control start threshold, increasing the charging power to the energy storage device to a third charging power greater than the second charging power. A method for controlling a power generation system.

8. A control device for a power generation system that includes a power generation device and an energy storage device, A step of measuring the power at the point of power reception between the power line to which the power generation device and the energy storage device are connected and the power grid, The steps include obtaining the charge level of the energy storage device, A step of controlling the charging and discharging of the energy storage device based on the power at the point of power reception and the charge rate, A program that executes, The step of controlling the charging and discharging is performed when the power at the receiving point falls below a predetermined first threshold. When the charge level is below a control start threshold that indicates a charge level lower than the upper limit of the charge level of the energy storage device, the charging power to the energy storage device is increased to a second charging power that is greater than the first charging power before the power at the receiving point falls below the first threshold. When the charge level is equal to or greater than the control start threshold, the charging power is limited to a charge limit value corresponding to the charge level. The step of controlling the charging and discharging involves increasing the charging power to the energy storage device to the second charging power, and then, if the power at the charging point falls below the first threshold and the charging rate is below the control start threshold, increasing the charging power to the energy storage device to a third charging power greater than the second charging power. program.

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