Control system, power supply system, and control method

Abstract

Provided is a control system for a storage battery using a voltage control method. The control system for a storage battery using a voltage control method comprises: a means for acquiring a frequency target value; a means for correcting the frequency target value by a correction amount of the frequency target value with respect to active power; a means for calculating a correction amount such that a power factor becomes constant with respect to a voltage target value of charge / discharge power of the storage battery and correcting the voltage target value; a means for correcting the voltage target value by a correction amount of the voltage target value with respect to reactive power; and a means for performing charge / discharge control by using a PWM method on the basis of the corrected frequency target value and voltage target value.

Description

Control system, power supply system and control method

[0001] The present disclosure relates to a control system for a microgrid system, a power supply system, and a control method. The present disclosure claims priority based on Japanese Patent Application No. 2025-039364 filed in Japan on March 12, 2025, the content of which is incorporated herein by reference.

[0002] A so-called microgrid system or off-grid system is disclosed, in which an inverter for renewable energy or a secondary battery (storage battery) is connected to a busbar generated by an alternator driven by an engine or the like, and power is supplied according to a load on the busbar (for example, Patent Document 1). Patent Document 1 discloses a control device for a secondary battery inverter that determines target values of active power and reactive power based on a voltage value and a frequency of a busbar. The control device described in Patent Document 1 is a GFL (Grid Following) method that controls output current, that is, a current-controlled PCS (Power Conditioning System). Current-controlled PCS does not support standalone operation. As another control method for PCS, a GFM (Grid Forming) method (voltage control method), which is compatible with standalone operation and targets output voltage for control, is known. Patent Document 1 does not disclose a voltage-controlled PCS.

[0003] Japanese Patent No. 7365123

[0004] There is a need for a storage battery control system based on a voltage control method.

[0005] The present disclosure provides a control system, a power supply system, and a control method that can solve the above-mentioned problems.

[0006] According to one aspect of the present disclosure, the control system is a voltage-controlled battery control system comprising: frequency target value acquisition means for acquiring a frequency target value of the charging and discharging power of the battery; frequency target value correction means for acquiring a correction amount of the frequency target value corresponding to the active power based on a first droop function showing a monotonically decreasing relationship between the active power and the correction amount of the frequency target value, and the active power of the charging and discharging power of the battery, and calculating a final frequency target value by correcting the frequency target value with the correction amount of the frequency target value; and a means for ensuring that the power factor of the charging and discharging power of the battery remains constant with respect to the voltage target value of the charging and discharging power of the battery. The system includes: a constant power factor control means that calculates a correction amount and corrects the voltage target value by the correction amount; a voltage target value acquisition means that acquires the corrected voltage target value; a second droop function that shows a monotonically decreasing relationship between the correction amount of the voltage target value and the reactive power of the charging and discharging power of the storage battery, and a voltage target value correction means that acquires a correction amount of the voltage target value corresponding to the reactive power and calculates a final voltage target value by correcting the corrected voltage target value by the correction amount of the voltage target value; and a charge / discharge control means that performs charge / discharge control in the PWM method based on the final frequency target value and the final voltage target value.

[0007] According to one aspect of the present disclosure, the power supply system comprises an engine generator connected to a busbar, the control system connected to the busbar, and a battery charged and discharged by the control system.

[0008] According to one aspect of the present disclosure, the control method is a voltage control method for a storage battery, comprising the steps of: obtaining a frequency target value of the charging and discharging power of the storage battery; obtaining a correction amount for the frequency target value corresponding to the active power based on a first droop function showing a monotonically decreasing relationship between the active power and the correction amount for the frequency target value, and the active power of the charging and discharging power of the storage battery; calculating a final frequency target value obtained by correcting the frequency target value with the correction amount for the frequency target value; and ensuring that the power factor of the charging and discharging power of the storage battery remains constant with respect to the voltage target value of the charging and discharging power of the storage battery. The method includes the steps of: calculating a correction amount and correcting the voltage target value by the correction amount; obtaining the corrected voltage target value; obtaining a correction amount for the voltage target value corresponding to the reactive power based on a second droop function showing a monotonically decreasing relationship between the correction amount for the voltage target value and the reactive power of the battery's charge / discharge power; calculating a final voltage target value by correcting the corrected voltage target value by the correction amount for the voltage target value; and performing charge / discharge control in a PWM manner based on the final frequency target value and the final voltage target value.

[0009] According to the control system, power supply system, and control method described above, the battery can be controlled by a voltage control method.

[0010] This figure shows a schematic configuration of the power supply system according to the first embodiment. This figure shows an example of the control logic of the engine generator according to the first embodiment. This is Figure 1 showing an example of the control logic of the governor according to the first embodiment. This figure shows an example of the droop characteristics of the governor according to the first embodiment. This is Figure 2 showing an example of the control logic of the governor according to the first embodiment. This is Figure 1 showing an example of the control logic of the AVR according to the first embodiment. This figure shows an example of the droop characteristics of the AVR according to the first embodiment. This is Figure 1 showing an example of the control logic of the PCS according to the first embodiment. This is Figure 2 showing an example of the control logic of the PCS according to the first embodiment. This is Figure 1 showing an example of the droop characteristics of the PCS according to the first embodiment. This is Figure 2 showing an example of the droop characteristics of the PCS according to the first embodiment. This figure shows another example of the configuration of the power supply system according to the first embodiment. This figure shows a schematic configuration of the power supply system according to the second embodiment. This is a schematic block diagram showing the configuration of the computer according to the embodiment.

[0011] <First Embodiment> The power supply system 1 and its control according to the present disclosure will be described below with reference to Figures 1 to 8. (Configuration of the power supply system) As shown in Figure 1, the power supply system 1 according to the first embodiment includes a power controller 10, an engine generator 20 connected to the busbar 2 via an isolation transformer 3a and a circuit breaker 4a, a voltage-controlled PCS 30 connected to the busbar 2 via an isolation transformer 3b and a circuit breaker 4b, a storage battery 32 that the PCS 30 charges and discharges, a grid 5 connected to the busbar 2 via a transformer 6 and a circuit breaker 4c, a solar power generator 7 connected to the busbar 2 via a circuit breaker 4d, a wind power generator 8 connected to the busbar 2 via a circuit breaker 4e, and a power supply destination load 9 connected to the busbar 2 via a circuit breaker 4f. The power controller 10 controls the engine generator 20 and the PCS 30. The engine generator 20, the PCS 30, the grid 5, the solar power generator 7 and the wind power generator 8 are connected to the busbar 2 and supply power to the load 9 via the busbar 2. The power supply system 1 is a microgrid system that can operate independently by opening the circuit breaker 4c when a problem occurs in the grid 5. In the power supply system 1, the engine generator 20 and PCS 30 function as voltage sources. The solar power generator 7 and wind power generator 8 are not essential components.

[0012] (Configuration of the engine generator) Figure 2 shows the control system 200 of the engine generator 20, which is part of the power supply system 1. The control system 200 includes a power controller 10, the engine generator 20, and a load 9. The engine generator 20 includes a governor 20a, an AVR 20b (Automatic Voltage Regulator), an engine 20c, and a generator 20d. The engine generator 20 is an AC generator that generates AC power by driving the generator 20d with the rotation of the engine 20c. In the control system 200, the power controller 10 obtains measured values ​​of voltage and current supplied from the generator 20d to the load 9 from a VT (transformer) and a CT (current transformer), and generates speed target values ​​and voltage target values. In the control system 200, the power controller 10 is responsible for low-speed control (control to respond to changes that occur over a relatively long period of time), while the governor 20a and AVR 20b are responsible for high-speed control (control to respond to instantaneous load changes).

[0013] The governor 20a obtains the speed target value and speed correction value for the rotational speed of the engine 20c from the power controller 10 and generates a fuel flow command that can achieve the speed target value. The governor 20a outputs the generated fuel flow command to the engine 20c. The governor 20a monitors the rotational speed of the engine 20c and performs PID control to achieve the speed target value. An example of the control logic of the governor 20a is shown in Figure 3A. The power controller 10 includes a speed correction control unit 11a and an adder 11b. The power controller 10 calculates a speed correction value to compensate for the deviation from the speed target value using the speed correction control unit 11a, calculates a governor target value by adding the speed correction value to the speed target value using the adder 11b, and outputs the calculated governor target value (speed target value) to the governor 20a. The governor 20a comprises a PID control unit 21a, a droop correction unit 21b, and an adder 21c. The governor 20a uses the adder 21c to obtain a governor target value (speed target value) from the power controller 10, and outputs a value (speed target value) obtained by adding a correction amount calculated by the droop correction unit 21b to the obtained governor target value to the PID control unit 21a. The PID control unit 21a calculates a fuel flow command value that can achieve the received speed target value and outputs it as governor output. Figure 3B shows the droop characteristic function used by the droop correction unit 21b to calculate the correction amount. The droop characteristic is represented by the slope of a linear function of active power and correction amount. That is, it is a characteristic in which the speed target value decreases as the active power increases. The droop correction unit 21b obtains the active power of the busbar and obtains a correction amount corresponding to the active power by referring to the function exemplified in Figure 3B. As illustrated in Figure 3C, the governor 20a can also be configured to use the governor output value as an input signal instead of the droop correction unit 21b. The droop correction unit 21d calculates the correction amount from the governor output value output by the PID control unit 21a by referring to a droop characteristic function (not shown) that defines the relationship between the governor output value and the correction amount.

[0014] The AVR 20b obtains the target voltage and voltage correction value of the engine 20c from the power controller 10 and generates a field command that can achieve the target voltage. The AVR 20b outputs the generated field command to the generator 20d. The AVR 20b monitors the voltage of the generator 20d and performs PID control to achieve the target voltage. An example of the control logic of the AVR 20b is shown in Figure 4A. The power controller 10 includes a voltage correction control unit 11c and an adder 11d. The power controller 10 calculates a voltage correction value to compensate for the deviation from the rated voltage and the actual voltage of the busbar 2 using the voltage correction control unit 11c, and outputs an AVR target value (target voltage value) which is the target voltage value plus the voltage correction value using the adder 11d to the AVR 20b. The AVR 20b includes a PID control unit 22a, a power calculation unit 22b, a droop correction unit 22c, and an adder 22d. The AVR 20b uses the adder 22d to obtain the AVR target value (voltage target value) from the power controller 10, and outputs a value (power target value) obtained by adding the correction amount calculated by the droop correction unit 22c to the obtained AVR target value to the PID control unit 22a. The PID control unit 22a calculates a field command that can achieve the received voltage target value and outputs it as the AVR output. Figure 4B shows the droop characteristic function used by the droop correction unit 22c to calculate the correction value. The droop characteristic is represented by the slope of a linear function of reactive power and correction amount. That is, it is a characteristic in which the voltage target value decreases as reactive power increases. The power calculation unit 22b obtains the bus voltage and calculates the reactive power. The power calculation unit 22b outputs the calculated reactive power to the droop correction unit 22c. The droop correction unit 22c obtains the correction amount corresponding to the reactive power by referring to the function exemplified in Figure 4B.

[0015] (PCS Configuration) Figure 5 shows the control system 300 of the PCS 30, which is part of the power supply system 1. The PCS 30 includes an inverter (DC / AC converter) and a controller that controls the inverter. The inverter converts the DC power output by the battery 32 into AC power based on a command from the controller and supplies it to the busbar 2. The inverter converts a portion of the AC power flowing through the busbar 2 into DC power based on a command from the controller and charges the battery 32.

[0016] The PCS 30 obtains the frequency target value and frequency correction value of the power used to charge and discharge the battery 32 from the power controller 10. The PCS 30 also obtains the voltage target value and voltage correction value of the power used to charge and discharge the battery 32 from the power controller 10. The PCS 30 controls the charging and discharging of the battery 32 to achieve the frequency target value and voltage target value, and supplies the DC power output (discharged) by the battery 32 to the busbar 2.

[0017] As shown in Figure 6, the power controller 10 includes an output correction control unit 12a, a frequency correction control unit 12b, adders 12c, 12d, 12e, and 12f, a voltage correction control unit 12g, a power factor calculation unit 12h, and a constant power factor control unit 12i. In the control system 200, the power controller 10 acquires measured values ​​of voltage and current supplied from the PCS 30 to the load 9 from the VT and CT, and generates a frequency target value and a voltage target value. The frequency target value is a parameter that controls the magnitude of active power charged and discharged from the battery 32, and the voltage target value is a parameter that controls the magnitude of reactive power charged and discharged from the battery 32. The PCS 30 includes droop correction units 31a and 31c, a frequency control unit 31b, a voltage control unit 31d, a PWM control unit 31e, a power calculation unit 31f, and adders 31g and 31h. In the control system 300, the power controller 10 is responsible for low-speed control, and the PCS 30 is responsible for high-speed control.

[0018] In the configuration example shown in Figure 6, the PCS 30 is provided with droop correction units 31a and 31c, but these can also be functions provided by the power controller 10. The power controller 10 is provided with a power factor calculation unit 12h and a constant power factor control unit 12i, but these can also be functions provided by the PCS 30.

[0019] The output correction control unit 12a acquires the active power deviation calculated from the target active power output of the storage battery 32 minus the actual active power output, and calculates a correction amount 1 to bring the actual active power to the target active power. In order to suppress the charging and discharging of the battery, the target active power is set to 0.

[0020] The frequency correction control unit 12b acquires the frequency deviation calculated by subtracting the actual frequency from the rated frequency of the power charged and discharged to the storage battery 32, and calculates a correction amount 2 to make the actual frequency the rated frequency. The power controller 10 adds the correction amount 1 to the frequency target value using the adder 12c, adds the correction amount 2 to the frequency target value after adding the correction amount 1 using the adder 12d, and outputs the frequency target value after adding the correction amount 1 and the correction amount 2 to the PCS 30.

[0021] The voltage correction control unit 12g acquires the voltage deviation calculated by subtracting the actual voltage from the rated voltage of the power being charged and discharged to the storage battery 32, and calculates a correction amount 3 to make the actual voltage the rated voltage. The power factor calculation unit 12h acquires the measured voltage and current values, calculates the power factor, and outputs the calculated power factor to the constant power factor control unit 12i.

[0022] The constant power factor control unit 12i acquires the reactive power measurement value and the active power measurement value, and calculates a voltage correction amount 4 such that the power factor cosθ, calculated as power factor = active power P ÷ apparent power S = cosθ, remains constant. Specifically, the relationship between the power factor (cosθ), active power (P), reactive power (Q), and apparent power (S) is S = sqrt(P^2 + Q^2), and as described above, cosθ = P ÷ S holds true. Therefore, the reactive power Q = P × sqrt((1 ÷ cosθ)^2 - 1). By substituting the target power factor for cosθ and the active power measurement value for P, the target reactive power required to control the power factor to the target value can be obtained. The constant power factor control unit 12i calculates the deviation between the target reactive power obtained in this way and the actual reactive power, and calculates a reactive power correction amount by PID control such that the calculated deviation becomes 0. The constant power factor control unit 12i calculates a correction amount 4 by converting the calculated reactive power correction amount into a voltage, and outputs the correction amount 4. The power controller 10 adds the correction amount 3 to the target voltage value using the adder 12e, adds the correction amount 4 to the target voltage value after adding the correction amount 3 using the adder 12f, and outputs the target voltage value after adding the correction amount 3 and the correction amount 4 to the PCS 30.

[0023] In the PCS 30, the adder 31g adds the correction amount calculated by the droop correction unit 31a to the frequency target value obtained from the power controller 10 and outputs the result (frequency target value) to the frequency control unit 31b. The frequency control unit 31b commands the frequency target value to the PWM control unit 31e. Figure 7A shows the droop characteristic function used by the droop correction unit 31a to calculate the correction value. The droop characteristic is represented by the slope of a linear function of active power and correction amount. That is, it is a characteristic in which the frequency target value decreases as the active power increases. The droop correction unit 31a obtains the active power charged and discharged from the storage battery 32 from the power calculation unit 31f and obtains the correction amount corresponding to the active power by referring to the function exemplified in Figure 7A.

[0024] The adder 31h outputs a value (voltage target value) obtained by adding a correction amount calculated by the droop correction unit 31c to the voltage control unit 31d. The voltage control unit 31d commands the voltage target value to the PWM control unit 31e. Figure 7B shows the droop characteristic function used by the droop correction unit 31c to calculate the correction value. The droop characteristic is represented by the slope of a linear function of reactive power and correction amount. That is, it is a characteristic in which the voltage target value decreases as reactive power increases. The droop correction unit 31c obtains the reactive power charged and discharged from the battery 32 from the power calculation unit 31f and obtains a correction amount corresponding to the reactive power by referring to the function exemplified in Figure 7B. The PWM control unit 31e performs charging and discharging in the PWM method based on the commanded frequency target value and voltage target value. The power calculation unit 31f calculates the active power and reactive power to be charged and discharged.

[0025] (Operation) When a load 9 is connected to the power supply system 1, active power is supplied from the PCS 30, and as the output of the engine generator 20 increases, the discharge of the battery 32 decreases and eventually reaches 0 kW. When the load is cut off, the PCS 30 responds and absorbs the load fluctuation by charging the battery 32. Regarding reactive power, if there were no constant power factor control unit 12i, the PCS 30 would bear the reactive power, and discharge from the battery 32 would continue after the load is applied, and discharge would continue for a while even after the load is cut off. However, according to this embodiment, it has been confirmed that the constant power factor control unit 12i can significantly suppress the reactive power output from the PCS 30. In other words, according to this embodiment, the reactive power output by the PCS 30 during load fluctuations can be suppressed, and excess discharge from the battery 32 can be avoided. It has also been confirmed that even when the system 5 is disconnected and the system switches to independent operation, there is no excessive supply of active or reactive power from the PCS 30 when the load is applied, and stable operation is possible.

[0026] In order to have the engine generator 20 bear both active and reactive power after load is applied, the frequency target value and the reactive power target value given to the PCS 30 may be reduced after the PCS 30 absorbs load fluctuations immediately after load is applied. Reducing the frequency target value suppresses the active power borne by the PCS 30, and performing constant power factor control by setting the target reactive power (the value of Q in the above formula) to 0, for example, also suppresses the reactive power borne by the PCS 30. For example, after a predetermined time has elapsed after load is applied, or when the difference between the output of the engine generator 20 and the preload falls within a predetermined range, the power controller 10 may be configured to reduce the frequency target value and the target reactive power to predetermined set values.

[0027] As explained above, the power supply system 1 allows the PCS 30 to be connected using a voltage control method in parallel operation with the engine generator 20 and in connection with the grid 5. Conventional PCSs are often connected using current control, but by adopting the voltage control method PCS 30, the following effects can be obtained. Specifically, in addition to performing charge and discharge control based on frequency target value and voltage target value, droop control is performed for each (for frequency control, the frequency target value is corrected by the droop correction unit 31a, and for voltage control, the voltage target value is corrected by the droop correction unit 31c), so that active power and reactive power can be supplied instantaneously and individually (at the end) in response to load fluctuations and bus frequency and voltage fluctuations. (In conventional current control, the output is determined by a command from a higher-level controller, so delays such as communication delays often occur.) Power factor control makes it possible to suppress excessive reactive power supply from the PCS 30, and it is possible to prevent exceeding the capacity of the PCS 30. In particular, in independent parallel operation with the engine generator 20, when load fluctuations occur, the fast-responding PCS will primarily handle reactive power. However, by suppressing the supply of reactive power from the PCS 30 through constant power factor control, reactive power control (i.e., busbar voltage control) on the engine generator 20 side can be made the primary method of control. This suppresses the apparent power output of the battery 32 and reduces the energy consumption of the battery 32. Because it is a voltage-controlled PCS, it can transition to independent operation without interruption even when the grid 5 is disconnected.

[0028] Because droop control is performed, parallel operation is possible without synchronization between PCSs, and capacity can be easily increased. Figure 8 shows an example configuration in which a voltage-controlled PCS 30' and a battery 32' connected to the busbar 2 via an isolation transformer 3b' and circuit breaker 4b' is added to the configuration of Figure 1. As illustrated in Figure 8, multiple PCS 30s and batteries 32 can be connected in parallel with the engine generator 20. In this configuration, when multiple PCS 30s are synchronously switched on, the voltage-controlled PCS can be linked on the output side (circuit breakers 4b and 4b' are switched on) to prevent overcurrent and disconnection.

[0029] <Second Embodiment> In the first embodiment, a configuration was shown in which a voltage-controlled PCS was linked with an engine generator. In the second embodiment, a configuration will be described in which a plurality of PCS 30 and a storage battery 32 are connected in parallel without connecting the engine generator 20.

[0030] As shown in Figure 9, the power supply system 1' according to the second embodiment includes a power controller 10, a voltage-controlled PCS 30a connected to the busbar 2 via an isolation transformer 3a and a circuit breaker 4a, a battery 32a that charges and discharges the PCS 30a, a voltage-controlled PCS 30b connected to the busbar 2 via an isolation transformer 3b and a circuit breaker 4b, a battery 32b that charges and discharges the PCS 30b, a voltage-controlled PCS 30c connected to the busbar 2 via an isolation transformer 3c and a circuit breaker 4c, a battery 32c that charges and discharges the PCS 30c, a grid 5 connected to the busbar 2 via a transformer 6 and a circuit breaker 4c, a solar power generator 7 connected to the busbar 2 via a circuit breaker 4d, a wind power generator 8 connected to the busbar 2 via a circuit breaker 4e, and a power supply destination load 9 connected to the busbar 2 via a circuit breaker 4f. The power supply system 1' is a microgrid system that can operate independently even when the grid 5 is disconnected. In the power supply system 1, PCS 30a to 30c function as voltage sources. The solar power generator 7 and wind power generator 8 are not essential components.

[0031] The control system 300 of the second embodiment has the same configuration as described with reference to Figures 5 and 6 of the first embodiment. In the configuration example shown in Figure 9, three control systems 300 are provided in parallel. In one of these systems, the constant power factor control is turned off in order to bear the active and reactive power instead of the engine generator 20, and correction is performed by the droop correction units 31a and 31c.

[0032] In the case of parallel operation of PCS, conventional PCS typically connect multiple PCS units using current control or synchronization signals and use them as a current source (when connected to the grid) or as a voltage source using a CVCF (Constant Voltage Constant Frequency) (when operating independently). However, according to the second embodiment, one unit is designated as the main voltage source (performing only droop control), and the other PCS units are configured to perform constant power factor control, thereby enabling the connection of multiple units. In the example shown in Figure 9, the power controller 10 does not add the correction amount calculated by the constant power factor control unit 12i to the voltage target value output to PCS 30a. PCS 30a, being the main voltage source, is primarily responsible for supplying active and reactive power, while the other PCS units 30b and 30c assist in supplying reactive power during load fluctuations, etc. If the reactive power supply from PCS 30a is insufficient, this can be addressed by changing the target value of the constant power factor control and increasing the reactive power supply from PCS units 30b and 30c. For PCS30b and 30c, the power factor can be ignored until load 9 is connected, so constant power factor control is started after load 9 is connected.

[0033] (Effects) As explained above, with the power supply system 1', it is possible to connect multiple PCS 30 in parallel using a voltage control method. This allows for instantaneous and individual (at each end) supply of active power and reactive power in response to load fluctuations and frequency / voltage fluctuations of the busbar 2, enabling a seamless transition to independent operation. During synchronous switching, overcurrent can be prevented and disconnection can be prevented by coordinating the voltage-controlled PCS 30a to 30c on the output side (closing the circuit breakers 4a to 4c). Constant power factor control makes it possible to suppress excessive reactive power supply from PCS 30b and 30c, preventing exceeding the capacity of PCS 30b and 30c. Constant power factor control also suppresses the apparent power output of batteries 32b and 32c, reducing the output from batteries 32b and 32c. Because droop control is performed, parallel operation is possible without synchronization between PCS, and capacity can be easily increased.

[0034] Figure 10 is a schematic block diagram showing the configuration of a computer according to an embodiment. The computer 90 includes a processor 91, main memory 92, storage 93, and interface 94. The command generation device 33 and control device 40 described above are each implemented in the computer 90. The operation of each of the above-described processing units is stored in the storage 93 in the form of a program. The processor 91 reads the program from the storage 93, loads it into the main memory 92, and executes the above-described processing according to the program. The processor 91 allocates storage areas in the main memory 92 corresponding to each of the above-described storage units according to the program. Examples of the processor 91 include a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and a microprocessor.

[0035] The program may be for implementing some of the functions that the computer 90 is to perform. For example, the program may perform functions in combination with other programs already stored in storage, or in combination with other programs implemented in other devices. In other embodiments, the computer 90 may include, in addition to or instead of the above configuration, a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device). Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions implemented by the processor 91 may be implemented by the integrated circuit. Such an integrated circuit is also included as an example of a processor.

[0036] Examples of storage 93 include HDDs (Hard Disk Drives), SSDs (Solid State Drives), magnetic disks, magneto-optical disks, CD-ROMs (Compact Disc Read Only Memory), DVD-ROMs (Digital Versatile Disc Read Only Memory), and semiconductor memory. Storage 93 may be an internal medium directly connected to the bus of the computer 90, or an external medium connected to the computer 90 via an interface 94 or a communication line. When this program is delivered to the computer 90 via a communication line, the computer 90 that receives the delivery may expand the program into the main memory 92 and execute the above processing. In at least one embodiment, storage 93 is a tangible storage medium that is not temporary.

[0037] 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.

[0038] <Note> The control system, power supply system, and control method described in each embodiment can be understood, for example, as follows.

[0039] (1) The control system according to the first embodiment is a battery control system using a voltage control method, comprising: frequency target value acquisition means for acquiring a frequency target value of the charging and discharging power of the battery; a first droop function showing a relationship in which the correction amount of the frequency target value decreases monotonically with respect to the active power; and the active power of the charging and discharging power of the battery, based on the active power, a frequency target value correction means for acquiring a correction amount of the frequency target value corresponding to the active power and calculating a final frequency target value by correcting the frequency target value with the correction amount of the frequency target value; and a voltage target value of the charging and discharging power of the battery, such that the power factor of the charging and discharging power becomes constant. The system includes: a constant power factor control means that calculates a correction amount and corrects the voltage target value by the correction amount; a voltage target value acquisition means that acquires the corrected voltage target value; a voltage target value correction means that acquires a correction amount for the voltage target value corresponding to the reactive power based on a second droop function showing a monotonically decreasing relationship between the correction amount for the voltage target value and the reactive power of the charging and discharging power of the storage battery, and calculates a final voltage target value by correcting the corrected voltage target value by the correction amount for the voltage target value; and a charge / discharge control means that performs charge / discharge control in a PWM manner based on the final frequency target value and the final voltage target value. This allows the storage battery to be controlled by a voltage control method.

[0040] (2) The control system according to the second embodiment is the control system of (1), wherein the constant power factor control means calculates a target value of reactive power by substituting the target value of power factor and the measured value of active power into the relational expression for active power, reactive power and apparent power and the relational expression for reactive power, active power and power factor derived from the relational expression for power factor, active power and reactive power, and calculates a correction amount to compensate for the deviation between the calculated target value of reactive power and the measured value of reactive power as a correction amount such that the power factor becomes constant. This makes it possible to suppress the reactive power output by the storage battery.

[0041] (3) The power supply system according to the third embodiment comprises an engine generator connected to a busbar, a control system as described in (1) or (2) connected to the busbar, and a battery charged and discharged by the control system. This enables parallel operation with the engine generator.

[0042] (4) A power supply system according to a fourth aspect is the power supply system according to (3), further comprising: means for reducing the frequency target value when a load is applied and a predetermined time elapses, or when a difference between an output of the engine generator and the load falls within a predetermined range. This makes it possible to suppress the output from the storage battery and cause the engine generator to take charge of the output.

[0043] (5) A power supply system according to a fifth aspect comprises a plurality of sets of the control system according to (1) or (2) connected to a busbar, and a storage battery charged and discharged by the control system, wherein in one of the plurality of control systems, correction of the voltage target value by the constant power factor control means is not performed. Accordingly, a configuration in which a plurality of PCSs are linked in parallel can be achieved.

[0044] (6) A control method according to a sixth aspect is a method for controlling a storage battery by a voltage control method, the method comprising: acquiring a frequency target value for charge / discharge power of the storage battery; acquiring a correction amount of the frequency target value corresponding to active power based on a first droop function representing a relationship in which the correction amount of the frequency target value monotonically decreases with respect to active power, and the active power of the charge / discharge power of the storage battery, and calculating a final frequency target value obtained by correcting the frequency target value with the correction amount of the frequency target value; calculating a correction amount for a voltage target value of the charge / discharge power of the storage battery such that a power factor of the charge / discharge power becomes constant, and correcting the voltage target value with the correction amount; acquiring the corrected voltage target value; acquiring a correction amount of the voltage target value corresponding to reactive power based on a second droop function representing a relationship in which the correction amount of the voltage target value monotonically decreases with respect to reactive power, and the reactive power of the charge / discharge power of the storage battery, and calculating a final voltage target value obtained by correcting the corrected voltage target value with the correction amount of the voltage target value; and performing charge / discharge control by a PWM method based on the final frequency target value and the final voltage target value.

[0045] According to the control system, power supply system, and control method described above, a storage battery can be controlled by a voltage control method.

[0046] 1...Power supply system, 2...Bus, 3a, 3b, 3c, 3d, 3e...Isolation transformer, 4a, 4b, 4c, 4d, 4e, 4f...Circuit breaker, 5...System, 6...Transformer, 7...Solar generator, 8...Wind turbine, 9...Load, 10...Power controller, 11a...Speed ​​correction control unit, 11b...Adder, 11c...Voltage correction control unit, 20...Engine generator, 12a...Output correction control unit, 12b...Frequency correction control unit, 12c, 12d, 12e, 12f...Adder, 12g...Voltage correction control unit, 12h...Power factor calculation unit, 12i...Constant power factor control unit, 20a...Governor, 20b...AVR, 20c... 20d...Engine, 21a...Generator, 21a...PID control unit, 21b, 21d...Droop correction unit, 21c...Adder, 22a...PID control unit, 22b...Power calculation unit, 22c...Droop correction unit, 22d...Adder, 30, 30a, 30b, 30c...PCS, 31a, 31c...Droop correction unit, 31b...Frequency control unit, 31d...Voltage control unit, 31e...PWM control unit, 31f...Power calculation unit, 31g, 31h...Adder, 32, 32a, 32b, 32c...Battery, 90...Computer, 91...Processor, 92...Main memory, 93...Storage, 94...Interface

Claims

1. A battery control system using a voltage control method, comprising: frequency target value acquisition means for acquiring a frequency target value of the charging and discharging power of the battery; frequency target value correction means for acquiring a correction amount of the frequency target value corresponding to the active power and calculating a final frequency target value corrected by the frequency target value correction amount based on a first droop function showing a monotonically decreasing relationship between the correction amount of the frequency target value and the active power of the charging and discharging power of the battery; power factor constant control means for calculating a correction amount such that the power factor of the charging and discharging power becomes constant with respect to the voltage target value of the charging and discharging power of the battery and correcting the voltage target value by the correction amount; voltage target value acquisition means for acquiring the corrected voltage target value; voltage target value correction means for acquiring a correction amount of the voltage target value corresponding to the reactive power and calculating a final voltage target value corrected by the voltage target value correction amount based on a second droop function showing a monotonically decreasing relationship between the correction amount of the voltage target value and the reactive power of the charging and discharging power of the battery; A control system comprising: a charge / discharge control means that performs charge / discharge control in a PWM manner based on the aforementioned final frequency target value and the aforementioned final voltage target value; 2. The constant power factor control means calculates a target value for reactive power by substituting a target value for power factor and a measured value for active power into a relational expression for active power, reactive power and apparent power, and a relational expression for reactive power, active power and power factor derived from the relational expression for power factor, active power and reactive power, and calculates a correction amount to compensate for the deviation between the calculated target value for reactive power and the measured value for reactive power, as a correction amount such that the power factor becomes constant, the control system according to claim 1.

3. A power supply system comprising: an engine generator connected to a busbar; a control system according to claim 1 or 2 connected to the busbar; and a battery charged and discharged by the control system.

4. The power supply system according to claim 3, further comprising means for reducing the frequency target value when a load is applied and a predetermined time has elapsed, or when the difference between the output of the engine generator and the load falls within a predetermined range.

5. A power supply system comprising a plurality of control systems according to claim 1 or claim 2 connected to a busbar, and a storage battery charged and discharged by the control system, wherein in one of the plurality of control systems, the voltage target value is not corrected by the constant power factor control means.

6. A method for controlling a battery using a voltage control method, comprising: a step of obtaining a frequency target value of the charging and discharging power of the battery; a step of obtaining a correction amount for the frequency target value corresponding to the active power based on a first droop function showing a monotonically decreasing relationship between the active power and the correction amount for the frequency target value, and calculating a final frequency target value by correcting the frequency target value with the correction amount for the frequency target value; a step of calculating a correction amount for the voltage target value of the charging and discharging power of the battery such that the power factor of the charging and discharging power becomes constant, and correcting the voltage target value with the correction amount; a step of obtaining the corrected voltage target value; a step of obtaining a correction amount for the voltage target value corresponding to the reactive power based on a second droop function showing a monotonically decreasing relationship between the reactive power and the reactive power of the charging and discharging power of the battery, and calculating a final voltage target value by correcting the corrected voltage target value with the correction amount for the voltage target value; and a step of performing charge and discharge control in a PWM method based on the final frequency target value and the final voltage target value. A control method having

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