Electric power control system

Abstract

The present invention provides an electric power control system that is connected to a DC power supply line to which are connected a load and a plurality of proportional charge / discharge controllers connected to each of a plurality of power supply sources including a renewable energy-using power generator, an energy storage device, and a commercial power source. The electric power control system comprises: a capacitor electrically connected to the DC power supply line such that the potential difference due to DC conversion with the load does not fluctuate; and a control unit that controls the plurality of proportional charge / discharge controllers. The control unit performs, with respect to one specific controller among the plurality of proportional charge / discharge controllers, a voltage control process to carry out DC voltage feedback control to bring the voltage of the DC power supply line closer to a target voltage, and a switching process to switch the specific controller from one proportional charge / discharge controller to another proportional charge / discharge controller.

Description

Power Control System

[0001] The present invention relates to a power control system.

[0002] A power control system has been known in the art that is connected to a DC power supply line to which a plurality of proportional charge / discharge controllers and a load are connected (see Patent Document 1 below). The plurality of proportional charge / discharge controllers are connected to a plurality of power supply sources, respectively. The plurality of power supply sources include a solar power generation system, a storage battery, and a commercial power supply. The commercial power supply is connected to the DC power supply line via a rectifier. In this power control system, the rectifier is voltage-controlled to control the charge / discharge of the storage battery, and the output voltage of the solar power generation system is controlled to be the maximum output voltage.

[0003] JP 2014-42417 A

[0004] In a conventional power control system, the voltage of the DC power supply line is likely to fluctuate in response to, for example, a sudden change in the load voltage. Therefore, if a configuration is adopted in which DC voltage feedback control is performed on only one specific controller among multiple proportional charge / discharge controllers, the fluctuation in the voltage of the DC power supply line may adversely affect the control of the other proportional charge / discharge controllers.

[0005] An object of the present invention is to provide a power control system that can solve the above-mentioned problems.

[0006] (1) A power control system disclosed in this specification is connected to a DC power supply line to which a load and a plurality of proportional charge / discharge controllers, each connected to a plurality of power supply sources including a renewable energy power generation device, a power storage device, and a commercial power source, are connected. The power control system includes a capacitor electrically connected to the DC power supply line so as to prevent a DC-equivalent potential difference between the load and the capacitor and the DC power supply line from fluctuating, and a control unit that controls the plurality of proportional charge / discharge controllers. The control unit performs a voltage control process for performing DC voltage feedback control on one specific controller of the plurality of proportional charge / discharge controllers to bring the voltage of the DC power supply line closer to a target voltage, and a switching process for switching the specific controller from one proportional charge / discharge controller to another proportional charge / discharge controller.

[0007] In this power control system, the capacitor is connected to the DC power supply line so that the DC-equivalent potential difference between the load and the power supply line does not fluctuate. This reduces the temporal change (response, amplitude) of the voltage on the DC power supply line. For example, the voltage on the DC power supply line fluctuates gradually in response to a sudden change in the load voltage. Therefore, even if a configuration is adopted in which DC voltage feedback control is performed only on a specific controller, the effect of voltage fluctuations on the DC power supply line on the control of other proportional charge / discharge controllers can be suppressed. Furthermore, the specific controller subject to DC voltage feedback control can be switched from one proportional charge / discharge controller to another. Therefore, this power control system allows power to be supplied to the load in a variety of power supply patterns compared to a configuration in which the specific controller is fixed to one proportional charge / discharge controller.

[0008] (2) In the power control system, the multiple power supply sources may include multiple power storage devices, and the control unit may be configured to include the proportional charge / discharge controllers connected to each of the multiple power storage devices as switching targets of the specific controller during the switching process. A power storage device (hereinafter referred to as a "target power storage device") connected to a proportional charge / discharge controller that is a switching target of the specific controller (DC voltage feedback control) cannot be charged or discharged by current control during that time. If only one of the multiple power storage devices is configured as the target power storage device, a problem occurs in which opportunities to charge or discharge by current control are limited for only that one power storage device. In contrast, according to this power control system, multiple power storage devices are configured as target power storage devices, and therefore, a problem in which opportunities to charge or discharge by current control for only a specific power storage device are limited among the multiple power storage devices can be prevented.

[0009] (3) In the above power control system, the control unit may be configured to execute a selection process to select one of the plurality of power storage devices based on a level of an evaluation of the power storage state based on at least one of an SOC, a C rate, a depth of discharge, and a degree of deterioration, and in the switching process, to preferentially switch the specific controller to the proportional charge / discharge controller connected to the power storage device selected in the selection process from the plurality of power storage devices. According to this embodiment, a power storage device from the plurality of power storage devices according to a level of evaluation of the power storage state can be set as the target power storage device.

[0010] (4) In the power control system, the plurality of power supply sources may include three or more of the power storage devices, the evaluation of the power storage state may be an SOC of the power storage devices, and the control unit may select, in the selection process, a power storage device having a medium SOC from among the plurality of power storage devices. According to this embodiment, a power storage device having a medium SOC and having a low need for charging / discharging can be selected as the target power storage device.

[0011] (5) In the above power control system, when the proportional charge / discharge controller connected to a plurality of power storage devices is not the specified controller, the control unit may be configured to perform a current control process of performing DC current feedback control on at least one of the plurality of power storage devices so as to suppress variation in evaluation of the power storage state based on at least one of the SOC, C rate, depth of discharge, and degree of deterioration for the plurality of power storage devices. According to this embodiment, it is possible to select, as the target power storage device, a power storage device having a medium SOC and low need for charging / discharging.

[0012] The present invention can also be realized in other forms, such as a power control system, a power control method, a power control program, and a non-transitory recording medium on which the power control program is recorded.

[0013] FIG. 1 is an explanatory diagram showing the electrical configuration of the power control system 100 and external devices according to an embodiment; FIG. 2 is a flowchart showing the power control process executed by the control unit 121 of the PCU 120; FIG. 3 is an explanatory diagram showing the control content of each proportional charge / discharge controller in each power supply mode; and FIG. 4 is a flowchart showing the SOC adjustment process executed by the control unit 121 of the PCU 120.

[0014] A. Embodiments: A-1. Electrical Configuration of Power Control System 100 and External Devices: FIG. 1 is an explanatory diagram showing the electrical configuration of a power control system 100 and external devices according to this embodiment. FIG. 1 shows external devices including a solar power generation system 10, a commercial power supply (grid) 20, a load 30, a master controller 40, and multiple LIB modules 50. These external devices are electrically connected to the power control system 100 via a DC power supply line LW. Examples of the load 30 include equipment used in manufacturing that accelerates and decelerates relatively quickly (machine tools, industrial robots, conveyance equipment, textile and food processing equipment, etc.), and equipment with relatively high output that must operate during a power outage (elevators, air conditioners, compressors, etc.). Note that FIG. 1 illustrates three LIB modules 50 (50A, 50B, 50C). The LIB modules 50 are an example of a power storage device.

[0015] The solar power generation system 10 generates electricity using photovoltaic power generation, which converts solar energy into electrical power. The solar power generation system 10 includes a solar panel 12 and a PV converter 14. The PV converter 14 includes a power generation device sensor 14A and a DC / DC converter 14B. The power generation device sensor 14A is a current / voltage sensor that detects the voltage and current values ​​of the power generated by the solar power generation system 10 and outputs detection signals corresponding to the detection results. The DC / DC converter 14B performs control to maximize the power generated by the solar panel 12 based on the detection results of the power generation device sensor 14A, and outputs DC power corresponding to the amount of power generated by the solar panel 12 to the power supply DC line LW. Hereinafter, the power output from the solar power generation system 10 will be referred to as "PV power Wp." In this embodiment, the PCU 120 (described later) controls the on / off operation of the DC / DC converter 14B. The solar panel 12 is an example of a renewable energy power generation system and a power supply source, and the DC / DC converter 14B is an example of a proportional charge / discharge controller.

[0016] The commercial power supply 20 is electrically connected to a DC power supply line LW via an AC / DC converter 22. AC power from the commercial power supply 20 is converted into DC power by the AC / DC converter 22 and output to the DC power supply line LW. Hereinafter, the DC power output from the commercial power supply 20 will be referred to as "commercial power Wa." The commercial power supply 20 is an example of a power supply source, and the AC / DC converter 22 is an example of a proportional charge / discharge controller.

[0017] The power control system 100 includes a LIC module 110 , a PCU (POWER CONTROL UNIT) 120 , a DC / DC converter 130 , a capacitor sensor 140 , and a load sensor 150 .

[0018] The LIC module 110 has a configuration in which multiple lithium ion capacitors (hereinafter referred to as "LICs") 112 are connected in series. One end (e.g., the positive electrode side) of the LIC module 110 is electrically connected to a power supply DC line LW without passing through a voltage converter such as a DC / DC converter. A load 30 is electrically connected to the power supply DC line LW via an AC / DC converter 22. That is, in this embodiment, the potential at the one end of the LIC module 110 is substantially the same as the potential at the side of the load 30 connected to the power supply DC line LW. The other end (e.g., the negative electrode side) of the LIC module 110 is electrically connected to a common line (e.g., a ground line). The power control system 100 may also have a configuration in which the load 30 is electrically connected to the power supply DC line LW via a DC / AC converter 160. Hereinafter, the power consumed by the load 30 will be referred to as "load power Wr."

[0019] The capacitor sensor 140 is a current / voltage sensor provided in the LIC module 110 connected in parallel to the power supply DC line LW (in other words, a current / voltage sensor provided in the current path between the LIC module 110 and the power supply DC line LW), which detects the current and voltage values ​​when the LIC module 110 is discharging or charging, and outputs detection signals according to the detection results. The load sensor 150 is a current / voltage sensor provided in the power supply DC line LW, in the current path between the LIC module 110 and the load 30, which detects the voltage value of the load 30 and the value of the current flowing through the load 30, and outputs detection signals according to the detection results.

[0020] One end of the DC / DC converter 130 is electrically connected to the power supply DC line LW, and the other end of the DC / DC converter 130 is electrically connected to a connection unit 132. One end (e.g., the positive electrode side) of the LIB module 50 is electrically connected to the connection unit 132. The other end (e.g., the negative electrode side) of the LIB module 50 is electrically connected to a common line (e.g., a ground line) side. The LIB module 50 is an example of a power supply source and a power storage device, and the DC / DC converter 130 is an example of a proportional charge / discharge controller.

[0021] The LIB module 50 is an energy storage medium with a lower output density (also referred to as "power density") than the LIC module 110. The LIB module 50 also has a higher energy density than the LIC module 110. In this embodiment, the LIB module 50 has, for example, a configuration in which a plurality of lithium ion batteries (hereinafter referred to as "LIBs") 52 are connected in series. The LIBs 52 are, for example, iron phosphate-based LIBs or ternary (nickel-manganese-cobalt-based, etc.) LIBs. Hereinafter, the power stored in the LIB module 50 will be referred to as "storage power Ws."

[0022] The PCU 120 includes a control unit 121, a storage unit 122, and an interface unit 123, and these units are connected to each other via a bus (not shown) so as to be able to communicate with each other.

[0023] The control unit 121 is configured with, for example, a CPU, and controls each proportional charge / discharge controller by executing a computer program read from the storage unit 122. Specifically, the control unit 121 controls the operation of the AC / DC converter 22, the DC / DC converter 14B of the PV converter 14, and the DC / DC converters 130 (130A, 130B, 130C). For example, the control unit 121 reads and executes a power control program (not shown) from the storage unit 122 to perform the power control process described below.

[0024] The storage unit 122 is configured with, for example, a ROM, a RAM, a hard disk drive (HDD), etc., and stores various data, programs, and models, and is used as a work area when executing various programs and models, and as a temporary storage area for data. The storage unit 122 also stores a power control program. The power control program is a computer program for executing the power control process described below. These programs are provided in a state stored on a computer-readable recording medium (not shown), such as a CD-ROM, a DVD-ROM, or a USB memory, and are stored in the storage unit 122 by being installed in the PCU 120.

[0025] The interface unit 123 is configured by, for example, a LAN interface or a USB interface, and communicates with other devices via wired or wireless communication. The PCU 120 detects the current, voltage, temperature, etc. of the LIC 112 in the LIC module 110 and the LIB 52 in the LIB module 50, and monitors the status of the LIC 112 and the LIB 52 (for example, whether or not an abnormal state such as over-discharge, over-charge, or high temperature has occurred) based on the detection results.

[0026] The master controller 40 is an external device communicatively connected to the power control system 100 and transmits various mode selection signals and the like to the PCU 120 .

[0027] When the power control system 100 is started, the PCU 120 executes a power control process to control the charging and discharging of the LIB module 50 while supplying power to the load 30 using the supplied power (PV power Wp, commercial power Wa) from the power supply unit (photovoltaic power generation device 10, commercial power source 20). Note that, as described above, controlling the charging and discharging of the LIB module 50 indirectly controls the charging and discharging of the LIC module 110. Specifically, the PCU 120 executes the power control process based on a mode selection signal from the master controller 40 and the various sensors 14A, 140, and 150. In this process, the PCU 120 controls the charging and discharging of the LIB module 50, for example, by operating the DC / DC converter 130, but does not directly control the charging and discharging of the LIC module 110. In other words, the PCU 120 indirectly controls the charging and discharging of the LIC module 110 by controlling the charging and discharging of the LIB module 50. In this specification, the term "charge and discharge" may refer to both charging and discharging, or may refer to only one of charging and discharging.

[0028] A-2. Suppression of mutual interference of DC voltage feedback control of proportional charge / discharge controllers: The power control system 100 has a configuration for suppressing mutual interference of DC voltage feedback control of proportional charge / discharge controllers. As described above, in this embodiment, the proportional charge / discharge controllers are the AC / DC converter 22 connected to the commercial power source 20, the DC / DC converter 14B connected to the solar panel 12, and the DC / DC converter 130 connected to the LIB module 50 (see FIG. 1). These multiple proportional charge / discharge controllers (22, 14B, 130) are controlled by the control unit 121.

[0029] If the control unit 121 were to individually perform DC voltage feedback control on multiple proportional charge / discharge controllers, mutual interference could occur due to discrepancies in the control timing or control amount. If mutual interference occurs in the DC voltage feedback control, for example, power generation by the solar power generation device 10 may stop due to unexpected fluctuations in the voltage of the power supply DC line LW, making it impossible to effectively utilize solar energy. In other words, if power generation by the solar power generation device 10 stops, solar energy cannot be converted into electricity and utilized.

[0030] In contrast to this, in this embodiment, the LIC module 110 is connected to the power supply DC line LW so that the potential difference between the LIC module 110 and the load 30 does not fluctuate in DC conversion, and DC voltage feedback control is performed on only one specific controller among the plurality of proportional charge / discharge controllers (see FIG. 1). With this configuration, it is possible to control the plurality of proportional charge / discharge controllers while suppressing the occurrence of mutual interference in the DC voltage feedback control.

[0031] That is, because the LIC module 110 is connected to the DC power supply line LW so that the DC-equivalent potential difference between the LIC module 110 and the load 30 does not fluctuate, the temporal change (response, amplitude) of the voltage of the DC power supply line LW is reduced according to the capacitance of the LIC module 110. For example, the voltage of the DC power supply line LW fluctuates gradually in response to a sudden change in the voltage of the load 30. Therefore, even if a configuration is adopted in which DC voltage feedback control is performed only on a specific controller, the influence of voltage fluctuations on the DC power supply line LW on the control of other proportional charge / discharge controllers can be suppressed. Moreover, in this embodiment, as described above, the capacitance of the LIC module 110 is set to a value large enough to reduce the amount of voltage fluctuation on the DC power supply line LW in response to instantaneous fluctuations to "0." This more reliably slows the response of voltage fluctuations on the DC power supply line LW to changes in load power, and more reliably reduces the amount of voltage fluctuation on the DC power supply line LW. This makes it possible to more effectively suppress the influence of fluctuations in the voltage of the power supply DC line LW on the control of other proportional charge / discharge controllers.

[0032] The PCU 120 performs (DC) current feedback control on the other proportional charge / discharge controllers, excluding the specific controller, among the plurality of proportional charge / discharge controllers, to bring the output current value closer to the target current value based on the storage power Ws and the PV power Wp. Note that the PCU 120 may also perform (DC) power feedback control on at least one of the other proportional charge / discharge controllers to bring the output power value closer to the target power value based on the storage power Ws and the power generation output value Wp1. By performing such control, the power supply source connected to the other proportional charge / discharge controller can be treated as a negative load (part of the load).

[0033] A-3. Power control process executed by the control unit 121 of the PCU 120: Figure 2 is a flowchart showing the power control process executed by the control unit 121 of the PCU 120, and Figure 3 is an explanatory diagram showing the control content of each proportional charge / discharge controller in each power supply mode. This power control process is a process in which DC voltage feedback control is performed only on a specific controller, and the specific controller is switched from one proportional charge / discharge controller to another proportional charge / discharge controller.

[0034] 2, the control unit 121 determines whether or not an independent operation condition is satisfied (S110). The independent operation condition is a condition under which the power control system 100 performs independent operation, such as a non-grid-connected state in which the commercial power source 20 is disconnected from the power supply DC line LW, such as during a power outage.

[0035] A-3-1. During grid connection: During grid connection, in which the commercial power supply 20 is connected to the DC power supply line LW, the control unit 121 determines that the stand-alone operation condition is not satisfied (S110: NO), and then determines whether the grid power control condition is satisfied (S120). The grid power control condition is a condition for performing power feedback control on the AC / DC converter 22 of the commercial power supply 20.

[0036] If the control unit 121 determines that the grid power control conditions are not satisfied (S120: NO), it executes the grid voltage control mode (S130). In the grid voltage control mode, the control unit 121 performs DC voltage feedback control on the AC / DC converter 22 of the commercial power source 20 (see FIG. 3 , an example of a voltage control process). At this time, the current flowing through the commercial power source 20 is uncontrolled, and therefore the power control system 100 cannot control the power supplied from the commercial power source 20 (or the power recovered from surplus power to the commercial power source 20). In addition, at this time, the AC / DC converter 22 is an example of a specific controller.

[0037] In addition, in the grid voltage control mode, the control unit 121 performs current feedback control or power feedback control on at least some of the DC / DC converters 130 (130A, 130B, 130C) of the multiple LIB modules 50 (50A, 50B, 50C) (see FIG. 3 and S250 in FIG. 4 described later). This allows the DC / DC converters 130 of at least some of the LIB modules 50 to be charged or discharged by current feedback control or power feedback control. In addition, the control unit 121 performs current feedback control or power feedback control on the DC / DC converter 14B of the solar power generation device 10 (see FIG. 3). Note that the current or power flowing through the solar power generation device 10 fluctuates depending on the weather. In this way, in the grid voltage control mode, the DC / DC converters 130 of all the LIB modules 50 are not subject to DC voltage feedback control, so the charge / discharge amounts of all the LIB modules 50 can be controlled.

[0038] If the control unit 121 determines that the grid power control conditions are satisfied (S120: YES), the control unit 121 executes the grid power control mode (S140). In the grid power control mode, the control unit 121 excludes the AC / DC converter 22 of the commercial power supply 20 from the target of the specific controller (DC voltage feedback control), and performs current feedback control or power feedback control (see FIG. 3). This enables the power control system 100 to control the power supplied from the commercial power supply 20 (or the surplus power recovered to the commercial power supply 20).

[0039] In the grid power control mode, the control unit 121 performs DC voltage feedback control on only one of the DC / DC converters 130 (130A, 130B, 130C) of the multiple LIB modules 50 (50A, 50B, 50C) (see FIG. 3 , an example of a voltage control process). This one DC / DC converter 130 is an example of a specific controller. The control unit 121 can also perform current control or power control to charge or discharge the remaining DC / DC converters 130 that are not subject to DC voltage feedback control (see S240 in FIG. 4 , described later). Note that the DC / DC converter 14B of the photovoltaic power generation device 10 is the same as in the grid voltage control mode. In this way, in the grid power control mode, in order to enable power control for the commercial power source 20, one of the DC / DC converters 130 of the multiple LIB modules 50 is subject to DC voltage feedback control, and charging or discharging by current control or power control is restricted.

[0040] A-3-2. Non-Grid-Connected Operation: When the commercial power source 20 is disconnected from the DC power supply line LW and the control unit 121 determines that the autonomous operation conditions are met (S110: YES), the control unit 121 executes the autonomous operation control mode (S150). The autonomous operation control mode is a mode in which the PV power Wp of the photovoltaic power generation device 10 and the storage power Ws of the LIB module 50 are used to supply power to the load 30, and the surplus power of the PV power Wp (= Wp - Wr) is used to charge the LIB module 50. At this time, the AC current of the AC / DC converter 22 varies depending on the power supplied to the load 30.

[0041] In the independent operation control mode, similarly to the grid power control mode, the control unit 121 performs DC voltage feedback control on only one of the DC / DC converters 130 (130A, 130B, 130C) of the multiple LIB modules 50 (50A, 50B, 50C) (see FIG. 3, an example of voltage control processing). The control unit 121 can also perform charging and discharging by current control or power control on the remaining DC / DC converters 130 that are not subject to DC voltage feedback control (see S240 in FIG. 4). The DC / DC converter 14B of the photovoltaic power generation device 10 is controlled in the same way as in the grid voltage control mode.

[0042] In this embodiment, the DC / DC converter 14B of the solar power generation device 10 is not subject to DC voltage feedback control in either mode. As described above, the DC / DC converter 14B needs to be controlled to maximize the power generated by the solar panel 12, and therefore it is preferable to avoid the current (power) being left to its own devices due to DC voltage feedback control.

[0043] After starting execution of each mode, the control unit 121 determines whether or not a stop command has been issued (S160). The control unit 121 may receive the stop command from the master controller 40, for example, or may output the stop command independently when it detects an abnormality in the power control system 100. If the control unit 121 determines that a stop command has not been received (S160: NO), the process returns to S110 and continues execution of the mode according to the conditions. If the control unit 121 determines that a stop command has been received (S160: YES), the control unit 121 terminates this power control process.

[0044] A-4. SOC adjustment process executed by the control unit 121 of the PCU 120: Figure 4 is a flowchart showing the SOC adjustment process executed by the control unit 121 of the PCU 120. The SOC adjustment process is a process for suppressing (uniformly equalizing) variations in SOC (State of Charge) among the multiple LIB modules 50 connected to the power control system 100. The control unit 121 repeatedly executes this SOC adjustment process at predetermined time intervals in parallel with the above-described power control process.

[0045] The control unit 121 estimates the SOC of each of the multiple LIB modules 50 (S210). Various known methods (e.g., the OCV (Open Circuit Voltage) method or the current integration method) can be used to estimate the SOC. Next, the control unit 121 determines whether any of the DC / DC converters 130 of the multiple LIB modules 50 is the target of the specific controller in the power control process. Specifically, if the grid voltage control mode (S130 in FIG. 3 ) is being executed, the control unit 121 determines that none of the multiple DC / DC converters 130 is the target of the specific controller, since the target of the specific controller is the AC / DC converter 22 of the commercial power source 20. On the other hand, if the grid power control mode or the isolated operation control mode (S140, S150 in FIG. 3 ) is being executed, the control unit 121 determines that any of the multiple DC / DC converters 130 is the target of the specific controller.

[0046] A-4-1. When the LIB module 50 is the target of switching of the specific controller: When the control unit 121 determines that any one of the DC / DC converters 130 of the multiple LIB modules 50 is the target of the specific controller (S220: YES), it selects one DC / DC converter 130 from the multiple DC / DC converters 130 as the target of switching of the specific controller (target of DC voltage feedback control) (S230). The processing of S230 is an example of selection processing. In this embodiment, the DC / DC converter 130 of the LIB module 50 whose estimated SOC is closest to the reference SOC is selected. The reference SOC is, for example, as follows: The SOC is an example of an evaluation of the state of charge. The average value of the SOC of each of the multiple LIB modules 50 The median value between the highest and lowest SOCs of each of the multiple LIB modules 50 (3) A predetermined fixed value (for example, 50%)

[0047] The control unit 121 subjects the DC / DC converters 130 that are not subject to switching of the specific controller (hereinafter, sometimes referred to as "non-target DC / DC converters 130") to current feedback control or power feedback control. The control unit 121 determines whether to charge or discharge each of the non-target DC / DC converters 130 based on the SOC (S240). For example, the following determinations may be made: (1) Non-target DC / DC converters 130 of LIB modules 50 where "SOC > reference SOC": Discharge (2) Non-target DC / DC converters 130 of LIB modules 50 where "SOC < reference SOC": Charge Furthermore, the following (3) may be added. (3) DC / DC converters 130 not targeted by the LIB module 50 whose difference from the reference SOC is within a reference range (for example, within ±5% of the reference SOC): Neither charging nor discharging is performed. Once the control content for each DC / DC converter 130 is determined, the control unit 121 performs control according to the determination (S260) and terminates this SOC adjustment process.

[0048] For example, in the configuration shown in FIG. 1 , if the SOC of the first LIB module 50A is 70%, the SOC of the second LIB module 50B is 20%, and the SOC of the third LIB module 50C is 45%, the respective control targets are determined as follows: Because the SOC of the third LIB module 50C is medium (closest to the reference SOC (e.g., 50%)), the third LIB module 50C has the lowest need for charging and discharging. Therefore, the third DC / DC converter 130C of the third LIB module 50C is selected as the target for switching of the specific controller, and DC voltage feedback control is performed on the third DC / DC converter 130C in the "grid power control mode" (S140) and "independent operation control mode" (S150) in the power control process.

[0049] As a result, the first DC / DC converter 130A and the second DC / DC converter 130B become non-target DC / DC converters 130. Because the SOC (70%) of the first LIB module 50A is greater than the reference SOC, it is decided to discharge the first DC / DC converter 130A, and in the "grid power control mode" and "independent operation control mode" in the power control process, discharge is performed on the first DC / DC converter 130A by current feedback control or power feedback control.

[0050] Because the SOC (20%) of the second LIB module 50B is lower than the reference SOC, it is decided to charge the second DC / DC converter 130B, and in the "grid power control mode" and "independent operation control mode" of the power control process, charging is performed by current feedback control or power feedback control for the second DC / DC converter 130B. As a result, the SOC of the first LIB module 50A decreases and approaches the SOC of the third LIB module 50C, and the SOC of the second LIB module 50B increases and approaches the SOC of the third LIB module 50C, thereby suppressing variations in the SOC of the three LIB modules 50A, 50B, and 50C.

[0051] A-4-2. When the LIB module 50 is not a target for switching of the specific controller: When the control unit 121 determines that the DC / DC converter 130 of the LIB module 50 is not a target for switching of the specific controller (S220: NO), the control unit 121 sets the non-target DC / DC converter 130 as a target for current feedback control or power feedback control. In this case, all DC / DC converters 130 are non-target DC / DC converters 130. The control unit 121 determines, based on the SOC, whether to charge, discharge, or not charge or discharge each of the non-target DC / DC converters 130 (S250). For example, the determination may be made as follows: (1) DC / DC converters 130 other than those of LIB modules 50 whose difference from the reference SOC is within the reference range (for example, within ±5% of the reference SOC): do not charge or discharge. (2) DC / DC converters 130 other than those of LIB modules 50 whose difference from the reference SOC is outside the reference range and whose SOC is greater than the reference SOC: discharge. (3) DC / DC converters 130 other than those of LIB modules 50 whose difference from the reference SOC is outside the reference range and whose SOC is less than the reference SOC: charge. Once the control content for each DC / DC converter 130 has been determined, the control unit 121 carries out control according to the determination (S260) and terminates this SOC adjustment process.

[0052] For example, in the configuration shown in FIG. 1 , if the SOC of the first LIB module 50A is 54%, the SOC of the second LIB module 50B is 47%, and the SOC of the third LIB module 50C is 25%, the respective control targets are determined as follows: Since the difference between the SOC of the first LIB module 50A and the SOC of the second LIB module 50B and the reference SOC (50%) is within the reference range (within 50% ±5%), it is determined that no charging or discharging will be performed. Since the SOC of the third LIB module 50C is outside the reference range and lower than the reference SOC, it is determined that charging will be performed. As a result, the SOC of the first LIB module 50A and the SOC of the second LIB module 50B is maintained within the reference range, and the SOC of the third LIB module 50C approaches the reference SOC, thereby suppressing the variation in the SOC of the three LIB modules 50A, 50B, and 50C.

[0053] A-5. Advantages of the Present Embodiment: In the power control system according to the present embodiment, the LIC module 110 is connected to the power supply DC line LW so that the potential difference between the LIC module 110 and the load 30, converted into DC, does not fluctuate. Therefore, the temporal change (response, amplitude) in the voltage of the power supply DC line LW decreases according to the capacity of the LIC module 110. For example, the voltage of the power supply DC line LW fluctuates gradually in response to a sudden change in the load voltage. Therefore, even if a configuration is adopted in which DC voltage feedback control is performed only on a specific controller, the influence of voltage fluctuations on the power supply DC line LW on the control of other proportional charge / discharge controllers can be suppressed. Furthermore, the specific controller that is the target of DC voltage feedback control can be switched from one proportional charge / discharge controller (e.g., the AC / DC converter 22) to another proportional charge / discharge controller (e.g., the DC / DC converter 130). Therefore, according to the present embodiment, power can be supplied to the load in a variety of power supply patterns compared to a configuration in which the specific controller is fixed to one proportional charge / discharge controller.

[0054] During this period, charging and discharging by current control cannot be performed on the LIB module 50 (hereinafter referred to as the "target LIB module") connected to the proportional charge / discharge controller that is the switching target of the specific controller (DC voltage feedback control). Here, if only one LIB module 50 out of the multiple target LIB modules 50 is designated as the target LIB module, a problem occurs in which opportunities to charge and discharge by current control are limited for only that one LIB module 50. In contrast, according to this embodiment, multiple LIB modules 50 are designated as target LIB modules, and therefore it is possible to prevent a problem from occurring in which opportunities to charge and discharge by current control are limited for only a specific LIB module 50 out of the multiple LIB modules 50.

[0055] B. Modifications The present invention is not limited to the above-described embodiment, and can be modified in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0056] The configuration of the power control system 100 and the like in the above embodiment is merely an example and can be modified in various ways. For example, in the above embodiment, the solar power generation device 10, the commercial power source 20, and the LIB module 50 are exemplified as power supply sources, but the power supply source may be a renewable energy power generation device that generates power using renewable energy other than solar energy (e.g., natural energy such as wind power, hydroelectric power, geothermal power, and thermal power). Furthermore, the power supply source may be a power generation device that does not use renewable energy, such as a gas generator, or a power supply source other than the commercial power source 20 and the LIB module 50.

[0057] In the above embodiment, the power control system 100 may be configured to incorporate at least one of the AC / DC converter 22, the DC / DC converter 14B, and the DC / DC converter 130. Furthermore, a plurality of power control systems 100 may be connected in series or in parallel. Furthermore, the plurality of devices (LIC module 110, DC / DC converter 130, etc.) that make up the power control system 100 are connected to a common power supply DC line LW, and therefore these devices are connected in parallel with one another. However, when a plurality of power control systems 100 are connected, some devices may be connected in series.

[0058] In the above embodiment, the AC / DC converter 22, the DC / DC converter 14B, and the DC / DC converter 130 are exemplified as proportional charge / discharge controllers, but any proportional charge / discharge controller in which the input and output are proportional may be used, for example, a proportional charge / discharge controller configured by combining an AC / DC converter and a DC / DC converter. Note that the proportional charge / discharge controller is not limited to a controller that controls both charging and discharging, but also includes a controller that controls only one of charging and discharging.

[0059] In the above embodiment, the LIC module 110 may be configured with a plurality of LICs 112 connected in parallel, a plurality of LICs 112 connected in series and parallel, or may be configured with only one LIC 112. Furthermore, in the above embodiment, the LIC module 110 (LIC 112) is exemplified as a capacitor, but it may also be, for example, an electric double layer capacitor (EDLC) or an electrolytic capacitor.

[0060] In the above embodiment, the LIB module 50 may be configured with a plurality of LIBs 52 connected in parallel, a plurality of LIBs 52 connected in series and parallel, or may be configured with only one LIB 52. Furthermore, in the above embodiment, the LIB module 50 (LIB 52) is exemplified as the power storage device, but other types of power storage devices, such as lead-acid batteries, may also be used. Furthermore, in the above embodiment, the number of LIB modules 50 connected to the power control system 100 may be one, two, or four or more.

[0061] In the above embodiment, the potential at the one end of the LIC module 110 and the potential at the side of the load 30 connected to the power supply DC line LW are substantially the same, but a configuration is also possible in which the potential at the one end of the LIC module 110 and the potential at the side of the load 30 connected to the power supply DC line LW are different and the difference between the two potentials does not fluctuate. Even in such a configuration, the LIC module 110 has a higher correlation between voltage and capacity than the LIB module 50, and therefore, by controlling the charging and discharging of the LIB module 50, it is possible to indirectly control the charging and discharging of the LIC module 110 without having a dedicated DC / DC converter.

[0062] The contents of the various processes in the above embodiment are merely examples and can be modified in various ways. In the flowchart shown in Figure 3 of the above embodiment, any one of the processes of S130 (grid voltage control mode), S140 (grid power control mode), and S150 (isolated operation control mode) may be omitted.

[0063] In the above embodiment, the SOC is used as an example of the evaluation of the state of charge. However, the evaluation is not limited to this, and may be based on the C rate, the depth of discharge, the degree of deterioration, or the like. The evaluation of the state of charge may also be based on a comprehensive evaluation of at least two of the SOC, the C rate, the depth of discharge, and the degree of deterioration (e.g., SOH, the number of charges, the charge time, the number of discharges, the discharge time, the number of charges and discharges, and the charge and discharge time). The evaluation of the state of charge may also be based on the temperature of the power storage device, or the like. In the process of S230 described above, when three or more LIB modules 50 are provided, the DC / DC converter 130 of the LIB module 50 with a medium SOC may simply be set as the target of the specific controller. Conversely, the non-target DC / DC converter 130 of the LIB module 50 with the highest or lowest SOC may not be set as the target of the specific controller.

[0064] In the above-described embodiment, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware.

[0065] 10: Photovoltaic power generation device 12: Solar panel 14: PV converter 14A: Power generation equipment sensor 14B: DC / DC converter 20: Commercial power supply 22: AC / DC converter 30: Load 40: Master controller 50: LIB module 52: LIB 100: Power control system 110: LIC module 112: LIC 120: PCU 121: Control unit 122: Memory unit 123: Interface unit 130: DC / DC converter 132: Connection unit 140: Capacitor sensor 150: Load sensor 160: DC / AC converter LW: Power supply DC line

Claims

1. A power control system connected to a power supply DC line to which a load and a plurality of proportional charge / discharge controllers each connected to a plurality of power supply sources including a renewable energy power generation device, a power storage device, and a commercial power source are connected, the power control system comprising: a capacitor electrically connected to the power supply DC line so that a potential difference in DC conversion with the load does not fluctuate; and a control unit which controls the plurality of proportional charge / discharge controllers, the control unit performing a voltage control process for performing DC voltage feedback control for one specific controller of the plurality of proportional charge / discharge controllers to bring the voltage of the power supply DC line closer to a target voltage; and a switching process for switching the specific controller from one of the proportional charge / discharge controllers to another of the proportional charge / discharge controllers.

2. A power control system as described in claim 1, wherein the multiple power supply sources include multiple power storage devices, and the control unit includes a proportional charge / discharge controller connected to each of the multiple power storage devices as a switching target for the specific controller in the switching process.

3. A power control system as described in claim 2, wherein the control unit executes a selection process to select one of the plurality of power storage devices based on a high or low evaluation of the storage state based on at least one of SOC, C rate, discharge depth, and degree of deterioration, and in the switching process, the specific controller is preferentially switched to the proportional charge / discharge controller connected to the power storage device selected in the selection process from among the plurality of power storage devices.

4. A power control system as described in claim 3, wherein the multiple power supply sources include three or more of the storage devices, the evaluation of the storage state is the SOC of the storage devices, and the control unit, in the selection process, selects the storage device having a medium SOC from among the multiple storage devices.

5. A power control system as described in claim 2, wherein the control unit, when the proportional charge / discharge controller connected to a plurality of power storage devices is not designated as the specific controller, performs a current control process of performing DC current feedback control on at least one of the plurality of power storage devices so as to suppress variation in the evaluation of the power storage state based on at least one of the SOC, C rate, discharge depth, and deterioration degree for the plurality of power storage devices.