Storage battery control device

Abstract

To provide a storage battery control device capable of reducing cost and improving output characteristics of a storage battery.SOLUTION: A storage battery control device comprises: an acquisition section for acquiring temperatures of a plurality of storage batteries included in a plurality of power supply circuits connected in parallel with each other so as to exchange power via a common terminal; and a control section for executing control of charge or discharge, with respect to a storage battery of which the temperature is equal to or lower than a threshold, with the other storage battery in the plurality of storage batteries.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a storage battery control device. [Background technology]

[0002] Regarding the control of a storage battery, for example, Patent Document 1 describes a method for increasing the temperature of a low-temperature secondary battery by driving a heater using surplus power from a fuel cell, thereby improving the output characteristics of the battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-133147 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, providing a heater in the storage battery may cause other problems such as an increase in circuit scale and an increase in device costs.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a storage battery control device that can improve the cost and output characteristics of a storage battery. [Means for solving the problem]

[0006] The battery control device of the present invention has an acquisition unit that acquires the temperature of each of multiple storage batteries included in multiple power supply circuits that are connected in parallel to each other so as to exchange power via a common terminal, and a control unit that performs control of charging or discharging between a storage battery among the multiple storage batteries that has a temperature below a threshold value and other storage batteries. Effect of the Invention

[0007] According to the present invention, the cost and output characteristics of a storage battery can be improved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a configuration diagram showing an example of a stationary storage battery system. [Diagram 2] FIG. 2 is a configuration diagram illustrating an example of a system control device. [Diagram 3] FIG. 3 is a time chart showing an example of charge / discharge control. [Figure 4] FIG. 4 is a flowchart showing an example of the operation of the system control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Configuration of stationary storage battery system) Fig. 1 is a configuration diagram showing an example of a stationary storage battery system 9. In order to promote efficient power utilization, the stationary storage battery system 9 stores electricity generated by, for example, wind power generation or solar power generation, and supplies the electricity to hybrid vehicles, electric vehicles, general households, etc. in a timely manner. The stationary storage battery system 9 includes a system control device 1, an EMS (Energy Management System) 5, a PCS (Power Conditioning System) 8, a PCS-ECU (Electronic Control Unit) 6, and power storage units 90a to 90c.

[0010] The power storage units 90a to 90c are an example of a plurality of power supply circuits. The power storage units 90a to 90c store power supplied from the power system 7 via the PCS 8 and supply the power to the power system 7 at appropriate times. The power system 7 is an AC power supply system including power plants, substations, general homes, power supply stations, etc. The power storage units 90a to 90c are connected in parallel to each other so as to exchange power with the power system 7 via a common pair of input / output terminals T.

[0011] The PCS 8 is, for example, an inverter, and converts AC current on the power system 7 side into DC current on the stationary storage battery system 9 side, and vice versa. The PCS-ECU 6 controls the conversion operation of the PCS 8. The system control device 1 is an example of a storage battery control device, and controls the charging and discharging of the power storage units 90a to 90c. The EMS 5 includes, for example, one or more servers, and instructs the system control device 1 and the PCS-ECU 6 to operate in accordance with the power supply and demand conditions of the entire power system 7.

[0012] The power storage units 90a-90c each include storage batteries 2a-2c such as lithium ion batteries, DC (Direct Current)-DC converters 3a-3c, output capacitors 44a-44c, CNV-ECUs 91a-91c, and BAT-ECUs 92a-92c. Each of the power storage units 90a-90c also includes a pair of relays 40, 41 and an input capacitor .

[0013] The storage batteries 2a to 2c are connected in parallel to an input capacitor 42 via connected relays 40, 41. One end of the input capacitor 42 is connected between the relay 40 and the DC-DC converters 3a to 3c, and the other end of the input capacitor 42 is connected between the relay 41 and the DC-DC converters 3a to 3c.

[0014] The DC-DC converters 3a to 3c are connected in parallel to a pair of input / output terminals T on the PCS 8 side. Each of the DC-DC converters 3a to 3c includes transistors 30 and 31 such as IGBTs (Insulated Gate Bipolar Transistors), free wheel diodes 32 and 33, and a reactor .

[0015] The emitter terminal of transistor 30 is connected to the collector terminal of transistor 31, and one end of reactor 34 is connected between the terminals. The cathode terminal of freewheel diode 33 is connected to the anode terminal of freewheel diode 32. The anode terminal and cathode terminal of freewheel diode 32 are connected to the emitter terminal and collector terminal, respectively, of transistor 30, and the anode terminal and cathode terminal of freewheel diode 33 are connected to the collector terminal and emitter terminal, respectively, of transistor 31. The collector terminal of transistor 30 and the emitter terminal of transistor 31 are connected to both ends of output capacitors 44a to 44c, respectively.

[0016] The CNV-ECUs 91a to 91c output PWM (Pulse Width Modulation) signals to the gate terminals of the transistors 30 and 31 as indicated by dotted lines. The CNV-ECUs 91a to 91c adjust the duty ratio of the PWM signals according to the target voltage value instructed by the system control device 1. The DC-DC converters 3a to 3c convert the voltages of the storage batteries 2a to 2c, respectively, by the transistors 30 and 31 performing switching operations according to the PWM signals. At this time, the reactor 34 accumulates and releases energy input from the storage batteries 2a to 2c according to the switching operations of the transistors 30 and 31. The freewheel diodes 32 and 33 pass current when the transistors 30 and 31 are turned off by the PWM signals.

[0017] Furthermore, the input capacitor 42 smoothes out voltage fluctuations input from the storage batteries 2a-2c to the DC-DC converters 3a-3c, respectively. The output capacitors 44a-44c smooth out fluctuations in the output voltages VHa-VHc output from the DC-DC converters 3a-3c to the PCS, respectively. Since the output capacitors 44a-44c are connected in parallel to the input / output terminal T, the output voltages VHa-VHc match the DC voltage E between the input / output terminals T.

[0018] The BAT-ECUs 92a to 92c collect the temperatures and SOC (State Of Charge) of the storage batteries 2a to 2c, respectively. The CNV-ECUs 91a to 91c and the BAT-ECUs 92a to 92c are each connected to the system control device 1 via a system bus 93. The system control device 1 is connected to the EMS 5, for example, via a LAN (Local Area Network).

[0019] (System Control Device) 2 is a configuration diagram showing an example of the system control device 1. The system control device 1 has a CPU (Central Processing Unit) 10, a ROM (Read Only Memory) 11, a RAM (Random Access Memory) 12, a system bus interface unit 13, and a communication port 14, which are electrically connected to each other via a bus 19. The system control device 1 is an example of a computer.

[0020] The ROM 11 stores a program that drives the CPU 10. The RAM 12 functions as a working memory for the CPU 10. The system bus interface unit 13 is a circuit that processes communication between the CPU 10 and the CNV-ECUs 91a to 91c and the BAT-ECUs 92a to 92c. The communication port 14 is, for example, a wireless LAN card, and is a circuit that processes communication between the CPU 10 and the EMS 5. When the CPU 10 reads the program from the ROM 11, it forms an operation control unit 100, a parameter acquisition unit 101, and a charge / discharge control unit 102 as functions.

[0021] The operation control unit 100 controls the overall operation of the system control device 1. The parameter acquisition unit 101 is an example of an acquisition unit. The parameter acquisition unit 101 acquires the temperature and SOC of each of the storage batteries 2a to 2c from the BAT-ECUs 92a to 92c via the system bus interface unit 13.

[0022] The charge / discharge control unit 102 is an example of a control unit. The charge / discharge control unit 102 controls charging or discharging between the storage batteries 2a-2c having a temperature equal to or lower than a threshold value and the other storage batteries 2a-2c. Specifically, the charge / discharge control unit 102 issues a command value of an output voltage VHa-VHc corresponding to charging or discharging to the CNV-ECUs 91a-91c corresponding to the storage batteries 2a-2c to be controlled via the system bus interface unit 13. At this time, the charge / discharge control unit 102 may determine whether to perform charging or discharging control depending on the magnitude relationship between the SOC of the storage batteries 2a-2c to be controlled and the other storage batteries 2a-2c.

[0023] The CNV-ECUs 91a to 91c that receive the command output PWM signals having duty ratios according to the command values ​​is / are output to the DC-DC converters 3a to 3c. The DC-DC converters 3a to 3c perform switching operations according to the PWM signals so as to bring the output voltages VHa to VHc closer to the target values.

[0024] On the other hand, the DC-DC converters 3a-3c of the other storage batteries 2a-2c that are not the control target perform switching operations so as to cancel out fluctuations in the DC voltage E caused by changes in the output voltages VHa-VHc caused by the switching operations of the DC-DC converters 3a-3c of the control target storage batteries 2a-2c. This is because the power storage units 90a-90c are connected in parallel to each other at the input / output terminals T, and therefore the DC-DC converters 3a-3c of the other storage batteries 2a-2c attempt to maintain the DC voltage E (=output voltages VHa-VHc) at a constant value.

[0025] As a result, power is exchanged between the storage batteries 2a-2c to be controlled and the other storage batteries 2a-2c. The storage batteries 2a-2c to be controlled are heated by an electrochemical reaction caused by the exchange of power, improving their output characteristics. At this time, the stationary storage battery system 9 does not require equipment such as a heater, which also improves costs.

[0026] Furthermore, the charge / discharge control unit 102 may perform the above-mentioned charge / discharge control when the PCS 8 is in an unloaded state, that is, when there is no exchange of power between the stationary storage battery system 9 and the power grid 7. When there is exchange of power, it is not necessarily necessary to perform charge / discharge control between the storage batteries 2a-2c, since each of the storage batteries 2a-2c can be heated by charging or discharging. Therefore, if charge / discharge control between the storage batteries 2a-2c is performed when the PCS 8 is in an unloaded state, it is possible to timely raise the temperature. The charge / discharge control unit 102 can determine the unloaded state of the PCS 8, for example, by communicating with the EMS 5.

[0027] (Example of charge / discharge control) Fig. 3 is a time chart showing an example of charge / discharge control. Fig. 3 shows the total output power (W) of the stationary battery system 9 with respect to time (seconds) for the storage battery 2a and the other storage batteries 2b and 2c, the output power (W) and output current (A) of each of the storage batteries 2a to 2c, the output voltages VHa to VHc (V), and their command values ​​(V).

[0028] In this example, charging control is performed on the storage battery 2a to charge the storage battery 2a from the other storage batteries 2b, 2c. In the initial state, the output voltages VHa to VHc and their command values ​​are the same, and the total output power, each output power, and each output current are 0. At time Ts, the charge / discharge control unit 102 instructs the CNV-ECU 91a to reduce the output voltage VHa below the current value. The command value of the output voltage VHa decreases to a value lower than the other output voltages VHb, VHc from time Ts to time Te.

[0029] The CNV-ECU 91a controls the duty ratio of the PWM signal so that the output current of the storage battery 2a decreases from 0 to the negative side from time Ts to time Te in accordance with the decrease in the command value. Accordingly, the output power of the storage battery 2a decreases from 0 to the negative side from time Ts to time Te.

[0030] On the other hand, the command values ​​for the output powers VHb, VHc are maintained constant, but the DC-DC converters 3b, 3c of the other storage batteries 2b, 2c perform switching operations to cancel out fluctuations in the DC voltage E caused by changes in the output voltages VHa-VHc. As a result, while the output voltages VHa-VHc and DC voltage E are maintained constant, the output currents of the storage batteries 2b, 2c increase from 0 to the positive side from time Ts to time Te, and the output power also increases from 0 to the positive side accordingly. The amount of increase is substantially half the amount of decrease in the output power of the storage battery 2a to be controlled, so that the total output power of the stationary storage battery system 9 is also maintained at 0.

[0031] In this way, the storage battery 2a is charged from the storage batteries 2b and 2c, so that the temperature of the storage battery 2a rises and the output characteristics are improved. Conversely to this example, if the charge / discharge control unit 102 increases the command value of the output power VHa of the storage battery 2a from the value at time Ts, the output power and output current of the storage battery 2a increase from 0 to the positive side, and the output power and output current of the other storage batteries 2b and 2c decrease from 0 to the negative side. As a result, the storage battery 2a discharges to the storage batteries 2b and 2c, so that the output characteristics are improved in the same manner as above.

[0032] (System control device operation) 4 is a flowchart showing an example of the operation of the system control device 1. This operation is executed, for example, at regular time intervals.

[0033] First, the operation control unit 100 judges whether the PCS 8 is in the no-load state based on a notification from the EMS 5 (step St1). If the PCS 8 is not in the no-load state (No in step St1), the operation of step St1 is executed again. If the PCS 8 is in the no-load state (Yes in step St1), the parameter acquisition unit 101 collects the temperature and SOC of each of the storage batteries 2a to 2c (step St2).

[0034] Next, the charge / discharge control unit 102 selects one of the storage batteries 2a-2c (step St3). In this example, the number of storage batteries in the stationary storage battery system 9 is three, but the number is not limited to three and may be two, four or more. Next, the charge / discharge control unit 102 compares the temperature of the selected storage battery 2a-2c with a threshold value THt (step St4). The threshold value THt is set in advance in the charge / discharge control unit 102 based on, for example, the temperature characteristics of the storage batteries 2a-2c. If the temperature>threshold value THt is satisfied (No in step St4), the operation of step St7 described below is performed.

[0035] If temperature≦threshold THt is satisfied (Yes in step St4), the charge / discharge control unit 102 determines whether the SOC of the selected battery 2a-2c is higher among all the batteries 2a-2c (step St5). For example, if the SOC of the battery 3a is the highest among the three batteries 2a-2c, its SOC is determined to be higher. If the SOC is higher (Yes in step St5), the charge / discharge control unit 102 executes discharge control from the selected battery 2a-2c to the other batteries 2a-2c (step St6).

[0036] If the SOC is not the highest (No in step St5), the charge / discharge control unit 102 determines whether the SOC of the selected battery 2a-2c is the lowest among all the batteries 2a-2c (step St8). For example, if the SOC of the battery 3a is the lowest among the three batteries 2a-2c, its SOC is determined to be the lowest. If the SOC is the lowest (Yes in step St8), the charge / discharge control unit 102 executes charge control of the selected battery 2a-2c from the other batteries 2a-2c (step St11).

[0037] If the SOC is not the lowest (No in step St8), the charge / discharge control unit 102 compares the average value of the higher SOCs with the threshold value THa (step St9). Here, the average value is the average of the SOCs from the first to third highest SOCs in the case where there are 10 storage batteries, for example. If the average value of the higher SOCs≧threshold value THa holds (Yes in step St9), the above-mentioned charge control is executed (step St11).

[0038] If the higher SOC average value<threshold value THa holds (No in step St9), the charge / discharge control unit 102 compares the lower SOC average value with threshold value THb (step St10). Here, the average value is the average of the SOCs from lowest to highest in a case where there are 10 batteries, for example. If the lower SOC average value≦threshold value THa holds (Yes in step St10), the above-mentioned discharge control is executed (step St6). If the lower SOC average value<threshold value THb holds (No in step St10), the above-mentioned charge control is executed (step St11).

[0039] Next, the charge / discharge control unit 102 determines whether or not there are any unselected storage batteries 2a-2c (step St7). If there are any unselected storage batteries 2a-2c (Yes in step St7), the operations from step St3 onwards are executed again. If there are no unselected storage batteries 2a-2c (No in step St7), this operation ends. The system control device 1 operates in this manner. Note that the system control device 1 of this example is not limited to the stationary storage battery system 1, and can also be used in a storage battery system for an electric vehicle having a similar configuration.

[0040] The above-described embodiment is a preferred example of the present invention, but the present invention is not limited to this embodiment and can be modified in various ways without departing from the scope of the present invention. [Explanation of symbols]

[0041] 1 System control device (storage battery control device), 2a to 2c storage battery, 10 CPU, 101 parameter acquisition unit, 102 charge / discharge control unit (control unit), 90a to 90c storage unit (power supply circuit), T input / output terminal (terminal)

Claims

[Claim 1] an acquisition unit that acquires temperatures of a plurality of storage batteries included in a plurality of power supply circuits that are connected in parallel to each other so as to exchange power via a common terminal; A control unit that controls charging or discharging between a storage battery having a temperature equal to or lower than a threshold value among the plurality of storage batteries and another storage battery. Battery control device.

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