Battery pack control device, battery pack control method, and energy storage system

Abstract

To protect a battery pack unit even when a composite failure occurs in the battery pack unit in which a plurality of battery packs are connected in series.SOLUTION: A battery pack control device 30 has: a switch part 25 composed of a plurality of FETs in which each of a plurality of battery packs 22 is connected or separated; a plurality of protection circuits 23 each of which is provided between the switch part 25 and the battery pack 22, and in which each protection circuit 23 includes a first rectifier element, a second rectifier element, and a resistance element, and when voltage of the battery pack 22 becomes equal to or more than a first threshold value by charged current by parasitic D of the FET, the first rectifier element operates, and the plurality of protection circuits 23 divide the charged current to the battery pack 22 into the resistance element; and a plurality od fuses 24 each of which is provided between the protection circuit 23 and the battery pack 22, and in which when the charged current is not blocked to the battery pack 22, the plurality of fuses 24 are blown out by the protection circuit 23.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present disclosure relates to a battery pack control device, a battery pack control method, and a power storage system.

Background Art

[0002] For example, Patent Document 1 describes a power distribution module having a structure capable of disconnecting a main relay from a battery. This power distribution module includes a power line connecting between a battery and a load, a main relay connected to the power line, an active fuse connected to the power line on the battery side of the main relay, a first voltage converter connected to the power line on the load side of the main relay, an abnormality detection unit for detecting an abnormality in the power line, and a first drive control wiring extending from the first voltage converter and connected to the active fuse. When an abnormality in the power line is detected by the abnormality detection unit, the first control unit mounted on the first voltage converter transmits a control signal for disconnecting the active fuse, and the active fuse is disconnected.

[0003] Further, Patent Document 2 describes a battery protection structure capable of reliably maintaining the disconnection from the outside of the battery even when the pressure switch returns after the electrical connection to the outside of the battery is cut off by the operation of the pressure switch. This battery protection structure includes a switch that is switched on by an abnormal pressure rise in the battery, and a fuse provided inside the battery that is blown by a short-circuit current of the battery due to the switching on of the switch and disconnects the inside of the battery from the outside of the battery.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, there are energy storage systems that consist of multiple battery packs (hereinafter also called "cartridges") connected in series to form a battery pack unit (hereinafter also called "string"). In this type of energy storage system, from the perspective of cost reduction, the switch for connecting or disconnecting the battery packs may be made of a field-effect transistor (FET). If the switch becomes stuck in the off position simultaneously due to a failure of the drive unit that drives this FET, the charging current to the battery pack unit cannot be cut off by a parasitic diode, and there is a risk of smoke and fire from the battery pack unit due to overcharging.

[0006] As a protective mechanism for this purpose, conventional systems sometimes employ a dual protection system to disconnect the power lines from the power conditioner (PCS): 1) setting a switch on the power line, and 2) shutting down the PCS. However, if these protective mechanisms fail to activate due to a chain reaction or complex failure, the battery pack unit will not be protected.

[0007] This disclosure is made in consideration of the above facts and aims to provide a battery pack control device, a battery pack control method, and an energy storage system that can protect a battery pack unit even when a complex failure occurs in a battery pack unit in which multiple battery packs are connected in series. [Means for solving the problem]

[0008] To achieve the above objective, the battery pack control device according to the first embodiment comprises: a battery pack unit in which a plurality of battery packs are connected in series; a switch unit composed of a plurality of field-effect transistors that connect or disconnect each of the plurality of battery packs; a plurality of protection circuits, each provided between the switch unit and the battery packs, wherein each protection circuit includes a first rectifier element, a second rectifier element connected in series with the first rectifier element, and a resistive element connected in series with the first rectifier element and in parallel with the second rectifier element, wherein when the voltage of the battery pack becomes above a first threshold due to the charging current by the parasitic diodes of the field-effect transistors, the first rectifier element operates and the charging current to the battery pack is diverted to the resistive element; and a plurality of fuses, each provided between the protection circuit and the battery pack, wherein the fuses are blown by the protection circuit when the charging current to the battery pack cannot be interrupted.

[0009] The battery pack control device according to the second embodiment is a battery pack control device according to the first embodiment in which, when the voltage of the battery pack due to the charging current becomes higher than the first threshold, the protection circuit further operates the second rectifier element, and the first and second rectifier elements form an external short-circuit path for the battery pack, thereby blowing the fuse.

[0010] A battery pack control device according to a third embodiment further includes, in the battery pack control device according to a first embodiment, an alarm signaling circuit which operates in conjunction with the first threshold value at which the first rectifier element operates.

[0011] The battery pack control device according to the fourth embodiment is the battery pack control device according to the first embodiment, wherein the first rectifier element and the second rectifier element are composed of a Zener diode or a thyristor.

[0012] To achieve the above objective, a battery pack control method according to the fifth embodiment is a battery pack control method using a battery pack control device comprising: a battery pack unit in which a plurality of battery packs are connected in series; a switch unit composed of a plurality of field-effect transistors that connect or disconnect each of the plurality of battery packs; a plurality of protection circuits, each provided between the switch unit and the battery pack, wherein each protection circuit includes a first rectifier element, a second rectifier element connected in series with the first rectifier element, and a resistive element connected in series with the first rectifier element and in parallel with the second rectifier element; and a plurality of fuses, each provided between the protection circuit and the battery pack, wherein when the voltage of the battery pack becomes greater than or equal to a first threshold due to the charging current by the parasitic diodes of the field-effect transistors, the first rectifier element operates, and the charging current to the battery pack is diverted to the resistive element, and if the charging current to the battery pack cannot be interrupted, the protection circuit blows the fuse.

[0013] The battery pack control method according to the sixth embodiment is a battery pack control method according to the fifth embodiment, wherein when the voltage of the battery pack due to the charging current becomes higher than the first threshold, the second rectifier element operates further, and the first and second rectifier elements form an external short-circuit path for the battery pack, thereby blowing the fuse.

[0014] To achieve the above objective, the energy storage system according to the seventh embodiment comprises a battery pack control device according to any one of the first to fourth embodiments, and a power conversion device connected to the battery pack control device. [Effects of the Invention]

[0015] As explained above, this disclosure provides the advantage of being able to protect a battery pack unit even if a complex failure occurs in a battery pack unit in which multiple battery packs are connected in series. [Brief explanation of the drawing]

[0016] [Figure 1]It is a diagram showing an example of the configuration of the power storage system according to the embodiment. [Figure 2] It is a graph for explaining the protection operation by the protection circuit according to the embodiment. [Figure 3] It is a flowchart showing an example of the flow of the protection operation by the protection circuit according to the embodiment.

Mode for Carrying Out the Invention

[0017] Hereinafter, an example of a mode for implementing the technology of the present disclosure will be described in detail with reference to the drawings. Note that components and processes having the same functions may be given the same reference numerals throughout the drawings, and redundant explanations may be omitted as appropriate. Each drawing schematically shows only to such an extent that the technology of the present disclosure can be sufficiently understood. Therefore, the technology of the present disclosure is not limited only to the illustrated examples. In addition, in the present embodiment, descriptions of configurations not directly related to the present disclosure and well-known configurations may be omitted.

[0018] FIG. 1 is a diagram showing an example of the configuration of the power storage system 100 according to the present embodiment.

[0019] As shown in FIG. 1, the power storage system 100 according to the present embodiment includes a battery pack control device 30 and power conversion equipment (power conditioner) 40.

[0020] One end of the power conversion equipment 40 is connected to the grid (transformer), and the other end is connected to the battery pack control device 30. The power conversion equipment 40 is, for example, a DC / AC converter.

[0021] The battery pack control device 30 includes an SCU 10, a string cut-off relay 20, a plurality of CMUs a21, b21, c21, a plurality of protection circuits 23, a plurality of fuses 24, and a switch unit 25. CMU is an abbreviation for Cartridge Management Unit (cartridge management unit). In this embodiment, three CMUs are illustrated, but the number is not limited to three and may be two or more. Also, in order to distinguish individual CMUs, a, b, and c are added after the CMU, but when there is no particular need to distinguish and explain, it is simply referred to as CMU.

[0022] Each of CMUs a21 to c21 includes a battery pack (cartridge) 22 composed of a plurality of cells. CMU a21 individually detects the voltage Va of the battery pack 22 and outputs the detected voltage Va to the SCU 10. CMU b21 individually detects the voltage Vb of the battery pack 22 and outputs the detected voltage Vb to the SCU 10. CMU c21 individually detects the voltage Vc of the battery pack 22 and outputs the detected voltage Vc to the SCU 10. Note that in order to distinguish individual voltages V, a, b, and c are added after the voltage V, but when there is no particular need to distinguish and explain, it is simply referred to as voltage V.

[0023] The switch unit 25 is composed of a plurality of field effect transistors (FETs) that connect or disconnect each of the plurality of battery packs 22. Specifically, the switch unit 25 includes SW1 and SW2 corresponding to the battery pack 22 of CMU a21, SW3 and SW4 corresponding to the battery pack 22 of CMU b21, and SW5 and SW6 corresponding to the battery pack 22 of CMU c21. Each of SW1 to SW6 is composed of an FET.

[0024] In the switch unit 25, when the battery pack 22 is disconnected under normal circumstances, SW1, SW3, and SW5 turn off (battery pack disconnected, parasitic diode (hereinafter referred to as "parasitic D") path exists), and SW2, SW4, and SW6 turn on (battery pack pass-through path turns on). On the other hand, if the FET drive unit turns off due to a malfunction or the like, SW1, SW3, and SW5 turn off (battery pack disconnected, parasitic D path exists), and SW2, SW4, and SW6 turn off (battery pack pass-through path turns off). In this case, the charging path to the battery pack via parasitic D remains active.

[0025] The battery pack 22 of CMUa21 is connected to the SCU10 and the power converter 40 via SW1 and SW2. The battery pack 22 of CMUb21 is connected to the SCU10 and the power converter 40 via SW3 and SW4. The battery pack 22 of CMUc21 is connected to the SCU10 and the power converter 40 via SW5 and SW6.

[0026] Each of the CMUa21 to CMUc21 units can communicate with the SCU10, for example, via CAN (Controller Area Network), a type of serial communication protocol.

[0027] SCU10 stands for String Control Unit. SCU10 is a signal processing unit that is a higher-level unit than CMUa21 to CMUc21. SCU10 is connected to a current sensor (not shown) installed on the power line 26, and detects the total current Io of multiple battery packs 22 connected in series in a battery pack unit (string) via the current sensor.

[0028] SCU10 is connected to each of SW1 to SW6 of the switch unit 25 and controls the on / off state of each of SW1 to SW6 of the switch unit 25.

[0029] The string disconnection relay 20 is installed on the power line 26 and is a relay switch for disconnecting the connection between the power conversion equipment 40 and the multiple battery packs 22.

[0030] Each of the protection circuits 23 is provided between the switch unit 25 and the battery pack 22. Each of the protection circuits 23 includes a first Zener diode ZD1, a second Zener diode ZD2, a resistor R1, and an alarm signaling circuit PHC1. The second Zener diode ZD2 is connected in series with the first Zener diode ZD1. The resistor R1 is connected in series with the first Zener diode ZD1 and in parallel with the second Zener diode ZD2. The first Zener diode ZD1 is an example of a first rectifier element, and the second Zener diode ZD2 is an example of a second rectifier element. These first and second rectifier elements may be replaced with thyristors instead of Zener diodes. The alarm signaling circuit PHC1 operates in conjunction with the operating voltage of the first Zener diode ZD1 and emits an alarm signal. For example, a photocoupler can be used for the alarm signaling circuit PHC1.

[0031] Each of the fuses 24 is located between the protection circuit 23 and the battery pack 22 and is connected to the first Zener diode ZD1, the resistor R1, and the second Zener diode ZD2.

[0032] Incidentally, if, for example, SW1 and SW2 become stuck in the OFF position simultaneously due to a failure in the drive unit that drives SW1 to SW6, which are composed of FETs, the charging current to the battery pack unit, in which multiple battery packs 22 are connected in series, cannot be interrupted by parasitic D, and there is a risk of smoke and fire from the battery pack unit due to overcharging. For this reason, as a means of interrupting the power line 26 from the power conversion device 40, a double protection measure may be implemented, which involves (1) setting a string interruption relay 20 on the power line 26, and (2) shutting down the power conversion device 40.

[0033] However, if the protection mechanisms described in (1) and (2) above cannot be activated due to a chain reaction or complex failure, the battery pack unit will not be protected.

[0034] Therefore, in the battery pack control device 30 according to this embodiment, a protection circuit 23 is provided as an independent protection mechanism separate from the protection mechanisms described in (1) and (2) above, as shown in Figure 1, which includes a first Zener diode ZD1, a second Zener diode ZD2, a resistor R1, and an alarm signaling circuit PHC1. Note that the alarm signaling circuit PHC1 is not mandatory, and the protection circuit 23 may be configured with only the first Zener diode ZD1, the second Zener diode ZD2, and the resistor R1.

[0035] The protection circuit 23 sets the operation trigger at a voltage threshold and performs a stepwise protection operation on the battery pack unit. This protection operation can protect the battery pack unit even if a complex failure occurs in the battery pack unit.

[0036] Specifically, the protection circuit 23 operates when the voltage of the battery pack 22 exceeds the first threshold Th1 due to the charging current caused by the parasitic current D of the FET. The first Zener diode ZD1 then operates, diverting the charging current to the battery pack 22 to the resistor R1. In other words, the operation of the first Zener diode ZD1 creates a current-diverted path where the current is limited by the resistor R1. The first Zener diode ZD1 has a pre-set operating voltage of the first threshold Th1.

[0037] At this time, the alarm signaling circuit PHC1 operates in conjunction with the first threshold Th1, which is the operating voltage of the first Zener diode ZD1, and emits an alarm signal. The alarm signal is a signal that prompts the user to manually shut down the system in an emergency, using, for example, sound, light (patrol light®, etc.).

[0038] Next, if the charging current to the battery pack 22 cannot be interrupted, the protection circuit 23 blows the fuse 24. Specifically, when the voltage of the battery pack 22 due to the charging current becomes higher than the second threshold Th2 (which is higher than the first threshold Th1), the protection circuit 23 further activates the second Zener diode ZD2, and the first Zener diode ZD1 and the second Zener diode ZD2 form an external short-circuit path to the battery pack 22, thereby blowing the fuse 24. In other words, the first Zener diode ZD1 and the second Zener diode ZD2 work together to form a path for overcurrent (external short circuit) to flow from the battery pack 22, and the overcurrent blows the fuse 24, interrupting the charging current. The second Zener diode ZD2 is pre-set as an operating voltage of the second threshold Th2 (> first threshold Th1).

[0039] The overcurrent only needs to be sufficient to blow the fuse 24, and is set appropriately considering the characteristics of the fuse 24 and the safety of the battery pack 22, wires, and circuit components. Furthermore, since the protection circuit 23 can be configured as an independent unit for each battery pack 22, it is possible to set an optimized operating voltage for each battery pack 22.

[0040] Figure 2 is a graph illustrating the protective operation by the protection circuit 23 according to this embodiment. In Figure 2, the vertical axis represents the battery voltage (V), and the horizontal axis represents time (s).

[0041] As shown in Figure 2, the first Zener diode ZD1 has a first threshold voltage Th1 pre-set as its operating voltage, and the second Zener diode ZD2 has a second threshold voltage Th2 (> first threshold voltage Th1) pre-set as its operating voltage.

[0042] In protection operation 1, when the voltage of the battery pack 22 reaches the first threshold Th1, the first Zener diode ZD1 and the alarm signaling circuit PHC1 switch from off to on, while the second Zener diode ZD2 remains off. As a result, a current diversion path for the charging current is formed by the resistor R1, suppressing the rise in the voltage of the battery pack 22. In addition, an alarm is triggered to prompt the user to manually shut down the system in an emergency.

[0043] If the system is not shut down by protection action 1 described above, and the voltage of the battery pack 22 rises further, protection action 2 is executed. In protection action 2, when the voltage of the battery pack 22 reaches the second threshold Th2 (> first threshold Th1), the second Zener diode ZD2 is switched from off to on. As a result, the first Zener diode ZD1 and the second Zener diode ZD2 form an external short-circuit path that allows the overcurrent from the battery pack 22 to flow, and the fuse 24 blows. This interrupts the charging of the battery pack 22.

[0044] Next, with reference to Figure 3, the operation of the battery pack control device 30 according to this embodiment will be explained.

[0045] Figure 3 is a flowchart showing an example of the flow of protection operation by the protection circuit 23 according to this embodiment.

[0046] In step S101 of Figure 3, if the voltage of the battery pack 22 becomes equal to or greater than the first threshold Th1 (positive determination), the process proceeds to step S102. If the voltage of the battery pack 22 is less than the first threshold Th1 (negative determination), the process remains in standby mode at step S101.

[0047] In step S102, the first Zener diode ZD1 operates in response to a battery voltage that is equal to or greater than the first threshold Th1.

[0048] In step S103, the charging current is divided through the resistor R1 in accordance with the operation of the first Zener diode ZD1, thereby suppressing the rise in voltage of the battery pack 22.

[0049] In step S104, the alarm signaling circuit PHC1 operates and outputs an alarm signal in response to a battery voltage that is equal to or greater than the first threshold Th1. As described above, the alarm signal is a signal that prompts the user to manually shut down the system in an emergency, using, for example, sound, light (patrol light®, etc.).

[0050] In step S105, if the user manually performs an emergency shutdown of the system in response to the alarm signal output from the alarm signaling circuit PHC1 (positive determination), the protective operation is terminated. If the system is not shut down (negative determination), the process proceeds to step S106.

[0051] In step S106, if the system is not shut down urgently and the voltage of the battery pack 22 rises further until the voltage of the battery pack 22 is equal to or greater than the second threshold Th2 (positive result), the process proceeds to step S107. If the voltage of the battery pack 22 is less than the second threshold Th2 (negative result), the process returns to step S105 and is repeated.

[0052] In step S107, the second Zener diode ZD2 operates in response to a battery voltage that is equal to or greater than the second threshold Th2.

[0053] In step S108, the first Zener diode ZD1 and the second Zener diode ZD2 form an external short-circuit path that allows the overcurrent from the battery pack 22 to flow, causing the fuse 24 to blow. This interrupts the charging of the battery pack 22, and the protection operation ends.

[0054] As described above, according to this embodiment, even if a complex failure occurs in a battery pack unit in which multiple battery packs are connected in series, the battery pack unit can be protected, thereby improving safety.

[0055] Furthermore, while the battery pack unit is ultimately protected by the blown fuse, the system can prompt the user to manually shut down the system before that happens.

[0056] Furthermore, since the protection circuit is composed of an independent unit for each battery pack, maintenance of the battery pack is easier, improving maintainability.

[0057] Furthermore, the configurations of the energy storage system and battery pack control device described in the above embodiments are examples and may be modified as needed without departing from the main purpose.

[0058] Furthermore, the processing flow described in the above embodiment is merely an example, and unnecessary steps may be deleted, new steps added, or the processing order rearranged, as long as it does not deviate from the main purpose. [Explanation of symbols]

[0059] 10 SCU 20 String Cutoff Relays 21 CMUa~CMUc 22 battery packs 23 Protection circuit 24 fuses 25 Switch section 26 Power lines 30 Battery Control Units 40 Power conversion equipment 100 Energy Storage Systems

Claims

1. A battery pack unit in which multiple battery packs are connected in series, A switch unit consisting of multiple field-effect transistors that connect or disconnect each of the multiple battery packs, Each of the multiple protection circuits provided between the switch unit and the battery pack includes a first rectifier element, a second rectifier element connected in series with the first rectifier element, and a resistive element connected in series with the first rectifier element and in parallel with the second rectifier element, wherein when the voltage of the battery pack exceeds a first threshold due to the charging current by the parasitic diode of the field-effect transistor, the first rectifier element operates, and the charging current to the battery pack is diverted to the resistive element. Each of the multiple fuses provided between the protection circuit and the battery pack is blown by the protection circuit when the charging current to the battery pack cannot be interrupted, A battery pack control device equipped with the following features.

2. The protection circuit, when the voltage of the battery pack rises above a second threshold (higher than the first threshold) due to the charging current, further activates the second rectifier element, and the first and second rectifier elements form an external short-circuit path for the battery pack, thereby blowing the fuse. The battery pack control device according to claim 1.

3. The protection circuit further includes an alarm signaling circuit that operates in conjunction with a first threshold value at which the first rectifier element operates. The battery pack control device according to claim 1.

4. The first rectifier element and the second rectifier element are composed of a Zener diode or a thyristor. The battery pack control device according to claim 1.

5. A battery pack unit in which multiple battery packs are connected in series, A switch unit consisting of multiple field-effect transistors that connect or disconnect each of the multiple battery packs, Each of the multiple protection circuits provided between the switch unit and the battery pack comprises a first rectifier element, a second rectifier element connected in series with the first rectifier element, and a resistive element connected in series with the first rectifier element and in parallel with the second rectifier element. Each of the following fuses is provided between the protection circuit and the battery pack: A battery pack control method using a battery pack control device equipped with, When the voltage of the battery pack rises above a first threshold due to the charging current by the parasitic diode of the field-effect transistor, the first rectifier element operates, and the charging current to the battery pack is divided and distributed to the resistive element. If the charging current to the battery pack cannot be interrupted, the protection circuit blows the fuse. Battery pack control method.

6. When the voltage of the battery pack rises to a second threshold or higher than the first threshold due to the charging current, the second rectifier element operates further, and the first and second rectifier elements form an external short-circuit path for the battery pack, thereby blowing the fuse. The battery pack control method according to claim 5.

7. A battery control device according to any one of claims 1 to 4, A power conversion device connected to the aforementioned battery pack control device, A well-equipped energy storage system.

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