Energy storage systems and their control methods

Abstract

This case relates to an energy storage system and its control method. The energy storage system includes a power grid, a DC bus, an energy storage converter, n first battery clusters, and m energy storage units. The DC bus includes a positive bus and a negative bus. The energy storage converter converts the AC power provided by the power grid into DC power and sends it to the DC bus. The first battery clusters are electrically connected between the positive and negative buses. The energy storage units include second battery clusters and a DC / DC converter. The DC / DC converter is electrically connected between the second battery clusters and the DC bus to convert the electrical energy between the second battery clusters and the DC bus.

Description

Technical Field

[0001] This case pertains to the field of energy storage, specifically an energy storage system and its control method. Background Technology

[0002] Traditional energy storage systems consist of multiple battery racks and multiple bidirectional DC-DC converters. Each battery rack and its corresponding bidirectional DC-DC converter are connected in series and then in parallel to the DC bus to achieve charging and discharging functions. However, when the energy storage system experiences a sudden change, such as a sudden increase or decrease in load, or a low-voltage event in the grid, the Energy Storage Unit (ESU), composed of multiple bidirectional DC-DC converters and battery racks, cannot respond simultaneously and in a timely manner. This causes some bidirectional DC-DC converters to malfunction and stop operating.

[0003] Therefore, developing an energy storage system and its control method that overcomes the above-mentioned shortcomings is an urgent need at present. Summary of the Invention

[0004] The purpose of this case is to provide an energy storage system and its control method.

[0005] To achieve the above objectives, one embodiment of this invention provides an energy storage system comprising a power grid, a DC bus, an energy storage converter, n first battery clusters, and m energy storage units, where n is a positive integer greater than or equal to 1, and m is a positive integer greater than or equal to 1. The power grid provides alternating current (AC). The DC bus includes a positive bus and a negative bus. The energy storage converter is electrically connected between the power grid and the DC bus to convert the AC power provided by the power grid into DC power for the DC bus. Each first battery cluster is electrically connected between the positive bus and the negative bus. Each energy storage unit includes a second battery cluster and a DC / DC converter. The DC / DC converter is electrically connected between the second battery cluster and the DC bus to convert the electrical energy between the second battery cluster and the DC bus.

[0006] To achieve the above objectives, another embodiment of this application provides a control method for an energy storage system. First, an energy storage system as described above is provided. Next, a control module is provided, electrically connected to the DC bus, each of the first battery clusters, each of the second battery clusters, and each DC / DC converter. The control module controls the operating state of each DC / DC converter based on the power of the DC bus, the power of each of the first battery clusters, and the power of each of the second battery clusters.

[0007] The energy storage system of this application comprises n first battery clusters and m energy storage units, and each energy storage unit comprises a second battery cluster and a DC / DC converter. This means that the energy storage system includes two different types of energy storage devices. When a step change occurs in the energy storage system, the first battery clusters directly connected to the DC bus can respond immediately, ensuring that the DC bus voltage does not change significantly within a certain period. This allows the system controller sufficient time to send current or voltage commands to the DC / DC converter to absorb or release battery energy, smoothly transitioning through the step change. Through the energy storage and buffering of the energy storage system, the system can still operate at a stable output level even under rapid load fluctuations. Attached Figure Description

[0008] Figure 1 This is a circuit topology diagram of the energy storage system in the first embodiment of this case.

[0009] Figure 2 for Figure 1 The diagram shows the detailed circuit topology of the control module of the energy storage system.

[0010] Figure 3 This is a circuit topology diagram of the energy storage system in the second embodiment of this case.

[0011] Figure 4 This is a circuit topology diagram of the energy storage system in the third embodiment of this case.

[0012] Figure 5 This is a control flowchart of the control method for the energy storage system in this case.

[0013] Figure 6 This is the control flowchart of the energy storage system in this case during discharge mode.

[0014] Figure 7 This is the control flowchart of the energy storage system in this case during charging mode.

[0015] The annotations in the attached figures are explained as follows:

[0016] 1, 1a, 1b: Energy storage system

[0017] 2: Power Grid

[0018] 3: DC bus

[0019] 31: Positive busbar

[0020] 32: Negative busbar

[0021] 4: Energy storage converter

[0022] 5: First battery cluster

[0023] 6: Energy storage unit

[0024] 61: Second battery cluster

[0025] 611: Positive terminal

[0026] 612: Negative terminal

[0027] 62: DC / DC converter

[0028] 621: First Positive End

[0029] 622: First negative end

[0030] 623: Second Positive End

[0031] 624: Second negative end

[0032] 7: Control Module

[0033] 71: First Detection Unit

[0034] 72: First Filter

[0035] 73: First Judgment Unit

[0036] 74: Second Detection Unit

[0037] 75: Second Filter

[0038] 76: Second Judgment Unit

[0039] 77: Storage Unit

[0040] 781: Arithmetic Unit

[0041] 782: Instruction Calculation Unit

[0042] 79: Limiter

[0043] K1, K2, S1, S2, M1, M2: Steps Detailed Implementation

[0044] Some typical embodiments that embody the features and advantages of this invention will be described in detail in the following description. It should be understood that this invention can have various variations in different forms, all of which do not depart from the scope of this invention, and the descriptions and drawings therein are essentially for illustrative purposes and not for limiting this invention.

[0045] Please see Figure 1 This is a circuit topology diagram of the energy storage system in the first embodiment of this case. Figure 1As shown, the energy storage system 1 in this embodiment includes a power grid 2, a DC bus 3, an energy storage converter 4, n first battery clusters 5, m energy storage units 6, and a control module 7, where n is a positive integer greater than or equal to 1, and m is a positive integer greater than or equal to 1. The power grid 2 provides AC power. The DC bus 3 includes a positive bus 31 and a negative bus 32. The energy storage converter 4 is a bidirectional AC / DC converter and is electrically connected between the power grid 2 and the positive bus 31 of the DC bus 3. The energy storage converter 4 converts the AC power provided by the power grid 2 into DC power for the DC bus 3. Each first battery cluster 5 is directly electrically connected between the positive bus 31 and the negative bus 32 of the DC bus 3, without needing any DC / DC converter, to receive DC power from the DC bus 3 for charging when the energy storage system 1 is in charging mode, or to provide DC power to the DC bus 3 when the energy storage system 1 is in discharging mode.

[0046] Each energy storage unit 6 includes a second battery cluster 61 and a DC / DC converter 62. The DC / DC converter 62 is electrically connected between the second battery cluster 61 and the DC bus 3 to convert the electrical energy between the second battery cluster 61 and the DC bus 3. The second battery cluster 61 includes a positive terminal 611 and a negative terminal 612. The negative terminal 612 of the second battery cluster 61 is electrically connected to the negative bus 32 of the DC bus 3. The DC / DC converter 62 in this embodiment is a bidirectional isolated converter, and can be a voltage-compensated converter or a current-compensated converter. The DC / DC converter 62 includes a first positive terminal 621, a first negative terminal 622, a second positive terminal 623, and a second negative terminal 624. The first positive terminal 621 of the DC / DC converter 62 is electrically connected to the positive bus 31 of the DC bus 3. The first negative terminal 622 of the DC / DC converter 62 is electrically connected to the positive terminal 611 of the second battery cluster 61. The second positive terminal 623 of the DC / DC converter 62 is electrically connected to the positive bus 31 of the DC bus 3. The second negative terminal 624 of the DC / DC converter 62 is electrically connected to the negative bus 32 of the DC bus 3. The different operating modes of the energy storage unit 6 in the energy storage system 1 will be described later.

[0047] The control module 7 is electrically connected to the positive bus 31 and negative bus 32 of the DC bus 3, each first battery cluster 5, the second battery cluster 61 of each energy storage unit 6, and the DC / DC converter 62. The control module 7 controls the operating state of the DC / DC converter 62 of each energy storage unit 6, such as bypass state or running state, according to the power (i.e., voltage and / or current) on the DC bus 3, the power (i.e., voltage and / or current) of each first battery cluster 5 and the power (i.e., voltage and / or current) of the second battery cluster 61 of each energy storage unit 6.

[0048] The following further explains the control method of the control module 7 controlling the DC / DC converter 62 when the energy storage system 1 is in different modes. When the energy storage system 1 is in standby mode, each first battery cluster 5 and each second battery cluster 61 has its own open-circuit voltage, and the open-circuit voltages of each first battery cluster 5 and each second battery cluster 61 are the same, which means that no current flows on each first battery cluster 5 and each second battery cluster 61, and the control module 7 controls the DC / DC converter 62 to work in bypass mode. At this time, no power flows on the DC bus 3 of the energy storage system 1.

[0049] When the energy storage system 1 switches from standby mode to discharge mode, the electrical energy provided by the first battery cluster 5 is directly transferred to the DC bus 3 within a transient period. Therefore, the power required by the DC bus 3 during the transient period is provided by the first battery cluster 5, which means that the voltage on the DC bus 3 can be clamped by the first battery cluster 5 during the transient period. Since the energy storage system 1 may experience a step change during the transient period after the mode switch, such as a sudden increase or decrease in load, or a low voltage ride-through in the power grid 2, the step change may cause the DC / DC converter 62 of the energy storage unit 6 to fail to respond in time and cause damage. Therefore, the above control method can ensure that when the energy storage system 1 experiences a step change, the battery cluster directly connected to the DC bus 3 can respond immediately, ensuring that the DC bus voltage will not change significantly within a certain period of time. This allows the control module 7 to have enough time to issue current or voltage commands to the DC / DC converter 62 to absorb or release battery energy and smoothly transition to the step change. The energy storage and buffering of the energy storage system 1 enables the system to operate at a stable output level even under rapid load fluctuations, thereby protecting the DC / DC converter 62.

[0050] After the transient period ends, the first battery cluster 5 continues to supply power to the DC bus 3. The control module 7 further controls the operating state of the DC / DC converter 62 of each energy storage unit 6 based on the power of the DC bus 3, the power of each first battery cluster 5, and the power of each second battery cluster 61. That is, the control module 7 can control the DC / DC converter 62 of the corresponding number of energy storage units 6 to be in an operating state, so that the power supplied by the corresponding second battery cluster 61 is transmitted to the DC bus 3 via the DC / DC converter 62. Therefore, the power required on the DC bus 3 at this time is provided by the first battery cluster 5 and the second battery cluster 61, thereby improving the discharge balance of the first battery cluster 5 and the second battery cluster 61. In some embodiments, according to different power supply requirements, in addition to controlling the DC / DC converter 62 of the corresponding number of energy storage units 6 to be in an operating state, the control module 7 can also control the amount of power supplied by the second battery cluster 61 to the DC bus 3 by adjusting the operating state of the DC / DC converter 62.

[0051] In one embodiment, when the energy storage system 1 switches from standby mode to discharge mode, it is assumed that there are two first battery clusters 5 and three energy storage units 6, i.e., there are three second battery clusters 61. When the power required on the DC bus 3 is 100kW, during the transient time, each first battery cluster 5 provides 25kW of power, and the three second battery clusters 61 provide a total of 50kW of power. The power provided by each first battery cluster 5 is greater than the power provided by each second battery cluster 61. After the transient time ends, each first battery cluster 5 and each second battery cluster 61 each provide 20kW of power.

[0052] When the energy storage system 1 switches from standby mode to charging mode, the DC power provided by the energy storage converter 4 is directly transmitted to the first battery cluster 5 via the DC bus 3 within a transient period. Therefore, the DC power provided by the energy storage converter 4 is transmitted to the first battery cluster 5 within a transient period.

[0053] After the transient period ends, the energy storage converter 4 continues to supply DC power to the first battery cluster 5 via the DC bus 3. The control module 7 further controls the operating state of the DC / DC converter 62 of each energy storage unit 6 based on the power of the DC bus 3, the power of each first battery cluster 5, and the power of each second battery cluster 61. That is, the control module 7 can control the DC / DC converter 62 of a corresponding number of energy storage units 6 to be in an operating state, so that the corresponding second battery cluster 61 receives the DC power provided by the energy storage converter 4 via the DC bus 3. Therefore, the DC power provided by the energy storage converter 4 can be simultaneously supplied to the first battery cluster 5 and the second battery cluster 61, thereby improving the charging balance of the first battery cluster 5 and the second battery cluster 61. In some embodiments, according to different charging requirements, in addition to controlling the DC / DC converter 62 of a corresponding number of energy storage units 6 to be in an operating state, the control module 7 can also control the amount of electricity received by the second battery cluster 61 by adjusting the operating state of the DC / DC converter 62.

[0054] Furthermore, the control method when the energy storage system 1 switches from charging mode to discharging mode, or from discharging mode to charging mode, is similar to the control method described above, so it will not be repeated here.

[0055] Please see Figure 2 , it is Figure 1 The diagram shows the detailed circuit topology of the control module of the energy storage system. Figure 2As shown, the control module 7 includes a first detection unit 71, a first filter 72, a first judgment unit 73, a second detection unit 74, a second filter 75, a second judgment unit 76, a storage unit 77, an arithmetic unit 781, an instruction calculation unit 782, and a limiter 79. The first detection unit 71 is electrically connected to the positive bus 31 and negative bus 32 of the DC bus 3 to detect the voltage and current signals of the DC bus 3 and output a first detection signal. The first filter 72 is electrically connected to the first detection unit 71 to filter the first detection signal. The first judgment unit 73 is electrically connected to the first filter 72 to calculate the power of the DC bus 3 and determine the power flow direction of the DC bus 3 based on the filtered first detection signal, and output a first judgment signal. The second detection unit 74 is electrically connected to each first battery cluster 5 and each second battery cluster 61 to detect the voltage and current signals of each first battery cluster 5 and each second battery cluster 61, and output a second detection signal. The second filter 75 is electrically connected to the second detection unit 74 to filter the second detection signal. The second judgment unit 76 is electrically connected to the second filter 75 to calculate the power of each first battery cluster 5 and determine the power flow direction of each first battery cluster 5, and to calculate the power of each second battery cluster 61 and determine the power flow direction of each second battery cluster 61 based on the filtered second detection signal, and outputs a second judgment signal. The storage unit 77 contains preset architecture data, which includes records of the original battery states of the first battery cluster 5 and the second battery cluster 61, records of the type of the DC / DC converter 62, etc. The arithmetic unit 781 is electrically connected to the first judgment unit 73, the second judgment unit 76 and the storage unit 77. The arithmetic unit 781 performs calculations on the first judgment signal output by the first judgment unit 73, the second judgment signal output by the second judgment unit 76 and the architecture data output by the storage unit 77 to obtain a power scheduling signal. The instruction calculation unit 782 is electrically connected to the arithmetic unit 781 to calculate voltage and current instructions based on the power scheduling signal output by the arithmetic unit 781. Limiter 79 is electrically connected to instruction calculation unit 782. Limiter 79 limits the voltage and current instructions output by instruction calculation unit 782, and control module 7 controls the working state of DC / DC converter 62 of each energy storage unit 6 according to the limited voltage and current instructions.

[0056] Please see Figure 3 This is a circuit topology diagram of the energy storage system in the second embodiment of this case. Compared to Figure 1 The second positive terminal 623 of the DC / DC converter 62 of the energy storage system 1 shown is electrically connected to the positive bus 31 of the DC bus 3. In this embodiment, the DC / DC converter 62 of the energy storage system 1a is a bidirectional isolated converter, and the second positive terminal 623 of the DC / DC converter 62 is electrically connected to the positive terminal 611 of the second battery cluster 61.

[0057] Please see Figure 4 This is a circuit topology diagram of the energy storage system according to the third embodiment of this case. Compared to Figure 1 The energy storage system 1 shown includes a second battery cluster 61 and a DC / DC converter 62. In this embodiment, the first positive terminal 621 and the first negative terminal 622 of the DC / DC converter 62 are electrically connected to the positive bus 31 and the negative bus 32 of the DC bus 3, respectively. The second positive terminal 623 and the second negative terminal 624 of the DC / DC converter 62 are electrically connected to the positive terminal 611 and the negative terminal 612 of the second battery cluster 61, respectively. In this embodiment, the DC / DC converter 62 of the energy storage system 1b is a bidirectional non-isolated converter.

[0058] This application also provides a control method for an energy storage system. Please refer to [link / reference]. Figure 5 This is a control flowchart of the control method for the energy storage system in this case. The control method is as follows: First, step K1 is executed, providing the energy storage system as described in any of the above embodiments. Next, step K2 is executed, providing a control module 7. The control module 7 is electrically connected to the DC bus 3, each first battery cluster 5, each second battery cluster 61, and each DC / DC converter 62. The control module 7 controls the operating state of each DC / DC converter 62 according to the power of the DC bus 3, the power of each first battery cluster 5, and the power of each second battery cluster 61.

[0059] Please see Figure 6 This is the control flowchart of the energy storage system in the discharge mode of this case. First, step S1 is executed. When the energy storage system 1 switches from standby mode to discharge mode, or from charging mode to discharge mode, during the transient time, the electrical energy provided by the n first battery clusters 5 is directly transferred to the DC bus 3. Next, step S2 is executed. After the transient time ends, the control module 7 controls the DC / DC converters 62 of the corresponding number of energy storage units 6 in the m energy storage units 6 to operate in the running state, so that the electrical energy provided by the corresponding second battery cluster 61 and the electrical energy provided by the n first battery clusters 5 are jointly transferred to the DC bus 3.

[0060] Please see Figure 7This is the control flowchart of the energy storage system in charging mode. First, step M1 is executed. When the energy storage system 1 switches from standby mode to charging mode, or from discharging mode to charging mode, during the transient time, the DC power provided by the energy storage converter 4 is directly transmitted to n first battery clusters 5 via the DC bus 3. Next, step M2 is executed. After the transient time ends, the control module 7 controls the DC / DC converters 62 of the corresponding number of energy storage units 6 in the m energy storage units 6 to operate in the running state, so that the corresponding second battery clusters 61 and first battery clusters 5 jointly receive the DC power provided by the energy storage converter 4.

[0061] In summary, the energy storage system of this invention comprises n first battery clusters and m energy storage units, and each energy storage unit includes a second battery cluster and a DC / DC converter. The control module can control the operating state of the DC / DC converter of each energy storage unit according to the power of the DC bus, the power of each first battery cluster, and the power of each second battery cluster. This means that the energy storage system of this invention includes two power supply devices. Therefore, compared with traditional energy storage systems that use multiple battery clusters directly connected to the DC bus and only include a single power supply device, the first battery clusters can charge or discharge during the transient time after mode switching. That is, the first battery clusters can immediately respond to step changes. Therefore, the energy storage units do not need to provide power or receive DC power transmitted by the energy storage converter during the transient time after mode switching, thereby protecting the DC / DC converter and reducing voltage fluctuations on the DC bus and the disturbance of the overall energy storage system. The energy storage units can provide or receive power in the stable state after the transient time, so that the overall energy storage system maintains a stable power output. Furthermore, the architecture of the energy storage system in this case can prevent damage to the energy storage system caused by voltage spikes or drops on the load, or by grid fluctuations caused by external interference, thereby improving power quality and reliability. Moreover, the energy storage system in this case can operate independently after a power outage and can perform reactive power compensation for the grid, thereby improving the power quality of the grid and reducing wire losses.

Claims

1. An energy storage system, characterized in that, Include: A power grid provides alternating current (AC) power. A DC busbar includes a positive busbar and a negative busbar; An energy storage converter is electrically connected between the power grid and the DC bus to convert the AC power provided by the power grid into DC power to the DC bus. There are n first battery clusters, where n is a positive integer greater than or equal to 1, and each first battery cluster is directly electrically connected between the positive bus and the negative bus on the DC side of the energy storage converter. There are m energy storage units, where m is a positive integer greater than or equal to 1. Each energy storage unit contains: A second battery cluster; and A DC / DC converter is electrically connected between the second battery cluster and the DC bus to convert the electrical energy between the second battery cluster and the DC bus. During a transient period, each of the first battery clusters responds to a power change on the DC bus; and after the transient period ends, each of the first battery clusters and each of the second battery clusters have the same operating state.

2. The energy storage system of claim 1, wherein the DC / DC converter includes a first positive terminal, a first negative terminal, a second positive terminal and a second negative terminal, the second battery cluster includes a positive terminal and a negative terminal, and the first positive terminal is electrically connected to the positive bus.

3. The energy storage system as described in claim 2, wherein the DC / DC converter is a bidirectional isolated converter, the first negative terminal of the DC / DC converter is electrically connected to the positive terminal of the second battery cluster, the second negative terminal is electrically connected to the negative bus, and the negative terminal of the second battery cluster is electrically connected to the negative bus.

4. The energy storage system of claim 3, wherein the second positive terminal of the DC / DC converter is electrically connected to the positive bus of the DC bus.

5. The energy storage system of claim 3, wherein the second positive terminal of the DC / DC converter is electrically connected to the positive terminal of the second battery cluster.

6. The energy storage system of claim 2, wherein the DC / DC converter is a bidirectional non-isolated converter, the first negative terminal is electrically connected to the negative bus, the positive terminal of the second battery cluster is electrically connected to the second positive terminal of the DC / DC converter, and the negative terminal of the second battery cluster is electrically connected to the second negative terminal of the DC / DC converter.

7. The energy storage system of claim 1, wherein the energy storage converter is a bidirectional AC / DC converter, and the energy storage system further includes a control module electrically connected to the DC bus, each of the first battery clusters, each of the second battery clusters, and each DC / DC converter, wherein the control module controls the operating state of each DC / DC converter according to the power of the DC bus, the power of each of the first battery clusters, and the power of each of the second battery clusters.

8. The energy storage system of claim 7, wherein the control module comprises: A first detection unit is electrically connected to the DC bus to detect the voltage and current signals of the DC bus and output a first detection signal; A first filter is electrically connected to the first detection unit to filter the first detection signal; A first judgment unit is electrically connected to the first filter to calculate the power of the DC bus and determine the power flow direction of the DC bus based on the first detection signal, and outputs a first judgment signal. A second detection unit is electrically connected to each of the first battery clusters and each of the second battery clusters to detect the voltage and current signals of each of the first battery clusters and the voltage and current signals of each of the second battery clusters, and outputs a second detection signal. A second filter is electrically connected to the second detection unit to filter the second detection signal; A second judgment unit is electrically connected to the first filter to calculate the power of each first battery cluster and determine the power flow direction of each first battery cluster based on the second detection signal, and to calculate the power of each second battery cluster and determine the power flow direction of each second battery cluster, and output a second judgment signal. A storage unit containing a pre-defined data structure; A processing unit, electrically connected to the first judgment unit, the second judgment unit, and the storage unit, performs calculations on the first judgment signal, the second judgment signal, and the architecture data to obtain a power scheduling signal; and An instruction calculation unit, electrically connected to the arithmetic unit, calculates a voltage and current instruction based on the power dispatch signal.

9. The energy storage system of claim 8, wherein the control module further includes a limiter electrically connected to the command calculation unit to limit the voltage and current command, wherein the control module controls the operating state of each DC / DC converter according to the limited voltage and current command.

10. The energy storage system of claim 7, wherein when the energy storage system is in standby mode, the control module controls the DC / DC converter to operate in bypass mode, and there is no power flow in the energy storage system.

11. The energy storage system of claim 7, wherein when the energy storage system switches from a standby mode to a discharge mode, or from a charging mode to the discharge mode, during the transient time, the electrical energy provided by the n first battery clusters is directly transmitted to the DC bus; after the transient time ends, the control module controls the corresponding DC / DC converter in the m energy storage units to operate in the running state, so that the electrical energy provided by the corresponding second battery cluster and the electrical energy provided by the n first battery clusters are jointly transmitted to the DC bus.

12. The energy storage system of claim 7, wherein when the energy storage system switches from a standby mode to a charging mode, or from a discharging mode to the charging mode, during the transient time, the DC power provided by the energy storage converter is directly transmitted to the n first battery clusters via the DC bus; after the transient time ends, the control module controls the corresponding DC / DC converter to operate in the running state, so that the corresponding second battery cluster and the first battery cluster jointly receive the DC power provided by the energy storage converter.

13. A control method for an energy storage system, characterized in that, Include: Provide an energy storage system as described in any one of claims 1-6; and A control module is provided, which is electrically connected to the DC bus, each of the first battery clusters, each of the second battery clusters, and each DC / DC converter. The control module controls the operating state of each DC / DC converter according to the power of the DC bus, the power of each of the first battery clusters, and the power of each of the second battery clusters.

14. The control method of claim 13, wherein the control method further comprises: When the energy storage system switches from a standby mode to a discharge mode, or from a charging mode to the discharge mode, during the transient time, the electrical energy provided by the n first battery clusters is directly transferred to the DC bus; and After the transient period ends, the control module controls the corresponding number of DC / DC converters in the m energy storage units to operate in the running state, so that the electrical energy provided by the corresponding second battery cluster and the electrical energy provided by the n first battery clusters are jointly transmitted to the DC bus.

15. The control method of claim 13, wherein the control method further comprises: When the energy storage system switches from a standby mode to a charging mode, or from a discharging mode to the charging mode, during the transient time, the DC power provided by the energy storage converter is directly transmitted to the n first battery clusters via the DC bus; and After the transient period ends, the control module controls the corresponding number of DC / DC converters to operate in the running state, so that the corresponding second battery cluster and the first battery cluster jointly receive the DC power provided by the energy storage converter.

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