A cell-level optimized battery plug-in box, energy storage system and its application

Abstract

The present invention provides a cell-level optimized battery plug-in box, an energy storage system and its application, which belong to the field of electrochemical energy storage. The cell-level optimized battery plug-in box includes: a plurality of cell assemblies connected in parallel on a DC bus; each of the cell assemblies includes a bypass switch, a through switch, at least one single cell, a main control unit and a DC / DC converter; the single cell is connected to the DC / DC converter, and the DC / DC converter is connected to the main control unit; the single cell and the DC bus are disconnected, directly connected or connected through the DC / DC converter through the bypass switch and the through switch. The present invention can completely avoid the short board effect of the energy storage system caused by the series and parallel connection of the cells, so that the cycle life of the energy storage system is consistent with the cycle life of the cells.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemical energy storage, and in particular relates to a cell-level optimized battery plug-in box, an energy storage system and applications thereof. Background Art

[0002] At present, large-scale energy storage systems have an increasing demand for the capacity of energy storage stacks, and the series and parallel connection of a large number of battery plug-ins in the stack has become the main means of expanding the capacity of the energy storage system. In actual projects, 1-10 batteries are generally connected in parallel to form a battery module, and then 12 to 24 battery modules are connected in series to form a battery plug-in box. The battery plug-in box is the smallest operating unit for stack maintenance. Generally, multiple battery plug-ins are connected in series to form a battery cluster, and the voltage of the battery cluster generally matches the DC voltage range of the energy storage inverter. The DC side of each energy storage inverter is connected to multiple parallel battery clusters to form a stack. For example Figure 1 The figure shows the composition of the battery stack and energy storage converter in a common energy storage system.

[0003] However, the inconsistencies between individual cells in series and parallel connections become a limiting factor in the overall performance of the stack. Once a single cell in the stack reaches its charge / discharge cutoff voltage, the entire stack must cease charging and discharging, otherwise it could lead to battery failure or even fire. Figure 8 The figure shows the charge and discharge curve of a single cell. Obviously, the cell voltage changes dramatically at the end of charge and discharge. The inconsistency of the cells causes the voltage difference of the cells in the entire battery stack to increase. Some cells have reached the over-voltage and under-voltage protection points, while some cells still have a certain available capacity.

[0004] Furthermore, although the energy storage converter is equipped with low-current charging modes such as constant voltage charging and float charging, overvoltage alarms often occur in individual cells in the stack during the late stages of high-power constant current charging, preventing the entire stack from entering constant voltage and float charging modes and shutting down. Based on engineering experience, this operating mode results in a loss of at least 4% of the stack's charge and discharge capacity. This loss of charge and discharge capacity increases further as the stack's operating time increases and its consistency deteriorates.

[0005] The current solution is to use a battery management system, which not only monitors the voltage, temperature and other operating conditions of each battery, but also uses active or passive balancing to reduce the charging of batteries with higher voltages and the discharge of batteries with lower voltages within a single battery box. However, the balancing capability is limited and can only manage the balancing between batteries within a single battery box. In actual projects, the battery stack often suffers from a short board effect. Figure 2 The figure shows the battery management system in an existing single battery plug-in box, including acquisition and balancing circuits.

[0006] Based on the use of battery management systems, some manufacturers have proposed the use of string energy storage inverters, that is, each battery cluster is connected to an energy storage inverter, and the battery clusters are no longer connected in parallel. This allows the battery cluster with a short board battery or battery plug-in box to be withdrawn at any time, while other battery clusters continue to charge and discharge. However, if a single battery or battery plug-in box reaches the charge and discharge cut-off voltage, the entire cluster stops operating, and the capacity utilization of other batteries is still limited. Figure 3 The figure shows the system composition of the existing string energy storage converter and battery stack. Summary of the Invention

[0007] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art and provide a cell-level optimized battery box, energy storage system and its application to avoid the short board effect caused by a battery or battery box in the battery stack reaching the cutoff voltage or failing.

[0008] The present invention is achieved through the following technical solutions:

[0009] A first aspect of the present invention provides a cell-level optimized battery plug-in box, the cell-level optimized battery plug-in box comprising: a plurality of cell assemblies connected in parallel on a DC bus;

[0010] Each of the battery cell assemblies includes a bypass switch, a pass switch, at least one single battery cell, a main control unit and a DC / DC converter;

[0011] The single battery cell is connected to a DC / DC converter, and the DC / DC converter is connected to a main control unit;

[0012] The bypass switch and the through switch are used to realize the disconnection between the single cell and the DC bus, direct connection or connection through the DC / DC converter.

[0013] A further improvement of the present invention is that each of the battery cell assemblies includes a single battery cell;

[0014] The positive and negative electrodes of the single battery cell are respectively connected to the positive and negative electrodes of the head end of the DC / DC converter, and the positive and negative electrodes of the tail end of the DC / DC converter are respectively connected to the positive and negative electrodes of the DC bus;

[0015] The positive and negative terminals of the bypass switch are connected to the positive and negative terminals of the DC / DC converter respectively, and the positive and negative terminals of the bypass switch are connected to the positive and negative terminals of the DC / DC converter respectively.

[0016] A through switch is connected in parallel to the line connected to the DC bus at the end of the DC / DC converter.

[0017] A further improvement of the present invention is that each of the battery cell assemblies comprises a plurality of single battery cells connected in series;

[0018] The positive and negative electrodes of the last single cell are connected to the positive and negative electrodes of the DC / DC converter, and the positive and negative electrodes of the DC / DC converter are connected to the positive and negative electrodes of the DC bus.

[0019] The positive and negative terminals of the bypass switch are connected to the positive and negative terminals of the DC / DC converter respectively, and the positive and negative terminals of the bypass switch are connected to the positive and negative terminals of the DC / DC converter respectively.

[0020] A through switch is connected in parallel to the line connected to the DC bus at the end of the DC / DC converter.

[0021] A further improvement of the present invention is that each of the battery cell assemblies further includes a high-speed communication interface, and the high-speed communication interface is connected to the main control unit.

[0022] Furthermore, each of the battery cell components also includes a data acquisition circuit, which is connected to the main control unit.

[0023] A second aspect of the present invention provides an energy storage system, comprising: a plurality of battery clusters, a plurality of energy storage converters, a plurality of cluster management systems, and a centralized control device;

[0024] The battery cluster, energy storage converter, and cluster management system correspond one to one;

[0025] Each battery cluster includes multiple cell-level optimized battery plug-ins, and the DC buses of the multiple cell-level optimized battery plug-ins are connected in series and then connected to the DC side of the energy storage converter;

[0026] The main control unit of each battery cell assembly in the same battery cluster communicates with the cluster management system corresponding to the battery cluster through a high-speed communication interface.

[0027] Furthermore, the energy storage system also includes a plurality of plug-in box battery management systems;

[0028] The subrack battery management system corresponds to each battery cluster one by one and communicates with each main control unit in the corresponding battery cluster.

[0029] A further improvement of the present invention is that all energy storage converters are respectively connected to a centralized control device;

[0030] All cluster management systems are connected to the centralized control device respectively;

[0031] All plug-in box battery management systems are connected to the centralized control device respectively.

[0032] A third aspect of the present invention provides a method for applying the above-mentioned energy storage system, the method comprising: a cluster management system makes a judgment based on the data uploaded by each main control unit in each cell-level optimization battery plug-in box, and then issues instructions to each main control unit respectively, so as to control the opening or closing of the bypass switch and the through switch in each cell assembly so that the cell assembly operates in the through, bypass or reduced voltage state.

[0033] A further improvement of the present invention is that the method specifically comprises:

[0034] When a single cell in the cell assembly is in the charge and discharge plateau period, the cluster management system sends a command to the main control unit of the cell assembly, which is: close the bypass switch and open the through switch; after the bypass switch is closed and the through switch is opened, the cell assembly operates in the through state;

[0035] When a single cell in the battery assembly is at the end of charge or discharge, the cluster management system sends a command to the main control unit of the battery assembly, which is to turn off the bypass switch and the through switch. After the bypass switch and the through switch are both turned off, the battery assembly operates in a reduced voltage state.

[0036] When a single cell of the cell assembly fails, the cluster management system sends an instruction to the main control unit, which is: close the through switch; after the through switch is closed, the cell assembly is in a bypass state.

[0037] Compared with the prior art, the present invention has the beneficial effect that the present invention can completely avoid the short board effect of the energy storage system caused by the series and parallel connection of battery cells, so that the cycle life of the energy storage system is consistent with the cycle life of the battery cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the primary topology diagram of the traditional DC side system.

[0039] Figure 2 This is the balancing topology diagram of the traditional battery management system.

[0040] Figure 3 This is the primary topology diagram of the string DC side system.

[0041] Figure 4 It is a primary topology diagram of the system of the present invention.

[0042] Figure 5 It is a communication topology diagram of the system of the present invention.

[0043] Figure 6 It is a structural diagram of embodiment 1 of the present invention.

[0044] Figure 7 It is a structural diagram of embodiment 2 of the present invention.

[0045] Figure 8 The curve of the battery cell when charging and discharging. DETAILED DESCRIPTION

[0046] The present invention is further described in detail below with reference to the accompanying drawings:

[0047] The present invention provides a cell-level optimized battery plug-in box, which includes a plurality of cell assemblies connected in parallel on a DC bus; each cell assembly includes a bypass switch, a pass-through switch, at least one single cell, a main control unit and a DC / DC converter; the single cell is connected to the DC / DC converter, and the DC / DC converter is connected to the main control unit; the bypass switch and the pass-through switch are used to achieve disconnection, direct connection or connection through the DC / DC converter between the single cell and the DC bus.

[0048] The embodiment of the cell-level optimized battery plug box of the present invention is as follows:

[0049] [Example 1]

[0050] Figure 6 An embodiment of a cell-level optimized battery plug-in box of the present invention is shown, which includes multiple cell assemblies, each cell assembly includes a single cell, a main control unit, and a high-speed communication interface. A DC / DC converter is connected to each single cell, and the DC / DC converter and the high-speed communication interface are respectively connected to the main control unit. The main control unit is used to receive instructions issued by the cluster management system and upload the status data of the cell to the cluster management system. Furthermore, an acquisition circuit is connected to the main control unit, and the main control unit collects the status data of the cell through the acquisition circuit. The functions of the acquisition circuit and the plug-in box battery management system are the same. The plug-in box battery management system can be used as a redundant configuration, or the plug-in box battery management system can be removed and only the acquisition circuit can be used.

[0051] Specifically, such as Figure 6As shown, the positive and negative poles of the individual battery cells are connected to the positive and negative poles at the head end of the DC / DC converter, and the positive and negative poles at the end of the DC / DC converter are respectively connected to the positive and negative poles of the DC bus. Furthermore, the present invention connects a bypass switch to each DC / DC converter, with the positive and negative poles at the head end of the bypass switch being respectively connected to the positive and negative poles at the head end of the DC / DC converter, and the positive and negative poles at the end of the bypass switch being respectively connected to the positive and negative poles at the end of the DC / DC converter. When the bypass switch is closed, the battery cells are directly connected to the DC bus. When the bypass switch is open, the battery cells are connected to the DC bus through the DC / DC converter. Furthermore, a through switch is connected in parallel to the line connecting the end of the DC / DC converter to the DC bus. When the through switch is closed, the positive and negative poles of the DC bus at the battery cell assembly are directly connected, thereby enabling the removal of individual battery cells from the battery cell assembly. Removal of the individual battery cells does not affect the operation of other battery cell assemblies.

[0052] In this way, the DC / DC converters in multiple cell assemblies within a cell-level optimized battery plug-in box are connected in parallel to the DC bus. For each battery cluster, the DC buses of multiple cell-level optimized battery plug-ins are connected in series and then connected to the DC side of the energy storage converter.

[0053] [Example 2]

[0054] Figure 7 Another embodiment of the cell-level optimized battery plug-in box of the present invention is shown, which includes multiple cell assemblies, each cell assembly includes multiple single cells connected in series, a main control unit, and a high-speed communication interface. In each cell assembly, a DC / DC converter is connected to the last single cell, and the DC / DC converter and the high-speed communication interface are respectively connected to the main control unit. Furthermore, an acquisition circuit is connected to the main control unit, and the main control unit collects the status data of the single cells through the acquisition circuit. The functions of the acquisition circuit and the plug-in box battery management system are the same. The plug-in box battery management system can be used as a redundant configuration, or the plug-in box battery management system can be removed and only the acquisition circuit can be used.

[0055] Specifically, such as Figure 7As shown, the positive and negative poles of the last single cell in each cell assembly are connected to the positive and negative poles at the head end of the DC / DC converter, and the positive and negative poles at the end of the DC / DC converter are connected to the positive and negative poles of the DC bus, respectively. Furthermore, the present invention connects a bypass switch to each DC / DC converter, with the positive and negative poles at the head end of the bypass switch connected to the positive and negative poles at the head end of the DC / DC converter, respectively, and the positive and negative poles at the end of the bypass switch connected to the positive and negative poles at the end of the DC / DC converter, respectively. When the bypass switch is closed, the cell is directly connected to the DC bus; when the bypass switch is open, the cell is connected to the DC bus through the DC / DC converter. Furthermore, a through switch is connected in parallel to the line connecting the end of the DC / DC converter to the DC bus. When the through switch is closed, the positive and negative poles of the DC bus at that cell assembly are directly connected, achieving the function of disconnecting all the single cells in the series connection of that cell assembly. Disconnecting all the single cells in that cell assembly does not affect the operation of other cell assemblies.

[0056] In this way, the DC / DC converters in multiple cell assemblies within a cell-level optimized battery plug-in box are connected in parallel to the DC bus. For each battery cluster, the DC buses of multiple cell-level optimized battery plug-ins are connected in series and then connected to the DC side of the energy storage converter.

[0057] The composition structure of the energy storage system of the present invention is as follows Figure 4 As shown, it includes a combiner cabinet (the combiner cabinet is for the convergence of the AC side, with multiple incoming lines and a single outgoing line. It is an existing product and will not be described here.), an energy storage converter, and a cell-level optimized battery plug-in box. Multiple cell-level optimized battery plug-ins are connected in series and then connected to an energy storage converter, and multiple energy storage converters are respectively connected to the combiner cabinet.

[0058] The embodiments of the energy storage system of the present invention are as follows:

[0059] [Example 3]

[0060] The structure of the energy storage system of the present invention is as follows Figure 5As shown, the system includes a centralized control device, multiple energy storage converters, multiple cluster management systems, and multiple battery clusters. Furthermore, the energy storage system may also include multiple plug-in battery management systems. The battery clusters, plug-in battery management systems, energy storage converters, and cluster management systems correspond one to one, meaning each battery cluster is equipped with a plug-in battery management system, an energy storage converter, and a cluster management system. Each battery cluster includes multiple cell-level optimized battery plug-ins, which are connected in series and then to the energy storage converter. The plug-in battery management systems of all battery clusters are connected to the centralized control device, the energy storage converters of all battery clusters are connected to the centralized control device, and the cluster management systems of all battery clusters are connected to the centralized control device. The main control unit of each cell assembly within a battery cluster communicates with the cluster management system of that cluster via a high-speed communication interface. Simultaneously, each plug-in battery management system communicates with the main control unit of each cell assembly within its corresponding battery cluster, transmitting collected data to the main control unit.

[0061] The cluster management system manages the main control unit in the cell-level optimized battery plug-in box, controls the switching between the DC / DC converter and the bypass, and uploads data to the centralized control system. The cluster management system can utilize existing PLCs, communication management machines, and other devices, which will not be detailed here.

[0062] The plug-in box battery management system is an existing product, which can collect data on the voltage, temperature and current of the battery cell. Figure 6 In the structure shown, the plug-in battery management system collects data from all single cells and uploads these data to the main control unit, which then uploads these data to the cluster management system. Figure 7 The plug-in battery management system collects data on each single cell, including current, voltage and temperature, and uploads the overall voltage, average temperature and current of multiple cells connected in series to the main control unit, which then uploads this data to the cluster management system.

[0063] The centralized control device is the master control unit within the entire stack. It is responsible for controlling the charge and discharge power of the energy storage converter, coordinating the charge and discharge power of each cluster, and switching between the PQ and VF sources of the energy storage converter. The centralized control device coordinates the power coordination control of each energy storage converter and the cluster management system, and can output the overall status of the entire energy storage system. These control and coordination methods are mature technologies and will not be elaborated here.

[0064] Specifically, in Figure 6 In the structure shown, the main control unit in each battery assembly collects the current, voltage and temperature of the single battery cell in the battery assembly. Figure 7In the illustrated structure, the master control unit of each cell assembly collects the total voltage, average temperature, and average current of the N series-connected cells in the assembly (i.e., it adds the voltages of all N series-connected individual cells in the assembly to obtain the total voltage, and averages the temperature and current of each individual cell). It then uploads all this data to the cluster management system. The cluster management system then makes decisions based on the data uploaded by each master control unit in each cell-level optimized battery plug-in box and issues instructions to each master control unit. By controlling the opening or closing of the bypass and pass-through switches in each cell assembly, the cluster management system enables the cell assembly to operate in the pass-through, bypass, or step-down mode. This allows the cluster management system to independently control the bypass and pass-through switches of each cell assembly. Simultaneously, the cluster management system uploads data such as the cell-level optimized battery plug-in box status, battery voltage, and the power available for charging and discharging during device operation to the centralized control device.

[0065] The present invention also provides a method for applying the above-mentioned energy storage system, which includes: the cluster management system makes judgments based on the data uploaded by each main control unit in each cell-level optimization battery plug-in box, and then issues instructions to each main control unit respectively, and controls the opening or closing of the bypass switch and the through switch in each cell assembly to make the cell assembly operate in the through, bypass or step-down state.

[0066] An embodiment of the method is as follows:

[0067] [Example 4]

[0068] The method specifically includes:

[0069] When a single cell in the battery cell assembly is in the charge and discharge plateau period (the cluster management system determines whether it is in the charge and discharge plateau period based on the data uploaded by the main control unit. The specific judgment method can adopt the existing method and will not be repeated here), it means that the consistency of the entire cluster battery is good and no adjustment is required. Then the cluster management system sends an instruction to the main control unit of the battery cell assembly. The instruction is: close the bypass switch and open the through switch. After the bypass switch is closed and the through switch is opened, the DC / DC converter does not participate in the operation, and the battery cell assembly operates in the through state, that is, the single cell is directly connected to the battery cluster without the conversion of the DC / DC converter (that is, the single cell is directly connected to the DC bus). This can reduce system losses.

[0070] When the single cell in the battery assembly is at the end of charge and discharge (the cluster management system determines whether it is at the end of charge and discharge based on the data uploaded by the main control unit. The specific judgment method can adopt the existing method and will not be repeated here), the voltage will change sharply at this time and approach the over / under voltage alarm value. The cluster management system will send an instruction to the main control unit of the battery assembly. The instruction is: disconnect the bypass switch and disconnect the through switch. After the bypass switch and the through switch are both disconnected, the DC / DC converter is put into operation (that is, the single cell is connected to the DC bus through the DC / DC converter), and the battery assembly operates in a step-down state. By reducing the voltage of the DC / DC converter, the charge and discharge power of the battery assembly is reduced, which can enable the battery in the battery plug box to achieve constant voltage, floating charge and other effects, thereby avoiding large current directly charging to the overvoltage alarm shutdown;

[0071] When a single cell in the battery assembly fails (the cluster management system determines whether a failure occurs based on the data uploaded by the main control unit. The specific judgment method can adopt the existing method and will not be repeated here), the cluster management system sends an instruction to the main control unit. The instruction is: close the through switch (the bypass switch remains unchanged and can be closed or open). After the through switch is closed, the battery assembly is in the bypass state, that is, the single cell in the battery assembly is disconnected from the DC bus, that is, the single cell is directly separated from the battery cluster, while ensuring that other battery plug-in boxes in the battery cluster can still charge and discharge normally.

[0072] The centralized control device communicates with all cluster management systems in the battery stack to collect information from all batteries. The cluster management system determines the operating status of each battery cell and whether it is necessary to reduce its charge / discharge current or even bypass it. When there are many battery boxes in the cluster operating in a step-down state, the centralized control device coordinates the energy storage converter to reduce the overall charging current or power. When there are many battery boxes disconnected from the cluster (for example, when the number of disconnected battery boxes reaches a preset threshold value), the operating DC voltage value required by the energy storage converter may not be reached. At this time, the centralized control device coordinates the energy storage converter to stop charging and discharging.

[0073] The present invention installs a DC / DC converter on each single battery cell. In a battery plug-in box, each battery cell is connected in parallel through a DC / DC converter. For each battery cluster, multiple battery plug-ins are connected in series and then connected to the DC side of the energy storage converter. In addition, the present invention provides a cluster management system for each cluster to perform centralized coordinated control of the battery plug-in boxes, battery management system, and energy storage converters at the cell level optimization within the cluster. In addition, the present invention provides a main control unit in each battery cell assembly, which can control the charging and discharging of the single battery cells in the battery cell assembly, thereby completely eliminating the short board effect caused by series connection in traditional systems.

[0074] In the description of the present invention, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0075] In the description of the present invention, unless otherwise specified, the terms "upper", "lower", "left", "right", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, they cannot be understood as limiting the present invention.

[0076] Finally, it should be noted that the above technical solution is only one embodiment of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific embodiment of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

Claims

1. A cell-level optimized battery plug-in box, characterized by: The cell-level optimized battery plug-in box includes: a plurality of cell assemblies connected in parallel on a DC bus; Each of the battery cell assemblies includes a bypass switch, a pass switch, at least one single battery cell, a main control unit and a DC / DC converter; The single battery cell is connected to a DC / DC converter, and the DC / DC converter is connected to a main control unit; When a single cell in the cell assembly is in a charge and discharge plateau period, the main control unit controls the bypass switch to be closed and the through switch to be opened, thereby achieving a direct connection between the single cell and the DC bus; When a single cell in the cell assembly is at the end of charge and discharge, the main control unit controls the bypass switch and the through switch to be turned off, so that the single cell is connected to the DC bus through the DC / DC converter; When a single cell of the cell assembly fails, the main control unit controls the through switch to close, thereby disconnecting the single cell from the DC bus.

2. The cell-level optimized battery plug-in box according to claim 1, characterized in that: Each of the battery cell assemblies includes a single battery cell; The positive and negative electrodes of the single battery cell are respectively connected to the positive and negative electrodes of the head end of the DC / DC converter, and the positive and negative electrodes of the tail end of the DC / DC converter are respectively connected to the positive and negative electrodes of the DC bus; The positive and negative terminals of the bypass switch are connected to the positive and negative terminals of the DC / DC converter respectively, and the positive and negative terminals of the bypass switch are connected to the positive and negative terminals of the DC / DC converter respectively. A through switch is connected in parallel to the line connected to the DC bus at the end of the DC / DC converter.

3. The cell-level optimized battery plug-in box according to claim 1, characterized in that: Each of the battery cell assemblies comprises a plurality of single battery cells connected in series; The positive and negative electrodes of the last single cell are connected to the positive and negative electrodes of the DC / DC converter, and the positive and negative electrodes of the DC / DC converter are connected to the positive and negative electrodes of the DC bus. The positive and negative terminals of the bypass switch are connected to the positive and negative terminals of the DC / DC converter respectively, and the positive and negative terminals of the bypass switch are connected to the positive and negative terminals of the DC / DC converter respectively. A through switch is connected in parallel to the line connected to the DC bus at the end of the DC / DC converter.

4. The cell-level optimized battery plug-in box according to claim 2 or 3, characterized in that: Each of the battery cell assemblies further includes a high-speed communication interface, which is connected to the main control unit.

5. The cell-level optimized battery plug-in box according to claim 2 or 3, characterized in that: Each of the battery cell components further includes an acquisition circuit, which is connected to the main control unit.

6. An energy storage system, characterized in that: The energy storage system includes: multiple battery clusters, multiple energy storage converters, multiple cluster management systems and a centralized control device; The battery cluster, energy storage converter, and cluster management system correspond one to one; Each battery cluster includes a plurality of cell-level optimized battery plug-ins according to any one of claims 1 to 5, wherein the DC buses of the plurality of cell-level optimized battery plug-ins are connected in series and then connected to the DC side of the energy storage converter; The main control unit of each battery cell assembly in the same battery cluster communicates with the cluster management system corresponding to the battery cluster through a high-speed communication interface.

7. The energy storage system according to claim 6, characterized in that: The energy storage system also includes multiple plug-in box battery management systems; The subrack battery management system corresponds to each battery cluster one by one and communicates with each main control unit in the corresponding battery cluster.

8. The cell-level optimized energy storage system according to claim 7, characterized in that: All energy storage converters are connected to the centralized control device respectively; All cluster management systems are connected to the centralized control device respectively; All plug-in box battery management systems are connected to the centralized control device respectively.

9. A method for applying the energy storage system according to any one of claims 6 to 8, characterized in that: The method includes: the cluster management system makes judgments based on the data uploaded by each main control unit in each cell-level optimization battery plug-in box, and then issues instructions to each main control unit respectively, and controls the opening or closing of the bypass switch and the through switch in each cell assembly so that the cell assembly operates in the through, bypass or reduced voltage state.

10. The method according to claim 9, characterized in that: The method specifically includes: When a single cell in the cell assembly is in the charge and discharge plateau period, the cluster management system sends a command to the main control unit of the cell assembly, which is: close the bypass switch and open the through switch; after the bypass switch is closed and the through switch is opened, the cell assembly operates in the through state; When a single cell in the battery assembly is at the end of charge or discharge, the cluster management system sends a command to the main control unit of the battery assembly, which is to turn off the bypass switch and the through switch. After the bypass switch and the through switch are both turned off, the battery assembly operates in a reduced voltage state. When a single cell of the cell assembly fails, the cluster management system sends an instruction to the main control unit, which is: close the through switch; after the through switch is closed, the cell assembly is in a bypass state.

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