A battery module, energy storage device and balanced control method

Abstract

The embodiment of the present application provides a battery module, including: a shell; a battery core, which is arranged inside the shell and is used to store and release electric energy; a battery monitoring and management module, which is arranged inside the shell and includes: a battery management unit, one end of which is electrically connected to the battery core, and the other end serves as the first group of power interfaces of the battery module, including a first power end and a second power end, the first power end and the second power end are respectively the positive pole and the negative pole of the above-mentioned first group of power interfaces; a power conversion unit, one end of which is coupled to the first group of power interfaces, and the other end serves as the second group of power interfaces of the battery module; the battery management unit and the power conversion unit are communicatively connected; the first communication interface is arranged on the outer surface of the shell and is communicatively connected with the battery monitoring and management module. Among them, at least one of the first group of power interfaces and the second group of power interfaces is arranged on the outer surface of the shell. The above-mentioned battery module has better adaptability and is easy to expand and expand the energy storage equipment.

Description

Technical Field

[0001] The embodiments of the present invention belong to the technical field of energy storage, and in particular, relate to a battery module, an energy storage device, and a balancing control method. Background Art

[0002] Electrochemical energy storage systems often use hundreds of battery cells connected in series. Due to the limitations of battery production technology, there are certain differences in parameters such as capacity and internal resistance between battery cells of the same model and specification, resulting in unbalanced power during the use of the hundreds of battery cells connected in series. In addition, the structure of a large number of battery cells connected in series makes the failure rate of the battery cluster much greater than the failure rate of the battery cells in any cluster, and the power of the battery cells that have not failed in the cluster cannot be fully used.

[0003] Existing battery management technology only manages the battery cells in series in a hierarchical manner. The entire series of battery cells is defined as a battery cluster, and each battery cluster is equipped with a control management unit to realize the external power exchange of the battery cluster and the power balance between battery clusters; the battery cluster is divided into several battery modules in series, and each battery module is equipped with a battery management unit to monitor and control the battery cells in the module in a limited manner. This limited control is manifested in: (1) the battery module can only be controlled to be on or off, and the output power of the battery cannot be controlled; (2) the energy balance of the battery cells in the battery module can be controlled, but the power balance between the battery modules cannot be achieved. This limitation in control, on the one hand, cannot completely solve the problem of battery imbalance, and on the other hand, the failure rate of the battery cluster is not improved, and it is also not conducive to the installation, maintenance and capacity expansion of the battery cluster. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a battery module that is compatible with and optimizes energy storage devices with existing battery series architectures; and can construct a new battery cluster architecture with better adaptability; and can perform modular management of battery modules to facilitate the expansion and expansion of energy storage devices.

[0005] In a first aspect, an embodiment of the present application provides a battery module, wherein the battery module is provided with a housing, and the battery module further comprises:

[0006] The battery core is disposed inside the housing and is configured to store and release electrical energy.

[0007] The battery monitoring management module is arranged inside the housing and includes:

[0008] A battery management unit, one end of which is electrically connected to the battery core, and the other end serves as the first power interface of the battery module. The first power interface includes a first power end and a second power end. The first power end and the second power end are respectively the positive and negative poles of the first power interface of the battery module.

[0009] The power conversion unit is provided with a primary power port and a secondary power port; the primary power port is coupled with a first group of power interfaces of the battery module; the secondary power port serves as a second group of power interfaces of the battery module. The power conversion unit is also connected to the battery management unit for communication.

[0010] The first communication interface is arranged on the outer surface of the battery module housing, and the first communication interface is in communication with the battery monitoring management module. At least one of the first power interface and the second power interface is arranged on the outer surface of the battery module housing.

[0011] In some embodiments, the battery cell is composed of a plurality of single cells connected in series.

[0012] In some embodiments, the battery monitoring management module further includes a communication bus that carries the communication between the power conversion unit and the battery management unit and the communication between the first communication interface and the battery monitoring management module.

[0013] In some embodiments, the power conversion unit is provided with a balancing controller for controlling the voltage of the second group of power interfaces of the battery module in which it is located.

[0014] In some embodiments, the balancing controller obtains at least one electrical parameter and SOC value of all battery modules in the energy storage device through the first communication interface.

[0015] In some embodiments, the second group of power interfaces is connected in parallel with the second group of power interfaces of other battery modules in the energy storage device; and the interfaces of the second group of power interfaces connected in parallel serve as the power interfaces of the energy storage device.

[0016] In some embodiments, the first group of power interfaces is connected in series with the first group of power interfaces of other battery modules in the energy storage device, and the second group of power interfaces is connected in parallel with the second group of power interfaces of other battery modules in the energy storage device; the interface connected in series with the first group of power interfaces serves as the power interface of the energy storage device.

[0017] In some embodiments, the first group of power interfaces is connected in series with the first group of power interfaces of other battery modules in the energy storage device; the second group of power interfaces is connected in parallel with the second group of power interfaces of other battery modules in the energy storage device; the interfaces of the first group of power interfaces in series and the interfaces of the second group of power interfaces in parallel serve as the first power interface and the second power interface of the energy storage device.

[0018] In some embodiments, the electrical parameters acquired by the balancing controller include voltage and current; the balancing controller calculates and obtains the voltage instruction of the second group of power interfaces of the battery module in which it is located.

[0019] In a second aspect, an embodiment of the present application provides a distributed energy storage device, which includes: a power conversion module and a plurality of the above-mentioned battery modules. The power conversion module includes a second communication interface, a third group of power interfaces and a first peripheral power interface.

[0020] The second groups of power interfaces of several battery modules are connected in parallel to form the third group of power interfaces mentioned above; the first communication interfaces of several battery modules are in communication connection with the second communication interfaces.

[0021] In a third aspect, an embodiment of the present application provides a direct-mounted energy storage device, which includes: a power conversion module and a plurality of the above-mentioned battery modules. The power conversion module includes a third communication interface, a fourth group of power interfaces, and a second peripheral power interface.

[0022] The second groups of power interfaces of several battery modules are connected in parallel, the first groups of power interfaces of several battery modules are connected in series and then connected to the fourth group of power interfaces, the second groups of power interfaces of several battery modules are connected in parallel, and the first communication interfaces of several battery modules are in communication with the third communication interface.

[0023] In a fourth aspect, an embodiment of the present application provides a hybrid energy storage device, the hybrid energy storage device comprising: a power conversion module and a plurality of the above-mentioned battery modules, wherein the power management module comprises a fourth communication interface, a fifth group power interface and a third peripheral power interface.

[0024] The first groups of power interfaces of several battery modules are connected in series and then connected to the fifth group of power interfaces, the second groups of power interfaces of several battery modules are connected in parallel to form a fourth peripheral power interface; and the first communication interfaces of several battery modules are connected to the fourth communication interface.

[0025] In a fifth aspect, an embodiment of the present application provides a method for balancing battery modules in a battery cluster. The battery cluster includes a plurality of the above-mentioned battery modules, and the second groups of power interfaces of all the battery modules are connected in parallel and simultaneously serve as the power interfaces of the battery cluster; the power conversion unit is provided with a balancing controller. The balancing method includes:

[0026] Step S10: Obtaining the voltage, current, and SOC value of the battery cells in all the battery modules;

[0027] Step S20: Control the voltage of the second power interface of the current battery module to maintain at a preset voltage value, so that in the discharge state, the first relationship is positively correlated with the second relationship, and in the charge state, the first relationship is positively correlated with the third relationship.

[0028] Among them, the first relationship is the relationship between the current or power of the battery cell of the current battery module and the current or power of the battery cell of other battery modules, the second relationship is the relationship between the SOC value of the current battery module and the SOC values ​​of other battery modules, and the third relationship is the relationship between the (1-SOC) value of the current battery module and the (1-SOC) values ​​of other battery modules.

[0029] In some embodiments, the preset voltage value is calculated by the equalization controller, and the calculation formula of the preset voltage value is:

[0030]

[0031] in, V * is the preset voltage constant, V E It is a balance control item.

[0032] In some embodiments, the calculation formula of the above preset voltage value is:

[0033]

[0034] in, V F is the control correction term.

[0035] In a sixth aspect, an embodiment of the present application further provides a method for balancing battery modules in a battery cluster in an energy storage device. The battery cluster includes a plurality of the above-mentioned battery modules, the first groups of power interfaces of all battery modules are connected in series as the power interfaces of the battery cluster, and the second groups of power interfaces of all battery modules are connected in parallel; the power conversion unit is provided with a balancing controller. The balancing method includes:

[0036] Step S40: Obtaining the voltage, current, and SOC value of the battery cells in all the battery modules;

[0037] Step S50: determining whether the difference in the SOC values ​​of all the battery modules exceeds a balancing threshold, if not, executing step S60, if yes, executing step S70 or S90;

[0038] Step S60: Control the power conversion unit to stop working and return to step S40;

[0039] Step S70: Determine whether the SOC value of the current battery module is the highest value of all the battery modules, if so, execute step S80, if not, execute step S110;

[0040] Step S80: raising the second power interface voltage of the current battery module to the highest value and operating in a discharge state;

[0041] Step S90: determining whether the SOC value of the current battery module is the lowest value of all the battery modules, if so, executing step S100, if not, executing step S110;

[0042] Step S100: reducing the second power interface voltage value of the current battery module to the lowest value and operating in a charging state;

[0043] Step S110: controlling the voltage of the second power interface of the current battery module to be maintained at a preset voltage value, so that in a discharging state, the fourth relationship is positively correlated with the fifth relationship, and in a charging state, the fourth relationship is positively correlated with the sixth relationship;

[0044] Among them, the fourth relationship is the relationship between the current or power of the battery cell of the current battery module and the current or power of the battery cells of other battery modules, the fifth relationship is the relationship between the SOC value of the current battery module and the SOC values ​​of other battery modules, and the sixth relationship is the relationship between the (1-SOC) value of the current battery module and the (1-SOC) values ​​of other battery modules.

[0045] In some embodiments, the preset voltage value is calculated by the equalization controller, and the calculation formula of the preset voltage value is:

[0046]

[0047] in, V * is the preset voltage constant, V E It is a balance control item.

[0048] In some embodiments, the calculation formula of the above preset voltage value is:

[0049]

[0050] in, V F is the control correction term.

[0051] Compared with the prior art, the embodiments of the present application have at least the following beneficial effects: the embodiments of the present application provide a battery module and an energy storage device, the energy storage device includes a plurality of battery modules, each of which includes a battery core, a power conversion unit, a first group of power interfaces, a second group of power interfaces, and a first communication interface. By adjusting the different connection methods of the first group of power interfaces and the second group of power interfaces of the battery module and coordinating with various functional modules, the energy storage device with the existing battery series architecture can be compatible and optimized; and a new battery cluster architecture can be constructed to adapt to power systems with different requirements, with a wider application field; in addition, modular management of battery modules in energy storage devices can be realized, which is easy to expand and expand the energy storage device. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0053] Figure 1 is a structural schematic diagram of a battery module provided in one embodiment of the present application;

[0054] Figure 2 is a structural schematic diagram of a battery module provided in another embodiment of the present application;

[0055] Figure 3 is a structural schematic diagram of a battery management unit in a battery module provided in an embodiment of the present application;

[0056] Figure 4 It is a structural schematic diagram of a power conversion unit in a battery module provided in an embodiment of the present application;

[0057] Figure 5 This is a schematic diagram of the connection relationship between battery modules in an energy storage device provided in an embodiment of the present application;

[0058] Figure 6 is a schematic diagram of the connection relationship between battery modules in an energy storage device provided in another embodiment of the present application;

[0059] Figure 7 is a schematic diagram of the connection relationship between battery modules in an energy storage device provided in another embodiment of the present application;

[0060] Figure 8 is a structural schematic diagram of a distributed energy storage device provided in one embodiment of the present application;

[0061] Fig. 9 It is a structural schematic diagram of a direct-mounted energy storage device provided in one embodiment of the present application;

[0062] Fig.10 is a structural schematic diagram of a hybrid energy storage device provided in one embodiment of the present application;

[0063] Fig.11 It is a flow chart of a method for balancing battery modules in a battery cluster provided by an embodiment of the present application;

[0064] Fig.12 It is a schematic diagram of a calculation process of a voltage preset value in a balancing control method provided in an embodiment of the present application;

[0065] Fig.13 is a schematic diagram of a calculation process of a voltage preset value in a balancing control method provided in another embodiment of the present application;

[0066] Fig.14a and Fig.14b is a flow chart of a balancing control method provided by an embodiment of the present application;

[0067] Fig.15 It is a schematic diagram of the working principle of the balancing control method provided by an embodiment of the present application;

[0068] Fig.16 is a schematic diagram of the working principle of a balancing control method provided by another embodiment of the present application;

[0069] Fig.17 It is a schematic diagram of the working principle of a balancing control method provided in another embodiment of the present application. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0071] It should be noted that, if there is no conflict, the various features in the embodiments of the present application can be combined with each other, all within the scope of protection of the present application. In addition, although the functional module division is performed in the device schematic, in some cases, the module division can be different from that in the device. In addition, the words "first", "second", etc. used herein do not limit the data and execution order, but only distinguish the same items or similar items with basically the same functions and effects.

[0072] In a first aspect, the present application provides a battery module, see Figure 1 , Figure 1The battery module 10 includes a housing 100 , a battery core 200 , a first group of power interfaces 300 , a battery monitoring and management module 400 , a second group of power interfaces 500 and a first communication interface 600 .

[0073] The battery core 200 is disposed inside the housing 100 and is configured to store and release electrical energy.

[0074] The battery monitoring management module 400 is disposed inside the housing 100 , and includes a battery management unit 4001 and a power conversion unit 4002 .

[0075] Among them, one end of the battery management unit 4001 is electrically connected to the battery core 200, and the other end serves as the first power interface 300 of the battery module. The first power interface 300 includes a first power terminal 3001 and a second power terminal 3002. The first power terminal 3001 and the second power terminal 3002 are respectively the positive electrode and the negative electrode of the first power interface 300 of the battery module 10;

[0076] The power conversion unit 4002 is provided with a primary power port and a secondary power port. The primary power port is coupled to the first power interface 300; the secondary power port serves as the second power interface 500 of the battery module 10. The second power interface 500 is used to connect a power source or a load. The power conversion unit 4002 is also connected to the battery management unit 4001 for communication.

[0077] The first communication interface 600 is disposed on the outer surface of the housing 100 and is in communication with the battery monitoring management module 400 .

[0078] It should be noted that at least one of the first group of power interfaces 300 and the second group of power interfaces 500 is disposed on the outer surface of the housing 100 (in the embodiment of the present application, only the case where both are disposed on the outer surface is used as an example for explanation).

[0079] Compared with the prior art, the embodiment of the present application provides a battery module, which includes a battery core, a battery monitoring and management module, a first group of power interfaces, a second group of power interfaces, and a first communication interface. By adjusting the different connection modes of the first group of power interfaces and the second group of power interfaces of the battery module and coordinating with various functional modules, it is possible to be compatible with and optimize the existing battery series architecture (such as the embodiment of the present application). Figure 6 and Fig. 9 The battery module structure in the embodiment shown in the figure) can be used as an energy storage device; and a new battery cluster structure can be constructed (such as in the embodiment of the present application Figure 5 , Figure 7 , Figure 8 and Fig.10The architecture of the battery module in the embodiment shown in the figure can be adapted to power systems with different needs, and has a wider application field. In addition, modular management of the battery modules in the energy storage device can be achieved, which facilitates the expansion and expansion of the energy storage device.

[0080] In some embodiments, see Figure 2 , Figure 2 The schematic diagram of the structure of the battery module provided by another embodiment of the present application is as follows: wherein the battery monitoring management module 400 in the battery module 10 further includes a communication bus 4003 .

[0081] The communication bus 4003 carries the communication between the power conversion unit 4002 and the battery management unit 4001 and the communication between the first communication interface 600 and the battery monitoring management module 400 .

[0082] In some embodiments, please refer again to Figure 2 A balancing controller is provided in the power conversion unit 4002.

[0083] The balancing controller controls the voltage of the second group of power interfaces of the battery module to indirectly control the current / power of the battery core in the battery module to achieve power balance among the battery modules.

[0084] In some embodiments, see Figure 3 , Figure 3 The schematic diagram of the structure of the battery management unit in the battery module provided in one embodiment of the present application. The battery management unit 4001 includes a voltage sampling circuit, an equalization circuit, a current sampling circuit, a temperature sampling circuit, a controller, a charge and discharge switch, a switch driving circuit, and other functional modules for monitoring the battery (such as insulation detection, low temperature heating control, etc.).

[0085] Among them, the voltage sampling circuit is electrically connected to each battery cell and the controller in the battery core 200, and is used to collect the voltages of all battery cells and the total voltage of the battery core and transmit them to the controller; the balancing circuit is electrically connected to each battery cell and the controller in the battery core 200, receives the control signal of the controller, and performs balancing control on the battery cells; the temperature sampling circuit is electrically connected to the controller, and is used to collect the temperature of the battery core, main circuit components and the ambient temperature and transmit them to the controller; the current sampling circuit is electrically connected to the battery core 200 and the controller, and is used to collect the current of the battery core 200 and transmit it to the controller; the charge and discharge switch is electrically connected to the battery core 200, and the switch drive circuit is electrically connected to the charge and discharge switch and the controller, and the three are combined to control the conduction and disconnection of the external power supply circuit of the battery core 200; the communication interface is respectively connected to the controller and the communication bus 4003.

[0086] The battery management unit 4001 is used to monitor and manage the battery core 200 in the battery module 10. Specifically, it mainly includes the following functions: monitoring the voltage and temperature of any battery cell in the battery core 200 and the total current of the battery core 200; obtaining and calculating the total voltage, SOC (battery remaining power percentage), SOH (battery current capacity and factory capacity percentage) and other information of the battery core 200; protecting the battery core 200 and / or the battery cells in the battery core 200 from over-voltage, over-current, high and low temperature, etc.; performing energy consumption equalization on battery cells with too high energy, etc. At the same time, it has a communication interface, which can be used for intra-group communication (i.e., communication between the battery management unit and the power conversion unit in a single battery module) and inter-group communication (i.e., communication between multiple battery modules).

[0087] In some embodiments, see Figure 4 , Figure 4 A schematic diagram of the structure of a power conversion unit in a battery module provided in an embodiment of the present application. The power conversion unit 4002 includes a bidirectional isolated DC-DC power circuit, a balancing controller, a current sampling circuit, a voltage sampling circuit, a switch tube driving circuit, and a communication interface. Among them, the implementation carrier of the balancing controller is any control chip with programmable functions that meet the peripheral resources required for the circuit operation. The embodiment of the present application is described by taking a DSP chip as an example. The DSP chip samples and collects the electrical parameters (such as voltage, current, power, etc.) of the bidirectional isolated DC-DC power circuit through an analog-to-digital converter ADC, and collects the electrical parameter information of other battery modules through a communication interface (eCAN, UART, etc.), processes it in the on-chip CPU, and finally generates a control signal, which is output through ePWM to control the switch tube action in the inverter circuit and the rectifier circuit of the bidirectional isolated DC-DC power circuit, thereby achieving voltage stability of its secondary power interface (that is, the second group of power interfaces of the battery module) and power balance between each battery module.

[0088] The primary power interface of the bidirectional isolated DC-DC power circuit is connected to the first group of power interfaces 300 (ie, the first power terminal 3001 and the second power terminal 3002 ), and the secondary power interface of the bidirectional isolated DC-DC power circuit serves as the second group of power interfaces 500 .

[0089] The bidirectional isolated DC-DC power circuit can be any common bidirectional, isolated, DC-DC conversion power topology, such as DAB, LLC-SRC, CLLC and other circuit topologies. It should be noted that the structures of the above circuit topologies are all prior art and will not be described in detail here. Please refer to the prior art.

[0090] The DSP chip is connected to the communication bus 4003 through the communication interface to obtain the SOC value, voltage, current, battery status and other information of the battery module in which it is located and other battery modules (i.e., intra-group or inter-group communication) to determine the DC operating point of the bidirectional isolated DC-DC power circuit.

[0091] The DSP chip obtains real-time voltage and current parameter information through a voltage sampling circuit and a current sampling circuit arranged on the side of the first power interface 300 and a voltage sampling circuit arranged on the side of the second power interface 500, so as to perform real-time control on the working state of the bidirectional isolated DC-DC power circuit based on the parameter information, thereby ensuring that the bidirectional isolated DC-DC power circuit operates stably at the corresponding DC operating point.

[0092] It should be noted that the communication mentioned in some of the above embodiments is to realize the intra-group communication and inter-group communication of the battery module in the form of bus communication. In some other embodiments, an independent communication method can also be used to realize the communication function. Specifically, the communication interface of the battery management unit or the power conversion unit in a single battery module serves as the first communication interface of the battery module, and shares data with other battery modules, that is, sends parameter information such as voltage, current, SOC, temperature, etc. in the battery module, and also receives the above parameter information of other battery modules. Then, through an independent intra-group communication line, the data in the battery module is shared with the power conversion unit or battery management unit of the battery module. In some other embodiments, the intra-group communication and inter-group communication of the above-mentioned battery modules can also adopt wireless communication, wired communication combined with wireless communication and other communication methods according to actual needs, and its communication method is not limited here.

[0093] In addition, by connecting the upper-layer device (such as a device for unified management of several energy storage devices, where the energy storage devices include several battery modules) to the first communication interface in the battery module, functions such as information interaction, control implementation, and firmware upgrade can also be realized.

[0094] In some embodiments, see Figure 5 , Figure 5 1 shows a connection relationship between battery modules provided in an energy storage device according to an embodiment of the present application. Figure 5 As shown: the second power interfaces 500 of each battery module 10 are connected in parallel, and the parallel interfaces serve as power interfaces of the energy storage device. It should be noted that, for the convenience of description, Figure 5 In the embodiment shown, the energy storage device has only three battery modules. In other embodiments, the number of battery modules in the energy storage device is not limited.

[0095] In some embodiments, see Figure 6 , Figure 6FIG. 2 shows another connection relationship between battery modules provided in the embodiment of the present application in the energy storage device. Figure 6 As shown: the second power interface 500 of each battery module 10 is connected in parallel, and the first power interface 300 of each battery module 10 is connected in series, and the series interface serves as the power interface of the energy storage device. It should be noted that, for the convenience of description, Figure 6 In the embodiment shown, the energy storage device has only three battery modules. In other embodiments, the number of battery modules in the energy storage device is not limited.

[0096] In some embodiments, see Figure 7 , Figure 7 FIG. 2 shows another connection relationship between battery modules provided in the embodiment of the present application in the energy storage device. Figure 7 As shown: the first group of power interfaces 300 of each battery module 10 are connected in series, and the interfaces connected in series serve as the first power interface of the energy storage device. The second group of power interfaces 500 of each battery module 10 are connected in parallel, and the interfaces connected in parallel serve as the second power interface of the energy storage device. It should be noted that, for the convenience of description, Figure 7 In the embodiment shown, the energy storage device has only three battery modules. In other embodiments, the number of battery modules in the energy storage device is not limited.

[0097] In a second aspect, the present application also provides a distributed energy storage device, see Figure 8 , Figure 8 A schematic diagram of the structure of a distributed energy storage device provided in one embodiment of the present application. The distributed energy storage device 1 includes a plurality of battery modules 10 and a power conversion module 20 provided in any embodiment of the present application. The power conversion module 20 includes a second communication interface 201, a third group power interface 202 and a first peripheral power interface 203.

[0098] The power conversion module in the power conversion module 20 is a DC-DC converter and / or a DC-AC converter. One side of the above-mentioned power conversion module is electrically connected to the third group power interface 202, and the other side is electrically connected to the first peripheral power interface 203. The first peripheral power interface 203 serves as an external power exchange interface of the distributed energy storage device; the second group power interfaces 500 of several battery modules 10 are connected in parallel to the third group power interface 202, and the first group power interfaces 300 of several battery modules 10 are disabled; the first communication interfaces 600 of several battery modules 10 are all communicated with the second communication interface 201.

[0099] It should be noted that, for the convenience of description, Figure 8 In the embodiment shown, there are two battery modules 10. In addition, the topological structure of the power conversion module in the power conversion module 20 is prior art, which will not be described here in detail. Please refer to the prior art.

[0100] In a third aspect, the present application also provides a direct-mounted energy storage device, see Fig. 9 , Fig. 9 A schematic diagram of the structure of a direct-mounted energy storage device provided in one embodiment of the present application. The direct-mounted energy storage device 2 includes a plurality of battery modules 10 and a power conversion module 30 provided in any embodiment of the present application, wherein the power conversion module 30 includes a third communication interface 301, a fourth power interface 302, and a second peripheral power interface 303.

[0101] The power conversion module in the power conversion module 30 is a DC-DC converter and / or a DC-AC converter. One side of the above-mentioned power conversion module is electrically connected to the fourth group power interface 302, and the other side is electrically connected to the second peripheral power interface 303. The second peripheral power interface 203 serves as an external power exchange interface of the direct-mounted energy storage device; the first group power interfaces 300 of several battery modules 10 are connected in series and then connected to the fourth group power interface, and the second group power interfaces 500 of several battery modules 10 are connected in parallel; the first communication interfaces 600 of several battery modules 10 are all communicated with the third communication interface 301.

[0102] It should be noted that, for the convenience of description, Fig. 9 In the embodiment shown, there are two battery modules 10. In addition, the topological structure of the power conversion module in the power conversion module 40 is prior art, which will not be described here in detail. Please refer to the prior art.

[0103] In a fourth aspect, the present application also provides a hybrid energy storage device, see Fig.10 , Fig.10 A schematic diagram of the structure of a hybrid energy storage device provided in one embodiment of the present application. The hybrid energy storage device 3 includes a plurality of battery modules 10 and a power conversion module 40 provided in any embodiment of the present application, wherein the power conversion module 40 includes a fourth communication interface 401, a fifth group power interface 302 and a third peripheral power interface 403.

[0104] The power conversion module in the power conversion module 40 is a DC-DC converter and / or a DC-AC converter. One side of the power conversion module is electrically connected to the fifth power interface 402, and the other side is electrically connected to the third peripheral power interface 303. The first power interfaces 300 of several battery modules 10 are connected in series and connected to the fifth power interface. The second power interfaces 500 of several battery modules 10 are connected in parallel to form a fourth peripheral power interface 404. The first communication interfaces 600 of several battery modules 10 are all in communication with the third communication interface 401. Among them, the third peripheral power interface 403 is used as an external power exchange interface of the series architecture in the hybrid energy storage device; the fourth peripheral power interface 404 is used as an external power exchange interface of the parallel architecture in the hybrid energy storage device.

[0105] It should be noted that, for the convenience of description, Fig.10 In the embodiment shown, there are two battery modules 10. In addition, the topological structure of the power conversion module in the power conversion module 30 is prior art, which will not be described here in detail. Please refer to the prior art.

[0106] In a fifth aspect, the present application also provides a method for balancing battery modules in a battery cluster, see Fig.11 , Fig.11 It is a flow chart of a method for balancing battery modules in a battery cluster. The battery cluster includes several battery modules 10 provided in the embodiments of the present application. The second group of power interfaces 500 of all battery modules 10 in the battery cluster are connected in parallel and serve as the power interface of the battery cluster at the same time; and the power conversion unit 4002 in the battery module 10 is provided with a balancing controller. The balancing controller obtains the voltage, current and SOC values ​​of the battery cells in all battery modules through the intra-group communication of the battery module (i.e. the communication between the battery management unit and the power conversion unit in the battery module) and the inter-group communication (i.e. the communication between different modules). Thereby, the balancing controller in the battery module can formulate corresponding control strategies based on the above-mentioned electrical parameters to achieve the effect of energy balancing. The balancing method specifically includes:

[0107] Step S10: Obtain the voltage, current, and SOC value of the battery cells in all the battery modules.

[0108] Specifically, the voltage, current, and SOC values ​​of the battery cells in all battery modules can be obtained through intra-group communication and inter-group communication of the battery modules.

[0109] Step S20: controlling the voltage of the second power interface of the current battery module to be maintained at a preset voltage value, so that, in a discharging state, the first relationship is positively correlated with the second relationship, and in a charging state, the first relationship is positively correlated with the third relationship;

[0110] Among them, the first relationship is the relationship between the current or power of the battery cell of the current battery module and the current or power of the battery cell of other battery modules, the second relationship is the relationship between the SOC value of the current battery module and the SOC values ​​of other battery modules, and the third relationship is the relationship between the (1-SOC) value of the current battery module and the (1-SOC) values ​​of other battery modules.

[0111] Specifically, in some embodiments, as shown in the following formula:

[0112]

[0113] In the discharge state, the ratio of the current or power of the battery cell of the battery module to the current or power of the battery cell of other battery modules is equal to the SOC value of the battery module and the SOC value of other battery modules. m The ratio of powers, where m ≥1.

[0114] In the charging state, the ratio of the current or power of the battery cell of the battery module to the current or power of the battery cell of other battery modules is equal to the 1-SOC value of the battery module and the (1-SOC value) of the other battery modules. m The ratio of powers, where m ≥1.

[0115] In some embodiments, the preset voltage value of the current battery module is calculated by a balancing controller in the battery module using the following formula:

[0116]

[0117] in, V * is the preset voltage constant, V Ei It is a balance control item. Preset voltage constant V * is a fixed constant, usually determined by the overall system solution. V * Characterizes the output voltage of the power conversion unit in the battery module when it is open circuit or no-load; balance control item V Ei It plays a major role in the output current / power distribution of the battery module and is characterized by the virtual output impedance (or transimpedance) characteristics of the bidirectional isolated DC-DC converter.

[0118] For the detailed calculation process, please refer to Fig.12 , Fig.12 The figure is a schematic diagram of the calculation process of the preset voltage value. i Taking a battery module as an example, the preset voltage value calculation process includes the following steps:

[0119] Step S201: Calculate the SOC mean or (1-SOC) mean of all battery modules based on the SOC values ​​of all modules, and calculate the current / power mean of all battery modules based on the current and voltage values ​​of all modules.

[0120] Step S202: Determine the power flow direction of the power conversion unit. If the power conversion unit is in a battery charging state, execute step S203; if the power conversion unit is in a battery discharging state, execute step S204.

[0121] Step S203: Calculate the ratio coefficient of the equalization control item of the charging state K SOC .

[0122] Specifically, in some embodiments, the ratio coefficient of the equalization control item of the current battery module charging state is ,in, is the 1-SOC mean of all battery modules, It is the 1-SOC value of the current battery module.

[0123] In some other embodiments, when there is a high requirement for the balancing speed, a power index can be introduced to increase the balancing difference of the SOC value. In this case, the ratio coefficient of the balancing control item is ,in, m ≥1.

[0124] Step S204: Calculate the ratio coefficient of the balanced control item of the discharge state K SOC .

[0125] Specifically, in some embodiments, the ratio coefficient of the balancing control item of the current discharge state of the battery module is ,in, is the average SOC value of all battery modules, SOC i It is the SOC value of the current battery module.

[0126] In some other embodiments, when there is a higher requirement for the balancing speed, a power index may be introduced to increase the balancing difference of the SOC value. In this case, the ratio coefficient of the balancing control item is: ,in, m ≥1.

[0127] Step S205: Based on the ratio coefficient of the balance control item K SOC , calculate the equilibrium control coefficient K ( K SOC ).

[0128] Specifically, the current battery module balancing control coefficient ,in, k To preset the coefficient, press k =Δ V max / I max or k =Δ V max / P max ,right k Value, where Δ V max It is the maximum voltage drop or voltage rise that the energy storage device can accept under the full range of working conditions. Correspondingly, I max or P max It is the maximum charge and discharge current / power of the battery module.

[0129] Step S206: According to the balance control item coefficient K ( K SOC ), calculate the value of the balance control item V E .

[0130] Specifically, the current battery module balancing control items or ,in, I i is the current of the battery cell in the current battery module, P i is the power of the battery cell in the current battery module, K SOCi It is the ratio coefficient of the balancing control item of the current battery module.

[0131] Step S207: According to the preset voltage constant V * and the droop balance value V E , calculate and obtain the voltage preset value . Specifically:

[0132]

[0133] in, V * is the preset voltage constant, V Ei It is the current battery module balance control item. Preset voltage constant V *is a fixed constant, usually determined by the overall system solution. V * Characterizes the output voltage of the above power conversion unit under open circuit or no-load condition.

[0134] In some embodiments, when the SOC values ​​of the battery modules in the battery cluster are slightly different, the required current / power distribution cannot be achieved because the output of the balancing control item is less than or close to the circuit voltage sampling deviation. Therefore, in some embodiments, when calculating the preset voltage value of the above battery module, an additional control correction item is set to make a slight correction to the preset voltage value, so as to ensure that the actual current / power can be distributed according to the preset ratio. Please refer to Fig.13 , Fig.13 Another calculation process of the preset voltage value is shown.

[0135] and Fig.12 The difference in the voltage preset value calculation process in the embodiment shown is that: Fig.13 Another voltage preset value calculation process shown also includes the following steps:

[0136] Step S307: Based on the ratio coefficient of the balance control item K SOC , calculate and obtain the given value of the control correction term Q .

[0137] Specifically, the current battery module correction item given value or .

[0138] in, K SOCi is the ratio coefficient of the current battery module’s balancing control item, is the average current of all battery modules, is the average power of all battery modules.

[0139] Step S308: Given a value according to the control correction term Q , calculate the control correction term value V F .

[0140] Specifically, taking the above-mentioned balancing controller as a proportional integral controller as an example, the control correction term of the current battery module is

[0141]

[0142] or, ,

[0143] in, K P is the proportional coefficient of the balancing controller (proportional-integral controller),K I is the integral coefficient of the balancing controller (proportional-integral controller). I i is the current of the battery cell in the current battery module, P i is the power of the battery cell in the current battery module, Q i Give a value to the control correction item of the current battery module.

[0144] Step S309: According to the preset voltage constant V * , control correction value V F and balance control values V E , calculate and obtain the voltage preset value . Specifically:

[0145]

[0146] in, V * is the preset voltage constant, V Ei It is the balancing control item of the current battery module. V Fi It is the control correction item of the current battery module.

[0147] In a sixth aspect, the present application also provides a method for balancing battery modules in a battery cluster in an energy storage device, please refer to Fig.14a and Fig.14b , Fig.14a and Fig.14b The present invention is a flow chart of a method for balancing a battery module in a battery cluster in an energy storage device. The battery cluster includes a plurality of battery modules 10 provided in an embodiment of the present application. The first group of power interfaces 300 of all battery modules 10 in the battery cluster are connected in series as the power interface of the battery cluster, and the second group of power interfaces 500 are connected in parallel; and the power conversion unit 4002 in the battery module 10 is provided with a balancing controller. The balancing method includes:

[0148] Step S40: Obtain the voltage, current and SOC value of the battery cells in all the battery modules.

[0149] Specifically, the voltage, current and SOC value of the battery cells in all battery modules can be obtained through intra-group communication and inter-group communication of the battery modules.

[0150] Step S50: Determine whether the SOC value difference of all the battery modules exceeds the balancing threshold, if not, execute step S60, if yes, execute step S70 or S90.

[0151] Step S60: Control the power conversion unit of the current battery module to stop working and return to step S40.

[0152] Step S70: Determine whether the SOC value of the current battery module is the highest value of all the battery modules. If so, execute step S80; if not, execute step S110.

[0153] Step S80: Raise the second power interface voltage of the current battery module to the highest value and operate in a discharge state.

[0154] Step S90: determining whether the SOC value of the current battery module is the lowest value of all the battery modules, if so, executing step S100, if not, executing step S110;

[0155] Step S100: reducing the second power interface voltage value of the current battery module to a minimum value and operating in a charging state.

[0156] Step S110: controlling the voltage of the second power interface of the current battery module to be maintained at a preset voltage value, so that in a discharging state, the fourth relationship is positively correlated with the fifth relationship, and in a charging state, the fourth relationship is positively correlated with the sixth relationship;

[0157] Among them, the fourth relationship is the relationship between the current or power of the battery cell of the current battery module and the current or power of the battery cell of other battery modules, the fifth relationship is the relationship between the SOC value of the current battery module and the SOC values ​​of other battery modules, and the sixth relationship is the relationship between the (1-SOC) value of the current battery module and the (1-SOC) values ​​of other battery modules.

[0158] In some embodiments, the calculation formula of the preset voltage value in the above step S110 is:

[0159]

[0160] It should be noted that the calculation process of the preset voltage value in this embodiment is the same as that in the embodiment of the present application. Fig.12 The calculation process of the illustrated embodiment is similar, and therefore will not be described in detail here.

[0161] Similarly, in some embodiments, when the SOC value difference of each battery module in the battery cluster is small, the compensation item when the required current / power distribution cannot be achieved because the output of the balancing control item is less than or close to the circuit voltage sampling deviation. Therefore, in some embodiments, when calculating the preset voltage value in step S110, an additional control correction item is set to make a slight correction to the preset voltage value, so as to ensure that the actual current / power can be distributed according to the preset ratio. The calculation formula of the preset voltage value is:

[0162]

[0163] It should be noted that the calculation process of the preset voltage value after setting the control correction term in this embodiment is the same as that in the embodiment of the present application. Fig.13 The calculation process of the illustrated embodiment is similar, and therefore, will not be described in detail here.

[0164] The balancing control method provided in the embodiment of the present application adopts a control method based on the SOC information of the battery module to achieve energy balancing of the battery module. The control logic is simple and the balancing system has good robustness. In addition, a control correction term is added in the control, which can overcome the negative impact on the balancing effect caused by errors in hardware sampling of the battery module and insufficient control accuracy.

[0165] In order to more clearly explain the working principle of the balancing control method provided in the embodiment of the present application, application embodiment 1 and application embodiment 2 are listed for illustration. The details are as follows:

[0166] In application example 1, the discharge operation of the battery modules 10 provided in the embodiment of the present application with two different SOC values ​​in a non-direct-mounted (such as distributed) energy storage device is described as an example. Assuming that the SOC value of the battery module 1# in the initial state is lower than the SOC value of the battery module 2#, at this time, the output characteristic curves of the two battery modules and the distribution of the output current are as follows: Fig.15 Assume that the load current is constant, in the initial state, the output characteristics of the two battery modules are K 1 and K 2 , the voltage on the third power interface is V P3 , the output currents of the battery cells in the corresponding two battery modules are I 1 and I 2 ,and I 2 > I 1 , the discharge speed of battery module 2# is greater than that of battery module 1#, and the difference in SOC values ​​of the two modules gradually narrows.

[0167] As the SOC value of battery module 1# approaches the SOC value of battery module 2#, its output characteristic changes from , the output characteristics of the corresponding battery module 2# are , the voltage at the third power interface is Down to The output current of battery module 1# and battery module 2# is determined by , and satisfies The SOC values ​​and discharge current differences of battery module 1# and battery module 2# both tend to decrease, and energy balance is finally achieved.

[0168] In some embodiments, due to the measurement accuracy deviation of the output voltage, the output characteristics of battery module 1# and battery module 2# cannot intersect at V * , the corresponding current distribution relationship also mismatches the SOC value relationship between battery module 1# and battery module 2#. This situation is particularly serious when the SOC value difference between the battery modules is small. At this time, set the control correction item, use the actual current as the feedback amount, and indirectly correct the current distribution by adjusting the voltage command given. At this time, please refer to Fig.16 The output characteristics of battery module 1# and battery module 2# are as follows: , the output current of battery module 1# and battery module 2# is , and satisfies , the voltage at the third power interface is , so that when the output characteristics of battery module 1# and battery module 2# extend to the Y axis, they intersect at V * .

[0169] In application example 2, three battery modules with different SOC values ​​are used as an example in a direct-mounted energy storage system architecture. The maximum input / output current capabilities of the three battery modules are the same, that is, In the initial state, the SOC values ​​of the three battery modules are SOC1, SOC2, and SOC3 respectively, and SOC1>SOC2>SOC3. Then the battery module 1# with the highest SOC switches to the forced output mode, and the output voltage is V * The output droop characteristic curves of battery module 2# and battery module 3# and the distribution of output current are shown in the figure below: Fig.17 shown.

[0170] The output characteristics of battery module 2# and battery module 3# are K 2 and K 3At this time, battery module 2# and battery module 3# are at working point A. As the output voltage of battery module 1# rises, the voltage on the fourth power interface formed by the three battery modules connected through their respective second power interfaces becomes V P4 Depend on V * Gradually rising, battery module 2# and battery module 3# switch to charging mode and the charging current I 2 , I 3 When battery module 2# and battery module 3# are at working point B, that is, the charging current of battery module 2# and battery module 3# is increased to And meet the conditions When the battery module 1# works at the maximum output current state, the fourth power interface voltage .

[0171] When SOC2 rises to meet SOC2=SOC1, the working mode of battery module 2# is the same as that of battery module 1#, switching to the maximum voltage V MAX Output, at this time the output characteristic curve of battery module 3# becomes .because , then the fourth group of power interface voltage , battery module 3# is at working point C, with maximum current I MAX Charge until the difference between SOC3 and SOC1 and SOC2 is reduced to within the balance threshold, thereby achieving the effect of balance control.

[0172] It should be noted that the preferred embodiments of the present application are given in the specification and drawings of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described in the specification. These embodiments are not intended to be additional limitations on the content of the present application. The purpose of providing these embodiments is to make the understanding of the disclosure of the application more thorough and comprehensive. In addition, the above-mentioned technical features continue to be combined with each other to form various embodiments not listed above, which are all considered to be within the scope of the present application specification; further, for ordinary technicians in this field, they can be improved or transformed according to the above description, and all these improvements and transformations should belong to the scope of protection of the claims attached to the present application.

Claims

1. An energy storage device, It is characterized in that include: At least two battery modules, each of which comprises a housing, a battery core and a battery monitoring and management module; The battery core is disposed inside the housing and is configured to store and release electrical energy; The battery monitoring management module is arranged inside the housing and includes: A battery management unit, one end of which is electrically connected to the battery core, and the other end of which serves as a first group of power interfaces of the battery module, wherein the first group of power interfaces includes a first power end and a second power end, wherein the first power end and the second power end are respectively the positive electrode and the negative electrode of the first group of power interfaces; A power conversion unit is provided with a primary power port, a secondary power port, a first communication interface and a balancing controller, wherein the primary power port is coupled to the first group of power interfaces, and the secondary power port serves as a second group of power interfaces of the battery module; Wherein, at least one of the first group of power interfaces and the second group of power interfaces is arranged on the outer surface of the housing, the second group of power interfaces is connected in parallel with the second group of power interfaces of other battery modules in the energy storage device, and the interfaces of the second group of power interfaces connected in parallel serve as the power interfaces of the energy storage device; The first communication interface is disposed on the outer surface of the housing and is configured to be communicatively connected with the battery management unit; The balancing controller is configured to obtain the voltage, current, and SOC value of the battery cells in all the battery modules, and control the voltage of the second group of power interfaces of the current battery module to be maintained at a preset voltage value, so that in a discharging state, the first relationship is positively correlated with the second relationship, and in a charging state, the first relationship is positively correlated with the third relationship; Among them, the first relationship is the relationship between the current or power of the battery cell of the current battery module and the current or power of the battery cell of other battery modules, the second relationship is the relationship between the SOC value of the current battery module and the SOC values ​​of other battery modules, and the third relationship is the relationship between the (1-SOC) value of the current battery module and the (1-SOC) values ​​of other battery modules.

2. The energy storage device according to claim 1, It is characterized in that The battery monitoring management module also includes a communication bus; the communication bus carries the communication between the power conversion unit and the battery management unit and the communication between the first communication interface and the battery monitoring management module.

3. The energy storage device according to claim 1, It is characterized in that The balancing controller obtains at least one electrical parameter and SOC value of all battery modules in the energy storage device through the first communication interface.

4. The energy storage device according to claim 3, It is characterized in that The first group of power interfaces is connected in series with the first group of power interfaces of other battery modules in the energy storage device; the second group of power interfaces is connected in parallel with the second group of power interfaces of other battery modules in the energy storage device; the interface connected in series with the first group of power interfaces serves as the power interface of the energy storage device.

5. The energy storage device according to any one of claims 3 or 4, It is characterized in that The electrical parameters acquired by the balancing controller include voltage and current; the balancing controller calculates and obtains the voltage instruction of the second group of power interfaces of the battery module.

6. The energy storage device according to claim 1, It is characterized in that Also includes: A first power conversion module, the first power conversion module comprising a second communication interface, a third group of power interfaces and a first peripheral power interface; The second group of power interfaces of the battery module is connected in parallel to the third group of power interfaces; and the first communication interface of the battery module is in communication with the second communication interface.

7. The energy storage device according to claim 1, It is characterized in that Also includes: A second power conversion module, wherein the second power conversion module includes a third communication interface, a fourth group of power interfaces, and a second peripheral power interface; The first group of power interfaces of the battery modules are connected in series and then connected to the fourth group of power interfaces, and the second group of power interfaces of the battery modules are connected in parallel; and the first communication interfaces of several of the battery modules are connected to the third communication interface.

8. The energy storage device according to claim 1, It is characterized in that Also includes: A third power conversion module, the third power conversion module comprising a fourth communication interface, a fifth group of power interfaces and a third peripheral power interface; The first group of power interfaces of the battery module are connected in series and then connected to the fifth group of power interfaces, and the second group of power interfaces of the battery module are connected in parallel to form a fourth peripheral power interface; and the first communication interfaces of several of the battery modules are connected to the fourth communication interface.

9. A method for balancing battery modules in an energy storage device, It is characterized in that include: At least two battery modules, each of which comprises a housing, a battery core and a battery monitoring and management module; The battery core is disposed inside the housing and is configured to store and release electrical energy; The battery monitoring management module is arranged inside the housing and includes: A battery management unit, one end of which is electrically connected to the battery core, and the other end of which serves as a first group of power interfaces of the battery module, wherein the first group of power interfaces includes a first power end and a second power end, wherein the first power end and the second power end are respectively the positive electrode and the negative electrode of the first group of power interfaces; A power conversion unit is provided with a primary power port, a secondary power port, a first communication interface and a balancing controller; the primary power port is coupled to the first group of power interfaces; the secondary power port serves as a second group of power interfaces of the battery module; Wherein, at least one of the first group of power interfaces and the second group of power interfaces is arranged on the outer surface of the housing, the second group of power interfaces is connected in parallel with the second group of power interfaces of other battery modules in the energy storage device, and the interfaces of the second group of power interfaces connected in parallel serve as the power interfaces of the energy storage device; The first communication interface is disposed on the outer surface of the housing and is configured to be communicatively connected with the battery management unit; The method comprises: Step S10: Obtaining the voltage, current, and SOC value of the battery cells in all the battery modules in the energy storage device; Step S20: controlling the voltage of the second power interface of the current battery module to be maintained at a preset voltage value, so that in a discharging state, the first relationship is positively correlated with the second relationship, and in a charging state, the first relationship is positively correlated with the third relationship; Among them, the first relationship is the relationship between the current or power of the battery cell of the current battery module and the current or power of the battery cell of other battery modules, the second relationship is the relationship between the SOC value of the current battery module and the SOC values ​​of other battery modules, and the third relationship is the relationship between the (1-SOC) value of the current battery module and the (1-SOC) values ​​of other battery modules.

10. The equalization method according to claim 9, It is characterized in that The preset voltage value is calculated by the equalization controller, and the calculation formula of the preset voltage value is: in, V * is the preset voltage constant, V E It is a balance control item.

11. The equalization method according to claim 9, It is characterized in that The calculation formula of the preset voltage value is: in, V F is the control correction term.

12. A method for balancing battery modules in a battery cluster in an energy storage device, It is characterized in that The energy storage device comprises: A battery cluster, wherein the battery cluster includes at least two battery modules, and the battery module includes a housing, a battery core, and a battery monitoring and management module; Wherein, the battery core is arranged inside the housing and is configured to store and release electrical energy; and, The battery monitoring management module is arranged inside the housing and includes: A battery management unit, one end of which is electrically connected to the battery core, and the other end of which serves as a first group of power interfaces of the battery module, wherein the first group of power interfaces includes a first power end and a second power end, wherein the first power end and the second power end are respectively the positive electrode and the negative electrode of the first group of power interfaces; A power conversion unit is provided with a primary power port, a secondary power port, a first communication interface and a balancing controller; the primary power port is coupled to the first group of power interfaces; the secondary power port serves as a second group of power interfaces of the battery module; Wherein, at least one of the first group of power interfaces and the second group of power interfaces is disposed on the outer surface of the housing; The first communication interface is disposed on the outer surface of the housing and is configured to be communicatively connected with the battery management unit; The first groups of power interfaces of all the battery modules are connected in series as the power interfaces of the battery cluster, and the second groups of power interfaces of all the battery modules are connected in parallel. The balancing method includes: Step S40: Obtaining the voltage, current, and SOC value of the battery cells in all the battery modules; Step S50: determining whether the SOC value difference of all the battery modules exceeds the equalization threshold, if not, executing step S60, if yes, executing step S70 or S90; Step S60: Control the power conversion unit of the current battery module to stop working and return to step S40; Step S70: Determine whether the SOC value of the current battery module is the highest value of all the battery modules, if so, execute step S80, if not, execute step S110; Step S80: raising the second power interface voltage of the current battery module to the highest value and operating in a discharge state; Step S90: determining whether the SOC value of the current battery module is the lowest value of all the battery modules, if so, executing step S100, if not, executing step S110; Step S100: reducing the second power interface voltage value of the current battery module to the lowest value and operating in a charging state; Step S110: controlling the voltage of the second power interface of the current battery module to be maintained at a preset voltage value, so that in a discharging state, the fourth relationship is positively correlated with the fifth relationship, and in a charging state, the fourth relationship is positively correlated with the sixth relationship; Among them, the fourth relationship is the relationship between the current or power of the battery cell of the current battery module and the current or power of the battery cell of other battery modules, the fifth relationship is the relationship between the SOC value of the current battery module and the SOC values ​​of other battery modules, and the sixth relationship is the relationship between the (1-SOC) value of the current battery module and the (1-SOC) values ​​of other battery modules.

13. The equalization method according to claim 12, It is characterized in that The preset voltage value is calculated by the equalization controller, and the calculation formula of the preset voltage value is: in, V * is the preset voltage constant, V E It is a balance control item.

14. The equalization method according to claim 13, It is characterized in that The charging state / discharging state is achieved by controlling the preset voltage value of each voltage of the second group of power interfaces of the other battery modules. The calculation formula of the preset voltage value is: in, V F is the control correction term.

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