Power supply system of vehicle and electric quantity balancing method

Abstract

The invention belongs to the technical field of electric energy management, and particularly relates to a power supply system of a vehicle and an electric quantity balancing method. The power supply system of the vehicle comprises a first battery branch, a second battery branch, an SOC balancing device, a first main load, a second main load, a first controller and a second controller, and the SOC balancing device is arranged between the first battery branch and the second battery branch, two ends of the SOC balancing device are respectively connected with the first battery branch and the second battery branch, and the SOC balancing device is used for balancing the SOC of the two battery branches. According to the scheme, long-time SOC balancing can be achieved only through the SOC balancing device, or the system operation requirement can be met by conducting moderate balancing under the condition that the SOC deviation is large; and the problems of cost, volume and the like of the DCDC in the prior art can be obviously limited.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric energy management, and specifically relates to a vehicle power supply system and a power balancing method. Background Art

[0002] The characteristics of new energy electric transmission vehicles are: using power batteries, fuel cells, etc. as power sources to supply power to the vehicle drive inverter device, which is converted into variable voltage and variable frequency (VVVF) power by the traction inverter to drive the traction motor and pull the entire vehicle. The electric drive traction system is the core component of new energy vehicles. The electric drive system is mainly composed of power battery packs, inverters, traction motors and other parts.

[0003] Based on traditional fuel vehicles, some vehicles use power batteries to power the electric drive system. By using the entire vehicle's battery power supply and leveraging the difference between electricity and oil prices, the vehicle achieves energy savings and zero carbon emissions. As vehicle load requirements vary from tens of tons to hundreds of tons, the power battery capacity requirements range from tens of kWh to thousands of kWh, and the battery voltage ranges from tens of volts to thousands of volts. The heavier the vehicle's load, the higher the battery voltage and capacity requirements. However, due to the current limitations of the voltage, capacity, and density of power battery cells, large-capacity power batteries are typically assembled using multiple battery clusters connected in parallel to achieve a large-capacity power battery pack.

[0004] For the large-capacity power battery system used in large-tonnage non-corporate dump trucks, existing patents all consider it as a whole (directly short-circuited in parallel) for direct output, and do not provide system-level consideration and targeted treatment for problems such as reduced battery performance, reduced available capacity, and insufficient redundancy performance caused by the multi-branch imbalance after multiple clusters of large-capacity power battery systems are directly connected in parallel. Summary of the Invention

[0005] In response to the above technical problems, the present invention proposes a vehicle power supply system and power balancing method. This application provides a vehicle power supply system, comprising: a first battery branch, a second battery branch, an SOC balancing device, a first main load, a second main load, a first controller, and a second controller; the first controller is connected to the first main load; the first battery branch is connected to the first controller, for supplying power to the first main load through the first controller; the second controller is connected to the second main load; the second battery branch is connected to the second controller, for supplying power to the second main load through the second controller; the SOC balancing device is installed between the first battery branch and the second battery branch, with its two ends respectively connected to the first battery branch and the second battery branch, for balancing the SOCs of the two battery branches. In the prior art, the DCDC must be full power (its power meets the full power demand of the load, including the surge power demand), while in this solution, only the SOC balancing device is needed to achieve long-term SOC balance, or moderate balancing can meet system operation requirements when the SOC deviation is large; this can significantly limit the cost, volume, and other problems of the DCDC in the prior art solution.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention includes two aspects.

[0007] In the first aspect, the present application provides a power supply system for a vehicle, comprising: a first battery branch, a second battery branch, an SOC balancing device, a first main load, a second main load, a first controller and a second controller; the first controller is connected to the first main load; the first battery branch is connected to the first controller, for supplying power to the first main load through the first controller; the second controller is connected to the second main load; the second battery branch is connected to the second controller, for supplying power to the second main load through the second controller; the SOC balancing device is installed between the first battery branch and the second battery branch, with its two ends respectively connected to the first battery branch and the second battery branch, for balancing the SOCs of the two battery branches.

[0008] In some embodiments, the system further includes: a third load and a third controller; the third load is connected to the SOC balancing device via the third controller, and is configured to obtain electrical energy from the SOC balancing device.

[0009] In some embodiments, the system further includes: a third battery branch; the third battery branch supplies power to the third load through the third controller; and the SOC balancing device includes at least three devices, which are respectively installed between the three battery branches.

[0010] In some embodiments, the SOC balancing device includes: a first converter, a second converter and a transformer; the first converter and the second converter are respectively located at two ends of the SOC balancing device and are respectively used to connect to battery branches; the transformer is installed between the first converter and the second converter for power transmission and isolation.

[0011] In some embodiments, the SOC balancing device further comprises: when the voltages of the two battery branches are different, the SOC balancing device is a BOOST boost chopper circuit.

[0012] In some embodiments, the SOC balancing device includes: two inverters and a transformer; the input ends of the two inverters are respectively connected to the first battery branch and the second battery branch; the output ends of the two inverters are both connected to the transformer; and the output end of the transformer is connected to the third controller.

[0013] In some embodiments, the SOC balancing device further includes: two Buck chopper circuits; the input ends of the two Buck chopper circuits are respectively connected to the first battery branch and the second battery branch; the output ends of the two Buck chopper circuits are connected in parallel and connected to the third controller.

[0014] In some embodiments, the SOC balancing device further includes: a first controlled switch and a second controlled switch; one end of the first controlled switch is connected to the first battery branch, and the other end is connected to the third controller; one end of the second controlled switch is connected to the second battery branch, and the other end is connected to the third controller.

[0015] In a second aspect, the present application proposes a power balancing method, which is applicable to any SOC balancing device described in the first aspect, including: respectively obtaining a first remaining power and a second remaining power of two battery branches connected to the SOC balancing device; controlling the SOC balancing device according to the first remaining power and the second remaining power so that the remaining power of the two battery branches is balanced.

[0016] In some embodiments, controlling the SOC balancing device according to the first remaining power and the second remaining power so that the remaining power of the two battery branches is balanced includes: when the first remaining power is greater than the second remaining power, controlling the SOC balancing device to transfer the power of the battery branch corresponding to the first remaining power to the battery branch corresponding to the second remaining power; when the first remaining power is less than the second remaining power, controlling the SOC balancing device to transfer the power of the battery branch corresponding to the second remaining power to the battery branch corresponding to the first remaining power.

[0017] In some embodiments, the method further comprises: when the third controller needs to take power, obtaining the required power of the third controller; and determining the current size and duration of the SOC balancing device taking power from the two battery branches respectively according to the first residual power, the second residual power and the required power.

[0018] The application has the following beneficial effects: the application provides a power supply system of a vehicle, which comprises a first battery branch, a second battery branch, an SOC balancing device, a first main load, a second main load, a first controller and a second controller. The first controller is connected with the first main load. The first battery branch is connected with the first controller, and is configured to supply power to the first main load through the first controller. The second controller is connected with the second main load. The second battery branch is connected with the second controller, and is configured to supply power to the second main load through the second controller. The SOC balancing device is installed between the first battery branch and the second battery branch, and is connected with the first battery branch and the second battery branch at two ends, and is configured to balance the SOC of the two battery branches. In the prior art, the DCDC must be full-power (the power meets the entire power demand of the load, including the demand of impact power), while in the application, the SOC balancing device can be used to realize long-time SOC balancing, or in the case of large SOC deviation, moderate balancing can meet the system operation requirements. The cost and size of the DCDC in the prior art can be significantly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0019] The scope of the present disclosure can be better understood by reading the following detailed description of exemplary embodiments, when read in conjunction with the attached drawings, in which:

[0020] Figure 1 A power supply system topology diagram of a vehicle provided by an embodiment of the application

[0021] Figure 2 A power supply system topology diagram of a vehicle provided by an embodiment of the application in three load cases

[0022] Figure 3 A power supply system topology diagram of a vehicle provided by an embodiment of the application in three battery branch cases

[0023] Figure 4 A structure diagram of an SOC balancing device provided by an embodiment of the application

[0024] Figure 5 A core circuit diagram of an SOC balancing device provided by an embodiment of the application

[0025] Figure 6A schematic structural diagram of another SOC balancing device provided in an embodiment of the present application;

[0026] Figure 7 A schematic diagram of the core circuit of another SOC balancing device provided in an embodiment of the present application;

[0027] Figure 8 A circuit diagram of a switch-controlled SOC balancing device provided in an embodiment of the present application;

[0028] Figure 9 An overall logic block diagram of a power balancing method provided in an embodiment of the present application;

[0029] Figure 10 This is a logic block diagram of another power balancing method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limiting this application. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0031] In the following description, reference is made to “some embodiments”, which describes a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0032] If similar descriptions of "first\second\third" appear in the application documents, the following explanation will be added. In the following description, the terms "first\second\third" are only used to distinguish similar objects and do not represent a specific order for the objects. It can be understood that "first\second\third" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein are for the purpose of describing the embodiments of this application only and are not intended to limit this application.

[0034] In existing technologies, the drive system primarily consists of multiple power battery packs (each composed of a certain number of parallel battery clusters, each independent of the other), a traction converter, and multiple drive loads. The traction converter is divided into multiple DC buses, each connected to a power battery pack. A controller controls the drive-related loads attached to the same bus. The power of each load group varies, and this inconsistency leads to inconsistent power consumption and SOCs across the battery packs. The overall system's usability is limited by the battery pack with the lowest SOC. Therefore, balancing the SOCs of the battery packs to ensure consistent SOCs and improve overall system utilization presents a new challenge.

[0035] In view of the problems existing in the prior art, such as Figure 1 、 Figure 2 as well as Figure 3 As shown, the present application provides a power supply system for a vehicle.

[0036] A vehicle power supply system includes: a first battery branch, a second battery branch, a SOC balancing device, a first main load, a second main load, a first controller, and a second controller. The first controller is connected to the first main load. The first battery branch is connected to the first controller for supplying power to the first main load via the first controller. The second controller is connected to the second main load. The second battery branch is connected to the second controller for supplying power to the second main load via the second controller. The SOC balancing device is installed between the first and second battery branches, with its two ends connected to the first and second battery branches, respectively, for balancing the SOCs of the two battery branches.

[0037] exist Figure 1In this application, we group the loads into a first main load and a second main load, where each main load mainly includes: a load motor and a braking resistor. Each main load is equipped with a controller, and each controller is used to provide the corresponding main load with the required power. To solve the problem of power balance, the batteries are also grouped in this application, divided into a first battery branch and a second battery branch, and the two battery branches perform functions for the corresponding main loads respectively. Because the power usage of the two main loads is different in actual working conditions, the remaining power of the two battery branches will be different. Eventually, one battery pack will be fully discharged while the other battery pack still has a lot of power. In the existing technology, at this time, each battery cluster will be forced to balance, including forced balancing of the SOC. As a result, the circulation and balancing problems between the battery clusters are more prominent, affecting the capacity, serviceability, and even lifespan of the battery system. To avoid such problems, the present application adds an SOC balancing device between the first battery branch and the second battery branch. The SOC balancing device can balance the SOC of the two battery branches during the discharge process of the battery branch, avoiding the problems caused by forced balancing that affect the capacity, serviceability, and even lifespan of the battery system.

[0038] Of course, for a vehicle, its own load cannot be only the motor load and the brake resistor, there will be other auxiliary loads. Since the auxiliary loads are used less frequently and have lower power consumption, the present application can use the auxiliary loads to balance the SOC of the two battery branches. Therefore, in some embodiments, such as Figure 2 As shown, the system further includes: a third load and a third controller.

[0039] The third load is connected to the SOC balancing device through the third controller, and is used to obtain electric energy from the SOC balancing device.

[0040] Of course, in actual needs, it may still be necessary to equip the auxiliary load with a corresponding battery branch. At this time, there are three battery branches in the entire system. At this time, the three battery branches need to be SOC balanced, so an SOC balancing device is set between each battery branch. Figure 3 As shown, the system further includes: a third battery branch.

[0041] The third battery branch supplies power to the third load through the third controller.

[0042] The SOC balancing devices include at least three, which are respectively installed between three battery branches.

[0043] for Figure 1 and Figure 3For the SOC balancing device in the system, its main function is to transfer the power of a battery branch with high power to the battery branch with low power to ensure the balance. Figure 4 and Figure 5 As shown, this application proposes two implementation methods of the SOC balancing device.

[0044] In some embodiments, as Figure 4 As shown, the SOC balancing device includes: a first converter, a second converter and a transformer.

[0045] The first converter and the second converter are respectively located at both ends of the SOC balancing device and are respectively used to connect to the battery branch. The transformer is installed between the first converter and the second converter and is used for power transmission and isolation.

[0046] Since the capacities of the battery branches may not be completely consistent, and the power and energy consumption of the battery branches corresponding to the load groups are different, resulting in different power consumption rates of the battery branches, there may be a certain or even large difference in the SOC of the two battery groups. The SOC balancing device in this solution is used to achieve energy flow between the two battery systems, thereby balancing the SOC in the two battery systems.

[0047] So if Figure 4 As shown, one implementation of the SOC balancing device of the present application is: it is composed of two converters and a transformer. The two converters are responsible for converting DC to AC or converting AC to DC, and the transformer is used for isolation, so that the two battery branches are electrically isolated, reducing the electrical coupling between the two battery pack systems, reducing the complexity of the system, and optimizing the electrical and electromagnetic environment. It is composed of controllable power electronic devices such as IGBT, IGCT and other components, which can realize the conversion of DC to AC. It can be a three-phase inverter circuit, a single-phase inverter circuit, or other power electronic circuits that can realize related functions. The matching transformer can be a three-phase transformer or a single-phase transformer. The deformation design of various circuits cannot change the purpose of realizing the bidirectional controllable flow of energy between the two battery busbars, and they are all within the scope of protection of this patent.

[0048] Without considering the isolation problem between the two battery branches, we can use Figure 5 The technical solution shown in the figure realizes the bidirectional flow of energy. Therefore, in some embodiments, the SOC balancing device further comprises: when the voltages of the two battery branches are different, the SOC balancing device is a BOOST boost chopper circuit. Figure 5 The premise of the technical solution is that there needs to be a significant voltage difference between the two battery branches.

[0049] And forFigure 2 In the case described above, the main function of the SOC balancing device is to draw power from the two battery branches, so Figure 6 、 Figure 7 and Figure 8 As shown, this application proposes two implementation methods of SOC balancing devices depending on whether there is isolation.

[0050] In some embodiments, as Figure 6 As shown, the SOC balancing device includes two inverters and a transformer. The input ends of the two inverters are connected to the first battery branch and the second battery branch, respectively. The output ends of the two inverters are connected to the transformer. The output end of the transformer is connected to the third controller.

[0051] In the implementation of this SOC balancing device, the third load can draw power from both the first and second battery branches. The inverter in this solution can be either a three-phase inverter or a unidirectional inverter, allowing the two inverters to draw power from the two battery branches, each isolated by a transformer, while simultaneously supplying power to the third load. While the solution is relatively complex, it can isolate the main circuit of the battery system and simplify the complexity of the system's electrical and electromagnetic environments.

[0052] In addition, without considering isolation, Figure 2 In this case, the SOC can also be implemented as follows Figure 7 As shown, in some embodiments, the SOC balancing device further includes two Buck chopper circuits. The inputs of the two Buck chopper circuits are connected to the first battery branch and the second battery branch, respectively. The outputs of the two Buck chopper circuits are connected in parallel and to the third controller. This solution is simple, but it does not isolate the main circuits of the two battery systems.

[0053] In addition, the present application also proposes an SOC balancing device that realizes power supply to two battery branches respectively through switch control. Figure 8 As shown, the SOC balancing device further includes: one end of the first controlled switch is connected to the first battery branch, and the other end is connected to the third controller; one end of the second controlled switch is connected to the second battery branch, and the other end is connected to the third controller.

[0054] During operation, the corresponding switches can be selected to be closed according to the remaining power of the two battery branches, so that the battery branch with higher remaining power supplies power to the third load.

[0055] Example 2:

[0056] Example 1 provides a power supply system that aims to achieve a balance between the SOCs of two battery packs by enabling energy flow between the two battery systems through the SOC balancing device in this solution. This system also requires a control method corresponding to the SOC balancing device.

[0057] So in the second aspect, Figure 9 and Figure 10 As shown, the present application also proposes a power balancing method, which is applied to electronic devices, and the electronic devices can be servers, mobile terminals, computers, cloud platforms, etc. The functions implemented by the device data processing provided in the embodiments of the present application can be implemented by calling program code by the processor of the electronic device, wherein the program code can be stored in a computer storage medium. The power balancing method includes:

[0058] Step S1: respectively obtaining a first remaining capacity and a second remaining capacity of two battery branches connected to an SOC balancing device.

[0059] Step S2: controlling the SOC balancing device according to the first remaining charge and the second remaining charge so that the remaining charges of the two battery branches are balanced.

[0060] In some embodiments, step S2 of “controlling the SOC balancing device according to the first remaining capacity and the second remaining capacity so that the remaining capacities of the two battery branches are balanced” includes:

[0061] Step S21: When the first remaining power is greater than the second remaining power, controlling the SOC balancing device to transfer power from the battery branch corresponding to the first remaining power to the battery branch corresponding to the second remaining power.

[0062] Step S22: When the first remaining power is less than the second remaining power, controlling the SOC balancing device to transfer power from the battery branch corresponding to the second remaining power to the battery branch corresponding to the first remaining power.

[0063] Method steps S1 to S22 are mainly for Figure 1 as well as Figure 3The corresponding power supply system, the main role of the SOC balancing device in the system is to deliver the electric energy of the one with high electric quantity to the one with low electric quantity, so only the residual electric quantity of the two battery branches is needed to be obtained, and then the controllable device on the SOC balancing device can be controlled according to the residual electric quantity, so that the electric quantities of the two battery branches are balanced with each other.

[0064] In some embodiments, for Figure 2 The corresponding power supply system, and for Figure 6 、 Figure 7 and Figure 8 The main purpose of the corresponding SOC balancing device is to determine the electric quantity extracted from each battery branch according to the residual electric quantity of the two battery branches, as shown in Figure 10 Therefore, the electric quantity balancing method further comprises:

[0065] Step S3: When the third controller needs to take electric quantity, the demand power of the third controller is obtained.

[0066] Step S4: According to the first residual electric quantity, the second residual electric quantity and the demand power, the current size and duration that the SOC balancing device takes electric quantity from the two battery branches respectively are determined.

[0067] The third load has total demand power, so we need to supply power to the third load according to the demand power of the third load, so the demand power of the third controller also needs to be obtained in the present application. After the demand power is determined, the total current size can be determined, and at this time the current size taken from each battery branch can be determined by the first residual electric quantity and the second residual electric quantity. Moreover, in order to ensure the balance of electric energy between the two battery branches, the duration of the current with the above size also needs to be determined, so as to ensure that the electric quantity of the battery branch is dynamically balanced as much as possible.

[0068] Through the system scheme and circuit topology design, multiple power battery branch groups and load controller groups are adopted, and each battery branch group is actually used independently without being directly connected in parallel to supply power to all loads; it can effectively solve a series of problems such as reduction of battery performance, reduction of available capacity, and insufficient redundancy performance caused by imbalance of multiple branches in the direct parallel connection of large-capacity power battery system. Moreover, in a large electric quantity power battery system, the traction system does not configure a large-power bidirectional DCDC device, which reduces a series of related problems such as cost, volume, efficiency loss, and complex control of the large-power DCDC. Further, the system can achieve SOC balancing of multiple battery system branches under the condition of only configuring a small bidirectional DCDC, and achieve better effect than the traction system configured with a large-power bidirectional DCDC device, which significantly reduces the cost, volume, efficiency loss and other related problems of the large-power DCDC.

[0069] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when the computer program is executed, the processes of the above-mentioned embodiments of the methods can be included. Any reference to memory, storage, database or other medium used in each embodiment provided by the present application can include at least one of non-volatile and volatile memory. The non-volatile memory can include read-only memory (Read-Only Memory, ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. The volatile memory can include random access memory (Random Access Memory, RAM) or external cache memory. As an illustration but not limitation, the RAM can be in various forms, such as static random access memory (Static Random Access Memory, SRAM) or dynamic random access memory (Dynamic Random Access Memory, DRAM), etc.

[0070] It should be understood that the "one embodiment" or "an embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily mean the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and the execution order of the processes should be determined by its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application. The above-mentioned sequence number of the embodiments of the present application is only for description, not representing the advantages and disadvantages of the embodiments.

[0071] It should be noted that in this paper, the term "include", "contain" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or device. Without more limitations, the element defined by the sentence "including a…" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0072] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other manners. The described device embodiments are merely schematic. For example, the division of the units is only a logical function division. There can be another division manner for the actual implementation, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed coupling, or direct coupling or communication connection between the components can be indirect coupling or communication connection through some interfaces, devices, or units, and can be electrical, mechanical, or in other forms.

[0073] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units; they can be located in one place, or distributed on multiple network units; and some or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0074] In addition, each functional unit in each embodiment of the present application can be integrated into one processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit; the integrated unit can be realized in the form of hardware or in the form of hardware plus software functional units.

[0075] Those of ordinary skill in the art can understand that all or part of the steps of the above-mentioned method embodiments can be completed by a program instructing related hardware, and the foregoing program can be stored in a computer readable storage medium, and the program executes the steps of the above-mentioned method embodiments when executed; and the foregoing storage medium includes mobile storage devices, read-only memories (ROMs), magnetic discs or optical discs, and various storage media that can store program codes.

[0076] Alternatively, the integrated units of the present application, if implemented in the form of software functional modules and sold or used as independent products, can also be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the embodiments of the present application can be embodied in the form of a software product, and the computer software product is stored in a storage medium, and includes several instructions for causing a controller to execute all or part of the methods described in the embodiments of the present application. The foregoing storage medium includes mobile storage devices, ROMs, magnetic discs or optical discs, and various storage media that can store program codes.

[0077] The above merely provides the implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the change or replacement within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A vehicle power supply system, characterized in that: include: A first battery branch, a second battery branch, an SOC balancing device, a first main load, a second main load, a first controller, and a second controller; The first controller is connected to the first main load; The first battery branch is connected to the first controller, and is used to supply power to the first main load through the first controller; The second controller is connected to the second main load; The second battery branch is connected to the second controller and is used to supply power to the second main load through the second controller; The SOC balancing device is installed between the first battery branch and the second battery branch, with two ends connected to the first battery branch and the second battery branch respectively, for balancing the SOCs of the two battery branches.

2. The system according to claim 1, wherein: The system further includes: a third load and a third controller; The third load is connected to the SOC balancing device through the third controller, and is used to obtain electric energy from the SOC balancing device.

3. The system according to claim 2, characterized in that The system further includes: a third battery branch; The third battery branch supplies power to the third load through the third controller; The SOC balancing devices include at least three, which are respectively installed between three battery branches.

4. The system according to any one of claims 1 to 3, characterized in that: The SOC balancing device includes: a first converter, a second converter and a transformer; The first converter and the second converter are respectively located at two ends of the SOC balancing device and are respectively used to be connected to the battery branch; The transformer is installed between the first converter and the second converter and is used for power transmission and isolation.

5. The system according to any one of claims 1 to 3, characterized in that: The SOC balancing device further includes: when the voltages of the two battery branches are different, the SOC balancing device is a BOOST boost chopper circuit.

6. The system according to claim 2, wherein: The SOC balancing device includes: two inverters and a transformer; The input ends of the two inverters are connected to the first battery branch and the second battery branch respectively; The output ends of the two inverters are both connected to the transformer; The output end of the transformer is connected to the third controller.

7. The system according to claim 2, wherein: The SOC balancing device further includes: two Buck chopper circuits; The input ends of the two Buck chopper circuits are connected to the first battery branch and the second battery branch respectively; The output ends of the two Buck chopper circuits are connected in parallel and connected to the third controller.

8. The system according to claim 2, wherein: The SOC balancing device further includes: a first controlled switch and a second controlled switch; One end of the first controlled switch is connected to the first battery branch, and the other end is connected to the third controller; One end of the second controlled switch is connected to the second battery branch, and the other end is connected to the third controller.

9. A power balancing method, characterized in that: The SOC balancing device according to any one of claims 1 to 8 comprises: respectively obtaining a first remaining capacity and a second remaining capacity of two battery branches connected to the SOC balancing device; The SOC balancing device is controlled according to the first remaining charge and the second remaining charge, so that the remaining charges of the two battery branches are balanced.

10. The method according to claim 9, characterized in that The controlling the SOC balancing device according to the first remaining power and the second remaining power so that the remaining power of the two battery branches is balanced includes: When the first remaining power is greater than the second remaining power, controlling the SOC balancing device to transfer power from the battery branch corresponding to the first remaining power to the battery branch corresponding to the second remaining power; When the first remaining power is less than the second remaining power, the SOC balancing device is controlled to transfer power from the battery branch corresponding to the second remaining power to the battery branch corresponding to the first remaining power.

11. The method according to claim 9, characterized in that The method further comprises: When the third controller needs to draw power, obtaining the required power of the third controller; The current magnitude and duration for which the SOC balancing device draws power from the two battery branches are determined according to the first remaining power, the second remaining power, and the required power.

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