Brake chopper circuit and method

Abstract

The embodiment of the application provides a brake chopper circuit and method. The circuit comprises a first driving circuit and a second driving circuit connected electrically; wherein the first driving circuit comprises a first motor and a first motor controller connected electrically; the second driving circuit comprises a second motor, a second motor controller, a three-phase contactor, a contactor module and a brake chopper resistance module; a first end of the three-phase contactor is connected with the second motor controller, and a second end of the three-phase contactor is connected with the second motor; one end of the contactor module is connected with the second end of the three-phase contactor, and the other end is connected with the brake chopper resistance module; the brake chopper resistance module is used for consuming the electric energy generated by the first driving circuit when the contactor module is closed. Through the brake chopper circuit, the brake energy chopping consumption function is realized, and the related controller and cooling circuit do not need to be configured separately, thereby saving the cost.

Description

Technical Field

[0001] This application relates to the field of vehicle brake chopper technology, and in particular to a brake chopper circuit and method. Background Technology

[0002] In pure electric vehicles and hybrid electric vehicles, regenerative braking technology effectively reduces energy consumption and improves range and fuel economy by converting the vehicle's kinetic energy into electrical energy and recharging the battery. However, during long downhill descents or continuous braking, due to limited battery capacity, when the battery's state of charge (SOC) is too high, the battery can no longer accept regenerative energy, and the regenerative braking function is turned off. The vehicle then relies solely on the mechanical braking system, and prolonged reliance on mechanical brakes can easily lead to overheating or even failure of the braking system, posing serious safety hazards.

[0003] In existing technologies, braking chopper technology is a common method to solve the above problems. This involves designing a braking chopper with independently configured dedicated components including a control unit, drive circuit, switching unit, and freewheeling circuit (diode). When the battery's state of charge (SOC) is too high, the electrical energy regenerative from the electric braking system can be loaded onto the braking resistor and dissipated as heat. This avoids the overheating safety risks associated with relying on traditional brakes and extends the lifespan of the braking system.

[0004] However, existing braking choppers suffer from high operating costs and low utilization rates. Summary of the Invention

[0005] This application provides a braking chopper circuit and method to solve the problems of high cost and low utilization rate of braking choppers in the prior art.

[0006] In a first aspect, embodiments of this application provide a braking chopper circuit, comprising: a first driving circuit and a second driving circuit electrically connected;

[0007] The first drive circuit includes a first motor and a first motor controller that are electrically connected.

[0008] The second drive circuit includes a second motor, a second motor controller, a three-phase contactor, a contactor module, and a braking chopper resistor module; the first terminal of the three-phase contactor is connected to the second motor controller, and the second terminal of the three-phase contactor is connected to the second motor; one terminal of the contactor module is connected to the second terminal of the three-phase contactor, and the other terminal is connected to the braking chopper resistor module; the braking chopper resistor module is used to consume the electrical energy generated by the first drive circuit when the contactor module is closed.

[0009] In one possible implementation, the circuit further includes:

[0010] A protection module, connected to the braking chopper resistor module, is used to monitor the status of the braking chopper resistor module in order to protect the safety of the braking chopper resistor module.

[0011] In one possible implementation, the protection module includes a temperature sensor embedded in the braking chopper resistor module.

[0012] In one possible implementation, the protection module includes a fuse connected between the braking chopper resistor module and the contactor module.

[0013] In one possible implementation, the contactor module includes three contactors, and correspondingly, the braking chopper resistor module includes three braking chopper resistors; wherein each of the contactors is electrically connected to one of the braking chopper resistors.

[0014] In one possible implementation, the second drive circuit further includes a three-phase current sensor for collecting the consumed current flowing through the braking chopper circuit module.

[0015] Secondly, embodiments of this application provide a braking chopping method, including:

[0016] Obtain the real-time state of charge of the battery;

[0017] When the real-time state of charge is greater than or equal to a preset threshold, a disconnect signal is sent to the three-phase contactor to disconnect the electrical connection between the second motor and the second motor controller.

[0018] Based on the real-time braking power, determine the target contactor that needs to be closed;

[0019] A closing signal is sent to the target contactor to close the target contactor, so that the braking chopper resistor connected to the target contactor consumes the electrical energy generated by the first drive circuit.

[0020] In one possible implementation, determining the target contactor to be closed based on the real-time braking power includes:

[0021] When the real-time braking power is greater than the first power threshold, the target contactors that need to be closed are determined to be the first contactor, the second contactor, and the third contactor;

[0022] When the real-time braking power is greater than the second power threshold and less than or equal to the first power threshold, the target contactors that need to be closed are determined to be the first contactor and the second contactor.

[0023] When the real-time braking power is less than or equal to the second power threshold, the target contactor that needs to be closed is determined to be the first contactor.

[0024] In one possible implementation, the method further includes:

[0025] Obtain the real-time line current flowing through the braking chopper resistor and the voltage between the positive and negative terminals of the bus;

[0026] The power consumption of the braking chopper resistor is calculated based on the real-time line current and the voltage.

[0027] The chopping power consumption of the braking chopper resistor is adjusted in real time according to the power consumption.

[0028] In one possible implementation, after sending a closing signal to the target contactor to close the target contactor, the method further includes:

[0029] When the real-time state of charge is less than the preset threshold, a closing signal is sent to the three-phase contactor to close the electrical connection between the second motor and the second motor controller.

[0030] This application provides a braking chopper circuit and braking chopper. The circuit includes two drive circuits: a first motor and its controller in the first drive circuit perform conventional drive and braking energy feedback functions; a second motor in the second drive circuit is decoupled under special operating conditions, and its controller is connected to the motor via a three-phase contactor. Simultaneously, the second motor port is switched to a braking chopper resistor module via a contactor module. When the system detects that the battery SOC is close to its upper limit and can no longer receive braking energy feedback, the control system disconnects the conventional connection between the second motor and its controller (the three-phase contactor is disconnected) and closes the contactor module, allowing the second motor terminal to construct an energy consumption path for the braking current through a resistor loop. At this time, the first motor controller still performs braking energy feedback generation, but the generated energy is no longer fed back to the battery. Instead, it flows into the second motor controller through the bus, and under the chopper control of its lower bridge tube, it is dissipated as heat energy through the braking resistor module, achieving precise consumption of the feedback energy. This circuit utilizes the existing drive system hardware structure, achieving functional expansion only through control logic and contactor switching, avoiding the need for additional high-power hardware devices, and has the advantages of low cost, fast response, and compact structure. Meanwhile, by integrating temperature sensing and overcurrent protection components into the braking resistor module, the thermal safety and reliability of the entire energy consumption process are ensured, significantly improving the braking stability and overall vehicle safety performance of electric vehicles in long downhill or high SOC scenarios. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0032] Figure 1 Circuit diagram of the braking chopper circuit provided in the embodiments of this application Figure 1 ;

[0033] Figure 2 Circuit diagram of the braking chopper circuit provided in the embodiments of this application Figure 2 ;

[0034] Figure 3 This is a schematic flowchart of the braking chopper method provided in an embodiment of this application.

[0035] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0036] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0037] In pure electric vehicles and hybrid electric vehicles, regenerative braking technology effectively reduces energy consumption and improves range and fuel economy by converting the vehicle's kinetic energy into electrical energy and recharging the battery. However, during long downhill descents or continuous braking, due to limited battery capacity, when the battery's state of charge (SOC) is too high, the battery can no longer accept regenerative energy, and the regenerative braking function is turned off. The vehicle then relies solely on the mechanical braking system, and prolonged reliance on mechanical brakes can easily lead to overheating or even failure of the braking system, posing serious safety hazards.

[0038] In existing technologies, braking chopper technology is a common method to solve the above problems. This involves designing a braking chopper that includes dedicated components such as a control unit, drive circuit, switching unit, and freewheeling circuit (diode). When the battery's state of charge (SOC) is too high, the electrical energy regenerative from the electric braking system can be applied to the braking resistor and dissipated as heat. This avoids the overheating safety risks associated with relying on traditional brakes and extends the lifespan of the braking system.

[0039] However, existing braking choppers require a separate set of complete chopper system components, resulting in high promotion costs. Furthermore, many vehicles are limited by space constraints, making it impossible to configure them, leading to low utilization of the chopper controller. They are only used when descending long slopes and when the state of charge (SOC) is too high, thus resulting in low cost-effectiveness.

[0040] Based on this, this application proposes a braking chopper circuit. Addressing the issue that existing braking choppers require a separate, complete chopper system, resulting in high promotion costs and poor cost-effectiveness, the inventors devised a solution that directly leverages the redundancy and controllability of the existing dual-motor architecture to further solve the energy release problem. Specifically, one motor, in its non-driving state, acts as a switching element in the energy consumption circuit. By controlling the inverter bridge of this motor controller, the lower transistor is chopped and turned on, ensuring that the electrical energy generated by the motor braking is not fed back to the battery. Instead, it is converted into heat energy and released through a series-connected controllable chopper resistor, thus forming an energy consumption path independent of the battery and achieving a continuous and stable electric braking effect. Compared to adding other hardware, this method fully utilizes the vehicle's existing motor and control system hardware, reducing cost and complexity. Furthermore, by combining multi-level power adjustment and temperature protection mechanisms in the resistor path, it not only ensures braking safety and reliability when descending long slopes but also further extends the service life of the mechanical braking system.

[0041] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0042] Figure 1 Circuit diagram of the braking chopper circuit provided in the embodiments of this application Figure 1 ;like Figure 1As shown: The braking chopper circuit includes a first drive circuit and a second drive circuit electrically connected. The first drive circuit includes a first motor 10 and a first motor controller 101 electrically connected, undertaking conventional drive and energy feedback functions. The second drive circuit includes a second motor 20, a second motor controller 201, a three-phase contactor 30, a contactor module 40, and a braking chopper resistor module 50, forming a controllable energy consumption path. The first end of the three-phase contactor 30 is connected to the second motor controller 201, and the second end of the three-phase contactor 30 is connected to the second motor 20. Under normal operating conditions, the three-phase contactor 30 connects the second motor 20 to the second motor controller 201 to achieve drive or auxiliary functions. When the vehicle is in electric braking state and the battery SOC is detected to be close to the upper limit and unable to continue receiving energy feedback, the control system disconnects the three-phase contactor 30, cutting off the conventional connection between the second motor 20 and its second motor controller 201, and simultaneously controls the chopper resistor module 50 to connect to the circuit through the contactor module 40. One end of the contactor module 40 is connected to the second end of the three-phase contactor 30, and the other end is connected to the braking chopper resistor module 50; the braking chopper resistor module 50 is used to consume the electrical energy generated by the first drive circuit when the contactor module is closed.

[0043] It should be noted that the contactor module includes three contactors, and correspondingly, the braking chopper resistor module includes three braking chopper resistors. The three contactors control the connection of the three braking chopper resistors respectively, realizing graded adjustment of energy consumption power and enhancing the adaptability and control accuracy of the system.

[0044] The second motor controller 201, through a lower bridge arm chopper conduction method, inputs the electric braking energy generated by the first motor 10 via the bus, which is then dissipated as heat energy through a resistor in the selected path, thus forming an energy release channel outside the battery. To achieve precise control and real-time monitoring, the second drive circuit also integrates a three-phase current sensor to collect the actual current data flowing through the braking chopper resistor module 50. Combined with bus voltage measurement, this enables closed-loop regulation of the chopper power consumption. Simultaneously, a temperature sensor embedded in the braking chopper resistor module 50 monitors the resistor's operating status in real time, preventing overheating failure and ensuring system safety. A fuse, acting as an overcurrent protection element, is located between the contactor module 40 and the braking chopper resistor module 50, and can quickly disconnect the circuit in abnormal conditions to prevent the fault from escalating. This circuit design effectively achieves safe release of braking energy, avoiding braking failure caused by the battery's inability to provide feedback, reducing reliance on the mechanical braking system, extending its service life, and improving the vehicle's braking stability and safety under complex operating conditions.

[0045] Understandably, the braking chopper circuit, through the proper coordination of the contactor module and the braking chopper resistor module, can rapidly release energy when there is excess regenerative energy in the system, preventing excessive DC bus voltage. Simultaneously, real-time monitoring of current and temperature by three-phase current and temperature sensors, combined with the ultimate protection function of the fuses, significantly improves the system's safety and stability. The phase-separated control design allows for more precise energy consumption, avoids overload of single components, and extends the service life of the braking chopper resistor module and contactor module. The overall solution not only effectively ensures the energy management capability of the motor drive system under braking conditions but also enhances the system's reliability and safety protection level.

[0046] This application provides a braking chopper circuit. The circuit includes two drive circuits: a first motor and its controller in the first drive circuit perform conventional drive and braking energy feedback functions; the second motor in the second drive circuit is decoupled under special operating conditions, and its controller is connected to the motor via a three-phase contactor. Simultaneously, the contactor module switches the second motor's port to a braking chopper resistor module. When the system detects that the battery's SOC is nearing its limit and can no longer receive braking energy feedback, the control system disconnects the conventional connection between the second motor and its controller (the three-phase contactor is disconnected) and closes the contactor module, allowing the second motor to establish an energy consumption path for the braking current through a resistor loop. At this time, the first motor controller still performs braking energy feedback generation, but the generated energy is no longer fed back to the battery. Instead, it flows into the second motor controller via the bus, and under the chopper control of its lower bridge tube, it is dissipated as heat energy through the braking resistor module, achieving precise consumption of the feedback energy. This circuit utilizes the existing drive system hardware structure, achieving functional expansion only through control logic and contactor switching, avoiding the need for additional high-power hardware devices. It has the advantages of low cost, fast response, and compact structure. Meanwhile, by integrating temperature sensing and overcurrent protection components into the braking resistor module, the thermal safety and reliability of the entire energy consumption process are ensured, significantly improving the braking stability and overall vehicle safety performance of electric vehicles in long downhill or high SOC scenarios.

[0047] Figure 2 Circuit diagram of the braking chopper circuit provided in the embodiments of this application Figure 2 ,like Figure 2 As shown, O1 and O2 are the upper and lower transistors of the half-bridge switching unit (IGBT) module; B+ and B- are the voltages between the positive and negative terminals of the bus; MCU is the control unit; and Ice is the line current of the chopper resistor.

[0048] The three-phase current sensor in the second motor controller was originally used to measure the three-phase current of the motor during drive and energy feedback. In chopper mode, it is multiplexed to measure the current consumed by the chopper resistor circuit for closed-loop control of power consumption, preventing excessive bus voltage and ensuring system safety and stability; that is, by collecting the line current Ice flowing through the chopper resistor and the voltage between the positive and negative terminals of the bus (B+B-), the power consumption is calculated in real time. Furthermore, by adjusting the duty cycle of pulse width modulation (PWM), the power consumption is precisely controlled to ensure that the bus voltage does not continue to rise due to the accumulation of feedback current.

[0049] This allows for stable regulation of the system voltage during regenerative braking of another motor, preventing excessive battery SOC or overcharging and achieving closed-loop control. Based on temperature data from a temperature sensor embedded in the chopper resistor, the resistor's heating status can be monitored in real time, preventing overheating and potential damage. Simultaneously, this temperature value can be fed back to the vehicle's thermal management system as a thermal balance control target, ensuring effective heat dissipation.

[0050] Figure 3 A flowchart illustrating the braking chopper method provided in this application embodiment. Figure 2 ,like Figure 3 As shown, the method includes:

[0051] S301. Obtain the real-time state of charge of the battery.

[0052] It should be understood that the current state of charge of the battery is obtained from the battery management system (BMS), such as the current battery charge percentage, in order to determine whether the battery can still accept the feedback of braking energy. If the battery's state of charge is already high (close to full charge), continuing to provide feedback will cause the risk of overcharging. Therefore, this judgment is the basis for subsequent decisions on whether to "chop energy consumption" or "energy feedback".

[0053] S302. When the real-time state of charge is greater than or equal to a preset threshold, a disconnection signal is sent to the three-phase contactor to disconnect the electrical connection between the second motor and the second motor controller.

[0054] It should be understood that when the real-time state of charge is greater than or equal to the preset threshold, in order to avoid the risk of battery overcharging and the risk of overheating due to reliance on braking, it is necessary to send a disconnect signal to the three-phase contactor to disconnect the electrical connection between the second motor and the second motor controller, and terminate its participation in energy feedback.

[0055] S303. Determine the target contactor that needs to be closed based on the real-time braking power.

[0056] In one possible approach, when the real-time braking power is greater than a first power threshold, the target contactors to be closed are first contactor, second contactor, and third contactor; then, when the real-time braking power is greater than a second power threshold and less than or equal to the first power threshold, the target contactors to be closed are first contactor and second contactor; finally, when the real-time braking power is less than or equal to the second power threshold, the target contactor to be closed is first contactor.

[0057] Understandably, by dynamically allocating the braking resistor path, the system's energy consumption capacity and braking energy level are matched to prevent resistor overload or underload; the current consumption path is effectively adjusted to improve system energy efficiency and heat dissipation safety.

[0058] It should also be noted that, firstly, the real-time line current flowing through the braking chopper resistor and the voltage between the positive and negative poles of the bus are obtained; then, based on the real-time line current and voltage, the power consumption of the braking chopper resistor is calculated; finally, the chopping power consumption of the braking chopper resistor is adjusted in real time based on the power consumption.

[0059] It should be understood that this calculation method can accurately match braking current with heat dissipation capacity, further optimizing safety and energy efficiency.

[0060] S304. Send a closing signal to the target contactor to close the target contactor, so that the braking chopper resistor connected to the target contactor consumes the electrical energy generated by the first drive circuit.

[0061] Optionally, after closing the target contactor, if the acquired real-time state of charge is less than a preset threshold, a closing signal is sent to the three-phase contactor to close the electrical connection between the second motor and the second motor controller.

[0062] It should be understood that after the resistor chopper has been running for a period of time, if the battery SOC decreases (consuming some power), the three-phase contactor will close again, restoring the electrical connection between the second motor and the second motor controller, allowing energy feedback and improving the feedback utilization rate.

[0063] It should be noted that the devices in the embodiments provided in this application are all common devices on the market. They can be selected according to the needs when used. The circuit connection relationship of each device is a simple series and parallel connection circuit, which can be easily implemented by those skilled in the art. It belongs to the prior art and will not be described in detail here.

[0064] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

[0066] The various embodiments or implementation methods described in this specification are presented in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0067] It should be noted that the terms "one embodiment," "embodiment," "exemplary embodiment," "some embodiments," etc., mentioned in the specification indicate that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0068] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0069] It should also be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0070] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A braking chopper circuit, characterized in that, include: The first and second drive circuits are electrically connected. The first drive circuit includes a first motor and a first motor controller that are electrically connected. The second drive circuit includes a second motor, a second motor controller, a three-phase contactor, a contactor module, and a braking chopper resistor module; the first terminal of the three-phase contactor is connected to the second motor controller, and the second terminal of the three-phase contactor is connected to the second motor; one terminal of the contactor module is connected to the second terminal of the three-phase contactor, and the other terminal is connected to the braking chopper resistor module; the braking chopper resistor module is used to consume the electrical energy generated by the first drive circuit when the contactor module is closed.

2. The braking chopper circuit according to claim 1, characterized in that, The circuit also includes: A protection module, connected to the braking chopper resistor module, is used to monitor the status of the braking chopper resistor module in order to protect the safety of the braking chopper resistor module.

3. The braking chopper circuit according to claim 2, characterized in that, The protection module includes a temperature sensor, which is embedded in the braking chopper resistor module.

4. The braking chopper circuit according to claim 2, characterized in that, The protection module includes a fuse, which is connected between the braking chopper resistor module and the contactor module.

5. The braking chopper circuit according to claim 1, characterized in that, The contactor module includes three contactors, and correspondingly, the braking chopper resistor module includes three braking chopper resistors; wherein each contactor is electrically connected to one of the braking chopper resistors.

6. The braking chopper circuit according to claim 1, characterized in that, The second drive circuit also includes a three-phase current sensor for collecting the current consumed by the braking chopper circuit module.

7. A braking chopper method, applied to the braking chopper circuit as described in any one of claims 1-6, characterized in that, The method includes: Obtain the real-time state of charge of the battery; When the real-time state of charge is greater than or equal to a preset threshold, a disconnect signal is sent to the three-phase contactor to disconnect the electrical connection between the second motor and the second motor controller. Based on the real-time braking power, determine the target contactor that needs to be closed; A closing signal is sent to the target contactor to close the target contactor, so that the braking chopper resistor connected to the target contactor consumes the electrical energy generated by the first drive circuit.

8. The method according to claim 7, characterized in that, The step of determining the target contactor that needs to be closed based on the real-time braking power includes: When the real-time braking power is greater than the first power threshold, the target contactors that need to be closed are determined to be the first contactor, the second contactor, and the third contactor; When the real-time braking power is greater than the second power threshold and less than or equal to the first power threshold, the target contactors that need to be closed are determined to be the first contactor and the second contactor. When the real-time braking power is less than or equal to the second power threshold, the target contactor that needs to be closed is determined to be the first contactor.

9. The method according to claim 7, characterized in that, The method further includes: Obtain the real-time line current flowing through the braking chopper resistor and the voltage between the positive and negative terminals of the bus; The power consumption of the braking chopper resistor is calculated based on the real-time line current and the voltage. The chopping power consumption of the braking chopper resistor is adjusted in real time according to the power consumption.

10. The method according to claim 7, characterized in that, After sending a closing signal to the target contactor to close the target contactor, the method further includes: When the real-time state of charge is less than the preset threshold, a closing signal is sent to the three-phase contactor to close the electrical connection between the second motor and the second motor controller.

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