Brake chopper circuit and method

Abstract

The embodiment of the invention provides a brake chopper circuit and method. The circuit comprises a first driving circuit and a second driving circuit which are electrically connected; wherein the first driving circuit comprises a first motor and a first motor controller which are electrically connected; the second driving circuit comprises a second motor, a second motor controller, a three-phase contactor, a contactor module and a brake chopping resistor module; the first end of the three-phase contactor is connected with the second motor controller, and the 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 chopping resistor module; the brake chopping resistor module is used for consuming electric energy generated by the first driving circuit when the contactor module is closed. By means of the brake chopper circuit, the brake energy chopper consumption function is achieved, relevant controllers and cooling loops do not need to be independently configured, and cost is saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vehicle brake chopper technology, in particular to a brake chopper circuit and method. BACKGROUND

[0002] In pure electric vehicles and hybrid electric vehicles, brake energy feedback technology effectively reduces energy consumption, improves endurance and fuel economy by converting the kinetic energy of the vehicle into electrical energy and charging the battery. However, in the case of long downhill or continuous braking, due to the limited capacity of the battery, when the state of charge (SOC) of the battery is too high, the battery will not be able to continue to accept feedback power, at which point the brake feedback function is turned off. The vehicle can only rely on the mechanical brake system, and long-term reliance on the mechanical brake system can easily lead to overheating of the brake system, and even failure, causing serious safety hazards.

[0003] In the prior art, brake chopper technology is a common means to solve the above problems, that is, by designing a brake chopper, independent configuration of special-purpose components including control unit, drive circuit, switch unit, freewheeling circuit (diode), etc. When the battery SOC is too high, the electric brake feedback power can be loaded on the brake resistor to dissipate in the form of heat. In this way, it can avoid the risk of overheating and prolong the service life of the brake system.

[0004] However, the brake chopper in the prior art has the problems of high use cost and low utilization rate. SUMMARY

[0005] The brake chopper circuit and method provided by the embodiments of the present application solve the problem of high use cost and low utilization rate of the brake chopper in the prior art.

[0006] In a first aspect, the embodiments of the present application provide a brake chopper circuit, comprising: a first drive circuit and a second drive circuit electrically connected;

[0007] The first drive circuit comprises a first motor and a first motor controller electrically connected;

[0008] The second drive circuit comprises a second motor, a second motor controller, a three-phase contactor, a contactor module, and a brake chopper resistor module; the first end of the three-phase contactor is connected with the second motor controller, and the 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 resistor module; the brake chopper resistor module is used to consume the electric energy generated by the first drive circuit when the contactor module is closed.

[0009] In a possible implementation, the circuit further comprises:

[0010] A protection module is connected with the brake-chopper resistor module, and is configured to monitor a state of the brake-chopper resistor module to protect safety of the brake-chopper resistor module.

[0011] In a possible implementation, the protection module comprises a temperature sensor, which is embedded in the brake-chopper resistor module.

[0012] In a possible implementation, the protection module comprises a fuse, which is connected between the brake-chopper resistor module and the contactor module.

[0013] In a possible implementation, the contactor module comprises three contactors, and the brake-chopper resistor module comprises three brake-chopper resistors; and each contactor is electrically connected with one brake-chopper resistor.

[0014] In a possible implementation, the second driving circuit further comprises a three-phase current sensor, which is configured to collect a consumption current flowing through the brake-chopper circuit module.

[0015] In a second aspect, an embodiment of the present application provides a brake-chopping method, comprising:

[0016] obtaining a real-time state of charge of a battery;

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

[0018] determining a target contactor that needs to be closed according to a real-time braking power;

[0019] sending a closing signal to the target contactor to close the target contactor, so that a brake-chopper resistor connected with the target contactor consumes electric energy generated by the first driving circuit.

[0020] In a possible implementation, the determining of the target contactor that needs to be closed according to the real-time braking power comprises:

[0021] when the real-time braking power is greater than a first power threshold, determining that the target contactor that needs to be closed is a first contactor, a second contactor and a third contactor;

[0022] when the real-time braking power is greater than a second power threshold and less than or equal to the first power threshold, determining that the target contactor that needs to be closed is 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 to be closed is determined as the first contactor.

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

[0025] acquiring a real-time line current flowing through the braking chopper resistor and a voltage between the positive and negative bus bars;

[0026] calculating a consumption power of the braking chopper resistor according to the real-time line current and the voltage;

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

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

[0029] When the acquired 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] Embodiments of the present application provide a braking chopper circuit and a braking chopper. The circuit includes two drive circuits: the first motor in the first drive circuit and its controller undertake the functions of conventional driving and braking energy feedback; the second motor in the second drive circuit is decoupled under special working conditions, and its controller is connected with the motor through a three-phase contactor, and the second motor port is switched and connected to a braking chopper resistor module through a contactor module. When the system detects that the battery SOC has approached the upper limit and cannot receive braking feedback power any more, 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, so that the second motor port builds a braking current energy consumption path through the resistor loop; at this time, the first motor controller still generates braking feedback power, and the generated power no longer feeds back to the battery, but flows into the second motor controller through the bus, and is dissipated as heat energy under the chopper control of the bridge arm, thereby realizing accurate consumption of the feedback power. The circuit uses the existing drive system hardware structure, and realizes function expansion only by control logic and contactor switching, avoids adding high-power hardware devices, and has the advantages of low cost, fast response, and compact structure. At the same time, by integrating temperature sensors and overcurrent protection elements in the braking resistor module, the thermal safety and reliability of the entire energy consumption process are guaranteed, and the braking stability and vehicle safety performance of the electric vehicle in the long downhill or high SOC scene are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

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

[0032] Figure 1 Circuit schematic of the brake chopper circuit provided for embodiments of the application Figure One ;

[0033] Figure 2 Circuit schematic of the brake chopper circuit provided for embodiments of the application Figure Two ;

[0034] Figure 3 Flowchart of the brake chopper method provided for embodiments of the application.

[0035] The specific embodiments of the application have been shown by way of example in the above-described figures, and will be described in more detail below. These figures and the written description together serve the purpose of describing embodiments of the application as they pertain to particular embodiments. The figures and written description are not intended to limit the scope of the concepts in any way. DETAILED DESCRIPTION

[0036] The exemplary embodiments will be described in detail herein with reference to the attached drawings. The description of the exemplary embodiments is intended to apply to any embodiment of the application, unless specifically stated otherwise. It is understood that the description of the exemplary embodiments is intended to be illustrative and not restrictive. Many embodiments of the application will be readily apparent to those of ordinary skill in the art in view of the following description, which describes in detail exemplary embodiments of the application and the best modes contemplated for carrying out the application. The application is capable of other embodiments or of being carried out in other related ways, as will be apparent to one skilled in the art from the description and the appended claims.

[0037] In the pure electric vehicle and hybrid electric vehicle, the brake energy feedback technology effectively reduces the energy consumption, improves the endurance and fuel economy by converting the kinetic energy of the vehicle into electrical energy and charging the battery. However, in the case of long downhill or continuous braking, due to the limited capacity of the battery, when the state of charge (SOC) of the battery is too high, the battery will not be able to continue to accept the feedback power, at this time the brake feedback function is turned off. The vehicle can only rely on the mechanical brake system, and long-term dependence on the mechanical brake is easy to cause the brake system to overheat and even fail, which brings serious safety hazards.

[0038] In the prior art, the brake chopper technology is a common means to solve the above problems, that is, by designing a brake chopper, including control unit, drive circuit, switch unit, freewheeling circuit (diode) and other function-specific components. When the battery SOC is too high, the electric brake feedback power can be loaded on the brake resistor to dissipate in the form of heat. In this way, it can avoid the overheat safety risk of relying on brake braking, and prolong the service life of the brake system.

[0039] However, the brake chopper in the prior art needs to separately configure a complete set of chopper system components, and the promotion cost is high; and many vehicles are limited by the vehicle space and cannot be configured, the utilization rate of the chopper controller is not high, and it is only used when the SOC is too high when going down a long slope, so the cost performance is low.

[0040] Based on this, the present application provides a brake chopper circuit, aiming at the problem that the brake chopper in the prior art needs to separately configure a complete set of chopper system components, and the promotion cost is high and the cost performance is low, the inventor thinks of directly using the redundancy and controllability of the existing double motor architecture to further solve the energy release problem, that is, using one of the motors as a switching element of the energy consumption loop in the non-driving state, controlling the inverter bridge of the motor controller, and turning on the chopper to make the electric energy generated by the motor braking not feedback to the battery, but converted into heat energy through the series controllable chopper resistor to release, thereby forming an independent electric energy consumption path from the battery, realizing the effect of continuous and stable electric braking. Compared with adding other hardware, this method fully utilizes the existing motor and control system hardware of the vehicle, reduces the cost and complexity, and combines the multi-gear power regulation and temperature protection mechanism of the resistor path, which not only guarantees the braking safety and reliability when going down a long slope, but also further prolongs the service life of the mechanical brake system.

[0041] The technical solutions of the present application and how the technical solutions of the present application solve the above technical problems will be described in detail below with specific embodiments. The following 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 the present application will be described below with reference to the drawings.

[0042] Figure 1 Circuit diagram of the brake chopper circuit provided by the embodiments of the present application Figure One ; as Figure 1As shown: the brake chopper circuit includes a first drive circuit and a second drive circuit connected by electricity; wherein the first drive circuit includes a first motor 10 and a first motor controller 101 connected by electricity, bearing the conventional drive and energy feedback function; 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 brake chopper resistance module 50 to form a set of controllable energy consumption path. The first end of the three-phase contactor 30 is connected with the second motor controller 201, and the second end of the three-phase contactor 30 is connected with the second motor 20; in the normal operating state, the three-phase contactor 30 connects the second motor 20 with the second motor controller 201, realizing the driving or auxiliary function; when the vehicle is in the electric braking state and the battery SOC is detected to be close to the upper limit, unable to continue to receive energy feedback, the control system disconnects the three-phase contactor 30, cutting off the normal connection between the second motor 20 and its second motor controller 201, and at the same time controls the chopper resistance module 50 to access the circuit through the contactor module 40. One end of the contactor module 40 is connected with the second end of the three-phase contactor 30, and the other end is connected with the brake chopper resistance module 50; the brake chopper resistance module 50 is used to consume the electric 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 brake chopper resistance module includes three brake chopper resistors; the three contactors control the access of the three brake chopper resistors respectively, realizing the step adjustment of the energy consumption power and enhancing the adaptability and control accuracy of the system.

[0044] The second motor controller 201 passes through the lower bridge arm chopper conduction mode, inputs the electric braking energy generated by the first motor 10 through the bus, and consumes it as heat through the resistance in the selected path, thereby forming an energy release channel outside the battery. In order to realize accurate control and real-time monitoring, the second drive circuit also integrates a three-phase current sensor for collecting actual current data flowing through the brake chopper resistance module 50, and cooperates with bus voltage measurement to realize closed-loop regulation of chopper consumption power. At the same time, the temperature sensor embedded in the brake chopper resistance module 50 is used to monitor the working state of the resistance in real time, prevent overheating failure, and ensure the safety of system operation; the fuse is used as an overcurrent protection element, located between the contactor module 40 and the brake chopper resistance module 50, and can quickly cut off the circuit in abnormal conditions to prevent fault expansion. Through the circuit design, the safe release of braking energy can be effectively realized, the problem of braking failure caused by the battery unable to feedback is avoided, the dependence on the mechanical brake system is reduced, the service life of the mechanical brake system is prolonged, and the braking stability and safety of the whole vehicle under complex working conditions are improved.

[0045] It can be understood that the brake chopper circuit can quickly release energy when the system has excess regenerative energy by the reasonable cooperation of the contactor module and the brake chopper resistor module, so as to prevent the DC bus voltage from being too high. At the same time, the real-time monitoring of the current and temperature by the three-phase current sensor and the temperature sensor, combined with the limit protection function of the fuse, significantly improves the safety and stability of the system. The structure design of the split-phase control makes the energy consumption more accurate, avoids the overload of a single component, and prolongs the service life of the brake chopper resistor module and the contactor module. The overall scheme not only effectively ensures the energy management capability of the motor drive system under the braking condition, but also improves the reliability and safety protection level of the system.

[0046] The embodiment of the application provides a brake chopper circuit. The circuit comprises two drive circuits: the first motor in the first drive circuit and its controller undertake the functions of conventional driving and braking energy feedback; the second motor in the second drive circuit is decoupled under special working conditions, its controller is connected with the motor through a three-phase contactor, and the second motor port is switched and connected to the brake chopper resistor module through the contactor module. When the system detects that the battery SOC has approached the upper limit and cannot receive the braking feedback power any more, the control system disconnects the conventional connection (the three-phase contactor is disconnected) of the second motor and its controller, and closes the contactor module, so that the second motor port builds an energy consumption path of the braking current through the resistor loop; at this time, the first motor controller still generates power for braking feedback, and the generated power no longer feeds back to the battery, but flows into the second motor controller through the bus, and is dissipated as heat energy through the braking resistor module under the bridge arm under the chopper control, so that the feedback power is accurately consumed. The circuit uses the existing drive system hardware structure, realizes function expansion only by control logic and contactor switching, avoids adding high-power hardware devices, has the advantages of low cost, fast response and compact structure. At the same time, by integrating temperature sensors and overcurrent protection elements in the braking resistor module, the thermal safety and reliability of the entire energy consumption process are ensured, and the braking stability and vehicle safety performance of the electric vehicle under the long downhill or high SOC scene are significantly improved.

[0047] Figure 2 The circuit schematic of the brake chopper circuit provided by the embodiment of the application Figure Two As shown in Figure 2 , wherein O1 and O2 are upper and lower tubes of a half-bridge switch unit (IGBT) module; B+ and B- are the voltage between the positive and negative poles of the bus; MCU is a control unit; and Ice is the line current of the chopper resistor.

[0048] The three-phase current sensor in the second motor controller is originally used to measure the motor three-phase current when driving and energy feedback. In the chopping mode, it is reused to measure the consumption current of the chopping resistance loop, which is used for closed-loop control of the consumption power to prevent the bus voltage from being too high and ensure system safety and stability; that is, by collecting the line current Ice flowing through the chopping resistance and the voltage (B+B-) between the positive and negative bus, the consumption power is calculated in real time: ; and by adjusting the pulse width modulation (PWM) duty cycle, the consumption power is accurately controlled to prevent the bus voltage from continuing to rise due to the accumulation of feedback current.

[0049] Thus, the system voltage can be stably regulated when another motor brakes and feeds back, preventing the battery SOC from being too high or overcharged, and achieving closed-loop control; based on the temperature data collected by the temperature sensor embedded in the chopping resistance, the heating of the resistance can be monitored in real time to prevent overheating and failure. At the same time, this temperature value can be fed back to the vehicle thermal management system as a thermal balance control target to ensure effective heat dissipation.

[0050] Figure 3 Flowchart of the braking and chopping method provided by the embodiments of the present application Figure Two As shown in Figure 3 , the method comprises:

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

[0052] It should be understood that the state of charge of the current battery, such as the percentage of the current battery capacity, is obtained from the battery management system (BMS), so as to determine whether the battery can still accept feedback of braking energy; if the state of charge of the battery is already high (close to full), continuing to feedback will cause the risk of overcharging; therefore, this determination is a basic condition for subsequent decision whether to "chop and consume energy" or "energy feedback".

[0053] S302, when the real-time state of charge is greater than or equal to a preset threshold, sending a disconnection signal 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 overcharging the battery and to avoid the risk of overheating and safety of relying on brake braking, a disconnection signal needs to be sent 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, determining the target contactor that needs to be closed according to the real-time braking power.

[0056] In an implementable manner, first, when the real-time braking power is greater than the first power threshold, the target contactors to be closed are determined as the first contactor, the second contactor and the third contactor; then, 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 to be closed are determined as the first contactor and the 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 determined as the first contactor.

[0057] It can be understood that by dynamically allocating the braking resistance path, the consumption capacity is matched with the braking energy level, and the resistance is prevented from being overloaded or insufficient; the current consumption path is effectively adjusted, and the system energy efficiency and heat dissipation safety are improved.

[0058] It should be further noted that first, the real-time line current flowing through the braking chopper resistance and the voltage between the positive and negative poles of the bus are acquired; then, the consumption power of the braking chopper resistance is calculated according to the real-time line current and the voltage; finally, the chopping consumption power of the braking chopper resistance is adjusted in real time according to the consumption power.

[0059] It should be understood that by this calculation method, the braking current and the heat consumption capacity can be accurately matched, and the safety and energy efficiency are further optimized.

[0060] S304, a closing signal is sent to the target contactor to close the target contactor, so that the braking chopper resistance connected with the target contactor consumes the electric energy generated by the first driving circuit.

[0061] Optionally, after the closing signal is sent to the target contactor to close the target contactor, when 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 resistance chopping runs for a period of time, if the battery SOC decreases (consumes part of the electric quantity), the three-phase contactor will be closed again to restore 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 the present application are common market devices, which can be selected according to needs during specific use, and the circuit connection relationship of each device is a simple series connection and parallel connection circuit, which can be easily realized by those skilled in the art, and belongs to the prior art, which will not be described here.

[0064] Each technical feature of the above-described embodiments can be combined arbitrarily, and to make the description concise, each technical feature in the above-described embodiments is not described in all possible combinations, however, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope of the present disclosure.

[0065] The above-described embodiments are merely illustrative of the present application, which is described in more detail and specifically, but should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make modifications and improvements to the above-described embodiments without departing from the concept of the present application, and these modifications and improvements are within the scope of the present application. Therefore, the scope of the patent should be determined by the appended claims

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

[0067] It should be noted that the terms "one embodiment", "an embodiment", "exemplary embodiment", "some embodiments", etc. in the specification mean that the described embodiment can include a specific feature, structure or characteristic, but not necessarily every embodiment. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when a specific feature, structure or characteristic is described in combination with an embodiment, it is within the knowledge of those skilled in the art to realize such feature, structure or characteristic in combination with other embodiments, whether explicitly described or not.

[0068] It should be noted that in this document, relational terms such as first and second, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0069] It should also be noted that the above embodiments are merely used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0070] It should be understood that many of the materials and devices exemplified in this disclosure are articles of manufacture (i.e., articles of manufacture) according to this disclosure. The articles of manufacture can be manufactured as such or can be manufactured by combining the materials and devices exemplified in this disclosure. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. It should be understood that, in some embodiments, equivalents to the specific electrode structures and / or methods described herein can be employed without departing from the scope of the application. Accordingly, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," "having," "containing," "involving," "characterized by," "characterized into," and variations thereof herein, is meant to encompass the items listed thereafter, and equivalents thereof as well as additional items. Although the foregoing application has been described in some detail by way of illustration and example, it is not to be limited thereby, but rather, only by the scope of the appended claims.

Claims

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

2. The brake chopper circuit according to claim 1, characterized in that: The circuit further comprises: The protection module is connected to the braking chopper resistor module and is used to monitor the state of the braking chopper resistor module to protect the safety of the braking chopper resistor module.

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

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

5. The brake 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 of the contactors is electrically connected to one of the braking chopper resistors.

6. The brake chopper circuit according to claim 1, characterized in that: The second driving circuit further includes a three-phase current sensor for collecting the consumption current flowing through the brake chopper circuit module.

7. A braking chopping method, applied to the braking chopping circuit according to any one of claims 1 to 6, characterized in that: The method comprises: Get 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, sending a disconnect signal to the three-phase contactor to disconnect the electrical connection between the second motor and the second motor controller; Determine the target contactor that needs to be closed based on the real-time braking power; 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 electric energy generated by the first driving circuit.

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

9. The method according to claim 7, characterized in that The method further comprises: Obtaining the real-time line current flowing through the braking chopper resistor and the voltage between the positive and negative poles of the busbar; Calculating the power consumption of the braking chopper resistor according to 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 acquired 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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