A pre-charge device and method for a high voltage system of a motor controller
By replacing the traditional pre-charge relay with a boost isolation module and MCU, and combining multi-level fault detection, the problems of large size, high price and single fault detection in the pre-charge scheme of the high voltage system of motor controller are solved, and the accurate pre-charge and safety improvement of the high voltage system are realized.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHENGZHOU JIACHEN ELECTRIC CO LTD
- Filing Date
- 2026-02-11
- Publication Date
- 2026-06-09
AI Technical Summary
Existing pre-charge solutions for high-voltage motor controllers are bulky, expensive, and have limited fault detection capabilities, which can easily lead to damage to the low-voltage system.
The traditional pre-charge relay is replaced by a boost isolation module and a microprocessor (MCU). Through multi-level fault detection and active protection mechanisms, the pre-charge of the high-voltage system is realized. This includes the system power supply end, battery pack output end, main contactor, anti-reverse module, boost isolation module, energy storage module, current limiting resistor, coil controller circuit, voltage detection module and high-voltage detection module, which perform multi-level voltage signal comparison and fault judgment.
It enables precise pre-charging of high-voltage systems, reduces hardware costs, improves safety, increases fault identification rate, prevents fault escalation, and adapts to different high-voltage platforms without requiring hardware replacement.
Smart Images
Figure CN122178520A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of vehicle technology, and in particular relates to a pre-charging device and method for a high-voltage system of a motor controller. Background Technology
[0002] Currently, with the widespread adoption of high-voltage systems, power-on processing of controller systems is becoming increasingly common, making pre-processing for high-voltage systems crucial. High-voltage pre-processing ensures smoother operation and higher system stability. Most existing pre-charging solutions for high-voltage controllers employ external pre-charging, which is uncontrolled at the start of power-on and requires additional control devices for subsequent shutdown. Furthermore, existing built-in pre-charging solutions utilize high-voltage relays, which are bulky and expensive.
[0003] The prior art, with application number CN201611128624.7 and titled "Method for Controlling High Voltage Power-On and Off of Electric Vehicle Controller," involves the vehicle controller detecting whether a main relay fault is reported. If no fault is found, the pre-charge relay is closed, and a fault of too fast or too slow pre-charge is detected. When the pre-charge voltage is reached, the main relay is closed after a delay, and the pre-charge relay is opened to complete the pre-charge power-on process. Otherwise, the pre-charge power-on process is stopped, and a main relay fault signal is given. In the above technical solution, the pre-charge circuit is directly linked to the low-voltage control circuit. If the vehicle controller directly controls the pre-charge relay, leakage or voltage fluctuations on the high-voltage side can easily be transmitted to the low-voltage system through the control circuit, damaging the MCU or other low-voltage components. In addition, the above technical solution only detects pre-charge faults through pre-charge time and voltage difference, which is a single fault detection dimension. Summary of the Invention
[0004] The purpose of this invention is to provide a pre-charging device and method for a high-voltage system of a motor controller, which is capable of...
[0005] This invention adopts the following technical solution: a pre-charging device for a high-voltage system of a motor controller, comprising a system power supply terminal, a battery pack output terminal, a main contactor, an anti-reverse module, a boost isolation module, a microprocessor, an energy storage module, a current-limiting resistor, a coil controller circuit, a voltage detection module, and a high-voltage detection module; wherein,
[0006] The system power supply terminal, boost isolation module, current limiting resistor, and energy storage module are connected in series to form a pre-charge system. The pre-charge system also includes an anti-reverse module, which is connected in series between the system power supply terminal and the boost isolation module. The voltage sampling module collects the first sampling voltage and outputs it to the microprocessor. The first sampling voltage represents the voltage of the first voltage signal of the system power supply terminal output through the anti-reverse module. The high voltage sampling module collects the second sampling voltage and the first bus voltage and outputs them to the microprocessor. The second sampling voltage represents the voltage of the second voltage signal after being boosted by the boost isolation module. The first bus voltage represents the voltage during bus pre-charge.
[0007] The battery pack output terminal, main contactor and energy storage module are connected in series to form the main circuit. The high voltage sampling module collects the second bus voltage and outputs it to the microprocessor. The second bus voltage represents the bus voltage after pre-charging is completed.
[0008] A pre-charging method for a high-voltage system of a motor controller, applicable to the aforementioned pre-charging device, comprising,
[0009] S1: The system power supply terminal outputs a power supply signal. The voltage sampling module acquires and outputs the first sampled voltage to the microprocessor. The microprocessor compares the first sampled voltage with the built-in power-on detection reference voltage to determine whether the pre-charging system is powered on normally.
[0010] If the microprocessor determines that the pre-charge system is powered on normally, execute S2;
[0011] If the microprocessor determines that the precharge system is abnormally powered on, it will output a fault signal and the precharge system will stop.
[0012] S2: If the power-on is normal, the microprocessor starts the boost isolation module, which increases the voltage output from the system power supply terminal to the preset target voltage and outputs the second voltage signal.
[0013] S3: The microprocessor receives the second sampling voltage and the first bus voltage collected and output by the high-voltage sampling module, compares them with the built-in boost detection reference voltage, and determines whether the bus pre-charge is normal.
[0014] If the microprocessor determines that the bus pre-charge is normal, proceed to step S4;
[0015] If the microprocessor determines that the bus pre-charge is abnormal, it will issue a bus pre-charge fault signal, and the pre-charge system will stop.
[0016] S4: If the bus pre-charge is normal, start the coil control circuit, the main contactor will engage, and the microprocessor will compare the received second bus voltage with the built-in main contactor detection reference voltage to perform main circuit detection.
[0017] If the microprocessor determines that the main circuit is normal, it means that the controller's high-voltage system is complete;
[0018] If the microprocessor determines that the main circuit is abnormal, it will output a fault in the main contactor and stop operation.
[0019] Furthermore, in S1, the power-on detection reference voltage includes a first reference voltage and a second reference voltage. The process of determining whether the pre-charge system is powered on normally includes:
[0020] S101: When the first sampling voltage is greater than or equal to the first reference voltage and the first sampling voltage is less than or equal to the second reference voltage, the microprocessor determines that the pre-charging system is powered on normally and executes step S2.
[0021] S102: When the first sampling voltage is less than the first reference voltage, or the first sampling voltage is greater than the second reference voltage, the microprocessor determines that the pre-charge system has a power-on fault, outputs a fault signal, and the pre-charge system stops.
[0022] Furthermore, in S2, the microprocessor outputs a first enable signal to start the boost isolation module.
[0023] Furthermore, in step S2, the voltage output from the system power supply terminal is increased to a preset target voltage, which is set to... The range of N is: N is the precharge voltage coefficient; It is the output voltage of the battery pack.
[0024] Furthermore, in S3, the boost detection reference voltage built into the microprocessor includes a third reference voltage and a fourth reference voltage. The process of determining whether the bus pre-charge is normal includes:
[0025] S301: When the second sampling voltage is greater than or equal to the third reference voltage and less than or equal to the fourth reference voltage, and the first bus voltage is greater than or equal to the third reference voltage and less than or equal to the fourth reference voltage, the microprocessor determines that the bus pre-charge is normal and executes step S4.
[0026] S302: When the second sampling voltage is less than the third reference voltage, the second sampling voltage is greater than the fourth reference voltage, the first bus voltage is less than the third reference voltage, or the first bus voltage is greater than the fourth reference voltage, the microprocessor determines that the bus pre-charging is abnormal, issues a bus pre-charging fault signal, and the pre-charging system stops.
[0027] Furthermore, in S4, the microprocessor sends a second enable signal to start the coil control circuit, at which point the main contactor closes.
[0028] Furthermore, in S4, the microprocessor-built-in main contactor detection reference voltage includes a fifth reference voltage and a sixth reference voltage; the main circuit detection includes:
[0029] S401: When the voltage of the second bus is greater than or equal to the fifth reference voltage and less than or equal to the sixth reference voltage, the main circuit is judged to be normal, indicating that the high-voltage system of the controller is completed.
[0030] S402: When the voltage of the second bus is less than the fifth reference voltage, or the voltage of the second bus is greater than the sixth reference voltage, the main circuit is determined to be abnormal, the second enable signal is turned off, the microprocessor outputs a main contactor fault, and operation is stopped.
[0031] This invention utilizes a low-voltage system to pre-charge a high-voltage system without accessing a high-voltage signal. Furthermore, the processing scheme described in this invention provides more precise protection and higher security.
[0032] Replacing the traditional pre-charging solution with a boost isolation module and MCU with a pre-charging relay results in lower hardware costs. It employs multi-level fault detection, covering three types of faults: abnormal input signal, abnormal pre-charging voltage, and abnormal main contactor, thereby increasing the fault identification rate and greatly reducing the risk of fault occurrence.
[0033] It also incorporates an active protection mechanism that immediately cuts off the pre-charge circuit or main contactor once a fault is detected to prevent the fault from escalating. With an adjustable output design that sets the target voltage after boosting, it can adapt to different high-voltage platforms without replacing the hardware. Attached Figure Description
[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0035] Figure 1 This is a schematic diagram of the pre-charging device of the high-voltage system for the motor controller provided by the present invention;
[0036] Figure 2 A schematic flowchart of the pre-charging method for the high-voltage system of the motor controller provided by the present invention. Detailed Implementation
[0037] To make the objectives, technical solutions, and advantages of the embodiments described herein clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments described herein, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are within the scope of protection of this document. It should be noted that, unless otherwise specified, the embodiments and features described herein can be arbitrarily combined with each other.
[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments:
[0039] A pre-charging device for a high-voltage system of a motor controller includes: a system power supply terminal, a battery pack output terminal, a main contactor, an anti-reverse module, a boost isolation module, a microprocessor (MCU), an energy storage module, a current limiting resistor, a coil controller circuit, a voltage detection module, and a high-voltage detection module;
[0040] The main contactor (K1) represents the main switch of the controller's high-voltage system circuit. It is controlled by the coil control circuit to connect or disconnect the power supply path from the battery pack output DC+ to the bus BUS.
[0041] The coil control circuit is used to receive the second enable signal EN2 from the microprocessor and drive the coil of the main contactor to achieve the engagement or disengagement of the main contactor.
[0042] The reverse protection module is used to prevent damage to the back-end circuits caused by reverse connection of the system power supply terminal, thus providing reverse protection.
[0043] The boost isolation module is used to boost the voltage input to the system power supply terminal to a preset target voltage and achieve electrical isolation, and output a second voltage signal SS+.
[0044] The current-limiting resistor (R1) is used to limit the current output from the boost isolation module to the bus (BUS) to prevent excessive current from damaging the circuit or energy storage module.
[0045] The energy storage module stores electrical energy through the bus capacitor (EC1) to stabilize the bus voltage or release electrical energy when needed.
[0046] The voltage sampling module is used to acquire the voltage of the first voltage signal S+ of the system power supply terminal output through the anti-reverse module and transmit it to the microprocessor.
[0047] The high-voltage sampling module is used to acquire and output the second sampling voltage. and the voltage of the first bus To the microprocessor, the second sampling voltage This represents the voltage of the second voltage signal SS+ after being boosted by the boost isolation module, and the first bus voltage. This indicates the voltage between the current-limiting resistor and the energy storage module.
[0048] The microprocessor has built-in power-on detection reference voltage, boost detection reference voltage, and main contactor detection reference voltage. It receives signals collected by the voltage sampling module and the high-voltage sampling module, compares and analyzes them with the power-on detection reference voltage, boost detection reference voltage, and main contactor detection reference voltage, and then issues a first enable signal EN1 and a second enable signal EN2 respectively. The first enable signal EN1 controls the working state of the boost isolation module, and the second enable signal EN2 is output to the coil control circuit. The coil control circuit controls the engagement of the main contactor to realize functions such as voltage regulation and circuit switching.
[0049] The system power supply terminal, boost isolation module, current limiting resistor and energy storage module are connected in series to form a pre-charging system. The pre-charging system also includes an anti-reverse module, which is connected in series between the system power supply terminal and the boost isolation module. The pre-charging system is used to pre-charge the bus and stores electrical energy through the bus capacitor EC1 in the energy storage module.
[0050] The voltage sampling module acquires and outputs the first sampled voltage to the microprocessor. This indicates the voltage of the first voltage signal S+ at the system power supply terminal output via the anti-reverse module;
[0051] The microprocessor sends a first enable signal EN1 to the boost isolation module, which then starts up and increases the voltage output from the system power supply to the preset target voltage. The boost isolation module then outputs a second voltage signal SS+.
[0052] The high-voltage sampling module acquires and outputs the second sampling voltage. and the voltage of the first bus To the microprocessor, the second sampling voltage This represents the voltage of the second voltage signal SS+ after being boosted by the boost isolation module, and the first bus voltage. This indicates the voltage during bus pre-charging between the current-limiting resistor and the energy storage module.
[0053] The microprocessor sends a second enable signal EN2 to the coil control circuit. At this time, the coil control circuit starts the main contactor to engage. After the main contactor engages, the battery pack output terminal is connected in series with the energy storage module through the main contactor. At this time, the battery pack output terminal, the main contactor and the energy storage module are connected in series to form the main circuit.
[0054] After the battery pack output terminal, main contactor, and energy storage module are connected in series to form the main circuit, the high-voltage sampling module collects and outputs the second bus voltage. To the microprocessor, second bus voltage This indicates the bus voltage between the main contactor and the energy storage module after pre-charging is complete, and is used to detect whether the main contactor is functioning properly.
[0055] The preset target voltage is set to The range of N is: N is the precharge voltage coefficient; This is the output voltage of the battery pack; the range of N is set to... This is because the core purpose of pre-charging is to bring the voltage of the bus capacitor EC1 in the energy storage module close to the battery pack voltage. When the voltage difference is less than 20% (i.e., N≥0.8), the inrush current of the closed main contactor will be controlled within a safe range, and there will be no large current due to direct short circuit.
[0056] A pre-charging method for a high-voltage system of a motor controller, applicable to the aforementioned pre-charging device, includes the following process:
[0057] S1: System power supply terminal outputs power supply signal The voltage sampling module acquires and outputs the first sampled voltage. The microprocessor will then process the first sampled voltage. The microprocessor compares the pre-charge system's voltage with the built-in power-on detection reference voltage to determine whether the pre-charge system is powered on normally.
[0058] The power-on detection reference voltage includes: the first reference voltage. Second reference voltage ;
[0059] S101: When the first sampling voltage Greater than or equal to the first reference voltage And the first sampling voltage Less than or equal to the second reference voltage ,Right now If the input signal at the system power supply terminal is normal, the microprocessor determines that the pre-charging system is powered on normally and executes step S2.
[0060] S102: When the first sampling voltage Less than the first reference voltage or the first sampling voltage Greater than the second reference voltage At that time, that is or This indicates an abnormal input signal at the system power supply end. The microprocessor determines that the pre-charging system has a power-on fault, outputs a fault signal, and the pre-charging system stops.
[0061] S2: If the power-on is normal, the microprocessor starts the boost isolation module. The boost isolation module increases the voltage output from the system power supply terminal to the preset target voltage and outputs the second voltage signal SS+.
[0062] The microprocessor outputs the first enable signal EN1 to start the boost isolation module, and the boost isolation module outputs the second voltage signal SS+.
[0063] In this embodiment, the voltage output from the system power supply terminal is increased to a preset target voltage, and the boost isolation module outputs a second voltage signal SS+, where N ranges from: ;
[0064] The preset target voltage is set to The range of N is: N is the precharge voltage coefficient; This is the output voltage of the battery pack; the range of N is set to... This is because the core purpose of pre-charging is to bring the voltage of the bus capacitor EC1 in the energy storage module close to the battery pack voltage. When the voltage difference is less than 20% (i.e., N≥0.8), the inrush current of the closed main contactor will be controlled within a safe range, and there will be no large current due to direct short circuit.
[0065] The first enable signal EN1 is used to charge the bus capacitor EC1 in the energy storage module through the current-limiting resistor, so that the voltage of the bus capacitor EC1 in the energy storage module is close to the voltage of the battery pack. ).
[0066] S3: The microprocessor receives the second sampling voltage acquired and output by the high-voltage sampling module. and the voltage of the first bus It compares the voltage with the built-in boost detection reference voltage to determine whether the bus pre-charge is normal;
[0067] The microprocessor's built-in boost detection reference voltage includes: a third reference voltage. and the fourth reference voltage ;
[0068] S301: When the second sampling voltage Greater than or equal to the third reference voltage At the same time, it is less than or equal to the fourth reference voltage. And the voltage of the first bus Greater than or equal to the third reference voltage At the same time, it is less than or equal to the fourth reference voltage. ,Right now and If the bus precharge voltage signal is normal, the microprocessor determines that the bus precharge is normal and executes step S4.
[0069] S302: When the second sampling voltage Less than the third reference voltage Second sampling voltage Greater than the fourth reference voltage First bus voltage Less than the third reference voltage Or the voltage of the first bus Greater than the fourth reference voltage That is, when , , or If the signal is abnormal, it indicates that the bus precharge voltage signal is abnormal. The microprocessor determines that the bus precharge is not normal, issues a bus precharge fault signal, and the precharge system stops.
[0070] S4: If the bus pre-charge is normal, start the coil control circuit, the main contactor will engage, and the microprocessor will receive the second bus voltage. The main circuit is detected by comparing the voltage with the built-in main contactor reference voltage.
[0071] The microprocessor sends a second enable signal EN2 to activate the coil control circuit and engage the main contactor. At this point, the pre-charge system is complete, and the bus pre-charge is finished. The battery pack output, main contactor, and energy storage module are connected in series to form the main circuit. The microprocessor's built-in main contactor detects reference voltages including: the fifth reference voltage. and the sixth reference voltage Perform main circuit testing:
[0072] S401: When the second bus voltage Greater than or equal to the fifth reference voltage And less than or equal to the sixth reference voltage That is, when When the main circuit is deemed normal, it indicates that the controller's high-voltage system is complete.
[0073] S402: When the second bus voltage Less than the fifth reference voltage or the voltage of the second bus Greater than the sixth reference voltage That is, when , When the main circuit is detected as abnormal, the EN2 signal is shut off, the microprocessor outputs a main contactor fault, and operation stops.
[0074] This invention utilizes a low-voltage system to pre-charge a high-voltage system without accessing a high-voltage signal. Furthermore, the processing scheme described in this invention provides more precise protection and higher security.
[0075] Replacing the traditional pre-charging solution with a boost isolation module and MCU with a pre-charging relay results in lower hardware costs. It employs multi-level fault detection, covering three types of faults: abnormal input signal, abnormal pre-charging voltage, and abnormal main contactor, thereby increasing the fault identification rate and greatly reducing the risk of fault occurrence.
[0076] An active protection mechanism is also incorporated. Upon detecting a fault, it immediately disconnects the pre-charge circuit or main contactor to prevent the fault from escalating. This is achieved by setting the target voltage after boosting. The adjustable output design (N can be 0.8 to 1, or both 0.8 and 1 are acceptable) allows for adaptation to different high-voltage platforms without hardware replacement.
[0077] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A pre-charging device for a high-voltage system of a motor controller, characterized in that: This includes the system power supply terminal, battery pack output terminal, main contactor, reverse polarity protection module, boost isolation module, microprocessor, energy storage module, current limiting resistor, coil controller circuit, voltage detection module, and high voltage detection module; among which, The system power supply terminal, boost isolation module, current limiting resistor, and energy storage module are connected in series to form a pre-charge system. The pre-charge system also includes an anti-reverse module, which is connected in series between the system power supply terminal and the boost isolation module. The voltage sampling module collects the first sampling voltage and outputs it to the microprocessor. The first sampling voltage represents the voltage of the first voltage signal of the system power supply terminal output through the anti-reverse module. The high voltage sampling module collects the second sampling voltage and the first bus voltage and outputs them to the microprocessor. The second sampling voltage represents the voltage of the second voltage signal after being boosted by the boost isolation module. The first bus voltage represents the voltage during bus pre-charge. The battery pack output terminal, main contactor and energy storage module are connected in series to form the main circuit. The high voltage sampling module collects the second bus voltage and outputs it to the microprocessor. The second bus voltage represents the bus voltage after pre-charging is completed.
2. A pre-charging method for a high-voltage system of a motor controller, applicable to the pre-charging device described in claim 1, characterized in that: include, S1: The system power supply terminal outputs a power supply signal. The voltage sampling module acquires and outputs the first sampled voltage to the microprocessor. The microprocessor compares the first sampled voltage with the built-in power-on detection reference voltage to determine whether the pre-charging system is powered on normally. If the microprocessor determines that the pre-charge system is powered on normally, execute S2; If the microprocessor determines that the precharge system is abnormally powered on, it will output a fault signal and the precharge system will stop. S2: If the power-on is normal, the microprocessor starts the boost isolation module, which increases the voltage output from the system power supply terminal to the preset target voltage and outputs the second voltage signal. S3: The microprocessor receives the second sampling voltage and the first bus voltage collected and output by the high-voltage sampling module, compares them with the built-in boost detection reference voltage, and determines whether the bus pre-charge is normal. If the microprocessor determines that the bus pre-charge is normal, proceed to step S4; If the microprocessor determines that the bus pre-charge is abnormal, it will issue a bus pre-charge fault signal, and the pre-charge system will stop. S4: If the bus pre-charge is normal, start the coil control circuit, the main contactor will engage, and the microprocessor will compare the received second bus voltage with the built-in main contactor detection reference voltage to perform main circuit detection. If the microprocessor determines that the main circuit is normal, it means that the controller's high-voltage system is complete; If the microprocessor determines that the main circuit is abnormal, it will output a fault in the main contactor and stop operation.
3. The pre-charging method according to claim 2, characterized in that: In S1, the power-on detection reference voltage includes a first reference voltage and a second reference voltage. The process of determining whether the pre-charge system is powered on normally includes: S101: When the first sampling voltage is greater than or equal to the first reference voltage and the first sampling voltage is less than or equal to the second reference voltage, the microprocessor determines that the pre-charging system is powered on normally and executes step S2. S102: When the first sampling voltage is less than the first reference voltage, or the first sampling voltage is greater than the second reference voltage, the microprocessor determines that the pre-charge system has a power-on fault, outputs a fault signal, and the pre-charge system stops.
4. The pre-charging method according to claim 2, characterized in that: In step S2, the microprocessor outputs a first enable signal to start the boost isolation module.
5. The pre-charging method according to claim 2, characterized in that: S2, wherein the voltage output from the system power supply terminal is increased to a preset target voltage, the target voltage being set to... The range of N is: N is the precharge voltage coefficient; It is the output voltage of the battery pack.
6. The pre-charging method according to claim 2, characterized in that: The aforementioned S3, where the microprocessor's built-in boost detection reference voltage includes a third reference voltage and a fourth reference voltage, determines whether the bus pre-charge is normal by including: S301: When the second sampling voltage is greater than or equal to the third reference voltage and less than or equal to the fourth reference voltage, and the first bus voltage is greater than or equal to the third reference voltage and less than or equal to the fourth reference voltage, the microprocessor determines that the bus pre-charge is normal and executes step S4. S302: When the second sampling voltage is less than the third reference voltage, the second sampling voltage is greater than the fourth reference voltage, the first bus voltage is less than the third reference voltage, or the first bus voltage is greater than the fourth reference voltage, the microprocessor determines that the bus pre-charging is abnormal, issues a bus pre-charging fault signal, and the pre-charging system stops.
7. The pre-charging method according to claim 2, characterized in that: In S4, the microprocessor sends a second enable signal to start the coil control circuit, at which point the main contactor closes.
8. The pre-charging method according to claim 7, characterized in that: In S4, the microprocessor-built-in main contactor detects reference voltages including a fifth reference voltage and a sixth reference voltage; the main circuit detection includes: S401: When the voltage of the second bus is greater than or equal to the fifth reference voltage and less than or equal to the sixth reference voltage, the main circuit is judged to be normal, indicating that the high-voltage system of the controller is completed. S402: When the voltage of the second bus is less than the fifth reference voltage, or the voltage of the second bus is greater than the sixth reference voltage, the main circuit is determined to be abnormal, the second enable signal is turned off, the microprocessor outputs a main contactor fault, and operation is stopped.