A new energy vehicle active discharging method and system based on DCDC

Abstract

The application discloses a DCDC-based active discharge method and system for new energy vehicles, and relates to the technical field of high-voltage safety of new energy vehicles.The method comprises the following steps: after receiving an electric control active discharge instruction, the state of a motor control system is acquired, and the motor winding is controlled to perform active discharge; the bus voltage is acquired during the active discharge of the motor winding; whether the discharge condition is met is determined according to the state of the motor control system; whether the motor winding is successfully discharged is determined according to whether the bus voltage is less than a set first voltage threshold after the set time of the active discharge of the motor winding; and the DCDC is controlled to perform active discharge when the motor control system does not meet the discharge condition or the motor winding cannot be successfully discharged.Through the construction of a dual-channel redundant discharge architecture with the DCDC as a backup discharge channel, and the accurate determination of the switching time based on the state of the motor control system, it is ensured that the high-voltage active discharge can be reliably completed under any working condition, and the functional safety level of the high-voltage system of the new energy vehicle is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of high-voltage safety technology for new energy vehicles, and in particular to an active discharge method and system for new energy vehicles based on DC-DC converters. Background Technology

[0002] To ensure high-voltage safety and avoid the risk of electric shock from residual electrical energy after a power outage in new energy vehicles, relevant standards stipulate that the motor control unit (MCU) must rapidly reduce the bus voltage to a safe threshold during power-off, collisions, or maintenance.

[0003] Existing technologies include a method that first discharges through the motor windings, and then actively discharges by charging the low-voltage battery through a DC-DC converter when the motor windings fail to discharge.

[0004] The above scheme has the following drawbacks: First, it uses the motor winding to discharge. When the motor winding discharge is successful, the discharge stops. When the motor winding discharge fails, the DC-DC discharge function is activated. The discharge response time is relatively long, which may lead to the technical problem that the high-voltage bus voltage cannot be reduced to below the safety threshold within the specified time. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for active discharge of new energy vehicles based on DC-DC converters, so as to solve the technical problem that the high-voltage bus voltage cannot be reduced to below the safety threshold within a specified time in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: Firstly, a DC-DC-based active discharge method for new energy vehicles is proposed, including: Upon receiving the active discharge command from the electronic control system, the status of the motor control system is obtained, and the motor windings are controlled to actively discharge. During the active discharge process of the motor windings, the bus voltage is obtained; Based on the status of the motor control system, determine whether the motor control system has the conditions for discharge; Based on whether the bus voltage is less than the set first voltage threshold after the motor winding actively discharges for a set time, it can be determined whether the motor winding can discharge successfully. When the motor control system does not meet the discharge conditions or the motor windings cannot discharge successfully, the DC-DC converter is controlled to perform active discharge.

[0007] Furthermore, when the DC-DC converter is actively discharging, the low-voltage battery status is obtained; When the low-voltage battery is in a charging-enabled state, control the DC-DC converter to charge the low-voltage battery. When the low-voltage battery is in a state where charging is prohibited, the DC-DC converter is controlled to charge the discharge resistor.

[0008] Furthermore, the state of charge and temperature of the low-voltage battery are obtained; When the low-voltage battery is fully charged or its temperature is greater than or equal to a set temperature threshold, the low-voltage battery is determined to be in a state where charging is prohibited. When the low-voltage battery is not at full charge and its temperature is below the set temperature threshold, the low-voltage battery is determined to be in a state where charging is permitted.

[0009] Furthermore, when the motor control system meets the discharge conditions and the motor windings can successfully discharge, the motor windings are controlled to continue to actively discharge until the bus voltage is lower than the safe voltage threshold.

[0010] Furthermore, after the set time for the motor winding to actively discharge, if the bus voltage is less than the set first voltage threshold, it is determined that the motor winding can successfully discharge. If the bus voltage is greater than or equal to the set first voltage threshold after the motor winding has been actively discharged for a set time, it is determined that the motor winding has failed to discharge successfully.

[0011] Furthermore, based on the status of the motor control system, if it is determined that the motor control system is faulty or in ASC state, it is determined that the motor control system does not meet the conditions for discharge. If the motor control system is determined to be fault-free and not in ASC state based on its status, then the motor control system is deemed to be ready to discharge.

[0012] Secondly, a DC-DC-based active discharge system for new energy vehicles is proposed, including: The instruction receiving unit is used to obtain the status of the motor control system and control the motor windings to perform active discharge after receiving the electronic control active discharge instruction. The bus voltage acquisition unit is used to acquire the bus voltage during the active discharge process of the motor windings. The determination unit is used to determine whether the motor control system has the conditions for discharge based on the status of the motor control system; and to determine whether the motor winding can successfully discharge based on whether the bus voltage is less than the set first voltage threshold after the motor winding actively discharges for a set time. The control unit is used to control the DC-DC converter to actively discharge when the motor control system does not meet the discharge conditions or the motor windings cannot discharge successfully.

[0013] Thirdly, a computer device is proposed, the device comprising: A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by the processor, implements the active discharge method for new energy vehicles based on DC-DC converters proposed in the first aspect.

[0014] Fourthly, a computer-readable storage medium is proposed, wherein the computer-readable storage medium stores a computer program adapted to be loaded and executed by a processor, which is a DC-DC-based active discharge method for new energy vehicles proposed in the first aspect.

[0015] Fifthly, a computer program product is proposed, which includes a computer program. When the computer program is executed by a processor, it implements the active discharge method for new energy vehicles based on DC-DC proposed in the first aspect.

[0016] The present invention has the following beneficial effects: This invention proposes a DC-DC-based active discharge method and system for new energy vehicles. Upon receiving an active discharge command from the electronic control system, the method simultaneously determines whether the motor control system meets the discharge conditions and whether the motor windings can successfully discharge. If the motor control system does not meet the discharge conditions or the motor windings cannot successfully discharge, the DC-DC-based system is directly controlled to perform active discharge. By determining in advance whether the motor windings can successfully discharge and whether the discharge conditions are met, the DC-DC-based system is controlled to perform active discharge in a timely manner, instead of first discharging through the motor windings and then activating the DC-DC-based system if the discharge fails. This shortens the discharge response time, ensures that the bus voltage is reduced to below the safety threshold within a specified time, and improves high-voltage safety. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of the active discharge method for new energy vehicles based on DC-DC converter according to the present invention. Figure 2 This is a schematic diagram of the hardware architecture of the active discharge method application system for new energy vehicles based on DC-DC according to the present invention. Detailed Implementation

[0018] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While some embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this application. It should be understood that the drawings and embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application. The term "comprising" and similar terms should be understood as open-ended inclusion, i.e., "including but not limited to". The term "based on" should be understood as "at least partially based on". The term "one embodiment" or "this embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc., may refer to different or the same objects.

[0019] To facilitate understanding of the technical solution of this application, the core terms involved in this application will be explained first.

[0020] The motor control system (MCU) is the core controller of the electric drive system of new energy vehicles. It is responsible for receiving instructions from the vehicle controller, controlling the power switching devices of the inverter, driving the motor, and also undertaking the active discharge function of the motor windings. In this application, the MCU is also responsible for acquiring the status of the motor control system, determining the discharge conditions, determining whether the motor windings have successfully discharged, and controlling the DC-DC converter to perform active discharge.

[0021] DC-DC converters are key components of power systems in new energy vehicles. Their main function is to convert the DC voltage of the high-voltage power battery into a low-voltage DC voltage to power onboard low-voltage electrical equipment and charge the low-voltage battery. In this application, the DC-DC converter functions as a backup active discharge channel, selecting to charge the low-voltage battery or the bleeder resistor based on the low-voltage battery's state, thereby achieving active discharge of the high-voltage bus.

[0022] High-voltage bus capacitors: High-voltage bus capacitors are connected between the positive and negative terminals of the high-voltage bus and are the main discharge targets for active discharge.

[0023] Bus voltage: Bus voltage is the voltage across the high-voltage bus capacitor. During active discharge, it must drop below the safe voltage threshold within a specified time.

[0024] Active discharge refers to the process by which a new energy vehicle, when powered off, involved in a collision, or undergoing maintenance, rapidly reduces the voltage of the high-voltage bus to below a safe threshold through active control measures. Relevant standards specify the active discharge time and the safe voltage threshold. For example, the national standard GB / T 18488 stipulates that the active discharge time should not exceed 3 seconds, and the safe voltage threshold is 60V.

[0025] To ensure high-voltage safety and avoid the risk of electric shock caused by residual electrical energy after a power outage in new energy vehicles, the motor control unit (MCU) must rapidly reduce the bus voltage to a safe threshold (≤60V) during power-off, collision, or maintenance to meet national standard requirements (GB / T 18488 specifies an active discharge time of ≤3 seconds).

[0026] In existing technologies, the mainstream active discharge schemes used in new energy vehicles include single-channel schemes and multi-stage serial schemes.

[0027] Single-channel solutions include: (1) Motor winding discharge: Inject D-axis current (Id) to consume energy using winding resistance, and set Q-axis current (Iq) to zero to avoid torque output, achieving millisecond-level discharge but relying on the health status of the system; (2) Dedicated resistor discharge: The circuit of a low resistance resistor (e.g., 5Ω) is closed by an electronic switch (e.g., IGBT), and the discharge is completed within 2-3 seconds. It has high reliability but increases hardware cost. (3) Bridge arm direct discharge: control power devices generate losses through high-frequency switching, which is low in cost but poses a risk of current surge.

[0028] This single-channel scheme primarily utilizes the motor windings for active discharge. Upon receiving the active discharge command, the MCU (Motor Control Unit) of the drive motor system discharges the bus capacitor through the motor windings. While this scheme can achieve millisecond-level rapid discharge when the motor control system is in good health, it suffers from the following significant drawbacks: Firstly, when the motor control system is in an Active Short Circuit (ASC) state, the motor windings are forcibly short-circuited, and the MCU cannot execute controlled winding discharge, rendering the active discharge function completely ineffective. Collision conditions are the most typical ASC triggering scenario, and these are precisely the scenarios where high-voltage safety requirements are most urgent; failure of existing technologies in this scenario is particularly dangerous.

[0029] Secondly, when there is a fault in the motor control system, the motor winding discharge function will also fail. Specific fault types include: resolver sensor failure (resulting in the loss of rotor position information and inability to accurately control the D-axis current), current sensor failure (resulting in the loss of phase current feedback information and inability to achieve current closed-loop control), motor body failure (winding open circuit or short circuit, energy cannot be consumed through the winding), drive circuit failure (PWM signal cannot be output normally, power switching devices cannot work properly), and power module failure (switching devices are damaged, current loop cannot be turned on or off).

[0030] Third, some other undetectable faults caused the motor windings to fail to discharge.

[0031] The multi-stage serial discharge scheme involves multiple pathways and controllers, sequentially attempting active discharge through multiple control components such as the motor windings, generator windings, DC-DC control module, battery management system pre-charge resistor, air conditioning system compressor, and heating system thermistor. Taking motor winding discharge and DC-DC discharge as examples, the following drawbacks of the multi-stage serial scheme are illustrated: First, the motor windings are used for discharge. When the motor windings discharge successfully, the discharge stops. When the motor windings fail to discharge, the DC-DC discharge function is activated. The discharge response time is relatively long, which can easily lead to technical problems such as the high-voltage bus voltage failing to drop below the safety threshold within the specified time.

[0032] To address the aforementioned issues, this invention proposes an active discharge method for new energy vehicles based on DC-DC converters. Upon receiving an active discharge command from the electronic control system, the method simultaneously checks whether the motor control system meets the discharge conditions and whether the motor windings can successfully discharge. If the motor control system does not meet the discharge conditions or the motor windings cannot successfully discharge, the DC-DC converter is directly controlled to perform active discharge, shortening the discharge response time and ensuring that the bus voltage is reduced to below the safety threshold within a specified time. This improves high-voltage safety and ensures that high-voltage active discharge can be reliably completed under any operating conditions.

[0033] The core technical concept of this invention is as follows: Upon receiving the active discharge command from the electric control system, the system simultaneously determines whether the motor control system meets the discharge conditions and whether the motor windings can successfully discharge. When the motor control system does not meet the discharge conditions or the motor windings cannot successfully discharge, the DC-DC converter is directly controlled to perform active discharge. By determining in advance whether the motor windings can successfully discharge and whether the discharge conditions are met, the DC-DC converter is controlled to perform active discharge in a timely manner, instead of first discharging through the motor windings and then starting the DC-DC converter to perform active discharge if the discharge fails. This shortens the discharge response time, ensures that the bus voltage is reduced to below the safety threshold within the specified time, improves high-voltage safety, and ensures that high-voltage active discharge can be reliably completed under any operating conditions.

[0034] Figure 2 A schematic diagram of the hardware architecture of the active discharge method for new energy vehicles based on DC-DC converter of the present invention is shown. Figure 2 As shown, the hardware architecture of the application system of the present invention includes a vehicle controller (VCU), a motor controller (MCU), a DC-DC converter, a high-voltage bus capacitor (C1), a power battery pack, a main positive relay (K1), a main negative relay (K2), a low-voltage battery, a discharge resistor, a drive motor, and a vehicle CAN bus.

[0035] The vehicle control unit (VCU) communicates with the MCU via the vehicle's CAN bus. Upon receiving a power-down request or collision signal, it sends an active discharge command to the MCU and receives the discharge result reported by the MCU.

[0036] The vehicle control unit (VCU) communicates with the MCU via the vehicle's CAN bus. Upon receiving a power-down request or collision signal, it sends an active discharge command to the MCU and receives the discharge result reported by the MCU.

[0037] The motor controller (MCU) is connected to the drive motor via a three-phase cable, communicates with the vehicle control unit (VCU) via the vehicle's CAN bus, and also communicates with the DC-DC converter. The MCU is the main execution carrier of the method of this invention, responsible for acquiring the status of the motor control system, controlling the discharge of the motor windings, determining whether the motor control system has the conditions for discharge and whether the discharge can be successful, controlling the DC-DC converter to actively discharge when necessary, and receiving status feedback from the DC-DC converter.

[0038] The high-voltage side of the DC-DC converter is connected to the positive and negative terminals of the high-voltage bus, while the low-voltage side is connected to both the low-voltage battery and the bleeder resistor. After receiving a discharge control command from the MCU, the DC-DC converter adjusts the duty cycles of the primary and secondary power transistors to convert the energy from the high-voltage bus capacitor into low-voltage energy via a transformer, which is then output to the low-voltage side (either the low-voltage battery or the bleeder resistor), thus achieving energy transfer from the high-voltage side to the low-voltage side. Depending on the state of the low-voltage battery, the DC-DC converter adaptively selects to charge the low-voltage battery (charging enabled) or charge the bleeder resistor (charging disabled).

[0039] The positive terminal of the high-voltage bus capacitor C1 is connected to the positive terminal of the power battery pack via the main positive relay K1, and the negative terminal is connected to the negative terminal of the power battery pack via the main negative relay K2. When power is off, K1 and K2 disconnect, and the high-voltage bus capacitor is electrically isolated from the power battery pack, becoming the main discharge target for active discharge.

[0040] Low-voltage batteries, typically 12V lead-acid or lithium batteries, are the preferred energy receivers during DC-DC discharge. When the low-voltage battery is in a charging-prohibited state, the DC-DC converter switches to charging the bleeder resistor to dissipate energy.

[0041] The bleeder resistor is integrated inside the DC-DC converter or is set up in conjunction with the DC-DC converter. Its rated power is not lower than the rated output power of the DC-DC converter, ensuring that it can dissipate the energy of the high-voltage bus capacitor with sufficient power when the low-voltage battery is prohibited from charging.

[0042] It should be understood that the above system architecture is described for illustrative purposes only. This invention can also be applied to other types of new energy vehicles such as plug-in hybrid electric vehicles and fuel cell vehicles, and these extensions or modifications are all within the protection scope of this application.

[0043] This embodiment provides a DC-DC-based active discharge method for new energy vehicles. Figure 1 A flowchart illustrating the method is shown. Figure 2A detailed flowchart of the DC-DC active discharge control logic is shown. Figure 1 and Figure 2 As shown, the method of this embodiment includes the following steps S101 to S104.

[0044] Step S101: Receive the active discharge command from the electric control system, obtain the status of the motor control system, and control the motor windings to start active discharge.

[0045] When the driver manually poweres down the vehicle, or when a collision occurs, the Vehicle Control Unit (VCU) sends an active electronic discharge command to the Microcontroller Unit (MCU). Upon receiving this command, the MCU immediately performs the following operations: First, the status of the motor control system is obtained. The MCU reads the following status information through its internal diagnostic mechanism: (1) Resolver sensor working status: Detect whether the resolver sensor has faults such as open circuit, short circuit, or abnormal signal. The resolver sensor is used to detect the rotor position of the motor and is a key input of the vector control algorithm. If the resolver sensor fails, the MCU cannot obtain accurate rotor position information, cannot accurately control the D-axis current, and the motor winding discharge function will fail.

[0046] (2) Current sensor operating status: Detect whether the current sensor has faults such as open circuit, short circuit, zero drift, or abnormal gain. The current sensor is used to detect the three-phase current of the motor and is the key feedback for current closed-loop control. If the current sensor fails, the MCU cannot obtain accurate phase current information, cannot realize current closed-loop control, and the motor winding discharge function will fail.

[0047] (3) Motor body working status: Check whether there are faults such as open circuit, short circuit, and inter-turn short circuit in the motor windings. If the motor body is faulty, energy cannot be consumed through the windings, and the motor winding discharge function will fail.

[0048] (4) Driving circuit working status: Detect whether there is power supply abnormality, PWM signal failure, driving chip failure, etc. in the driving circuit. The driving circuit is responsible for amplifying the PWM signal output by the MCU and driving the power switching device. If the driving circuit fails, the power switching device cannot work normally, and the motor winding discharge function fails.

[0049] (5) Power module operating status: Detect whether the power module (IGBT or MOSFET) has over-temperature protection triggering, short-circuit protection triggering, open-circuit fault, etc. If the power module fails, the current loop cannot be turned on or off, and the motor winding discharge function fails.

[0050] (6) Whether the system is in active short circuit (ASC) state: detect whether the system automatically enters ASC state due to collision signal or other dangerous operating conditions. In ASC state, the upper or lower bridge arm of the inverter is fully connected to form a short circuit loop, the motor winding is forcibly short-circuited, the MCU cannot perform controlled winding discharge, and the motor winding discharge function fails.

[0051] The above status information constitutes a complete description of the motor control system status, providing an accurate basis for determining the discharge conditions in the subsequent step S103.

[0052] Secondly, while acquiring the status of the motor control system, the MCU initiates active discharge of the motor windings. The MCU injects D-axis current into the three-phase windings of the motor through a vector control algorithm. The D-axis current is determined through calibration. For example, if the D-axis current is set to 50%-100% of the rated current, the energy in the high-voltage bus capacitor is consumed by the winding resistance. At the same time, the Q-axis current is set to zero to avoid generating electromagnetic torque. If torque is generated, it will cause the motor to rotate, posing a mechanical safety risk.

[0053] The technical effect of this step is that by synchronously acquiring the system status and initiating winding discharge, necessary information is provided for subsequent discharge condition judgment and whether the motor winding can discharge successfully without adding additional time delay, thus achieving a rapid response in the active discharge process.

[0054] Step S102: Obtain the bus voltage during the active discharge process of the motor windings.

[0055] While controlling the motor windings to actively discharge, the MCU simultaneously acquires the bus voltage Vbus in real time via a high-voltage bus voltage sensor. The sampling period is typically 1ms to 10ms to ensure the real-time performance and accuracy of the bus voltage data. The acquired bus voltage data is used for two purposes: firstly, as a basis for determining whether the motor winding discharge was successful in step S103; and secondly, as a basis for determining whether the discharge was completed.

[0056] The technical effect of this step is that real-time acquisition of the bus voltage is the core feedback signal for active discharge control, ensuring that the discharge judgment logic is based on the actual system state and avoiding misjudgment.

[0057] Step S103: Based on the status of the motor control system, determine whether the motor control system has the conditions for discharge; based on whether the bus voltage is less than the set first voltage threshold after the motor winding actively discharges for a set time, determine whether the motor winding can discharge successfully.

[0058] Based on the motor control system status obtained in step S101, the MCU determines whether the motor control system meets the discharge conditions according to the following logic: Based on the status of the motor control system, if it is determined that the motor control system has a fault or is in ASC state, it is determined that the motor control system does not have the conditions for discharge. If the motor control system is determined to be fault-free and not in ASC state based on its status, then the motor control system is deemed to be ready to discharge.

[0059] ASC state (Active Short Circuit): When the electric drive system detects a collision signal or other dangerous operating condition, to protect the power devices and motor windings, the system automatically turns on all of the upper or lower bridge arms of the inverter, forming a short circuit loop. At this time, the motor windings are forcibly short-circuited, and the controlled active discharge function cannot be performed. In this application, the ASC state is one of the conditions for determining that the motor control system does not meet the conditions for discharge.

[0060] Specifically, if, based on the status of the motor control system, one or more of the following faults are identified: resolver sensor failure, current sensor failure, motor body failure, drive circuit failure, and power module failure, the motor control system is deemed to have a fault; if none of the above faults are identified, the motor control system is deemed to have no fault.

[0061] The technical benefits of this step are as follows: By accurately enumerating fault types and detecting ASC status, the system quickly skips the invalid winding discharge wait when discharge conditions are not met, and directly activates the DC-DC backup discharge channel, significantly shortening the discharge response time under fault conditions and improving high-voltage safety. The switching criteria of this invention are more precise and direct. Existing technologies cannot accurately identify the specific fault type within the motor control system. For example, when the motor control system has a resolver sensor fault but the motor speed is just below the threshold, existing technologies will still attempt to discharge through the motor windings, resulting in invalid waiting. This invention directly detects the status of the motor control system and immediately switches to DC-DC for active discharge when a fault or ASC status is detected, significantly improving response speed. Furthermore, existing technologies rely on collision detection signals to determine whether to enter passive discharge mode. When the system enters the ASC state due to other dangerous conditions (non-collision), the switching logic of existing technologies may not respond in time. This invention directly detects the ASC status, and regardless of the cause of the ASC status trigger, it can switch to the DC-DC backup discharge channel in time, making the switching criteria more comprehensive and reliable.

[0062] Upon receiving an active discharge command from the electric control system, this invention, while acquiring the status of the motor control system, also synchronously controls the motor windings to actively discharge. By analyzing the active discharge duration of the motor windings and the bus voltage during the discharge process, it can predict in advance whether the motor windings can successfully discharge. The specific judgment logic is as follows: After the set time for active discharge of the motor windings, if the bus voltage is less than the set first voltage threshold, it is determined that the motor windings can successfully discharge. If the bus voltage is greater than or equal to the set first voltage threshold after the motor winding has been actively discharged for a set time, it is determined that the motor winding has failed to discharge successfully.

[0063] When the MCU initiates active discharge of the motor windings, it also starts a discharge timeout timer. The default value for the timeout threshold T_set (i.e., the "set time") is 500ms, and the calibrable range is 100ms to 3000ms. After T_set expires, the MCU reads the current bus voltage Vbus and compares it with the set first voltage threshold V1. The first voltage threshold V1 is usually set to 100V to 200V and can be calibrated according to the actual system parameters, and is higher than the safe voltage threshold of 60V.

[0064] The technical advantages of this step are as follows: Employing a dual criterion of "set time + voltage threshold," it can promptly identify low discharge efficiency or potential faults in the motor windings. For example, if the voltage does not drop below V1 after the timeout, it may indicate abnormal winding resistance, abnormal current control, or other potential faults. It also avoids misjudgments caused by brief disturbances. The judgment logic is simple and reliable, and the engineering implementation is simple. Compared to existing technologies that rely on a step-by-step failure trial criterion, the criteria of this invention are more direct and accurate: existing technologies require sequentially trying each level of discharge path, switching to the next level only after each level fails, resulting in a long accumulated waiting time; this invention, through dual criteria, can predict whether the motor windings will successfully discharge in a single judgment, eliminating the need for step-by-step trials and resulting in faster judgment speed.

[0065] Step S104: When the motor control system does not meet the discharge conditions or the motor windings cannot discharge successfully, control the DC-DC converter to perform active discharge. When the motor control system meets the discharge conditions and the motor windings can discharge successfully, the motor windings are controlled to continue to discharge actively until the bus voltage is lower than the safe voltage threshold.

[0066] When the motor control system meets the discharge conditions and the motor windings can successfully discharge, the MCU continues to control the motor windings to actively discharge, continuously monitoring the bus voltage Vbus until Vbus drops below the safe voltage threshold. Afterward, the MCU stops the motor windings from discharging and reports the successful active discharge status to the VCU. The VCU confirms that the high-voltage bus has been safely discharged and continues to issue subsequent power-down commands to complete the complete power-down of the vehicle.

[0067] The technical benefits of this step are: under normal operating conditions where the motor windings are successfully discharged, the rapid discharge capability of the motor windings is fully utilized, eliminating the need to start the DC-DC converter, reducing system power consumption, and shortening the discharge time.

[0068] When the motor control system does not meet the discharge conditions, or the motor windings cannot discharge successfully, the MCU controls the DC-DC converter to perform active discharge. The detailed control logic for active DC-DC discharge is as follows: When controlling the DC-DC converter to actively discharge, the low-voltage battery status is obtained; When the low-voltage battery is in a charging-enabled state, control the DC-DC converter to charge the low-voltage battery. When the low-voltage battery is in a state where charging is prohibited, the DC-DC converter is controlled to charge the discharge resistor.

[0069] Among these, the state of charge and temperature of the low-voltage battery are obtained; When the low-voltage battery is fully charged or its temperature is greater than or equal to a set temperature threshold, the low-voltage battery is determined to be in a state where charging is prohibited. When the low-voltage battery is not at full charge and its temperature is below the set temperature threshold, the low-voltage battery is determined to be in a state where charging is permitted.

[0070] The state of charge (SOC) and temperature (T_bat) of the low-voltage battery are obtained through a low-voltage battery management system (or directly through voltage and temperature sensors). The SOC reflects the current level of electrical charge stored in the battery, and the temperature (T_bat) reflects the current thermal state of the battery.

[0071] When the state of charge (SOC) of the low-voltage battery reaches 100% or exceeds the set full-load threshold SOC_max, the low-voltage battery is determined to be fully charged; when the SOC of the low-voltage battery is lower than SOC_max, the low-voltage battery is determined to be not fully charged.

[0072] SOC_max is typically 95% to 100% and can be calibrated.

[0073] The temperature threshold T_max can be calibrated, typically ranging from 50°C to 60°C.

[0074] When the low-voltage battery is in a charging-permitted state, the DC-DC converter converts the electrical energy from the high-voltage bus capacitor into low-voltage electrical energy, which is then output to the low-voltage battery terminal to charge the battery. The energy transfer path is: high-voltage bus capacitor → DC-DC converter → low-voltage battery. The electrical energy of the high-voltage bus capacitor is continuously transferred to the low-voltage battery, and the bus voltage continuously decreases.

[0075] In this invention, the DC-DC converter converts high-voltage bus power into low-voltage power by adjusting the duty cycle of the primary / secondary power transistors, and then charges the low-voltage battery. This fully utilizes the inherent high-to-low voltage energy transfer capability of the DC-DC converter, achieving energy recovery while the low-voltage battery is allowed to charge. This process both actively discharges the high-voltage bus and replenishes the low-voltage battery, resulting in significantly higher energy utilization than the high-frequency switching power consumption method of the comparative patent. Furthermore, charging the low-voltage battery reduces the thermal stress on the high-voltage side power devices (energy is transferred to the low-voltage side instead of dissipated on the high-voltage side), improving system reliability.

[0076] During charging, the state of charge (SOC) and temperature (T_bat) of the low-voltage battery are continuously monitored. If the SOC reaches full charge or the T_bat reaches the temperature threshold (T_max) during charging, the system immediately switches to charging the discharge resistor via DC-DC converter to continue discharging, ensuring that the discharge process is not interrupted due to changes in the battery's state.

[0077] This invention ensures that the DC-DC discharge channel remains uninterrupted under any low-voltage side condition by switching to a charging mode for the discharge resistor when the low-voltage battery is prohibited from charging, thus completely solving the problem of discharge channel interruption caused by changes in the low-voltage side condition.

[0078] When the low-voltage battery is in a non-charging state, the DC-DC converter converts the energy from the high-voltage bus capacitor into low-voltage energy, which is then output to the bleed resistor and dissipated as heat. The energy transfer path is: high-voltage bus capacitor → DC-DC converter → bleed resistor R_dis (heat dissipation). The energy of the high-voltage bus capacitor is continuously consumed, and the bus voltage continuously decreases. The rated power of the bleed resistor is not less than the rated output power of the DC-DC converter to ensure that the energy dissipation rate meets the active discharge time requirements.

[0079] The technical effect of this step: Existing DC-DC discharge channels do not detect or judge the state of charge (SOC) and temperature of the low-voltage battery. This leads to the DC-DC discharge channel (if using a battery charging method) being interrupted due to the inability to transfer energy to the low-voltage side or safety risks when the low-voltage battery is fully charged or its temperature exceeds a threshold and charging is prohibited. This invention, by acquiring two key parameters, SOC and temperature, provides a data foundation for subsequent low-voltage battery state judgment and adaptive switching of charging / discharging resistor modes, fundamentally solving the problem of discharge channel interruption caused by changes in the low-voltage side state. Furthermore, this invention accurately identifies the low-voltage battery state through SOC and temperature dual-parameter judgment, providing a decision basis for subsequent adaptive switching of charging / discharging resistor modes, ensuring that the DC-DC discharge channel remains uninterrupted under any low-voltage side state.

[0080] Step S105: The bus voltage drops below the safe voltage threshold, completing the active discharge.

[0081] Regardless of whether motor winding discharge or DC-DC discharge is used, the MCU continuously monitors the bus voltage Vbus. When Vbus drops below the safe voltage threshold of 60V within a preset time (usually 1 to 5 seconds, calibrable), the MCU determines that the active discharge is complete and reports a successful active discharge status to the VCU. The VCU confirms that the high-voltage bus has been safely discharged and continues to issue subsequent power-down commands to complete the complete power-down of the vehicle. If Vbus fails to drop below 60V within the preset time, the MCU determines that the active discharge has failed and reports a failure status to the VCU. The VCU takes corresponding safety measures based on the fault information, such as triggering an alarm, recording a fault code, or preventing the vehicle from being powered on again.

[0082] The technical benefits of this step are: using the bus voltage dropping below the safety threshold as the criterion for determining the completion of active discharge, which meets the discharge requirements stipulated in relevant standards, and the judgment logic is simple and clear, making it easy to implement and verify in engineering.

[0083] Through the above steps S101 to S105, the active discharge method for new energy vehicles based on DC-DC converters in this embodiment achieves the following technical effects: First, the dual-channel redundant architecture, combined with precise judgment of the motor control system status, significantly improves the switching response speed. This invention constructs a dual-channel redundant discharge architecture with a DC-DC converter as the backup discharge channel and an MCU as the core control unit. Upon receiving an active discharge command from the electronic control unit, it initiates active discharge based on the motor control system status and the control of the motor windings. Simultaneously, it precisely judges whether the motor control system meets the discharge conditions and whether the motor windings can successfully discharge. When the motor control system does not meet the discharge conditions or the motor windings cannot successfully discharge, it directly controls the DC-DC converter to initiate active discharge. By judging in advance whether the motor windings can successfully discharge and whether the discharge conditions are met, it promptly controls the DC-DC converter to initiate active discharge, without first attempting discharge through the motor windings and then restarting the DC-DC converter if the discharge fails. This eliminates the need to wait for successive failure attempts or rely on collision detection signals. Compared with existing technologies that rely on collision detection or motor speed judgment for step-by-step switching, the switching criteria of this invention are more accurate and direct, shortening the discharge response time and significantly improving the switching response speed. It fundamentally solves the problem of insufficient reliability caused by relying solely on motor winding discharge in existing technologies and the response delay problem caused by inaccurate switching criteria in multi-stage serial discharge schemes. It significantly improves the reliability and rapid response capability of the active discharge function, ensuring that the bus voltage is reduced to below the safety threshold within a specified time, thereby improving high-voltage safety.

[0084] Secondly, the DC-DC converter achieves high-to-low voltage energy transfer by adjusting the duty cycle of the primary / secondary power transistors, resulting in higher energy utilization. The working principle of the DC-DC converter in this invention is as follows: by adjusting the duty cycle of the primary and secondary power transistors, the electrical energy of the high-voltage bus capacitor is converted into low-voltage electrical energy via a transformer and output to the low-voltage side (low-voltage battery or bleed resistor). This method is fundamentally different from the existing technology where the "DC-DC control module uses high-frequency switching to dissipate power and / or the first resistor for active discharge": existing DC-DC converters only dissipate energy on the high-voltage side through high-frequency switching, resulting in complete energy waste; this invention fully utilizes the inherent high-to-low voltage energy transfer capability of the DC-DC converter, enabling energy recovery by charging the low-voltage battery when it is allowed to charge, resulting in higher energy utilization. Simultaneously, it reduces the thermal stress on the high-voltage side power devices, improving system reliability.

[0085] Third, this invention innovatively introduces a dual-parameter adaptive switching mechanism for low-voltage battery SOC and temperature, completely solving the problem of discharge channel interruption caused by changes in the low-voltage side state. This invention acquires two key parameters—the state of charge (SOC) and temperature—of the low-voltage battery and adaptively determines whether the battery is in a charging-allowed or charging-prohibited state: when the low-voltage battery's SOC is not fully charged and the temperature is normal, the DC-DC converter is controlled to charge the low-voltage battery, achieving energy recovery; when the low-voltage battery's SOC is fully charged or the temperature exceeds a threshold, it automatically switches to charging the bleeder resistor, consuming the energy of the high-voltage bus capacitor through the bleeder resistor, ensuring that the DC-DC discharge channel is uninterrupted under any low-voltage side state. The existing technologies do not involve the detection and adaptive switching of low-voltage battery status. In the prior art, when the low-voltage battery is fully loaded or overheated, its DC-DC discharge channel (if the battery is charged) will be interrupted because it cannot transfer energy to the low-voltage side, resulting in active discharge failure. The present invention completely solves this problem through a dual-parameter adaptive switching mechanism, ensuring that the discharge process can continue under any operating conditions until the high-voltage bus voltage drops below the safety threshold, which significantly improves the high-voltage safety assurance capability of the system under extreme operating conditions.

[0086] Fourth, the invention employs a dual criterion of "set time + first voltage threshold" to predict whether the motor windings can successfully discharge, ensuring objective and reliable judgment logic. This invention uses a dual criterion of "set time + first voltage threshold" to predict whether the motor windings can successfully discharge: after the set time for active discharge of the motor windings has elapsed, if the bus voltage is less than the set first voltage threshold, it is determined that the discharge was successful, and the motor windings continue discharging until below the safe voltage threshold; if the bus voltage is greater than or equal to the first voltage threshold, it is determined that the discharge was unsuccessful, and the system switches to the DC-DC discharge channel. This dual criterion can predict whether the motor windings can successfully discharge in advance, while avoiding misjudgments caused by brief disturbances. The judgment logic is objective and reliable, and the engineering implementation is simple. Compared with existing technologies that rely on a step-by-step failure trial criterion, the criterion of this invention is more direct and accurate, and it shortens the judgment time.

[0087] Fifth, the simplified dual-channel redundant architecture for pure electric vehicle scenarios offers excellent economy and deployability. Compared with existing technologies, the architecture of this invention is more streamlined and focused, avoiding the complexity of multi-stage serial discharge schemes and the dependence on the normal operation of multiple control components, while reducing system costs and exhibiting good economy and deployability.

[0088] This embodiment provides an active discharge system for new energy vehicles based on DC-DC converters, corresponding to the method in Embodiment 1, with each functional unit and method step corresponding one-to-one.

[0089] An active discharge system for new energy vehicles based on DC-DC converters includes: The instruction receiving unit is used to obtain the status of the motor control system and control the motor windings to perform active discharge after receiving the electronic control active discharge instruction. The bus voltage acquisition unit is used to acquire the bus voltage during the active discharge process of the motor windings. The determination unit is used to determine whether the motor control system has the conditions for discharge based on the status of the motor control system; and to determine whether the motor winding can successfully discharge based on whether the bus voltage is less than the set first voltage threshold after the motor winding actively discharges for a set time. The control unit is used to control the DC-DC converter to actively discharge when the motor control system does not meet the discharge conditions or the motor windings cannot discharge successfully. The instruction receiving unit (corresponding to step S101) is integrated inside the MCU and is used to receive the active discharge instruction sent by the vehicle controller VCU, obtain the status of the motor control system (including the status of the resolver sensor, the current sensor, the motor body, the drive circuit, the power module, and the ASC), and control the motor windings to start active discharge.

[0090] Bus voltage acquisition unit (corresponding to step S102): used to acquire the bus voltage Vbus in real time through the high voltage bus voltage sensor during the active discharge process of the motor winding, and provide the acquired voltage data to the judgment unit and control unit.

[0091] Determination unit (corresponding to step S103): It is used to perform two core judgment tasks: First, based on the status of the motor control system, it determines whether the motor control system has the conditions for discharge (if there is a fault or it is in ASC state, it does not have the conditions; otherwise, it does); Second, based on the comparison between the bus voltage Vbus after the active discharge set time T_set of the motor winding and the first voltage threshold V1, it determines whether the motor winding has successfully discharged (if Vbus is less than V1, it is successful; if Vbus is greater than or equal to V1, it is unsuccessful).

[0092] Control unit (corresponding to step S104): used to execute corresponding control actions according to the output result of the judgment unit: when the motor control system has the discharge conditions and the motor winding discharges successfully, control the motor winding to continue to actively discharge until the bus voltage is lower than the safe voltage threshold; when the motor control system does not have the discharge conditions or the motor winding discharge fails, control the DC-DC converter to actively discharge.

[0093] In addition, the system also includes a low-voltage battery status detection unit and a DC-DC converter; Low-voltage battery status detection unit: Connected to the control unit, it is used to acquire the state of charge (SOC) and temperature (T_bat) of the low-voltage battery, and determine whether the low-voltage battery is in a charging-allowed state or a charging-prohibited state based on the SOC and T_bat, providing a basis for the control unit to switch the discharge mode.

[0094] The DC-DC converter is connected to the positive and negative terminals of the high-voltage bus on the high-voltage side, and to both the low-voltage battery and the bleeder resistor R_dis on the low-voltage side. Upon receiving the active discharge control command from the control unit, the DC-DC converter selects the discharge mode based on the low-voltage battery status: charging the low-voltage battery when charging is permitted, and charging the bleeder resistor R_dis when charging is prohibited. Energy conversion is performed by adjusting the duty cycle of the power transistor, thereby consuming the energy of the high-voltage bus capacitor.

[0095] Through the coordinated operation of the above functional units, the DC-DC-based active discharge system for new energy vehicles in this embodiment achieves the same technical effect as the method in Embodiment 1, and constructs a highly reliable dual-channel redundant active discharge control system.

[0096] The present invention also discloses a computer device, which may be an in-vehicle domain controller, a vehicle control unit (VCU), or a motor control unit (MCU), the device comprising: A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by the processor, implements a DC-DC-based active discharge method for new energy vehicles disclosed in an embodiment of the present invention.

[0097] The processor can be a central processing unit (CPU), microcontroller unit (MCU), digital signal processor (DSP), field-programmable gate array (FPGA), or application-specific integrated circuit (ASIC), etc. The memory can be read-only memory (ROM), random access memory (RAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, hard disk, or other forms of non-volatile storage media. The communication interface can be a CAN bus interface, LIN bus interface, Ethernet interface, or other vehicle communication interface.

[0098] One or more embodiments of this application also provide an electronic device, the electronic device including one or more processors, one or more memories coupled to the processors, and a communication module coupled to the processors. The memories may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, at least one of the following: read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, hard disk, optical disc (CD), digital video disc (DVD), or other magnetic and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) or other volatile memories that do not persist during power-off periods. A computer program may be stored in the ROM, and when the processor executes the computer program, it implements the above-described DC-DC-based active discharge method for new energy vehicles.

[0099] The present invention also discloses a computer-readable storage medium storing a computer program adapted for loading and execution by a processor of a DC-DC-based active discharge method for new energy vehicles disclosed in the embodiments of the present invention.

[0100] The storage medium can be ROM, RAM, EPROM, EEPROM, flash memory, hard disk, CD-ROM, USB flash drive, or other forms of non-volatile storage media.

[0101] In some embodiments, the program may be tangibly contained in a computer-readable medium, which may include a device (such as a memory) or other storage device accessible by the device. The program may be loaded from the computer-readable medium into RAM for execution. The computer-readable medium may include any type of tangible non-volatile memory, such as ROM, EPROM, flash memory, or hard disk, storing a computer program that, when executed by a processor, implements the aforementioned DC-DC-based active discharge method for new energy vehicles.

[0102] The present invention also discloses a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements a DC-DC-based active discharge method for new energy vehicles disclosed in the embodiments of the present invention.

[0103] This computer program product can be a software installation package, firmware upgrade package, or application, which can be downloaded to electronic devices via wired or wireless means, or pre-installed in the memory of electronic devices. This computer program product supports remote upgrades and online updates, and new versions can be deployed to electronic devices via OTA (Over-The-Air) upgrades, eliminating the need for factory repairs.

[0104] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When these computer program instructions are loaded and executed on a server or terminal, they generate all or part of the processes or functions described in the embodiments of this application. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic cable, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means.

[0105] Furthermore, although the operations are described in a specific order, this should be understood as requiring that such operations be performed in the specific order shown or in sequential order, or requiring that all illustrated operations be performed to achieve the desired result. In certain environments, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of this application. Certain features described in the context of individual embodiments may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented individually or in any suitable sub-combination in multiple implementations.

[0106] Although the subject matter has been described using language specific to structural features and / or methodological logic, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are merely illustrative examples of implementing the claims.

[0107] The above description is merely an exemplary embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for active discharge of new energy vehicles based on DC-DC converters, characterized in that, include: Upon receiving the active discharge command from the electronic control system, the status of the motor control system is obtained, and the motor windings are controlled to actively discharge. During the active discharge process of the motor windings, the bus voltage is obtained; Based on the status of the motor control system, determine whether the motor control system has the conditions for discharge; Based on whether the bus voltage is less than the set first voltage threshold after the motor winding actively discharges for a set time, it can be determined whether the motor winding can discharge successfully. When the motor control system does not meet the discharge conditions or the motor windings cannot discharge successfully, the DC-DC converter is controlled to perform active discharge.

2. The active discharge method for new energy vehicles based on DC-DC converters as described in claim 1, characterized in that, When controlling the DC-DC converter to actively discharge, the low-voltage battery status is obtained; When the low-voltage battery is in a charging-enabled state, control the DC-DC converter to charge the low-voltage battery. When the low-voltage battery is in a state where charging is prohibited, the DC-DC converter is controlled to charge the discharge resistor.

3. The active discharge method for new energy vehicles based on DC-DC converters as described in claim 2, characterized in that, Obtain the state of charge and temperature of the low-voltage battery; When the low-voltage battery is fully charged or its temperature is greater than or equal to a set temperature threshold, the low-voltage battery is determined to be in a state where charging is prohibited. When the low-voltage battery is not at full charge and its temperature is below the set temperature threshold, the low-voltage battery is determined to be in a state where charging is permitted.

4. The active discharge method for new energy vehicles based on DC-DC converters as described in claim 1, characterized in that, When the motor control system meets the discharge conditions and the motor windings can discharge successfully, the motor windings are controlled to continue to discharge actively until the bus voltage is lower than the safe voltage threshold.

5. The active discharge method for new energy vehicles based on DC-DC converters as described in claim 1, characterized in that, After the set time for active discharge of the motor windings, if the bus voltage is less than the set first voltage threshold, it is determined that the motor windings can successfully discharge. If the bus voltage is greater than or equal to the set first voltage threshold after the motor winding has been actively discharged for a set time, it is determined that the motor winding has failed to discharge successfully.

6. The active discharge method for new energy vehicles based on DC-DC as described in claim 1, characterized in that, Based on the status of the motor control system, if it is determined that the motor control system has a fault or is in ASC state, it is determined that the motor control system does not have the conditions for discharge. Based on the status of the motor control system, if it is determined that the motor control system is free of faults and is not in ASC state, then the motor control system is deemed to be ready to discharge.

7. A DC-DC-based active discharge system for new energy vehicles, characterized in that, include: The instruction receiving unit is used to obtain the status of the motor control system and control the motor windings to perform active discharge after receiving the electronic control active discharge instruction. The bus voltage acquisition unit is used to acquire the bus voltage during the active discharge process of the motor windings. The determination unit is used to determine whether the motor control system has the conditions for discharge based on the status of the motor control system; and to determine whether the motor winding can successfully discharge based on whether the bus voltage is less than the set first voltage threshold after the motor winding actively discharges for a set time. The control unit is used to control the DC-DC converter to actively discharge when the motor control system does not meet the discharge conditions or the motor windings cannot discharge successfully.

8. An electronic device, characterized in that, The device includes: A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by the processor, implements the active discharge method for a new energy vehicle based on DC-DC converter as described in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program adapted for loading and execution by a processor of the active discharge method for new energy vehicles based on DC-DC as described in any one of claims 1-6.

10. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements the active discharge method for new energy vehicles based on DC-DC converters as described in any one of claims 1-6.

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