A new energy electric drive backup power system and active discharge method thereof

Abstract

The present invention discloses a backup power supply system and an active discharge method thereof driven by a new energy source, and a high-voltage backup power supply is used to convert the DC bus voltage into a low-voltage input active discharge circuit, so that the active discharge circuit can still perform active discharge under low-voltage power failure conditions; the active discharge circuit includes a low-voltage power supply, a system basic chip, a microprocessor, and a discharge circuit, the low-voltage power supply is electrically connected to the system basic chip, the system basic chip is electrically connected to the microprocessor, and the microprocessor is powered; the microprocessor is connected to the discharge circuit communication, and the discharge circuit is controlled to perform discharge according to the active discharge strategy. The discharge control circuit is all on the low-voltage side, and they are all low-voltage electronic components, with low cost and safer discharge process; and the active discharge circuit is independent of the power module and the motor, and will not affect the motor control circuit.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy electric drive systems, and in particular relates to a new energy electric drive backup power supply system and an active discharge method thereof. Background Art

[0002] The new energy electric drive system is the link between the electric vehicle energy storage system and the wheels. Its function is to convert the energy (chemical energy, electrical energy) output by the energy storage system into mechanical energy, drive the vehicle to overcome various rolling resistance, air resistance, acceleration resistance and climbing resistance, and convert kinetic energy into electrical energy and feed it back to the energy storage system during braking.

[0003] Usually, in addition to the main power supply system, the new energy electric drive system is also provided with a backup power supply system to supply power when the main power supply system is insufficient.

[0004] In the existing backup power supply system of new energy electric drive, there are the following defects: 1. Add control chips and switch tubes in the high-voltage area and discharge through power resistors, which is costly; 2. The hardware has no backup power module and no high-voltage side control chip. When the low voltage is off, the active discharge function cannot be performed. If the vehicle speed is relatively high at this time, the inverter cannot be guaranteed to be in a safe state, and there is a potential risk of damage; 3. The hardware has no active discharge circuit module, and uses the equivalent resistance of the motor winding to consume the energy in the bus capacitor. When the discharge is out of control, the motor may generate unexpected motor torque, and the vehicle cannot be kept in a stable state (the motor shakes abnormally), which is potentially harmful; 4. Discharging is performed by forming a conduction loop through the power module and the DC bus capacitor, and adjusting the duty cycle of the forward conduction voltage of the power module to control the direct-on time of the half-bridge circuit, which will cause the discharge to be out of control. Summary of the invention

[0005] The purpose of the present invention is to provide a new energy electric drive backup power supply system and a discharge method thereof. The discharge control circuit is all on the low-voltage side. When the low voltage is powered off, the active discharge function can still be performed to avoid damage to the inverter. In addition, they are all low-voltage electronic components, with low cost and a safer discharge process.

[0006] To solve the above problems, the technical solution of the present invention is: A backup power supply system for new energy electric drive, comprising: a high-voltage backup power supply, an active discharge circuit, wherein the high-voltage backup power supply converts a DC bus voltage into a low voltage and inputs the low-voltage backup power supply into the active discharge circuit, so that the active discharge circuit can still perform active discharge in the case of low-voltage power failure; The active discharge circuit includes a low-voltage power supply, a system basic chip, a microprocessor, and a discharge circuit. The low-voltage power supply is electrically connected to the system basic chip, and the system basic chip is electrically connected to the microprocessor to power the microprocessor. The microprocessor is in communication connection with the discharge circuit to control the discharge circuit to perform discharge according to the active discharge strategy. The output end of the high-voltage backup power supply is connected to the system basic chip. The discharge circuit includes a discharge resistor, a first switch tube, a second switch tube and a current sampling resistor, one end of the discharge resistor is connected to the output end of the high-voltage backup power supply, and the other end is connected to the source of the first switch tube, the gate of the first switch tube is connected to the first output end of the microprocessor, the drain of the first switch tube is connected to the source of the second switch tube, the gate of the second switch tube is connected to the second output end of the microprocessor, the drain of the second switch tube is connected to one end of the current sampling resistor, and the other end of the current sampling resistor is grounded; The first sampling end of the microprocessor is connected to the input end signal of the high-voltage backup power supply. The microprocessor generates a first PWM control signal and a second PWM control signal based on the active discharge strategy according to the real-time acquisition of the input end signal of the high-voltage backup power supply. The first PWM control signal and the second PWM control signal respectively control the first switch tube and the second switch tube through the first output end and the second output end, thereby realizing active discharge.

[0007] According to one embodiment of the present invention, during high-speed operation of the vehicle, when the low-voltage power supply loses power and the generated back electromotive force is greater than a preset threshold, the high-voltage backup power supply output voltage supplies power to the system basic chip, and the system basic chip output voltage supplies power to the microprocessor to ensure the normal execution of active discharge.

[0008] According to one embodiment of the present invention, the first output end of the microprocessor outputs a PWM_A enable signal with a fixed frequency and a fixed duty cycle to the first switch tube, and the second output end of the microprocessor outputs a PWM_B active discharge enable signal with a variable duty cycle to the second switch tube to provide protection when the discharge circuit fails.

[0009] According to an embodiment of the present invention, the PWM_A enable signal is converted into a DC signal by a DC blocking capacitor and a rectifier circuit, and then input into the first switch tube to prevent false triggering due to signal interference.

[0010] According to an embodiment of the present invention, the second output terminal of the microprocessor outputs a PWM_B active discharge enable signal to control the second switch tube, and controls the discharge rate by changing the duty cycle of the PWM_B signal according to the following formula: W=U·(U / R)·T·D Among them, W is the single pulse width discharge energy, U is the bus voltage, R is the discharge resistance, T is the discharge period, and D is the duty cycle; The microcontroller is configured to release energy constantly during the first discharge cycle, and then change the duty cycle of the PWM_B active discharge enable signal until the duty cycle reaches a threshold value, thereby entering a constant time discharge.

[0011] According to an embodiment of the present invention, the microprocessor monitors the temperature of the discharge resistor in real time through a temperature sensor, and adjusts the duty cycle of the PWM_B active discharge enable signal according to the temperature to control the discharge time and prevent the discharge resistor from being damaged by overheating.

[0012] According to an embodiment of the present invention, the microcontroller detects the temperature of the discharge resistor in real time and calculates the equivalent heat load according to the following formula: E thermal =(85-T NTC )·K+E const Among them, E thermal is the thermal load, simulating the current thermal load of the PCB and the discharge resistor; T NTC is the discharge resistor temperature, K is the equivalent coefficient, E const is the equivalent thermal resistance constant of PCB; When the equivalent thermal load reaches a preset thermal load threshold, the discharge circuit is controlled to perform discharge power derating.

[0013] According to an embodiment of the present invention, the microprocessor is configured to perform discharge according to the following active discharge strategy: Real-time monitoring of the voltage drop of the high-voltage DC bus, when the voltage drop reaches a preset value, performing active discharge for a first preset time; Continuously monitoring the voltage drop of the high-voltage DC bus, and when the voltage drop is less than a preset value, suspending the discharge for a second preset time; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; if the voltage drop is less than the preset value, suspend discharge for a third preset time; The voltage drop of the high-voltage DC bus continues to be monitored, and if the voltage drop is still less than the preset value, the discharge is suspended for a fourth preset time.

[0014] According to an embodiment of the present invention, the microcontroller is further configured to monitor the voltage gradient of the high-voltage DC bus during the active discharge process, and perform discharge power derating if the voltage gradient is less than a preset gradient value.

[0015] An active discharge method for a backup power system of a new energy electric drive, comprising: Real-time monitoring of the voltage drop of the high-voltage DC bus, when the voltage drop reaches a preset value, performing active discharge for a first preset time; Continuously monitoring the voltage drop of the high-voltage DC bus, and when the voltage drop is less than a preset value, suspending the discharge for a second preset time; Execute the above steps repeatedly for a preset number of times; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; if the voltage drop is less than the preset value, suspend discharge for a third preset time; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; if the voltage drop is less than the preset value, suspend discharge for a fourth preset time; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; if the voltage drop is less than the preset value, suspend discharge for a fifth preset time; Continue to monitor the voltage drop of the high-voltage DC bus to determine whether to perform active discharge; During the active discharge process, the voltage gradient of the high-voltage DC bus is monitored, and if the voltage gradient is less than a preset gradient value, power derating discharge is performed.

[0016] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: The backup power supply system of the new energy electric drive in one embodiment of the present invention adopts a high-voltage backup power supply to convert the DC bus voltage into a low-voltage input active discharge circuit, so that the active discharge circuit can still perform active discharge in the case of low-voltage power failure; the active discharge circuit includes a low-voltage power supply, a system basic chip, a microprocessor, and a discharge circuit, the low-voltage power supply is electrically connected to the system basic chip, the system basic chip is electrically connected to the microprocessor, and the microprocessor is powered; the microprocessor is connected to the discharge circuit in communication, and the discharge circuit is controlled to perform discharge according to the active discharge strategy. The discharge control circuit is all on the low-voltage side, and they are all low-voltage electronic components, with low cost and safer discharge process; and the active discharge circuit is independent of the power module and the motor, and will not affect the motor control circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A circuit diagram of a backup power supply system for a new energy electric drive in one embodiment of the present invention; Figure 2 A circuit diagram of a high voltage standby power supply in one embodiment of the present invention; Figure 3 is a schematic diagram of an active discharge strategy in an embodiment of the present invention; Figure 4 is a schematic diagram of an active discharge state machine in an embodiment of the present invention; Figure 5 FIG. 4 is a timing diagram of a du / dt test cycle in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following is a further detailed description of a new energy electric drive backup power supply system proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims.

[0019] This embodiment provides a new energy electric drive backup power system, please refer to Figure 1 , the backup power supply system includes a high-voltage area and a low-voltage area. In the high-voltage area, the high-voltage backup power supply is connected to the DC bus to receive high-voltage input, and converts the DC bus voltage into a low voltage and outputs it to the active discharge circuit in the low-voltage area, so that the active discharge circuit can still perform active discharge in the case of low-voltage power failure. The function of the active discharge circuit is to ensure that the battery-end relay is disconnected and discharge the electricity on the bus capacitor. The specific discharge path is: bus capacitor X1→high-voltage backup power supply→D2→R1→Q1→Q2→R2. When the bus voltage is lower than the starting threshold of the high-voltage backup power supply, the high-voltage backup power supply stops outputting, and the discharge stops at this time; when the voltage on the bus capacitor is <60V, it meets the standard requirements of chapters 3.14 and 3.16 of the national standard GB / T 18488.1, and the voltage on the bus capacitor will be consumed by the high-voltage backup power supply and the discharge resistor.

[0020] For details, please see Figure 2 , the high-voltage backup power supply includes an anti-reverse diode D3, a high-voltage isolation transformer TR, an isolation optocoupler, a main output filter circuit, an auxiliary output filter circuit, and a transformer control circuit; wherein the positive pole of the anti-reverse diode D3 is connected to the high-voltage input, the negative pole of the anti-reverse diode D3 is connected to the input end of the high-voltage isolation transformer TR, and the output end of the high-voltage isolation transformer TR is connected to the main output filter circuit. The high-voltage isolation transformer TR includes four coils, namely N1, N2, N3, and N4, one end of N1 is connected to the negative pole of the anti-reverse diode D3, and the other end is connected to the transformer control circuit; N2 and the auxiliary output filter circuit form a loop; N3 and the main output filter circuit form a loop; N4 and N3 are connected in parallel. The output end of the auxiliary output filter circuit is connected to the transformer control circuit, and the auxiliary voltage is output to the transformer control circuit. The output end of the main output filter circuit is connected to the transformer control circuit through an isolation optocoupler to provide a main feedback reference voltage for the transformer control circuit. The anti-reverse diode D3, N1 and N2 of the high-voltage isolation transformer TR, the output end of the isolation optocoupler, the auxiliary output filter circuit and the transformer control circuit are in the high-voltage area; the main output filter circuit, N3 and N4 of the high-voltage isolation transformer TR, and the input end of the isolation optocoupler are in the low-voltage area.

[0021] In the low-voltage area, the active discharge circuit includes a low-voltage power supply, a system basic chip SBC, a microprocessor, and a discharge circuit, wherein the low-voltage power supply is electrically connected to the system basic chip SBC and outputs 12V to power the system basic chip SBC. The low-voltage power supply is a low-voltage battery connected to the KL30 power line. The system basic chip SBC is electrically connected to the microprocessor and outputs 5V to power the microprocessor. The microprocessor is in communication with the discharge circuit and controls the discharge circuit to perform discharge according to the active discharge strategy.

[0022] The discharge circuit includes a discharge resistor R1, a first switch tube Q1, a second switch tube Q2 and a current sampling resistor R2. One end of the discharge resistor R1 is connected to the output end of the high-voltage standby power supply, and the other end is connected to the source of the first switch tube Q1; the gate of the first switch tube Q1 is connected to the first output end of the microprocessor, and the drain of the first switch tube Q1 is connected to the source of the second switch tube Q2; the gate of the second switch tube Q2 is connected to the second output end of the microprocessor, and the drain of the second switch tube Q2 is connected to one end of the current sampling resistor R2, and the other end of the current sampling resistor R2 is grounded.

[0023] The output end of the high-voltage backup power supply is connected to the diode D2, and the output low voltage 11V is connected to the system basic chip SBC after passing through the diode D1 to power the system basic chip SBC, ensuring that the active discharge circuit can also perform discharge when the low-voltage power supply is powered off, and at the same time ensuring that the system basic chip SBC is woken up when the inverter is in sleep mode.

[0024] In actual applications, when the vehicle is stationary, the low-voltage KL30 loses power and the inverter cannot supply high voltage. At this time, there is no need to perform active discharge; when the vehicle is running and the speed is very low, the low-voltage KL30 loses power. The electric drive system determines that the motor speed is very low at this time. If the generated back electromotive force is <45V, there is no need to perform active discharge. When the vehicle is running at high speed, if the low voltage of the whole vehicle is powered off, the 12V input of the low-voltage battery is 0, and the generated back electromotive force is ≥45V. At this time, the high-voltage backup power supply works, and the output voltage of the high-voltage backup power supply passes through diodes D2 and D1, and outputs 10V to power the system basic chip SBC. The system basic chip SBC normally outputs a low voltage of 5V to power the microcontroller, ensuring the normal operation of the microcontroller and performing the active discharge function.

[0025] The first sampling terminal of the microprocessor is connected to the input terminal of the high-voltage backup power supply to collect the high-voltage DC bus voltage in real time so that the active discharge can be turned off before an abnormality occurs. When the microprocessor performs active discharge, it performs discharge according to the following active discharge strategy: Real-time monitoring of the voltage drop of the high-voltage DC bus, when the voltage drop reaches a preset value, performing active discharge for a first preset time; Continuously monitoring the voltage drop of the high-voltage DC bus, and when the voltage drop is less than a preset value, suspending the discharge for a second preset time; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; if the voltage drop is less than the preset value, suspend discharge for a third preset time; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop is still less than the preset value, suspend the discharge for a fourth preset time; Continue to monitor the high-voltage DC bus voltage drop to determine whether to perform active discharge.

[0026] During the active discharge process, the voltage gradient of the high-voltage DC bus is monitored, and if the voltage gradient is less than a preset gradient value, the discharge power is derated.

[0027] For details, please see Figure 3 The active discharge strategy includes the first and second stages. In the first stage, the high-voltage DC bus voltage drop du / dt is monitored in real time to detect whether discharge is possible. Figure 4 , if |du / dt| >15V / 200ms, then normal full power discharge is performed for 200ms, and continuous detection of |du / dt| is performed. If |du / dt| ≤15V / 200ms, then pause for 800ms, and repeat three times. Continue to judge |du / dt. If |du / dt|>15V / 200ms, normal active discharge is performed. If |du / dt|≤ 15V / 200ms, then pause for 1800ms; continue to judge. If |du / dt|≤ 15V / 200ms, then pause for 4800ms; continue to judge. If |du / dt|≤ 15V / 200ms, then pause for 9800ms, and continue to judge and detect the cycle waiting. When the busbar battery switch is closed, please refer to the du / dt test cycle timing. Figure 5 .

[0028] During the active discharge process, the voltage gradient of the high-voltage DC bus is monitored. If the voltage gradient is less than 100v / s, the second stage test is carried out to perform the discharge power derating. In addition, the active discharge will be suspended due to thermal protection, and after the maximum suspension time, the active discharge will be activated again.

[0029] When the microprocessor performs active discharge, its first output terminal outputs a PWM_A enable signal with a fixed frequency and a fixed duty cycle to the first switch tube Q1, and its second output terminal outputs a PWM_B active discharge enable signal with a variable duty cycle to the second switch tube Q2, so as to provide protection when the discharge circuit fails.

[0030] The PWM_A enable signal can be a square wave signal with a fixed frequency of 10kHz and a fixed duty cycle of 50%. After the PWM_A enable signal is converted into a DC signal by a DC blocking capacitor and a rectifier circuit, it is input into the first switch tube Q1 to prevent false triggering due to signal interference.

[0031] The PWM_B active discharge enable signal can be a fixed frequency modulation wave signal to control the second switch tube Q2. The PWM_B active discharge enable signal has a variable duty cycle and can control the discharge rate in real time according to the change of the bus voltage.

[0032] Specifically, the first sampling terminal of the microprocessor is connected to the input terminal of the high-voltage backup power supply to collect the high-voltage DC bus voltage in real time. On the one hand, it can determine whether the bus voltage is abnormal, so that the active discharge is closed before the abnormality occurs; on the other hand, the discharge rate is controlled by changing the duty cycle of the PWM_B signal according to the following formula; W=U·(U / R)·T·D Where W is the single pulse width discharge energy, U is the bus voltage, R is the discharge resistance, T is the discharge period, and D is the duty cycle. The duty cycle D varies from about 3% to 50%, the frequency is 1kHz, and the period T=1ms.

[0033] In actual applications, when discharging starts, the energy released in a single switching cycle is constant, and then the duty cycle of the PWM_B active discharge enable signal is changed until the duty cycle reaches 50%, entering a constant time discharge until the discharge ends.

[0034] During the discharge process, the microprocessor also monitors the temperature of the discharge resistor in real time through the temperature sensor, and adjusts the duty cycle of the PWM_B active discharge enable signal according to the temperature to control the discharge time and prevent the discharge resistor from being damaged by overheating. For example, an NTC (Negative Temperature Coefficient) temperature detection resistor can be added next to the discharge resistor to monitor the temperature of the discharge resistor in real time; a PTC (Positive Temperature Coefficient) resistor can also be used to replace the discharge resistor R1, and the discharge temperature can be monitored by using its own thermal protection.

[0035] The microcontroller detects the temperature of the discharge resistor in real time and calculates the equivalent heat load according to the following formula: E thermal =(85-T NTC )·K+E const Among them, E thermal is the thermal load, simulating the current thermal load of the PCB and the discharge resistor; T NTC is the discharge resistor temperature, K is the equivalent coefficient, E const is the PCB equivalent thermal resistance constant; When the equivalent heat load reaches the preset heat load threshold, the discharge circuit is controlled to perform discharge power derating. thermal ≤ E threshold时，满功率30W放电 ； When E thermal > E threshold When the discharge is reduced to 15W; During each pause, the power is derated to 0W for cooling. threshold The value can be set according to actual situation.

[0036] In addition, the second sampling terminal of the microprocessor is connected to the current sampling resistor R2 to detect the current in the discharge circuit in real time to ensure that the discharge strategy is executed normally.

[0037] Based on the above-mentioned backup power supply system driven by new energy, this embodiment also provides an active discharge method of the backup power supply system driven by new energy, and the specific steps are as follows: Real-time monitoring of the voltage drop of the high-voltage DC bus, when the voltage drop reaches a preset value, performing active discharge for a first preset time; Continuously monitoring the voltage drop of the high-voltage DC bus, and when the voltage drop is less than a preset value, suspending the discharge for a second preset time; Execute the above steps repeatedly for a preset number of times; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; if the voltage drop is less than the preset value, suspend discharge for a third preset time; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; if the voltage drop is less than the preset value, suspend discharge for a fourth preset time; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; if the voltage drop is less than the preset value, suspend discharge for a fifth preset time; Continue to monitor the voltage drop of the high-voltage DC bus to determine whether to perform active discharge; During the active discharge process, the voltage gradient of the high-voltage DC bus is monitored, and if the voltage gradient is less than a preset gradient value, power derating discharge is performed.

[0038] The settings of the first preset time, the second preset time, the third preset time, the fourth preset time, the fifth preset time and the preset gradient value may be determined according to actual conditions.

[0039] In summary, the new energy electric drive backup power supply system and its discharge method provided in this embodiment have discharge control loops all on the low-voltage side, and are all low-voltage electronic components, which reduces costs and makes the discharge process safer. The switch tube is controlled by a microprocessor to protect when the discharge circuit fails; and the voltage gradient or voltage drop of the high-voltage DC bus is monitored in real time, and the discharge rate is controlled according to the change of the bus voltage, so that the active discharge can be turned off within a safe range before damage occurs. The discharge resistor temperature is also monitored in real time. When the NTC temperature is too high, PWM_B can adjust the duty cycle to control the discharge time to protect the discharge resistor from damage due to overheating.

[0040] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the protection scope of the present invention.

Claims

1. A new energy electric drive backup power system, characterized in that: include: A high-voltage backup power supply and an active discharge circuit, wherein the high-voltage backup power supply converts a DC bus voltage into a low voltage and inputs the low-voltage backup power supply into the active discharge circuit, so that the active discharge circuit can still perform active discharge in the case of a low-voltage power failure; The active discharge circuit includes a low-voltage power supply, a system basic chip, a microprocessor, and a discharge circuit. The low-voltage power supply is electrically connected to the system basic chip, and the system basic chip is electrically connected to the microprocessor to power the microprocessor. The microprocessor is in communication connection with the discharge circuit to control the discharge circuit to perform discharge according to the active discharge strategy. The output end of the high-voltage backup power supply is connected to the system basic chip. The discharge circuit includes a discharge resistor, a first switch tube, a second switch tube and a current sampling resistor, one end of the discharge resistor is connected to the output end of the high-voltage backup power supply, and the other end is connected to the source of the first switch tube, the gate of the first switch tube is connected to the first output end of the microprocessor, the drain of the first switch tube is connected to the source of the second switch tube, the gate of the second switch tube is connected to the second output end of the microprocessor, the drain of the second switch tube is connected to one end of the current sampling resistor, and the other end of the current sampling resistor is grounded; The first sampling end of the microprocessor is connected to the input end signal of the high-voltage backup power supply. The microprocessor generates a first PWM control signal and a second PWM control signal based on the active discharge strategy according to the real-time acquisition of the input end signal of the high-voltage backup power supply. The first PWM control signal and the second PWM control signal respectively control the first switch tube and the second switch tube through the first output end and the second output end, thereby realizing active discharge.

2. The backup power supply system for new energy electric drive according to claim 1, characterized in that: During high-speed operation of the vehicle, when the low-voltage power supply is powered off and the generated back electromotive force is greater than a preset threshold, the high-voltage backup power supply output voltage powers the system basic chip, and the system basic chip output voltage powers the microprocessor to ensure the normal execution of active discharge.

3. The backup power supply system of the new energy electric drive according to claim 1, characterized in that: The first output end of the microprocessor outputs a PWM_A enable signal with a fixed frequency and a fixed duty cycle to the first switch tube, and the second output end of the microprocessor outputs a PWM_B active discharge enable signal with a variable duty cycle to the second switch tube to provide protection when the discharge circuit fails.

4. The backup power supply system of the new energy electric drive according to claim 3, characterized in that: The PWM_A enable signal is converted into a DC signal by a DC blocking capacitor and a rectifier circuit, and then input into the first switch tube to prevent false triggering due to signal interference.

5. The backup power supply system of the new energy electric drive according to claim 3, characterized in that: The second output terminal of the microprocessor outputs a PWM_B active discharge enable signal to control the second switch tube, and controls the discharge rate by changing the duty cycle of the PWM_B signal according to the following formula; W=U·(U / R)·T·D Among them, W is the single pulse width discharge energy, U is the bus voltage, R is the discharge resistance, T is the discharge period, and D is the duty cycle; The microcontroller is configured to release energy constantly during the first discharge cycle, and then change the duty cycle of the PWM_B active discharge enable signal until the duty cycle reaches a threshold value, thereby entering a constant time discharge.

6. The backup power supply system of the new energy electric drive according to claim 3, characterized in that: The microprocessor monitors the temperature of the discharge resistor in real time through a temperature sensor, and adjusts the duty cycle of the PWM_B active discharge enable signal according to the temperature to control the discharge time and prevent the discharge resistor from being damaged due to overheating.

7. The backup power supply system of the new energy electric drive according to claim 6, characterized in that: The microcontroller detects the temperature of the discharge resistor in real time and calculates the equivalent heat load according to the following formula: E thermal =(85-T NTC )·K+E const Among them, E thermal is the thermal load, simulating the current thermal load of the PCB and the discharge resistor; T NTC is the discharge resistor temperature, K is the equivalent coefficient, E const is the PCB equivalent thermal resistance constant; When the equivalent thermal load reaches a preset thermal load threshold, the discharge circuit is controlled to perform discharge power derating.

8. The backup power supply system of the new energy electric drive according to claim 1, characterized in that: The microprocessor is configured to perform discharge according to the following active discharge strategy: Real-time monitoring of the voltage drop of the high-voltage DC bus, when the voltage drop reaches a preset value, performing active discharge for a first preset time; Continuously monitoring the voltage drop of the high-voltage DC bus, and when the voltage drop is less than a preset value, suspending the discharge for a second preset time; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; If the voltage drop is less than the preset value, suspending the discharge for a third preset time; The voltage drop of the high-voltage DC bus continues to be monitored, and if the voltage drop is still less than the preset value, the discharge is suspended for a fourth preset time.

9. The backup power supply system of the new energy electric drive according to claim 8, characterized in that: The microcontroller is further configured to monitor the voltage gradient of the high-voltage DC bus during the active discharge process, and to perform a discharge power derating if the voltage gradient is less than a preset gradient value.

10. An active discharge method for a backup power system driven by new energy, characterized in that: include: Real-time monitoring of the voltage drop of the high-voltage DC bus, when the voltage drop reaches a preset value, performing active discharge for a first preset time; Continuously monitoring the voltage drop of the high-voltage DC bus, and when the voltage drop is less than a preset value, suspending the discharge for a second preset time; Execute the above steps repeatedly for a preset number of times; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; If the voltage drop is less than the preset value, suspending the discharge for a third preset time; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; If the voltage drop is less than the preset value, suspending the discharge for a fourth preset time; Continue to monitor the voltage drop of the high-voltage DC bus, and if the voltage drop reaches a preset value, perform active discharge for a first preset time; If the voltage drop is less than the preset value, suspending the discharge for a fifth preset time; Continue to monitor the voltage drop of the high-voltage DC bus to determine whether to perform active discharge; During the active discharge process, the voltage gradient of the high-voltage DC bus is monitored, and if the voltage gradient is less than a preset gradient value, power derating discharge is performed.

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