Motor controller active discharge system and control method

Abstract

An active discharge system and control method for a motor controller include a thin film capacitor, an IGBT circuit and a motor arranged on a bus, an IGBT temperature sampling circuit connected to the IGBT circuit and a drive circuit with a power supply circuit, a bus voltage sampling circuit connected to the thin film capacitor, a motor temperature sampling circuit and a motor speed sampling circuit connected to the motor, and a drive circuit. When the system finds that a problem occurs with a motor winding or an IGBT module, the system can select a discharge path respectively, thereby reducing the risk of failure of the active discharge IGBT and solving the problem of discharge speed.

Description

Technical Field

[0001] The present invention relates to a technology in the field of motor drive control, in particular to an active discharge system and control method of a motor controller. Background Art

[0002] To ensure personal safety, the motor controller must have an active discharge function. The current active discharge technology mainly focuses on the following three discharge paths: 1. Discharge through the motor winding, add D-axis current, and the discharge time is fast, but it will bring unexpected torque and affect the driving experience; 2. Through an external discharge circuit, the risk is small and reliable, but it will increase the hardware cost; 3. Bridge wall direct discharge, this method has low cost and fast discharge speed, but the instantaneous current is large. Due to the stray inductance in the high-voltage circuit, the voltage stress of the IGBT (insulated gate bipolar transistor) is large when it is turned off. The test object is a 750V / 820A IGBT module. When the bus voltage is 520V, a single pulse short-circuit test is performed. The actual measured data of channel three, Vce, rushes to 716V. As the bus voltage rises, the short-circuit current increases, the shutdown speed is accelerated, and the peak voltage will increase further until it exceeds the limit voltage of 750V. In actual working conditions, when the motor is running at high speed and the main relay of the power battery is disconnected, the film capacitor will be charged to above the maximum back electromotive force by the motor energy feedback. At this time, direct short-circuit discharge will cause damage to the IGBT or even breakdown. Summary of the invention

[0003] In view of the above-mentioned shortcomings of the prior art, the present invention proposes an active discharge system and control method for a motor controller, which adds a logic judgment mechanism to perform graded discharge. CE The monitoring circuit will generate an adjustment signal when Vce is large, which is input to the power supply circuit to adjust the power supply circuit and limit the short-circuit current. At the same time, TVS charges the gate capacitor to slow down the shutdown speed and reduce V CE The control unit can shield the feedback signal through the trigger at any time to restore the drive circuit power supply to normal working state.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to an active discharge system of a motor controller, comprising: a film capacitor arranged on a bus, an IGBT circuit and a motor, an IGBT temperature sampling circuit connected to the IGBT circuit and a drive circuit with a power supply circuit, a bus voltage sampling circuit connected to the film capacitor, a motor temperature sampling circuit connected to the motor and a motor speed sampling circuit, wherein: the IGBT circuit converts a DC high voltage in the bus into a three-phase AC voltage and outputs it to a motor winding, the bus voltage sampling circuit collects the voltage across the film capacitor, the control unit obtains the system stray inductance, the IGBT temperature, the motor temperature, the motor speed through a double pulse test and calculates the IGBT off-tube voltage stress when the bridge wall is short-circuited and determines whether the bridge wall short-circuit discharge is satisfied, and switches to the motor winding short-circuit discharge when it is not satisfied, that is, the zero torque mode discharge is performed so that no unexpected torque occurs; when the voltage across the film capacitor drops to meet the bridge wall short-circuit discharge condition, the control unit estimates the discharge time and generates a corresponding PWM output to the IGBT circuit through the drive circuit; the power supply circuit adjusts the power supply circuit voltage according to the feedback adjustment signal and supplies it to the drive circuit.

[0006] The IGBT circuit is a three-phase bridge inverter circuit, comprising: three bridge arms connected in parallel, each bridge arm having two IGBT single tubes connected in series, wherein: the center points of the three bridge arms are used as three AC ends and are respectively connected to the three-phase AC ports of the motor.

[0007] The power supply circuit converts the vehicle battery into 15V and then produces the driving voltage on the high-voltage side through the transformer, outputs +15V and -5V to supply the driving circuit for the open-tube driving of the IGBT, and specifically includes: a power supply chip, a power component and a transformer.

[0008] The power supply circuit is further provided with a power supply circuit feedback regulation circuit and a power supply circuit sampling circuit.

[0009] The driving circuit is used for PWM power amplification, and specifically comprises: six groups of driving components connected to each other by IGBT circuits, and the six components correspond to six IGBT single tubes.

[0010] The driving circuit is further provided with a Vce monitoring loop, which specifically includes: an operational amplifier, a photosensitive semiconductor, a TVS chain and a trigger.

[0011] A motor temperature sampling circuit and a motor speed sampling circuit are provided between the control unit and the motor.

[0012] An IGBT temperature sampling circuit is provided between the control unit and the IGBT circuit.

[0013] For the estimation, the control unit preferably calculates the discharge time based on the active discharge time by looking up the table and calibrating the narrow pulse discharge speed.

[0014] Technical Effects

[0015] Compared with the prior art, the control unit of the present invention evaluates the current film capacitor voltage and energy, estimates the discharge time of different modes, the voltage stress of IGBT short circuit, etc., and then generates PWM signals and trigger control signals to control the discharge circuit to discharge. In terms of hardware, hardware feedback regulation is introduced during bridge wall short circuit discharge. When the Vce stress is too large, a rapid response of several hundred nS level limits the IGBT short circuit current, slows down the shutdown speed, and reduces the risk of IGBT failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a system structure diagram of the present invention;

[0017] In the figure: input bus 1, IGBT circuit 2, motor 3, control unit 4, bus voltage sampling circuit 5, motor temperature sampling circuit 6, IGBT temperature sampling circuit 7, motor speed sampling circuit 8, drive circuit 9, power supply circuit 10;

[0018] Figure 2 Schematic diagram of drive circuit and IGBT circuit;

[0019] Figure 3 This is a control flow chart of the present invention;

[0020] Figure 4 Schematic diagram of the power supply circuit structure;

[0021] Figure 5 It is a schematic diagram of the effect of the embodiment;

[0022] In the figure: Channel 1 is the fault signal, channel 2 is the warranty cancellation and detection signal, and channel 3 is the V CE , channel 4 is V GE . DETAILED DESCRIPTION

[0023] like Figure 1 As shown, an active discharge system of a motor controller involved in this embodiment includes: an input bus 1, an IGBT circuit 2, a drive circuit 9, a motor 3 and a control unit 4, wherein: the input bus 1, the IGBT circuit 2, the motor 3 and the control unit 4 are connected in series to form a loop, and the input end and the output end of the drive circuit 9 are respectively connected to the control unit 4 and the IGBT circuit 2.

[0024] The IGBT circuit 2 is a three-phase bridge inverter circuit, including: three bridge arms connected in parallel, each bridge arm has two IGBT single tubes a~f connected in series, wherein: the center points of the three bridge arms are connected to the three-phase AC ports of the motor 3 as U, V, and W ends respectively.

[0025] The driving circuit includes: six groups of identical driving components. Taking the U-phase upper bridge as an example, the input end of the driving chip is connected to PWM_H and PWM_L, the low-voltage side power supply, and the high-voltage side power supply. The output end is connected to the IGBT circuit. The added Vce monitoring loop, the TVS chain feedback signal is used as a power follower through the operational amplifier, and is input to the isolation optocoupler through the resistor voltage divider for high-voltage and low-voltage isolation, and then output to the trigger. The trigger is controlled by the control unit and PWM_L, and the output end is sent to the power circuit regulation circuit as a feedback regulation signal.

[0026] The control unit 4 is provided with a bus voltage sampling circuit 5 connected to the input bus 1 , wherein the bus voltage sampling circuit 5 is connected to a voltage sampling port VDC_SAMPLE of the control unit 4 .

[0027] The control unit 4 is provided with a motor temperature sampling circuit 6 connected to the motor 3 , wherein the motor temperature sampling circuit 6 is connected to a motor temperature sampling port MOTOR_TEMP_SAMPLE of the control unit 4 .

[0028] The control unit 4 is provided with an IGBT temperature sampling circuit 7 connected to the IGBT circuit 2 , wherein the IGBT temperature sampling circuit 7 is connected to an IGBT temperature sampling port IGBT_TEM_SAMPLE of the control unit 4 .

[0029] The control unit 4 is provided with a motor speed sampling circuit 8 connected to the motor 3 , wherein the motor speed sampling circuit 8 is connected to a motor speed sampling port MOTOR_SPEED_SAMPLE of the control unit 4 .

[0030] like Figure 4 As shown, the driving circuit 9 is provided with a power circuit 10, which includes: a power chip, a MOS tube, an inductor, a resistor, a capacitor and a transformer, wherein: the power chip and its peripheral components receive the input of KL30 (the whole vehicle battery) and output 15V as the transformer input; the MOS switch tube receives the control unit PWM signal, converts 15V into 15V and -5V and outputs it to the driving circuit, and the transformer is used for high-voltage and low-voltage isolation.

[0031] like Figure 5 As shown, the Vce monitoring circuit includes: an operational amplifier, a photosensitive semiconductor, a TVS chain and a trigger, wherein: the non-inverting input terminal of the operational amplifier is connected to the feedback terminal of the TVS chain, the input terminal of the photosensitive semiconductor is connected to the output terminal of the resistor voltage divider, the feedback terminal of the TVS chain is connected to the non-inverting input terminal of the operational amplifier, and the input terminal of the trigger is connected to the output terminal of the photosensitive semiconductor; when V CEWhen the voltage is too large to break through the TVS chain, it will charge the IGBT gate capacitor, slow down the drop of the driving voltage, and slow down the shutdown speed. At the same time, the output enable signal is output to the photosensitive semiconductor through the operational amplifier, and then to the trigger after isolation. The trigger is controlled by the PWM input signal and the control unit signal enable at the same time. When the PWM is turned off or the control unit sends an enable signal to the trigger, the trigger will output a high level as a feedback regulation signal to the power circuit.

[0032] This embodiment relates to a control method for the above device, which specifically includes the following steps:

[0033] Step 1. After receiving the power-off command from the vehicle control unit (CAN communication), the control unit determines that the main relay is disengaged. The control unit determines that the active discharge conditions are met based on the motor speed and responds to the active discharge request. The control unit detects the voltage value of the film capacitor through the bus voltage sampling circuit, and then estimates the energy of the current residual high voltage of the capacitor and the stress of the short-circuit discharge IGBT. At the same time, the IGBT circuit feeds back the status monitoring information of the six IGBT single tubes to the control unit through the drive circuit. The control unit confirms the discharge strategy based on the status information; when the control unit determines that the IGBT unit fails and does not meet the active discharge conditions, it directly alarms; when it is determined that the voltage is too high, execute step 2.

[0034] The specific steps of confirming the conditions for through discharge include:

[0035] 1) The bus voltage sampling circuit collects the capacitor voltage;

[0036] 2) Estimate energy based on current capacity P = 0.5 CU 2 ,,According to the maximum short-circuit energy provided in the IGBT manual, the fastest discharge time is estimated, and the slowest discharge time is calibrated according to the motor winding discharge time. The system discharge time requirement is stored in the control unit;

[0037] 3) According to the IGBT double pulse test calibration loop stray inductance L, estimate To determine the voltage stress, where: dt is the turn-off time, di is the short-circuit current of the IGBT;

[0038] The status monitoring information includes: IGBT temperature, bus voltage, drive voltage, fault signal, V CE ;

[0039] Step 2, the control unit alternately sends: ① PWM control signal to the drive circuit to drive the first, third and fifth IGBT tubes a, c, e of the IGBT circuit, which are turned on at a 50% duty cycle, so that the winding of the motor 3 is charged; ② PWM control signal to the drive circuit to drive the second, fourth and sixth IGBT tubes b, d, f of the IGBT circuit, which are turned on at a 50% duty cycle, so that the winding of the motor 3 is short-circuited and discharged; at the same time, the motor temperature sampling circuit monitors the motor winding temperature in real time, and stops the action of the PWM control signal when an abnormality occurs, until the temperature drops and the execution is resumed; the bus voltage sampling circuit feeds back the bus voltage until it drops below the threshold. At this time, the control unit confirms whether it is necessary to start the bridge wall short-circuit discharge according to the discharge time requirement. If it is determined that the discharge time may be exceeded, step 3 is executed.

[0040] The active discharge logic means: releasing the interlocking restriction of the upper and lower bridges of the U phase, allowing the upper and lower bridges of the IGBT circuit to pass directly.

[0041] Step 3, the three-phase lower bridges b, d, and f enter the active short-circuit state, and the IGBT temperature sampling circuit outputs the current three-phase bridge arm temperature to the control unit. The control unit adjusts the U-phase PWM signal according to the current temperature condition and performs narrow pulse bridge wall short-circuit discharge until the capacitor voltage is discharged to the specified voltage; when the IGBT temperature is overheated, the discharge is suspended, and the temperature is dropped to within the threshold, and the operation is repeated; when the monitoring circuit is activated, step 4 is executed;

[0042] Step 4: U-phase IGBT direct pass, V CE Too large, due to L is a fixed value, V CE The monitoring loop is fed back to the IGBT gate to delay shutdown and increase the shutdown time dt; V CE The monitoring loop feeds back to the power circuit, thereby reducing the drive voltage and the short-circuit current of the IGBT, that is, reducing di, and ultimately limiting V CE At the same time, the on-resistance of IGBT increases, the heat consumption increases, and the discharge speed is accelerated.

[0043] This method detects the bus voltage through the control unit, and estimates the voltage stress and discharge time according to the system stray inductance, the maximum short-circuit energy of the IGBT, and the IGBT turn-off time. When the bus voltage is large, such as when the controller is in the state of high-speed main relay disconnection, the capacitor is charged to more than 500V, and the motor winding 0 torque mode is first used for discharge. After the voltage drops to the threshold, the 0 torque mode is calibrated to check whether it meets the discharge time requirement. If not, the bridge wall short-circuit discharge is started, and the Vce feedback regulation circuit introduced can respond quickly in hundreds of nS to suppress the short-circuit current, thereby suppressing the turn-off voltage spike, and effectively reducing the risk of IGBT failure.

[0044] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A motor controller active discharge system, characterized in that: include: The thin film capacitor, IGBT circuit and motor are arranged on the bus, the IGBT temperature sampling circuit connected to the IGBT circuit and the driving circuit with a power supply circuit, the bus voltage sampling circuit connected to the thin film capacitor, the motor temperature sampling circuit and the motor speed sampling circuit connected to the motor, wherein: the IGBT circuit converts the DC high voltage in the bus into a three-phase AC voltage and outputs it to the motor winding, the bus voltage sampling circuit collects the voltage across the thin film capacitor, the control unit obtains the system stray inductance, the IGBT temperature, the motor temperature, the motor speed through a double pulse test and calculates the IGBT off-tube voltage stress when the bridge arm is short-circuited and determines whether the bridge arm short-circuit discharge is satisfied. If it is not satisfied, it switches to the motor winding short-circuit discharge, that is, 0 torque mode discharge so that no unexpected torque occurs; when the voltage across the thin film capacitor drops to meet the bridge arm short-circuit discharge condition, the control unit estimates the discharge time and generates a corresponding PWM output to the IGBT circuit through the driving circuit; The IGBT circuit is a three-phase bridge inverter circuit, comprising: three bridge arms connected in parallel, each bridge arm having two IGBT single tubes connected in series, wherein: the center points of the three bridge arms are used as three AC ends and are respectively connected to the three-phase AC ports of the motor; The power supply circuit adjusts the voltage supplied to the driving circuit according to the feedback regulation signal, which is specifically achieved in the following manner: the driving circuit is further provided with a Vce monitoring loop, which specifically includes: an operational amplifier, a photosensitive semiconductor, a TVS chain and a trigger, wherein: the non-inverting input terminal of the operational amplifier is connected to the feedback end of the TVS chain, the input terminal of the photosensitive semiconductor is connected to the output terminal of the resistor voltage divider, and the input terminal of the trigger is connected to the output terminal of the photosensitive semiconductor; when V CE When the voltage is too large to break through the TVS chain, it will charge the IGBT gate capacitor, slow down the drop of the driving voltage, and slow down the shutdown speed. At the same time, the output enable signal is output to the photosensitive semiconductor through the operational amplifier. After isolation, it is output to the trigger. The trigger is controlled by the PWM input signal and the control unit signal enable. When the PWM is turned off or the control unit sends an enable signal to the trigger, the trigger will output a high level as a feedback adjustment signal to the power supply circuit.

2. The motor controller active discharge system according to claim 1, characterized in that: The power supply circuit includes: a power chip, a MOS tube, an inductor, a resistor, a capacitor and a transformer, wherein: the power chip and its peripheral components receive the input of the vehicle battery and output 15V as the transformer input; the MOS switch tube receives the control unit PWM signal, converts 15V into 15V and -5V and outputs it to the drive circuit, and the transformer is used for high-voltage and low-voltage isolation.

3. The motor controller active discharge system according to claim 1, characterized in that: The power supply circuit is further provided with a power supply circuit feedback regulation circuit and a power supply circuit sampling circuit.

4. The motor controller active discharge system according to claim 1, characterized in that: The driving circuit is used for PWM power amplification, and specifically comprises: six groups of driving components connected to each other by IGBT circuits, and the six components correspond to six IGBT single tubes.

5. The motor controller active discharge system according to claim 1, characterized in that: An IGBT temperature sampling circuit is provided between the control unit and the IGBT circuit.

6. The motor controller active discharge system according to claim 1, characterized in that: In the estimation, the control unit calculates the discharge time according to the active discharge time by looking up the table and calibrating the narrow pulse discharge speed.

7. A control method of the system according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: After receiving the power-off command from the vehicle control unit, the control unit determines that the main relay is disconnected. At this time, the voltage value on the DC blocking capacitor is detected by the bus voltage sampling circuit, and the energy of the current residual high voltage of the capacitor is estimated according to the capacitor energy. At the same time, the IGBT circuit feeds back the status monitoring information of the six IGBT single tubes to the control unit through the drive circuit, and the control unit confirms the conditions for through-discharge according to the status information; Step 2) The control unit alternately sends: ① PWM control signals to the drive circuit to drive the first, third and fifth IGBT tubes of the IGBT circuit to be turned on at a 50% duty cycle, so that the motor winding is charged; ② PWM control signals to the drive circuit to drive the second, fourth and sixth IGBT tubes of the IGBT circuit to be turned on at a 50% duty cycle, so that the motor winding is short-circuited and discharged; at the same time, the motor temperature sampling circuit monitors the motor winding temperature in real time, and stops the action of the PWM control signal when an abnormality occurs, and resumes execution after the temperature drops; the bus voltage sampling circuit feeds back the bus voltage, and the control unit judges the capacitor energy in real time. When it is less than the threshold, the active discharge logic is switched to use the IGBT circuit for direct discharge; Step 3) The IGBT temperature sampling circuit outputs the current three-phase bridge arm temperature to the control unit, and the control unit adjusts U according to the current temperature condition to execute short circuit and narrow pulse direct discharge until the capacitor voltage is discharged to the specified voltage; when the IGBT temperature is overheated, the discharge is suspended, and the temperature is dropped to within the threshold, and the operation is repeated; when the monitoring circuit is activated, step 4 is executed; Step 4) U-phase IGBT is directly connected, V CE Too large, due to L is a fixed value, V CE The monitoring loop is fed back to the IGBT gate, delaying shutdown and increasing the shutdown time dt; V CE The monitoring loop feeds back to the power circuit, thereby reducing the drive voltage and the short-circuit current of the IGBT, that is, reducing di, and ultimately limiting V CE ; At the same time, the on-resistance of IGBT increases, the heat consumption increases, and the discharge speed is accelerated; The active discharge logic means: releasing the interlocking restriction of the upper and lower bridges of the U phase, allowing the upper and lower bridges of the IGBT circuit to pass directly; The status monitoring information includes: IGBT temperature, bus voltage, drive voltage, fault signal, V CE .

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