Motor stall detection method based on vector control

Abstract

This invention discloses a motor stall detection method based on vector control, comprising: S1, detecting motor stall conditions; S2, determining whether to perform motor stall detection; S3, signal acquisition and processing: the motor controller MCU acquires the DC bus voltage signal and the motor three-phase current signal through sensors; S4, acquiring control signal values: referencing the output signal value of the SVPWM module during the vector control process within the motor controller MCU; S5, signal calculation: calculating the controller output three-phase voltage value and motor input power using the acquired DC bus voltage value, the referenced signal value, and the motor three-phase current value, and simultaneously calculating the absolute value of the motor three-phase current; S6, determining whether the motor is in a stall condition: determining whether the motor is stalled based on the calculated signal value; S7, assigning a stall fault level. This invention can simultaneously identify and distinguish the severity of stall when the motor is operating in a stall condition.

Description

Technical Field

[0001] This invention relates to the field of power motors for new energy vehicles, and specifically to a method for detecting motor stall based on vector control. Background Technology

[0002] AC drive motors (such as AC asynchronous motors and permanent magnet synchronous motors) are being widely used in new energy vehicles (such as pure electric vehicles, hybrid electric vehicles, and hydrogen fuel cell vehicles). During the operation of a new energy vehicle, the motor controller receives instructions from the vehicle control unit to control the drive motor in electric mode to convert three-phase AC power into mechanical energy output, and in generator mode to convert mechanical energy back into three-phase AC power. Since the vehicle's battery is a high-voltage DC power source, the conversion between DC and three-phase AC power is also necessary during this process. Currently, this is mainly achieved through IGBTs (Inductively Coupled Bits) power semiconductor devices in the motor controller.

[0003] Because the drive motor and its controller are core components of new energy vehicles, their reliability and safety largely determine the overall vehicle performance. The IGBT (Inductively Coupled Bit) power semiconductor device plays a crucial role in the motor controller, and its cost is the highest among all components within the controller. Therefore, during motor controller operation, it is often necessary to monitor, diagnose faults, and protect the drive motor and the controller itself. Stall condition detection of the motor is one such method.

[0004] When a motor is stalled, the motor rotor does not rotate. Current methods for detecting motor stall include whether the effective value of the three-phase current is continuously greater than a preset threshold; whether the motor speed or back electromotive force is continuously less than a preset threshold; and whether the estimated motor output torque or the torque command received by the MCU from the vehicle control unit is greater than a preset threshold within a preset detection time.

[0005] When the controller employs a rotor field-oriented vector control method, the current in the three-phase windings of the motor is direct current, and the amplitudes of the three-phase currents are not the same. The maximum phase current is related to the current position of the rotor. Therefore, when the motor is stalled, the temperature rise of the three-phase stator windings is different. Currently, automotive drive motors typically embed only one or two temperature sensors in their windings. Thus, when the motor stalls, the temperature detected by these one or two winding sensors may not be the highest among the three phases. Simultaneously, the effective current flowing through each arm of the IGBT module in the corresponding motor controller is also different, meaning the temperature rise of the six IGBTs is different. Most current IGBT modules only have a temperature sensor built into each arm, but there is still a certain temperature difference between this sensor and the junction temperature of the IGBT chip. Therefore, during the operation of the electric drive system, protection cannot be simply based on the detected winding and IGBT temperatures. It is necessary to identify the stalled operation condition of the motor to provide input for the controller to implement a fast, accurate protection strategy that meets the requirements of the entire vehicle operation. Summary of the Invention

[0006] This invention provides a method for detecting motor stall, which can simultaneously identify and differentiate the severity of stall when the motor is operating in a stall condition.

[0007] The technical solution to the above problem is as follows:

[0008] A motor stall detection method based on vector control is characterized by the following steps:

[0009] S1, perform motor stall condition detection;

[0010] S2, Whether to perform motor stall detection and judgment;

[0011] S3, Signal Acquisition and Processing: The motor controller MCU acquires DC bus voltage signal and motor three-phase current signal through sensors;

[0012] S4, Control signal value acquisition: Refer to the value of the SVPWM module output signal during the vector control process inside the motor controller MCU;

[0013] S5, Signal Calculation: Calculate the controller output three-phase voltage value and motor input power using the collected DC bus voltage value, referenced signal value, and motor three-phase current value, and simultaneously calculate the absolute value of the motor three-phase current;

[0014] S6, Determine if the motor is in a stalled state: Determine whether the motor is stalled based on the calculated signal value;

[0015] S7 stall fault level assignment.

[0016] This invention, during motor operation, uses FOC vector control to obtain the duty cycles of the A, B, and C phases calculated by the voltage space vector pulse width modulation (SVPWM) module, and calculates the current input power of the motor by collecting the controller's DC bus voltage and the motor's three-phase current. Combining the input power value and the absolute value of the motor's three-phase current, it detects whether the motor is operating in a stall condition and the severity of the stall. It can quickly and accurately detect the motor stall condition without increasing the hardware cost, using existing motor winding temperature and IGBT module temperature detection technologies. This provides input for the controller to select a reasonable protection strategy.

[0017] The beneficial technical effects of this invention are as follows:

[0018] 1. This invention is based on FOC vector control. By collecting the three-phase current of the motor and the DC bus voltage, and combining the absolute value of the three-phase current of the motor with the calculated motor input power, the motor stall detection is performed. Compared with the method of detection based solely on the three-phase current of the motor, the estimated motor output torque, or the torque command received by the motor controller from the vehicle control unit, this method is more accurate and will not cause false detection or false protection, thus affecting the safe operation of the vehicle.

[0019] 2. In the process of detecting motor stall conditions, this invention confirms that the motor is operating in a stall condition and simultaneously identifies and distinguishes the severity of the stall. This provides input for the controller to implement different protection strategies based on the severity of the stall. While ensuring the safety of the electric drive system, the performance of the controller can be utilized to the limit, thereby improving the performance of the entire vehicle. Attached Figure Description

[0020] Figure 1 This is a block diagram of AC motor vector control during the implementation of this invention.

[0021] Figure 2 This is the main flowchart for detecting motor stall during the implementation of this invention.

[0022] Figure 3 This is part of the auxiliary flowchart for motor stall detection during the implementation of this invention.

[0023] Figure 4 This is another part of the auxiliary flowchart for motor stall detection during the implementation of this invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be described in more detail with reference to the accompanying drawings. The described embodiments are some, but not all, of the embodiments of the present invention. The embodiments described with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be simply construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] like Figures 1 to 4 As shown, the motor stall detection method based on vector control of the present invention includes the following steps:

[0026] S1, perform motor stall condition detection.

[0027] Step S1, motor stall condition detection, includes reading the motor stall detection function enable flag and the value of the controller's current operating mode, i.e., detecting: 1) the value of the motor stall detection function enable flag; 2) the value of the controller's operating mode variable.

[0028] S2, whether to perform motor stall detection.

[0029] In step S2, it is determined whether the value of the motor stall detection function enable flag is valid and whether the controller is in normal operating mode. If the enable flag is valid and the controller is in normal operating mode, the process proceeds to signal acquisition and processing in step S3; otherwise, condition detection continues. Only after the enable flag is detected as valid and the controller is in normal operating mode, and this condition is maintained for a certain period, can the process proceed to signal acquisition and processing in step S3.

[0030] S3, Signal Acquisition and Processing: The motor controller MCU acquires the DC bus voltage signal and the three-phase current signal of the motor through sensors. In step S3, the acquired DC bus voltage is filtered. If the motor controller MCU only uses two current sensors to acquire the A and B phase currents, then the C phase current i... c via i c =-(i a +i b ) Calculated;

[0031] i a Indicates the current of phase A, i b Indicates the B-phase current, i c This represents the C-phase current.

[0032] The collected DC bus voltage values ​​are filtered using a direct type I IIR digital filter.

[0033] S4, Control Signal Value Acquisition: Referencing the output signal value of the SVPWM module during the vector control process within the motor controller MCU; in step S4, the duty cycle S of the three phases A, B, and C is calculated by reading the voltage space vector pulse width modulation (SVPWM) module during the FOC vector control (rotor field orientation-based vector control) process. a S b S c This is used as the input for calculating the S5 signal.

[0034] The FOC vector control process is as follows:

[0035] S41, the motor controller MCU receives the torque command T from the vehicle control unit. * Based on the current motor operating speed and the controller DC bus voltage, the direct-axis target current i is obtained by referring to the reference ammeter. d * Cross-axis target current i q * ;

[0036] S42, the three-phase currents i of A, B, and C collected by the current sensor a i b i c The i-axis feedback current is transformed into the α-axis feedback current in the α and β coordinate systems through Clarke coordinate transformation. α and β-axis feedback current i β The Clarke transform formula is as follows:

[0037]

[0038] Then, the Park transformation is used to convert iα and iβ into direct-axis feedback current i in the d and q-axis coordinate system. d With cross-axis feedback current i q The Park transformation formula is as follows:

[0039]

[0040] θ is the angle between the d-axis in the d-q rotating coordinate system and the a-axis in the three-phase stationary coordinate system.

[0041] S43, Direct-axis target current i d * Cross-axis target current i q * and direct-axis feedback current i d Cross-axis feedback current i q The direct-axis target voltage u is obtained through the action of the current controller. d Cross-axis target voltage u qThe target voltages on the direct and quadrature axes are then subjected to an inverse Park transformation to obtain the target voltage u in the α and β coordinate systems. α and u β The formula for the inverse Park transform is as follows:

[0042]

[0043] S44, target voltage u α and u β The duty cycle S of phases A, B, and C is calculated and output through the voltage space vector pulse width modulation (SVPWM) module. a S b S c It drives the three-phase inverter IGBT to operate, thereby controlling the output torque of the motor.

[0044] S5, Signal Calculation: Calculate the controller output three-phase voltage and motor input power using the collected DC bus voltage, referenced signal values, and motor three-phase current values, while also calculating the absolute value of the motor three-phase current.

[0045] In step S5, the three-phase voltage value output by the motor controller is calculated using the DC bus voltage value after digital filtering and the duty cycle of the three phases A, B, and C. The motor input power is calculated in combination with the collected motor three-phase current value, and the absolute values ​​of the motor A, B, and C three-phase currents are calculated.

[0046] The controller outputs three-phase voltage u using the following calculation formula. a u b u c :

[0047]

[0048] Motor input power: P motor =u a* i a +u b* i b +u c* i c

[0049] u a The output voltage of phase A, u b For phase B output voltage, u c For the C-phase output voltage, i a Indicates the output current of phase A, i b Indicates the output current of phase B, i c U represents the output current of phase C. DC S is the DC bus voltage after digital filtering. a Let S be the duty cycle of phase A. b For phase B duty cycle, S cFor the C phase duty cycle, P motor This is the input power to the motor.

[0050] S6, Determine if the motor is in a stall condition: Determine if the motor is stalled based on the calculated signal value; In step S6, the calculated motor input power and the absolute values ​​of the three-phase currents A, B, and C are compared with a preset threshold, and the stall condition is determined based on the duration of this state.

[0051] The steps for determining stalled operation based on the duration of the stall condition are as follows:

[0052] S601, determine the current motor input power P motor Is it less than or equal to the preset power threshold P? x If yes, then proceed.

[0053] S602, if yes, otherwise proceed to S603, where a preset power threshold P is... x Selected from motor stall test bench calibration data;

[0054] S602, Calculate the first stall detection time t1 = t1 + T s That is, add the stall fault detection period T to the current cumulative time t1 value. s Calculate the duration of the stall;

[0055] S603, Determine whether the absolute value of the phase A current is greater than or equal to the preset current threshold I. x If yes, proceed to S604; otherwise, proceed to S605, where a preset current threshold I is set. x Selected from motor stall test bench calibration data;

[0056] S604, Calculate the second stall detection time t2 = t2 + T s That is, add the stall fault detection period T to the current cumulative time t2 value. s Calculate the duration of the stall;

[0057] Step 5: S605 determines whether the absolute value of the phase B current is greater than or equal to the preset current threshold I. x If yes, then proceed.

[0058] S607, if yes, otherwise proceed to S608;

[0059] S606, Calculate the third stall detection time t3 = t3 + T s That is, add the stall fault detection period T to the current cumulative time t3 value. s Calculate the duration of the stall;

[0060] S607, Determine whether the absolute value of the C-phase current is greater than or equal to the preset current threshold I. x， If yes, proceed to S608; otherwise, proceed to S609.

[0061] S608, Calculate the fourth stall detection time t4 = t4 + T s That is, add the stall fault detection period T to the current cumulative time t4 value. s Calculate the duration of the stall;

[0062] S609, determine ((t2≥threshold 2T)) x )||(t3≥threshold2T x )||(t4≥threshold2T x ))&&(t1≥threshold2T x If the condition is true, proceed to S612 to set the motor's operating status to level 3 stall fault; otherwise, proceed to S610, where the stall detection judgment time T is preset. x Selected from motor stall test bench calibration data;

[0063] S610, determine ((t2≥threshold T)) x )||(t3≥thresholdT) x )||(t4≥thresholdT) x ))&&(t1≥thresholdT x If true, proceed to S613 to set the motor's operating status to Level 2 stall fault; otherwise, proceed to S611.

[0064] S611, determine if (t2≥threshold 0.5T) x )||(t3≥threshold0.5T x )||(t4≥threshold0.5T x ))&&(t1≥threshold0.5T x If the value is true, proceed to S614 to set the motor's operating status to Level 1 stall fault; otherwise, proceed to S615, indicating that the motor currently has no stall fault.

[0065] S7 Stall Fault Level Assignment. Based on the judgment results of S609, S610, and S611, the state of motor stall fault is assigned a value. According to the judgment results of S609, S610, and S611, the motor operating state can be divided into 4 types: no stall fault, level 1 stall fault, level 2 stall fault, and level 3 stall fault.

Claims

1. A motor stall detection method based on vector control, characterized in that, Includes the following steps: S1, conduct stall condition testing on the power motor of new energy vehicles; Step S1, motor stall condition detection, includes reading the motor stall detection function enable flag and the value of the controller's current operating mode; S2, Whether to perform motor stall detection and judgment; In step S2, it is determined whether the value of the motor stall detection function enable flag is valid and whether the controller is in normal working mode. When the enable flag is detected to be valid and the controller is in normal working mode, it can only proceed to S3 signal acquisition and processing after maintaining this for a period of time; otherwise, condition detection continues. S3, Signal Acquisition and Processing: The motor controller MCU acquires DC bus voltage signal and motor three-phase current signal through sensors; S4, Control signal value acquisition: Refer to the value of the SVPWM module output signal during the vector control process inside the motor controller MCU; S5, Signal Calculation: Calculate the controller output three-phase voltage value and motor input power using the collected DC bus voltage value, referenced signal value, and motor three-phase current value, and simultaneously calculate the absolute value of the motor three-phase current; S6, Determine if the motor is in a stalled state: Determine whether the motor is stalled based on the calculated signal value; In step S6, the calculated absolute values ​​of the motor input power and the three-phase currents A, B, and C are compared with preset thresholds, and the stall condition is determined based on the duration of the state as follows: S601, determine the current motor input power P motor Is it less than or equal to the preset power threshold P? x If yes, proceed to S602; otherwise, proceed to S603, where a preset power threshold P is set. x Selected from motor stall test bench calibration data; S602, calculate the first stall time t1 = t1 + T s That is, add the stall fault detection period T to the current cumulative time t1 value. s Calculate the duration of the stall; S603, Determine whether the absolute value of the phase A current is greater than or equal to the preset current threshold I. x If yes, proceed to S604; otherwise, proceed to S605, where a preset current threshold I is set. x Selected from motor stall test bench calibration data; S604, calculate the second stall time t2 = t2 + T s That is, add the stall fault detection period T to the current cumulative time t2 value. s Calculate the duration of the stall; Step 5: S605 determines whether the absolute value of the phase B current is greater than or equal to the preset current threshold I. x If yes, proceed to S607; otherwise, proceed to S608. S606, calculate the third stall time t3 = t3 + T s That is, add the stall fault detection period T to the current cumulative time t3 value. s Calculate the duration of the stall; S607, Determine whether the absolute value of the C-phase current is greater than or equal to the preset current threshold I. x， If yes, proceed to S608; otherwise, proceed to S609. S608, calculate the fourth stall time t4 = t4 + T s That is, add the stall fault detection period T to the current cumulative time t4 value. s Calculate the duration of the stall; S609, determine ((t2≥threshold 2T)) x )||(t3≥threshold2T x )||(t4≥threshold2T x ))&&(t1≥threshold2T x If the condition is true, proceed to S612 to set the motor's operating status to level 3 stall fault; otherwise, proceed to S610, where the stall detection judgment time T is preset. x Selected from motor stall test bench calibration data; S610, determine ((t2≥threshold T)) x )||(t3≥thresholdT) x )||(t4≥thresholdT) x ))&&(t1≥thresholdT x If true, proceed to S613 to set the motor's operating status to Level 2 stall fault; otherwise, proceed to S611. S611, determine if (t2≥threshold 0.5T) x )||(t3≥threshold0.5T x )||(t4≥threshold0.5T x ))&&(t1≥threshold0.5T x If true, proceed to S614 to set the motor's operating status to Level 1 stall fault; otherwise, proceed to S615, indicating that the current motor has no stall fault. S7, assigned a stall fault level.

2. The motor stall detection method based on vector control according to claim 1, characterized in that, In step S3, the collected DC bus voltage is filtered. If the motor controller only uses two current sensors to collect the currents of phases A and B, then the current of phase C, i... c via i c =-(i a +i b ) was calculated; i a Indicates the current of phase A, i b Indicates the B-phase current, i c This represents the C-phase current.

3. The motor stall detection method based on vector control according to claim 1, characterized in that, In step S4, the duty cycles S of the three phases A, B, and C are calculated by reading the voltage space vector pulse width modulation (SVPWM) module output during the FOC vector control process. a S b S c This is used as the input for calculating the S5 signal.

4. The motor stall detection method based on vector control according to claim 3, characterized in that, The FOC vector control process is as follows: S41, the motor controller MCU receives the torque command T from the vehicle control unit. * Based on the current motor operating speed and the controller DC bus voltage, the direct-axis target current i is obtained by referring to the reference ammeter. d * Cross-axis target current i q * ; S42, the three-phase currents i of A, B, and C collected by the current sensor a i b i c Transform i into the α and β coordinate systems using Clarke coordinate transformation. α and i β The Clarke transform formula is as follows: ； Then, the Park transformation is used to convert iα and iβ into direct-axis feedback current i in the d and q-axis coordinate system. d With cross-axis feedback current i q The Park transformation formula is as follows: ； S43, Direct-axis target current i d * Cross-axis target current i q * and direct-axis feedback current i d Cross-axis feedback current i q The direct-axis target voltage u is obtained through the action of the current controller. d Cross-axis target voltage u q The target voltages on the direct and quadrature axes are then subjected to an inverse Park transformation to obtain the target voltage u in the α and β coordinate systems. α and u β The formula for the inverse Park transform is as follows: ； S44, target voltage u α and u β The duty cycle S of phases A, B, and C is calculated and output through the voltage space vector pulse width modulation (SVPWM) module. a S b S c It drives the three-phase inverter IGBT to operate, thereby controlling the output torque of the motor.

5. The motor stall detection method based on vector control according to claim 1, characterized in that, In step S5, the three-phase voltage value output by the motor controller is calculated using the DC bus voltage value after digital filtering and the duty cycle of the three phases A, B, and C. The motor input power is calculated in combination with the collected motor three-phase current value, and the absolute values ​​of the motor A, B, and C three-phase currents are calculated.

6. The motor stall detection method based on vector control according to claim 5, characterized in that, The controller outputs three-phase voltage u using the following calculation formula. a u b u c : ； Motor input power: P motor =u a* i a +u b* i b +u c* i c； u a The output voltage of phase A, u b For phase B output voltage, u c For the C-phase output voltage, i a Indicates the output current of phase A, i b Indicates the output current of phase B, i c U represents the output current of phase C. DC S is the DC bus voltage after digital filtering. a Let S be the duty cycle of phase A. b For phase B duty cycle, S c For the C phase duty cycle, P motor This is the input power to the motor.

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