A permanent magnet synchronous motor power-off control method and calibration method

Abstract

The present application discloses a power-off control method and calibration method for a permanent magnet synchronous motor, wherein, when the motor vehicle is in a preset state, the motor controller MCU will consult the fast power-off calibration table stored in the system to obtain the three-phase winding required current value at the current position of the permanent magnet synchronous motor, and the three-phase winding required current can ensure that the synthetic magnetic field or synthetic current at the current position of the permanent magnet synchronous motor is only located on the direct axis, and the synthetic magnetic field or synthetic current value of the cross axis is 0. At the same time, the actual current is made consistent with the theoretical current through the closed-loop proportional integral PI control of the current. While ensuring that the permanent magnet synchronous motor has a faster discharge current, it avoids the occurrence of uncontrollable cross-axis current in the permanent magnet synchronous motor due to the hysteresis of the control system, thereby causing the motor to rotate suddenly, causing serious consequences for driving safety.

Description

Technical Field

[0001] The present application relates to the field of vehicle engineering technology, and more specifically, to a power-off control method and a calibration method for a permanent magnet synchronous motor. Background Art

[0002] With the continuous development of new energy technologies, there are more and more types of electric vehicles. Electric buses have become an important choice for more and more cities due to their zero emissions and high torque.

[0003] However, in actual application, it was found that after the electric bus is powered off, the capacitor of the permanent magnet synchronous motor will slowly release the stored electrical energy, causing the voltage to drop slowly. At this time, if the vehicle needs to be restarted, the entire vehicle will not be able to be powered on, resulting in abnormal starting of the vehicle.

[0004] At present, there are not many patents specifically for the power-off control method of permanent magnet synchronous motors, and the related patents are mainly concentrated on the power-off control circuit design and control method of permanent magnet synchronous motors. For example, the invention patent application: a power-off control circuit and a power-off control method, patent number: 201911387123.4, discloses a power-off control circuit and a power-off control method, obtains the current of the PSE power supply through the current detection circuit and converts it into a voltage, and controls the second PSE chip through the second overcurrent comparison circuit according to the voltage, thereby controlling the power on and off of the PD corresponding to the second PSE chip. The hierarchical control of PD power-off is realized. When the load changes abnormally, unimportant PDs can be controlled to power off first, and important PDs can be controlled last to reduce the impact. However, this method adds additional circuits, which will increase the cost of the controller.

[0005] The present application discloses a power-off control method and calibration method for a permanent magnet synchronous motor. Among the related patents for the power-off control method for a permanent magnet synchronous motor, there is an invention patent: A power-off control method and power-off control system for a permanent magnet synchronous motor, patent number: 202011065033.6. It proposes a method for controlling the rapid power-off of a permanent magnet synchronous motor by changing the switching frequency of a control circuit. However, in practical applications, this method causes a large change in the theoretical reference current of the system during control due to the rapid change in the bus voltage of the system. At the same time, due to the hysteresis of the electronic control system, the current synthesized by the actual three-phase current will have a cross-axis current component, which causes the rotation of the motor and affects driving safety.

[0006] In summary, the current innovations in the control methods for powering off permanent magnet synchronous motors are all focused on designing new control algorithms to achieve complete decoupling of the motor's AC and DC axes, or using a specific switching sequence of the inverter power devices.

[0007] At present, the applicant has not found any patents or documents in the field of using calibration method to achieve decoupling of AC and DC axis currents during power-off of permanent magnet synchronous motors, and applying the calibration table obtained through calibration to achieve power-off control of permanent magnet synchronous motors, through searches at home and abroad. Summary of the invention

[0008] In order to solve the above technical problems, the present application provides a permanent magnet synchronous motor power-off control method and a calibration method to solve the problem of unexpected cross-axis current and sudden rotation of the motor during the power-off process of the permanent magnet synchronous motor.

[0009] In order to achieve the above technical objectives, the embodiments of the present application provide the following technical solutions.

[0010] A method for controlling power-off of a permanent magnet synchronous motor comprises:

[0011] S101: The vehicle controller detects the state of the motor vehicle and provides a fast power-off control signal to the motor controller of the permanent magnet synchronous motor when the motor vehicle is in a preset state.

[0012] S102: After receiving the fast power-off control signal, the motor controller enters the fast power-off mode and consults a pre-calibrated calibration table stored in the fast power-off table lookup module to obtain the required current value of the three-phase winding at the current position.

[0013] S103: The motor controller directly sends the required current value of the three-phase winding at the current position to the proportional-integral PI module for closed-loop control to obtain the A-phase regulated voltage U a , B phase regulation voltage U b , C phase regulation voltage U c , and adjust the three-phase current.

[0014] S104: Determine whether the bus voltage of the permanent magnet synchronous motor is less than or equal to the preset voltage. If yes, exit the power-off control process; if no, return to S103 to cycle.

[0015] Preferably, the calibration table records the required current values ​​of the three-phase windings at different rotor electrical position angles.

[0016] Preferably, the synthetic magnetic field of the required current values ​​of the three-phase windings at the current rotor position is all located at the position of the rotor direct axis d, and there is no magnetic field component on the quadrature axis q.

[0017] Preferably, the angular variable in the calibration table is the electrical position angle of the motor, the step size of the electrical position angle variable is X°, X is a positive integer divisible by 360, the composite current of the three-phase current is 5S amperes, S is a positive integer selected by the calibration personnel according to actual needs, and the direction of the composite current is on the direct axis.

[0018] Preferably, the required current value of the three-phase winding obtained in step S102 does not change during this fast power-off control process.

[0019] A power-off calibration method for a permanent magnet synchronous motor, the calibration method comprising:

[0020] S401: Determine the direct-axis current of the permanent magnet synchronous motor.

[0021] S402: Acquire a plurality of electrical position angles equally divided according to a preset step size. When the electrical position angle is 0°, the direct axis of the permanent magnet synchronous motor coincides with the A-phase axis.

[0022] S403: Based on the direct-axis current value and the electrical position angle, the A-phase current value, the B-phase current value, and the C-phase current value at each electrical position angle are calculated and prepared into the calibration table.

[0023] S404: Rotate the permanent magnet synchronous motor shaft to the electrical position angle corresponding to the Yth column in the calibration table, where Y represents the number of columns in the calibration table and the initial value is 1, and set the required values ​​of the A-phase current value, the B-phase current value, and the C-phase current value to the current values ​​under the Yth column in the calibration table in the calibration software.

[0024] S405: Disconnect the power supply of the permanent magnet synchronous motor control system to put the permanent magnet synchronous motor into a power-off state.

[0025] S406: During the power-off process, observe whether the shaft of the permanent magnet synchronous motor rotates. If not, modify the A-phase current value, B-phase current value, and C-phase current value under the electrical position angle corresponding to the Yth column of the power-off calibration table to the required values ​​set in the calibration software, end the calibration of the electrical position angle corresponding to the Yth column, and jump to step S409. If yes, jump to S407.

[0026] S407: Observe the cross-axis current during rotation. If a positive Q-axis current appears, subtract Z° from the electrical position angle, where Z is a rational number. If a negative Q-axis current appears, increase the electrical position angle by Z°. Recalculate the A-phase current value, the B-phase current value, and the C-phase current value based on the modified electrical position angle.

[0027] It should be noted that the modified electrical position angle is only used in the calculation of the A-phase current value, the B-phase current value, and the C-phase current value in S408, and will not be used to change the data in the electrical position angle column in the calibration table obtained in step S403.

[0028] S408: Modify the A-phase current value, B-phase current value, and C-phase current value under the electrical position angle corresponding to the Yth column of the power-off calibration table to the values ​​recalculated in step S407, and return to step S405.

[0029] S409: Obtain the electrical position angle corresponding to the Y+1th column of the calibration table, and repeat steps S404 to S408 until all electrical position angles are calibrated.

[0030] Preferably, step S403 includes the following specific steps.

[0031] According to formula I a =I d cos(θ), determine the A-phase winding current value.

[0032] According to formula I b =I d cos(θ-2π / 3), determine the B-phase winding current value.

[0033] According to formula I c =I d cos(θ+2π / 3), determine the C-phase winding current value.

[0034] Where θ is the electrical position angle, I d is the direct axis current.

[0035] It can be seen from the above technical scheme that the embodiment of the present application provides a permanent magnet synchronous motor power-off control method and a calibration method, wherein, in the power-off control method of the permanent magnet synchronous motor, when the motor enters the fast power-off state, the motor controller will consult the calibrated rotor position-three-phase ammeter stored in the fast power-off table lookup module, obtain a set of three-phase winding demand current values, and perform fast power-off control. The following are the beneficial effects of the invention.

[0036] 1. The three-phase required current value obtained by looking up the table will not change during this rapid power-off process, that is, the calibration table is only queried once during a rapid power-off process; and the control process does not involve the transformation of the stationary coordinate system and the rotating coordinate system, and does not require decoupling calculations on the motor direct axis d and quadrature axis q, which shortens the running time of the rapid power-off control program.

[0037] 2. Since there is no calculation of the demand current value during the control process, the theoretical three-phase current calculation value caused by the rapid drop in voltage and the lag of the control system will be avoided, and the synthetic current will have unexpected components on the quadrature axis, thereby avoiding unexpected rotation of the motor and improving driving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0039] Figure 1 A rotor position-three-phase current calibration table for a power-off control method of a permanent magnet synchronous motor is provided as an embodiment of the present application.

[0040] Figure 2 A schematic flow chart of a power-off control method for a permanent magnet synchronous motor is provided as an embodiment of the present application.

[0041] Figure 3 A schematic flow chart of a power-off control method for a permanent magnet synchronous motor is provided as another embodiment of the present application.

[0042] Figure 4 A control block diagram of a power-off control system of a permanent magnet synchronous motor provided in one embodiment of the present application.

[0043] Figure 5 A schematic flow chart of a power-off calibration method for a permanent magnet synchronous motor is provided as an embodiment of the present application. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0045] The embodiment of the present application provides a method for controlling power-off of a permanent magnet synchronous motor, which is used to control the power-off process of a permanent magnet synchronous motor of a motor vehicle, such as Figure 2 As shown, the power-off control method of the permanent magnet synchronous motor includes:

[0046] S101: The vehicle controller detects the state of the motor vehicle and provides a fast power-off control signal to the motor controller of the permanent magnet synchronous motor when the motor vehicle is in a preset state.

[0047] S102: After receiving the fast power-off control signal, the motor controller enters the fast power-off mode and consults a pre-calibrated calibration table stored in the fast power-off table lookup module to obtain the required current value of the three-phase winding at the current position.

[0048] The fast power-off calibration table has an independent variable which is the electrical angle value of the rotor position of the permanent magnet synchronous motor, and a step size of X°, where X is a number divisible by 360; the output variable is the current value of the three-phase A, B, and C of the permanent magnet synchronous motor, and the composite current of the currents of the three-phase A, B, and C has a numerical value of 5S, where S is a positive integer selected by the calibration personnel according to actual needs, and the direction of the composite current is on the direct axis.

[0049] Optionally, in the example of the present application, the rotor position-three-phase current calibration table is specifically provided, such as Figure 1 In this table, X=30, so the rotor position is 0°, 30°, 60°…330°, 360°;

[0050] S=2, so the magnitude of the composite current is 10A.

[0051] S103: The motor controller directly sends the required current value of the three-phase winding at the current position to the proportional-integral PI module for closed-loop control to obtain the A phase regulated voltage (U a )、B phase regulated voltage(U b )、C phase regulation voltage(U c ), and adjust the three-phase current.

[0052] S104: Determine whether the bus voltage of the permanent magnet synchronous motor is less than or equal to the preset voltage. If yes, exit the power-off control process; if no, return to S103 to cycle.

[0053] In this embodiment, the specific execution subject of the state of the motor vehicle and the process of controlling the power-off of the permanent magnet synchronous motor is specified. Generally, reference is made to Figure 3 , after step S101 and before step S102, it may also include: S1012, judging whether the permanent magnet synchronous motor has a fault based on the motor controller; when the permanent magnet synchronous motor does not have a fault, the subsequent control signal providing process is performed, and when the permanent magnet synchronous motor has a fault, the entire power-off control process is exited.

[0054] The power-off control system of the permanent magnet synchronous motor provided in the embodiment of the present application is described below. The power-off control system of the permanent magnet synchronous motor described below can be referenced to the power-off control method of the permanent magnet synchronous motor described above.

[0055] Accordingly, the embodiment of the present application provides a power-off control system for a permanent magnet synchronous motor, such as Figure 4 As shown, it is used to control the power-off process of a permanent magnet synchronous motor of a motor vehicle, and the power-off control system of the permanent magnet synchronous motor includes.

[0056] The state detection module 100 is used to detect the state of the motor vehicle and provide a control signal to the permanent magnet synchronous motor when the motor vehicle is in a preset state to control the permanent magnet synchronous motor to power off, wherein the control signal is a PWM signal.

[0057] The signal processing module 200 is used to receive the control signal, process the control signal, and make a corresponding response.

[0058] The fast power-off table lookup module 300 is used to store the calibration table and output the three-phase required current value under the rotor electrical position angle.

[0059] The current closed-loop module 400 is used to perform closed-loop processing on the three-phase required current values ​​and output corresponding PWM signals.

[0060] The voltage judgment module 500 is used to judge whether the bus voltage of the permanent magnet synchronous motor is less than or equal to a preset voltage, and if so, exit the power-off control process.

[0061] The following describes the power-off calibration method of the permanent magnet synchronous motor provided in the embodiment of the present application. Figure 5 As shown, the power-off calibration method of the permanent magnet synchronous motor described below can correspond to the power-off control method of the permanent magnet synchronous motor described above.

[0062] S401: Determine the direct-axis current of the permanent magnet synchronous motor; optionally, in an embodiment of the present application, the direct-axis current of the permanent magnet synchronous motor is specified to be 10 amperes.

[0063] S402: Acquire a plurality of electrical position angles equally divided according to a preset step size. When the electrical position angle is 0°, the direct axis of the permanent magnet synchronous motor coincides with the A-phase axis.

[0064] Optionally, in the example of the present application, the preset step size X=30 is specified, so the electrical position angle is 30°, 60°...330°, 360°.

[0065] S403: Based on the direct-axis current value and the electrical position angle, the A-phase current value, the B-phase current value, and the C-phase current value at each electrical position angle are calculated and prepared into the calibration table.

[0066] In this step, according to formula I a =I d cos(θ), determine the A-phase winding current value.

[0067] According to formula I b =I d cos(θ-2π / 3), determine the B-phase winding current value.

[0068] According to formula I c =I d cos(θ+2π / 3), determine the C-phase winding current value.

[0069] Where θ is the electrical position angle, I d is the direct axis current.

[0070] In the example of this application, the calibration table is specifically described, as shown in Table 1.

[0071] S404: Rotate the permanent magnet synchronous motor shaft to the electrical position angle corresponding to the Yth column in the calibration table, where Y represents the number of columns in the calibration table and the initial value is 1, and set the required values ​​of the A-phase current value, the B-phase current value, and the C-phase current value to the current values ​​under the Yth column in the calibration table in the calibration software.

[0072] S405: Disconnect the power supply of the permanent magnet synchronous motor control system to put the permanent magnet synchronous motor into a power-off state.

[0073] S406: During the power-off process, observe whether the shaft of the permanent magnet synchronous motor rotates. If not, modify the A-phase current value, B-phase current value, and C-phase current value under the electrical position angle corresponding to the Yth column of the power-off calibration table to the required values ​​set in the calibration software, end the calibration of the electrical position angle corresponding to the Yth column, and jump to step S409. If yes, jump to S407.

[0074] S407: Observe the cross-axis current during rotation. If a positive Q-axis current appears, subtract Z° from the electrical position angle. Z is a rational number and can be 0.5, 0.3, 0.1, etc. according to actual needs. If a negative Q-axis current appears, increase the electrical position angle by Z°. Recalculate the A-phase current value, B-phase current value, and C-phase current value based on the modified electrical position angle.

[0075] It should be noted that the modified electrical position angle is only used in the calculation of the A-phase current value, the B-phase current value, and the C-phase current value in S408, and will not be used to change the data in the electrical position angle column in the calibration table obtained in step S403.

[0076] S408: Modify the A-phase current value, B-phase current value, and C-phase current value under the electrical position angle corresponding to the Yth column of the power-off calibration table to the values ​​recalculated in step S407, and return to step S405.

[0077] S409: Obtain the electrical position angle corresponding to the Y+1th column of the calibration table, and repeat steps S404 to S408 until all electrical position angles are calibrated.

[0078] In summary, a power-off control method and calibration method for a permanent magnet synchronous motor is provided, wherein, when the motor vehicle is in a preset state, the MCU will consult the fast power-off calibration table stored in the system to obtain the three-phase winding demand current value at the current position of the permanent magnet synchronous motor, and the synthetic magnetic field or synthetic current of the three-phase winding demand current is all located on the direct axis of the motor, and the synthetic magnetic field or synthetic current value of the cross axis is 0. At the same time, the actual current is made consistent with the theoretical current through the closed-loop PI control of the current. While ensuring that the permanent magnet synchronous motor has a faster discharge current, it avoids the occurrence of uncontrollable cross-axis current in the permanent magnet synchronous motor due to the hysteresis of the control system, thereby causing the motor to rotate suddenly, causing serious consequences for driving safety.

[0079] The features described in the embodiments of the present specification may be replaced or combined with each other. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments may be referenced to each other.

[0080] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for power-off calibration of a permanent magnet synchronous motor, characterized in that: The calibration method comprises: S401: Determine the direct-axis current of the permanent magnet synchronous motor; S402: Acquire a plurality of electrical position angles equally divided according to a preset step length, and when the electrical position angle is 0°, the direct axis of the permanent magnet synchronous motor coincides with the A phase axis; S403: Based on the direct axis current and the electrical position angle, calculate the A-phase current value, the B-phase current value, and the C-phase current value at each electrical position angle, and make a calibration table; S404: Rotate the permanent magnet synchronous motor shaft to the electrical position angle corresponding to the Yth column in the calibration table, where Y represents the number of columns in the calibration table and the initial value is 1, and set the required values ​​of the A-phase current value, the B-phase current value, and the C-phase current value to the current values ​​under the Yth column in the calibration table in the calibration software; S405: disconnecting the permanent magnet synchronous motor control system power supply, so that the permanent magnet synchronous motor enters a power-off state; S406: During the power-off process, observe whether the shaft of the permanent magnet synchronous motor rotates. If not, modify the A-phase current value, B-phase current value, and C-phase current value under the electrical position angle corresponding to the Yth column of the power-off calibration table to the required value set in the calibration software, end the calibration of the electrical position angle corresponding to the Yth column, and jump to step S409. If yes, jump to S407; S407: Observe the quadrature axis current during rotation. If a positive Q axis current appears, subtract Z° from the electrical position angle, where Z is a rational number. If a negative Q axis current appears, increase the electrical position angle by Z°, and recalculate the A phase current value, the B phase current value, and the C phase current value according to the modified electrical position angle. S408: modify the A-phase current value, the B-phase current value, and the C-phase current value under the electrical position angle corresponding to the Yth column of the power-off calibration table to the values ​​recalculated in step S407, and return to step S405; S409: Obtain the electrical position angle corresponding to the Y+1th column of the calibration table, and repeat steps S404 to S408 until all electrical position angles are calibrated.

2. The power-off calibration method of a permanent magnet synchronous motor according to claim 1, characterized in that: Step S403 includes the following specific steps: According to formula I a =I d cos(θ), determine the current value of phase A winding; According to formula I b =I d cos(θ-2π / 3), determine the current value of the B phase winding; According to formula I c =I d cos(θ+2π / 3), determine the C phase winding current value; Where θ is the electrical position angle, I d is the direct axis current.

3. The control method of the power-off calibration method of the permanent magnet synchronous motor according to claim 1, characterized in that: The control method comprises: S101: The vehicle controller detects the state of the motor vehicle and provides a fast power-off control signal to the motor controller of the permanent magnet synchronous motor when the motor vehicle is in a preset state; S102: After receiving the fast power-off control signal, the motor controller enters the fast power-off mode, and consults a pre-calibrated calibration table stored in the fast power-off table lookup module to obtain the required current value of the three-phase winding at the current position; S103: The motor controller directly sends the required current value of the three-phase winding under the current rotor position to the proportional-integral PI module for closed-loop control to obtain the A phase regulation voltage (U a )、B phase regulated voltage (U b )、C phase regulation voltage (U c ), and adjust the three-phase current; S104: Determine whether the bus voltage of the permanent magnet synchronous motor is less than or equal to the preset voltage. If yes, exit the power-off control process; if no, return to S103 to cycle.

4. The control method of the power-off calibration method of the permanent magnet synchronous motor according to claim 1, characterized in that: The synthetic magnetic field of the required current values ​​of the three-phase windings at the current rotor position is all located on the rotor direct axis, and there is no magnetic field component on the quadrature axis.

5. The control method of the power-off calibration method of the permanent magnet synchronous motor according to claim 1, characterized in that: The calibration table records the required current values ​​of the three-phase winding under different rotor electrical position angles. The angle variable of the calibration table is the electrical position angle of the motor. The step size of the electrical position angle variable is X°, where X is a positive integer divisible by 360. The synthesized current of the required current values ​​of the three-phase winding is 5S amperes, where S is a positive integer and its direction is on the direct axis.

6. The control method of the power-off calibration method of the permanent magnet synchronous motor according to claim 1, characterized in that: The required current values ​​of the three-phase windings obtained in step S102 do not change during this rapid power-off control process.

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