Weak magnetic control method and device of motor, storage medium and vehicle

Abstract

The invention discloses a field weakening control method and device of a motor, a storage medium and a vehicle, and the method comprises the steps: determining and inputting an electrical parameter corresponding to a given reference torque of the motor to the motor based on a pre-established current lookup table; when the output voltage of a current controller of the motor exceeds the output voltage limit of an inverter of the motor, determining corresponding motor parameters based on the electrical parameters obtained through real-time monitoring and a pre-established motor parameter lookup table; determining a target included angle based on the electrical parameters and the motor parameters; determining a weak magnetic area where the motor is located based on the target included angle; and based on the weak magnetic area where the motor is located, determining a corresponding electrical parameter correction value, and correcting the electrical parameter to control the output torque of the motor. According to the method, the electrical parameters can be effectively corrected based on the change of the motor parameters, the torque can be accurately output in the flux-weakening acceleration process of the motor, and the torque control precision of the motor under the flux-weakening working condition is improved.

Description

Technical Field

[0001] The present application relates to the field of permanent magnet synchronous motor control, and in particular to a method, device, storage medium and vehicle for controlling magnetic field of a motor. Background Art

[0002] At present, there are mainly the following methods for the weak magnetic control of permanent magnet synchronous motors in high-speed areas: (1) table lookup method. The current mainstream table lookup methods are divided into speed torque table lookup method and flux torque table lookup method. Both methods require a large amount of motor test data to be calibrated on the test bench, and the motor calibration data is processed to obtain a two-dimensional lookup table of the d and q axis currents changing with torque and speed / flux. When controlling the motor, the reference values ​​of the d and q axis currents are obtained in real time through interpolation based on the reference torque and motor speed / flux; (2) voltage closed-loop feedback method. This method uses the difference between the inverter output voltage limit value and the current controller output voltage as PI (Proportional Current Control). The input of the proportional integral (PI) controller forms a voltage feedback closed loop, and the PI controller outputs the d-axis current compensation to realize the weak magnetic control of the motor and drive the motor to operate in the weak magnetic area. The working voltage is always within the inverter output voltage limit; (3) the single current regulator method, when the motor enters the weak magnetic area, the weak magnetic control is realized by retaining the d-axis current regulator and removing the q-axis current regulator; (4) the gradient descent method, this method determines the weak magnetic area where the motor is working based on the information of the constant torque direction, the torque increasing direction, and the voltage decreasing direction, and then calculates the correction values ​​of the d and q axis currents according to the weak magnetic area where the motor is located, reasonably plans the trajectory of the motor working current, and realizes the weak magnetic speed increase control of the motor.

[0003] Among the above methods, the table lookup method has good robustness, fast dynamic response speed, simplicity and reliability, but it requires a large amount of motor test data to be calibrated on the test bench, which is a large workload, and the algorithm has poor portability; the voltage closed-loop feedback method does not rely on the motor parameters, the method is simple, and has certain versatility, but the dynamic performance is poor, the control stability is poor when the motor enters the deep field weakening area, and MTPV (Maximum Torque per Volt, maximum torque voltage ratio) control; the single current regulator method has a simple structure and can solve the problem of easy saturation of the dual current regulator when the motor is running at high speed, and improve the weak magnetic depth of the motor. However, this method has the disadvantages of weak torque control ability, poor dynamic response performance and low efficiency, and can only be used for positive torque (electric) conditions, not for negative torque (generation) conditions. Therefore, this method is not suitable for automotive permanent magnet synchronous motor weak magnetic control; the gradient descent method can realize reasonable and efficient planning of the d and q axis current trajectories of the motor in the weak magnetic area, with high control accuracy and fast response speed. When the motor enters the deep weak magnetic area, the d and q axis current trajectories can be planned along the MTPV curve, thereby widening the speed regulation range of the motor. However, this method is highly dependent on the motor parameters and is easily affected by changes in the motor parameters. Especially in the case of large current and large load, the deviation of the motor parameters will reduce the torque control accuracy. Summary of the Invention

[0004] The present application provides a motor weak magnetic control method, device, storage medium and vehicle, the purpose of which is to improve the torque control accuracy of the new energy vehicle drive motor under weak magnetic conditions.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] A magnetic field weakening control method for a motor, comprising:

[0007] Based on a pre-established current lookup table, determining and inputting electrical parameters corresponding to a given reference torque of the motor into the motor;

[0008] When the output voltage of the current controller of the motor exceeds the output voltage limit of the inverter of the motor, the corresponding motor parameters are determined based on the electrical parameters obtained by real-time monitoring and a pre-established motor parameter lookup table;

[0009] Determining a target angle based on the electrical parameters and the motor parameters; wherein the target angle is used to represent the angle between the constant torque direction and the voltage decreasing direction of the motor;

[0010] Determining a magnetic weakening region of the motor based on the target angle;

[0011] Based on the weakening magnetic region in which the motor is located, a corresponding electrical parameter correction value is determined, and the electrical parameter is corrected to control the output torque of the motor.

[0012] Optionally, the process of constructing the motor parameter lookup table includes:

[0013] According to the rough calibration step of the motor parameters, a plurality of electrical parameter calibration values ​​and corresponding motor parameter calibration values ​​are obtained; the electrical parameter calibration values ​​include a q-axis current calibration value and a d-axis current calibration value; the motor parameter calibration values ​​include a q-axis inductance calibration value, a d-axis inductance calibration value and a permanent magnet flux calibration value;

[0014] Constructing the motor parameter lookup table based on the plurality of electrical parameter calibration values ​​and the corresponding motor parameter calibration values;

[0015] Among them, the rough calibration step of the motor parameters includes: pre-installing a pair of drag motors on a test bench; the pair of drag motors includes a drag motor and a measured motor, and the model of the measured motor is the same as that of the motor; controlling the drag motor to operate in a speed control mode, and the measured motor to operate in a d-axis and q-axis current control mode; controlling the bus voltage of the drag motor to be a specified voltage value, and fixing the speed to a specified speed value; while keeping the temperature, bus voltage and speed of the measured motor unchanged, testing and recording the d-axis voltage and q-axis voltage of the measured motor during steady-state operation under multiple current conditions, and the current condition is determined based on the d-axis current and the q-axis current; based on the d-axis voltage and q-axis voltage under different current conditions, calculating the corresponding permanent magnet flux; based on the permanent magnet flux under different current conditions, calculating the corresponding q-axis inductance and d-axis inductance.

[0016] Optionally, the electrical parameters include q-axis current and d-axis current; the motor parameters include q-axis inductance, d-axis inductance, and permanent magnet flux; and determining the target angle based on the electrical parameters and the motor parameters includes:

[0017] Substituting the q-axis current, the d-axis current, the q-axis inductance, the d-axis inductance, and the permanent magnet flux into a constant torque direction expression to obtain a first parameter and a second parameter; the first parameter represents a change direction of the d-axis current on the constant torque curve of the motor, and the second parameter represents a change direction of the q-axis current on the constant torque curve;

[0018] Determining a q-axis voltage and a d-axis voltage of the motor;

[0019] Substituting the q-axis voltage, the d-axis voltage, the q-axis inductance, and the d-axis inductance into a voltage decreasing direction expression to obtain a third parameter and a fourth parameter; the third parameter represents a change direction of the d-axis voltage on the voltage limit ellipse of the motor, and the fourth parameter represents a change direction of the q-axis voltage on the voltage limit ellipse;

[0020] Substitute the first parameter, the second parameter, the third parameter, and the fourth parameter into the vector angle formula to obtain a target angle.

[0021] Optionally, determining the magnetic weakening region of the motor based on the target angle includes:

[0022] If the target angle is less than a specified angle, determining that the magnetic weakening region where the motor is located is a magnetic weakening region 1;

[0023] If the target angle is greater than or equal to the specified angle, it is determined that the magnetic weakening region where the motor is located is the second magnetic weakening region.

[0024] Optionally, determining a corresponding electrical parameter correction value based on the weakening magnetic region in which the motor is located includes:

[0025] When the motor is in a magnetic weakening zone 1, determining a q-axis current correction value and a d-axis current correction value based on the first parameter, the second parameter, and a target voltage difference; the target voltage difference includes a voltage difference between an output voltage of the current controller and an output voltage limit of the inverter;

[0026] An electrical parameter correction value is determined based on the q-axis current correction value and the d-axis current correction value.

[0027] Optionally, determining a corresponding electrical parameter correction value based on the weakening magnetic region in which the motor is located includes:

[0028] When the weak magnetic region in which the motor is located is the weak magnetic region 2, the q-axis current, the d-axis current, the q-axis inductance, the d-axis inductance, and the permanent magnet flux are substituted into the tangent direction expression of the maximum torque-voltage ratio curve to obtain a fifth parameter and a sixth parameter; the fifth parameter represents the direction of change of the d-axis current on the maximum torque-voltage ratio curve of the motor, and the sixth parameter represents the direction of change of the q-axis current on the maximum torque-voltage ratio curve;

[0029] determining a q-axis current correction value and a d-axis current correction value based on the fifth parameter, the sixth parameter, and a target voltage difference; the target voltage difference comprising a voltage difference between an output voltage of the current controller and an output voltage limit of the inverter;

[0030] An electrical parameter correction value is determined based on the q-axis current correction value and the d-axis current correction value.

[0031] Optionally, the method further includes:

[0032] The electrical parameters obtained by real-time monitoring and the corresponding motor parameters are substituted into the compensation voltage calculation formula to obtain the d-axis feedforward decoupling compensation voltage and the q-axis feedforward decoupling compensation voltage to compensate for the output voltage of the motor; the output voltage of the motor includes the d-axis voltage and the q-axis voltage, the d-axis feedforward decoupling compensation voltage is used to achieve the decoupling of the d-axis voltage, and the q-axis feedforward decoupling compensation voltage is used to achieve the decoupling of the q-axis voltage.

[0033] A magnetic field weakening control device for a motor, comprising:

[0034] an electrical parameter monitoring unit, configured to determine and input into the motor an electrical parameter corresponding to a given reference torque of the motor based on a pre-established current lookup table;

[0035] a motor parameter monitoring unit, configured to determine corresponding motor parameters based on electrical parameters obtained through real-time monitoring and a pre-established motor parameter lookup table when the output voltage of the motor's current controller exceeds the output voltage limit of the motor's inverter;

[0036] a target angle determination unit, configured to determine a target angle based on the electrical parameters and the motor parameters; the target angle being used to represent the angle between the constant torque direction and the voltage decreasing direction of the motor;

[0037] a magnetic field weakening region determining unit, configured to determine a magnetic field weakening region in which the motor is located based on the target angle;

[0038] The electrical parameter correction unit is used to determine the corresponding electrical parameter correction value based on the weak magnetic area where the motor is located, and correct the electrical parameter to control the output torque of the motor.

[0039] A storage medium includes a stored program, wherein the program executes the motor flux weakening control method when the program is run by a processor.

[0040] A vehicle comprises: a current controller, a motor and a bus; the current controller and the motor are connected via the bus;

[0041] The current controller is used to run a program, wherein the program executes the motor flux weakening control method when the current controller runs the program.

[0042] The technical solution provided by the present application determines and inputs electrical parameters corresponding to a given reference torque of the motor to the motor based on a pre-established current lookup table. When the output voltage of the motor's current controller exceeds the output voltage limit of the motor's inverter, the corresponding motor parameters are determined based on the electrical parameters obtained through real-time monitoring and a pre-established motor parameter lookup table. Based on the electrical parameters and the motor parameters, a target angle is determined. Based on the target angle, the weak magnetic region in which the motor is located is determined. Based on the weak magnetic region in which the motor is located, the corresponding electrical parameter correction values ​​are determined, and the electrical parameters are corrected to control the output torque of the motor. The present application takes into account the influence of motor parameters changing with current, and queries the motor parameter lookup table in real time through the electrical parameters obtained through real-time monitoring, updates the motor parameters in real time, and obtains electrical parameter correction values ​​to achieve effective correction of the motor's electrical parameters, thereby more accurately calculating and planning the motor's working current trajectory in the weak magnetic region, ensuring that the motor outputs torque as accurately as possible during the weak magnetic speed-up process, and improving the torque control accuracy of the motor under weak magnetic working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0044] Figure 1 A schematic flow chart of a magnetic field weakening control method for a motor provided in an embodiment of the present application;

[0045] Figure 2 A schematic flow chart of another method for controlling magnetic field weakening of a motor provided in an embodiment of the present application;

[0046] Figure 3 A schematic flow chart of another method for controlling magnetic field weakening of a motor provided in an embodiment of the present application;

[0047] Figure 4 A schematic diagram of the structure of a magnetic field weakening control device for a motor provided in an embodiment of the present application;

[0048] Figure 5 A schematic diagram of a weak magnetic field area division provided in an embodiment of the present application;

[0049] Figure 6 Another schematic diagram of the weak magnetic field area division provided in an embodiment of the present application;

[0050] Figure 7 A schematic diagram of a storage medium provided in an embodiment of the present application;

[0051] Figure 8 A schematic diagram of a vehicle provided in an embodiment of the present application. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0053] In this application, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. The terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or apparatus comprising the element.

[0054] like Figure 1 , which is a flow chart of a magnetic weakening control method for a motor provided in an embodiment of the present application, including the following steps.

[0055] S101 : Based on a pre-established current lookup table, determine and input electrical parameters corresponding to a given reference torque of the motor into the motor.

[0056] The electrical parameters include the d-axis current and the q-axis current of the motor.

[0057] In some examples, the given reference torque of the motor is derived from a torque command issued to the motor in real time by an onboard computer during vehicle driving, or can be set by a technician based on actual conditions.

[0058] In some examples, the motor may be a permanent magnet synchronous motor.

[0059] In some examples, the current lookup table includes multiple torque calibration values ​​for the motor and the corresponding electrical parameter calibration values. When the motor is under MTPA control, the motor operates at low speed. The core concept of MTPA control is to find the minimum current that can meet the corresponding given torque based on the torque setpoint, thereby minimizing copper losses during motor operation. To implement MTPA control, the motor is pre-calibrated through the MTPA process to establish a corresponding current lookup table, so that the electrical parameters corresponding to the given reference torque can be directly obtained by lookup.

[0060] In some examples, the motor MTPA calibration process can be as follows: first, set up a pair of drag motors (including a drag motor and a motor under test) on a test bench; control the drag motor to run in a speed control mode, and the motor under test to run in a d-axis and q-axis current control mode, so that the drag motor runs at a constant speed to maintain the constant speed of the motor under test (i.e., a test for a given torque value); then set the running speed of the drag motor to 2100 rpm, and enter the current calibration phase of the motor under test; in the current calibration phase, according to the calibrated current vector and the current vector angle , calculate the d-axis current and q-axis current of the motor under test, and the calculation process can be used as well as implementation, where is the d-axis current of the motor, is the q-axis current of the motor.

[0061] In a possible embodiment, the current vector Starting from 0, the current vector increases with equal intervals to the maximum current vector allowed by the motor. , the maximum motor current vector The current vector starts at 0 A and increases to 330 A at intervals of 10 A. At each current vector, the current vector angle starts from the optimal angle corresponding to the previous current vector and increases at equal intervals until the output torque of the measured motor is maximum. The current vector amplitude, current vector angle, and corresponding d-axis and q-axis current values ​​and torque under this working condition are recorded. The above steps are repeated to obtain a series of torques and corresponding d-axis and q-axis current combinations (which can be regarded as current working conditions). Finally, the torque-current lookup table generated by the MBC (Model Based Calibration) toolbox is used as the current lookup table for the motor.

[0062] S102: When the output voltage of the motor's current controller exceeds the output voltage limit of the motor's inverter, corresponding motor parameters are determined based on electrical parameters obtained through real-time monitoring and a pre-established motor parameter lookup table.

[0063] Electrical parameters include q-axis current and d-axis current, and motor parameters include q-axis inductance, d-axis inductance, and permanent magnet flux. When the output voltage of the motor's current controller exceeds the output voltage limit of the motor's inverter, it can be determined that the motor speed is higher than the base speed and the motor enters the constant power (i.e., flux-weakening) control region.

[0064] In some examples, the base speed of a permanent magnet synchronous motor refers to the maximum speed at which the motor can output rated torque at rated voltage and rated frequency. When the motor speed is less than the base speed, the motor usually adopts constant torque control. When the motor speed is higher than the base speed, the motor enters the constant power (i.e., weak magnetic control) control area.

[0065] In some examples, the base speed can be set by a technician according to actual conditions.

[0066] It should be noted that whether the motor requires flux weakening control is determined based on the output voltage of the current controller (such as the current loop PI controller). Specifically, the SVPWM (Space Vector Pulse Width Modulation) method can be used to monitor the maximum voltage that the motor inverter can output within the linear modulation region. The arithmetic formula of this maximum voltage is usually expressed as Udc / √3, where Udc represents the DC bus voltage of the inverter. When the output voltage of the current controller is less than the output voltage limit of the inverter, it is determined that the motor is operating in the base speed region (i.e., the motor speed is lower than the base speed), and no flux weakening control of the motor is required. When the output voltage of the current controller is greater than or equal to (i.e., exceeds) the output voltage limit of the inverter, it is determined that the motor is operating in the high-speed region (i.e., the motor speed is higher than the base speed), and flux weakening control of the motor is required.

[0067] In some examples, motor flux weakening control is a technology that extends the high-speed operating range of the motor by adjusting the strength of the motor's magnetic field. It is suitable for electric vehicles, industrial drives and other fields.

[0068] It should be noted that the electrical parameters obtained by real-time monitoring include but are not limited to q-axis current and d-axis current. The q-axis current and d-axis current are key concepts in field-oriented control, used to describe the components of the motor stator current in the rotor coordinate system. By adjusting the d-axis current, the motor's magnetic field strength can be controlled, and by adjusting the q-axis current, the motor's torque can be controlled. Generally speaking, the motor's rotor coordinate system can be recorded as the dq coordinate system, where the d-axis is aligned with the direction of the rotor magnetic field and the q-axis is perpendicular to the d-axis. The d-axis current can be regarded as the current component along the d-axis direction, and the q-axis current can be regarded as the current component along the q-axis direction.

[0069] Optionally, the process of constructing the motor parameter lookup table includes: according to the rough calibration steps of the motor parameters, obtaining multiple electrical parameter calibration values ​​and corresponding motor parameter calibration values, the electrical parameter calibration values ​​include q-axis current calibration values ​​and d-axis current calibration values, and the motor parameter calibration values ​​include q-axis inductance calibration values, d-axis inductance calibration values ​​and permanent magnet flux calibration values; based on multiple electrical parameter calibration values ​​and corresponding motor parameter calibration values, constructing a motor parameter lookup table.

[0070] Optionally, the rough calibration step of the motor parameters includes: pre-installing the towing motor on the test bench; the towing motor includes a traction motor and a measured motor, and the model of the measured motor is the same as the motor; controlling the traction motor to operate in a speed control mode, and the measured motor to operate in a d-axis and q-axis current control mode; controlling the bus voltage of the traction motor to be a specified voltage value (for example, 400V), and fixing the speed to a specified speed value (for example, 2100rpm); while keeping the temperature, bus voltage and speed of the measured motor unchanged, testing and recording the d-axis voltage and q-axis voltage of the measured motor during steady-state operation under multiple current conditions, the current condition being determined based on the d-axis current and the q-axis current; based on the d-axis voltage and q-axis voltage under different current conditions, calculating the corresponding permanent magnet flux; based on the permanent magnet flux under different current conditions, calculating the corresponding q-axis inductance and d-axis inductance.

[0071] In some examples, during the operation of the motor, due to the magnetic saturation effect, cross-coupling effect and the increase in motor temperature, motor parameters related to motor control, such as d-axis inductance, q-axis inductance and permanent magnet flux, will be affected by d-axis current, q-axis current and temperature, among which the influence of current is the greatest, followed by the influence of motor temperature. Considering the changes of the above motor parameters during the operation of the motor, the motor parameters of the motor are roughly calibrated on the test bench to establish a motor parameter lookup table. Considering that the influence of motor temperature on motor parameters is smaller than that of current, and in order to reduce the workload of motor calibration, the influence of temperature changes on motor parameters is not considered during the rough calibration process.

[0072] In some examples, a test bench is a structure used to support, fix, or test equipment. It is commonly found in industries such as industry and automotive repair, and is used to fix equipment (i.e., motors) for performance testing.

[0073] In some examples, paired motors (a driving motor and a motor under test) are driven by each other through a mechanical connection (such as a coupling) to test the performance of the motor under test. The d-axis voltage and q-axis voltage are concepts used in vector control to describe the components of the motor's stator voltage in the rotor coordinate system.

[0074] It should be noted that since the bus voltage of the motor under test is maintained at 400 V and the current limit is 330 A, the value range of the d-axis current and the q-axis current can be 0~330 A, so the operating current range of the motor under test can be expressed as shown in formula (1).

[0075] (1)

[0076] In formula (1), represents the d-axis current, Represents the q-axis current. Within the entire operating current range, test the motor under test and record the d-axis voltage and q-axis voltage under each current condition. The d-axis voltage and q-axis voltage can be calculated based on the motor voltage formula in the rotor coordinate, such as formulas (2) and (3).

[0077] (2)

[0078] (3)

[0079] In formulas (2) and (3), represents the d-axis voltage, represents the motor winding, represents the d-axis current, represents the d-axis inductance, represents the electrical angular velocity of the motor, represents the q-axis voltage, represents the q-axis current, represents the q-axis inductance, Represents the flux linkage of the permanent magnet.

[0080] In some examples, the electrical angular velocity It is the angular velocity of the motor rotor magnetic field. The electrical angular velocity can be obtained by measuring the actual speed of the motor and combining it with the number of pole pairs. The calculation process is shown in formula (4).

[0081] (4)

[0082] In formula (4), Represents the number of pole pairs of the motor, Represents the speed of the motor.

[0083] In some examples, the differential terms in equations (2) and (3) are small and can be ignored. Therefore, the voltage equations after steady state can be expressed as shown in equations (5) and (6).

[0084] (5)

[0085] (6)

[0086] Furthermore, based on formulas (5) and (6), the d-axis flux during steady-state operation of the motor is It can be expressed as formula (7), q-axis magnetic flux It can be expressed as formula (8).

[0087] (7)

[0088] (8)

[0089] From formulas (7) and (8), it can be seen that the d-axis voltage during steady-state operation of the motor is equal to the output of the d-axis current controller, and the q-axis voltage is equal to the output of the q-axis current controller. Therefore, the d-axis voltage and the q-axis voltage can be collected through the current controller. It can be actually measured that the electrical angular velocity Based on the speed, the d-axis flux and q-axis flux of the motor in steady state are calculated by calibrating the data. The stator d-axis flux consists of the permanent magnet flux and the d-axis inductor flux. These two parts are coupled together and difficult to decouple in the steady state of the motor. Therefore, the influence of the d-axis current on the permanent magnet flux is ignored. The value of the permanent magnet flux linkage is calculated when , and a set of permanent magnet flux linkage and corresponding q-axis current values ​​are obtained. Then, a one-dimensional lookup table of the permanent magnet flux linkage changing with the q-axis current is fitted according to the MBC toolbox (which can be regarded as a part of the motor parameter lookup table). The corresponding relationship between the permanent magnet flux linkage and the q-axis current shown in the one-dimensional lookup table can be expressed as formula (9).

[0090] (9)

[0091] Furthermore, after obtaining the value of the permanent magnet flux, the value of the permanent magnet flux is substituted into the stator d-axis flux corresponding to the d-axis current, that is, formula (7), and the d-axis inductance can be obtained. The value of q-axis inductance can be obtained by the stator q-axis flux corresponding to the q-axis current, that is, formula (8): The obtained data is then fitted through the MBC toolbox to produce a two-dimensional lookup table of the d-axis inductance changing with the d-axis current (which can be regarded as part of the motor parameter lookup table), and a two-dimensional lookup table of the q-axis inductance changing with the q-axis current (which can be regarded as part of the motor parameter lookup table). The corresponding relationship between the d-axis inductance and the d-axis current can be recorded as formula (10), and the corresponding relationship between the q-axis inductance and the q-axis current can be recorded as formula (11).

[0092] (10)

[0093] (11)

[0094] Based on the corresponding relationships shown in formulas (9), (10) and (11), the corresponding relationships among the q-axis current calibration value, the d-axis current calibration value, the q-axis inductance calibration value, the d-axis inductance calibration value and the permanent magnet flux calibration value can be established, thereby obtaining multiple electrical parameter calibration values ​​and corresponding motor parameter calibration values ​​to establish a corresponding motor parameter lookup table. Through the motor parameter lookup table, the motor parameters corresponding to the electrical parameters obtained by real-time monitoring can be determined, thereby realizing real-time dynamic update of the motor parameters (i.e., q-axis inductance, d-axis inductance and permanent magnet flux).

[0095] S103: Determine a target angle based on electrical parameters and motor parameters.

[0096] The target angle is used to represent the angle between the constant torque direction and the voltage decreasing direction of the motor.

[0097] In some examples, the constant torque direction of a motor means that the torque remains constant and the direction does not change during the operation of the motor. The constant torque direction means that the torque size and direction of the motor remain stable during operation. It is suitable for occasions that require stable load and continuous power, such as the operation scenarios of new energy vehicles.

[0098] In some examples, the direction of the motor's voltage decrease is usually related to the motor's magnetic weakening control. When the motor speed increases, the back electromotive force increases accordingly, which may cause the voltage to reach the output limit of the inverter. In order to maintain the high-speed operation of the motor, it is necessary to use magnetic weakening control to reduce the back electromotive force to avoid voltage saturation. For this reason, the voltage decrease direction can be understood as the direction in which the voltage gradually decreases during the magnetic weakening control process.

[0099] Optionally, the target angle can be determined based on the electrical and motor parameters. Figure 2 The steps are shown and the corresponding explanations.

[0100] S104: Determine the magnetic weakening region where the motor is located based on the target angle.

[0101] The magnetic weakening region of the motor is usually defined as the middle area between the MTPA (Maximum Torque Per Ampere Control) curve and the MTPV curve as magnetic weakening region 1, and the MTPV curve as magnetic weakening region 2.

[0102] In some examples, the division of the weak magnetic zone 1 (e.g., weak magnetic zone 1) and the weak magnetic zone 2 (e.g., weak magnetic zone 2) can be found in Figure 5 shown.

[0103] For automotive permanent magnet synchronous motors, it is required that the motor output torque remains as constant as possible during the field weakening speed increase. Therefore, the trajectory of the full-speed operating current of the automotive permanent magnet synchronous motor is as follows: Figure 6 As shown in the figure, when the motor operates in the base speed area, the motor operating current is located at point A on the MTPA curve, the output torque is T1, and the speed continues to increase. When the speed exceeds the base speed and the motor operating voltage is greater than the inverter voltage limit, the motor enters the weakening magnetic area. In order to maintain the output torque unchanged, the motor's operating current in the weakening magnetic area is located at the intersection of the constant torque curve corresponding to torque T1 and the voltage limit ellipse, that is, Figure 6 The point on the curve from point A to point B. When the motor speed continues to increase, the motor enters the second field weakening zone, and the motor's operating current is Figure 6 At points along the MTPV curve from point B to point C, the motor can no longer maintain its previous torque, and the output torque decreases continuously as the speed increases. In summary, for automotive permanent magnet synchronous motors, in the first field weakening zone, the operating current is modified along the constant torque curve, and in the second field weakening zone, the operating current is modified along the MTPV curve.

[0104] In some examples, the MTPA curve of a motor refers to the relationship curve between the maximum torque that the motor can output and the current under a specific current. The core goal of the MTPA curve is to achieve maximum torque output per unit current, thereby improving motor efficiency. To this end, the MTPA curve describes the maximum torque that the motor can output under different currents.

[0105] In some examples, the MTPV curve of a motor refers to the relationship curve between the maximum torque that the motor can output and the voltage at a specific voltage. The core goal of the MTPV curve is to achieve maximum torque output at a given voltage, thereby optimizing motor performance. To this end, the MTPV curve describes the maximum torque that the motor can output at different voltages.

[0106] It should be noted that since the target angle represents the angle between the constant torque direction and the voltage decreasing direction of the motor, and the constant torque curve and voltage limit ellipse of the motor are referred to during the calculation of the target angle, the target angle can be used to determine the weak magnetic region in which the motor is located.

[0107] Optionally, the implementation process of determining the weak magnetic area in which the motor is located based on the target angle can be: if the target angle is less than the specified angle, the weak magnetic area in which the motor is located is determined to be weak magnetic area zone 1; if the target angle is greater than or equal to the specified angle, the weak magnetic area in which the motor is located is determined to be weak magnetic area zone 2.

[0108] In some examples, when the target angle When the target angle is less than 90 degrees, the motor is determined to be operating in the weak magnetic zone 1. When the angle is ≥90 degrees, the motor is determined to be operating in the second field weakening zone.

[0109] S105: Based on the weak magnetic field region where the motor is located, a corresponding electrical parameter correction value is determined, and the electrical parameter is corrected to control the output torque of the motor.

[0110] After determining the weakening magnetic region where the motor is located, the corresponding electrical correction parameter value is determined based on the weakening magnetic region where the motor is located, so as to provide a reliable reference basis for the correction process of the electrical parameters.

[0111] Optionally, the implementation process of determining the corresponding electrical parameter correction value based on the weak magnetic area in which the motor is located can be: when the weak magnetic area in which the motor is located is the weak magnetic area 1, the q-axis current correction value and the d-axis current correction value are determined based on the first parameter, the second parameter and the target pressure difference; the target pressure difference includes the voltage difference between the output voltage of the current controller and the output voltage limit of the inverter; based on the q-axis current correction value and the d-axis current correction value, the electrical parameter correction value is determined.

[0112] In some examples, the process of determining the q-axis current correction value and the d-axis current correction value based on the first parameter, the second parameter, and the target pressure difference can be shown in formula (19).

[0113] (19)

[0114] In formula (19), represents the d-axis current correction value, Represents the gain coefficient of the electrical parameter correction value when the motor works in the weak magnetic zone 1. represents the q-axis current correction value, Represents the target pressure difference.

[0115] Optionally, when the motor operates in the second field weakening zone, the process of determining the corresponding electrical parameter correction value can be found in Figure 3 The steps are shown and the corresponding explanations.

[0116] It should be emphasized that by using the electrical parameter correction value to correct the electrical parameters, the corrected electrical parameters for controlling the output torque of the motor can be obtained.

[0117] In some examples, the corrected electrical parameters include a corrected d-axis current and a corrected q-axis current of the motor.

[0118] In some examples, the electrical parameters are corrected using the electrical parameter correction values ​​to obtain the corrected electrical parameters, as shown in formulas (24) and (25).

[0119] (twenty four)

[0120] (25)

[0121] In formulas (24) and (25), represents the d-axis correction current, represents the q-axis corrected current, Represents the d-axis current in the electrical parameters, Represents the q-axis current in the electrical parameters, represents the d-axis current correction value, Represents the q-axis current correction value.

[0122] It should be noted that the gradient descent field weakening algorithm is highly dependent on motor parameters. The constant torque direction expression, the tangent direction expression of the MTPV curve, and the voltage decreasing direction expression are all functions of motor parameters and electrical parameters. Deviations in the motor parameters will lead to inaccurate determination of the field weakening region and inaccurate current correction values, affecting the accuracy of the final torque output. Considering the impact of changes in the d-axis current and q-axis current during motor operation on the motor parameters, the motor parameter lookup table is queried in real time based on the actual d-axis current and q-axis current feedback during the motor control process. The motor parameters are updated in real time and used in the gradient descent field weakening algorithm to obtain more accurate current correction values, ensuring more accurate torque output.

[0123] In addition, the embodiment of the present application shows a weak magnetic field control method for the new energy vehicle drive motor that takes into account the changes in motor parameters. Since the changes in motor parameters are taken into account in the algorithm design, the control method also improves the torque control accuracy of the motor under weak magnetic conditions. At the same time, the motor parameters can also be applied to the d-axis and q-axis feedforward decoupling of current control, thereby improving the dynamic characteristics and accuracy of current control.

[0124] Optionally, the process of realizing the d-axis and q-axis feedforward decoupling of current control can be as follows: the electrical parameters obtained by real-time monitoring and the corresponding motor parameters are substituted into the compensation voltage calculation formula to obtain the d-axis feedforward decoupling compensation voltage and the q-axis feedforward decoupling compensation voltage to compensate for the output voltage of the motor; the output voltage of the motor includes the d-axis voltage and the q-axis voltage, the d-axis feedforward decoupling compensation voltage is used to realize the decoupling of the d-axis voltage, and the q-axis feedforward decoupling compensation voltage is used to realize the decoupling of the q-axis voltage.

[0125] In some examples, the compensation voltage calculation formula can be determined based on the voltage equation of the permanent magnet synchronous motor, which is shown in equations (26) and (27).

[0126] (26)

[0127] (27)

[0128] In formulas (26) and (27), the d-axis voltage There is a cross-coupling term caused by the q-axis current , and the q-axis voltage There is a cross-coupling term caused by the d-axis current and the permanent magnet flux linkage , and the higher the motor speed, the larger the cross-coupling term, and the greater the impact on the dynamic performance of the current control. Decoupling of the d-axis and q-axis voltages is usually achieved by adding a compensation voltage to the output voltages of the d-axis and q-axis current controllers. Based on the calculation method of the compensation voltage, the d-axis feedforward decoupling compensation voltage can be shown in Formula (28), and the q-axis feedforward decoupling compensation voltage can be shown in Formula (29).

[0129] (28)

[0130] (29)

[0131] In formulas (28) and (29), represents the d-axis feedforward decoupling compensation voltage, represents the q-axis corrected current, represents the q-axis feedforward decoupling compensation voltage, Represents the d-axis correction current.

[0132] It can be seen that the accuracy of the compensation voltage is highly dependent on the motor parameters. According to the actual d-axis and q-axis currents fed back during the motor control process, the motor parameter lookup table is queried in real time, the motor parameters are updated in real time, and the updated motor parameters are brought into the compensation voltage calculation formula to obtain more accurate d-axis and q-axis feedforward decoupling compensation voltages, ensuring that the d-axis and q-axis voltages are completely decoupled as much as possible, thereby improving the dynamic performance of current control.

[0133] The process shown in S101-S105 above takes into account the influence of motor parameters changing with current, queries the motor parameter lookup table in real time through real-time monitoring of the electrical parameters, updates the motor parameters in real time, and obtains electrical parameter correction values ​​to achieve effective correction of the motor's electrical parameters, thereby more accurately calculating and planning the working current trajectory of the motor in the weak magnetic field area, ensuring that the motor outputs torque as accurately as possible during the weak magnetic field acceleration process, and improving the torque control accuracy of the motor under weak magnetic field conditions.

[0134] like Figure 2 As shown, it is a flow chart of another method for weakening magnetic field control of a motor provided in an embodiment of the present application, which includes the following steps.

[0135] S201: Substitute the q-axis current, d-axis current, q-axis inductance, d-axis inductance, and permanent magnet flux into the constant torque direction expression to obtain the first parameter and the second parameter.

[0136] The first parameter represents the changing direction of the d-axis current on the constant torque curve of the motor, and the second parameter represents the changing direction of the q-axis current on the constant torque curve.

[0137] In some examples, the constant torque curve of a motor is a curve that describes the relationship between the speed and torque of the motor when the motor is in a constant torque operating state. That is, the constant torque curve represents the relationship between the speed and torque of the motor under the condition of constant output torque. In the constant torque area, the motor can provide stable torque output. In the constant power area, the speed decreases as the speed increases.

[0138] In some examples, the constant torque direction expression is converted based on the torque formula of the permanent magnet synchronous motor. Specifically, the torque formula of the permanent magnet synchronous motor is shown in formula (12).

[0139] (12)

[0140] In formula (12), Represents the output torque of the motor, Represents the number of pole pairs of the motor. Using formula (12), the constant torque direction expression is obtained as shown in formula (13).

[0141] (13)

[0142] In formula (13), Represents the first parameter, Represents the second parameter, Represents the direction of constant torque.

[0143] S202: Determine the q-axis voltage and the d-axis voltage of the motor.

[0144] Among them, the q-axis voltage and d-axis voltage of the motor can be collected in real time through the current controller.

[0145] S203: Substitute the q-axis voltage, the d-axis voltage, the q-axis inductance, and the d-axis inductance into the voltage decreasing direction expression to obtain the third parameter and the fourth parameter.

[0146] The third parameter represents the changing direction of the d-axis voltage on the voltage limit ellipse of the motor, and the fourth parameter represents the changing direction of the q-axis voltage on the voltage limit ellipse.

[0147] In some examples, a motor's voltage limit ellipse is a graphic depicting the motor's operating range within voltage limits. The voltage limit ellipse represents the speed and torque combination within which the motor can stably operate at a given voltage. As motor speed increases, the back EMF increases, reducing the voltage available to generate torque and thus limiting the motor's maximum output torque. Generally speaking, torque is higher at low speeds and gradually decreases as speed increases or decreases, forming an ellipse.

[0148] In some examples, the voltage decreasing direction expression is determined based on the opposite direction of the voltage limit ellipse. Specifically, the voltage decreasing direction expression can be defined as formula (14).

[0149] (14)

[0150] In formula (14), Represents the direction of voltage decrease, Represents the d-axis voltage of the motor in steady state, ignoring the current differential term and the motor winding voltage drop, Represents the q-axis voltage of the motor in steady state, ignoring the current differential term and the motor winding voltage drop. Specifically, The expression of can be found in formula (15), The expression of can be found in formula (16).

[0151] (15)

[0152] (16)

[0153] Substituting formulas (15) and (16) into formula (14), the expression for the voltage decreasing direction can be obtained as formula (17).

[0154] (17)

[0155] In formula (17), Represents the third parameter, Represents the fourth parameter.

[0156] S204: Substitute the first parameter, the second parameter, the third parameter, and the fourth parameter into the vector angle formula to obtain a target angle.

[0157] The vector angle formula can be found in formula (18).

[0158] (18)

[0159] In formula (18), Represents the target angle.

[0160] The process shown in S201-S204 can calculate the target angle using the q-axis current, d-axis current, q-axis inductance, d-axis inductance, permanent magnet flux, q-axis voltage, and d-axis voltage, thereby providing an effective reference for the subsequent determination of the weakening magnetic area.

[0161] like Figure 3 , which is a flow chart of another method for weakening magnetic field control of a motor provided in an embodiment of the present application, including the following steps.

[0162] S301: When the motor is in the second magnetic weakening zone, the q-axis current, d-axis current, q-axis inductance, d-axis inductance, and permanent magnet flux are substituted into the tangent direction expression of the maximum torque-voltage ratio curve to obtain the fifth parameter and the sixth parameter.

[0163] The fifth parameter represents the changing direction of the d-axis current on the maximum torque-voltage ratio curve of the motor, and the sixth parameter represents the changing direction of the q-axis current on the maximum torque-voltage ratio curve.

[0164] It should be noted that the tangent direction expression of the maximum torque-to-voltage ratio curve is determined based on the MTPV curve equation. Specifically, the motor's operating current in the second field-weakening region is corrected along the MTPV curve toward the center of the voltage limit ellipse. The MTPV curve can be considered as a curve formed by the tangent points of the constant torque curve and the voltage limit ellipse. Therefore, the MTPV curve equation can be expressed as shown in Formula (19).

[0165]

[0166] In formula (19), represents the operating voltage when the motor is running in steady state, ignoring the current differential term and the voltage drop of the motor winding, and The calculation process of can be seen in formula (20).

[0167] (20)

[0168] Further, Substituting into the MTPV curve equation, we obtain formula (21).

[0169] (twenty one)

[0170] Based on formula (21), the tangent direction expression of the maximum torque-voltage ratio curve is further determined, as shown in formula (22).

[0171] (twenty two)

[0172] In formula (22), represents the fifth parameter, represents the sixth parameter, Represents the tangent direction of the maximum torque-voltage ratio curve.

[0173] S302 : Determine a q-axis current correction value and a d-axis current correction value based on the fifth parameter, the sixth parameter, and the target pressure difference.

[0174] The target voltage difference includes the voltage difference between the output voltage of the current controller and the output voltage limit of the inverter.

[0175] In some examples, the process of determining the q-axis current correction value and the d-axis current correction value based on the fifth parameter, the sixth parameter, and the target pressure difference can be shown in formula (23).

[0176] (twenty three)

[0177] In formula (23), Represents the gain coefficient of the electrical parameter correction value when the motor operates in the second field weakening zone.

[0178] S303: Determine an electrical parameter correction value based on the q-axis current correction value and the d-axis current correction value.

[0179] The q-axis current correction value may be used to correct the q-axis current, and the d-axis current correction value may be used to correct the d-axis current.

[0180] In the above process S301-S303, when the motor is in the second field weakening zone, the corresponding electrical parameter correction value can be determined based on the tangent direction of the maximum torque-to-voltage ratio curve as a reference and in combination with the electrical parameters and motor parameters.

[0181] like Figure 4 , which is a schematic diagram of the architecture of a magnetic field weakening control device for a motor provided in an embodiment of the present application, including the units shown below.

[0182] The electrical parameter monitoring unit 100 is used to determine and input electrical parameters corresponding to a given reference torque of the motor to the motor based on a pre-established current lookup table.

[0183] The motor parameter monitoring unit 200 is used to determine corresponding motor parameters based on electrical parameters obtained through real-time monitoring and a pre-established motor parameter lookup table when the output voltage of the motor's current controller exceeds the output voltage limit of the motor's inverter.

[0184] Optionally, the motor parameter monitoring unit 200 implements a process of constructing a motor parameter lookup table, including: obtaining a plurality of electrical parameter calibration values ​​and corresponding motor parameter calibration values ​​according to a rough calibration step of the motor parameters; the electrical parameter calibration values ​​include a q-axis current calibration value and a d-axis current calibration value; the motor parameter calibration values ​​include a q-axis inductance calibration value, a d-axis inductance calibration value and a permanent magnet flux calibration value; constructing a motor parameter lookup table based on a plurality of electrical parameter calibration values ​​and corresponding motor parameter calibration values; wherein the rough calibration step of the motor parameters includes: pre-installing a pair of drag motors on a test bench; the pair of drag motors includes a drag motor and a motor to be measured, and the motor to be measured The model is the same as the motor; the drag motor is controlled to run in the speed control mode, and the motor under test is run in the d-axis and q-axis current control mode; the bus voltage of the drag motor is controlled to be a specified voltage value, and the speed is fixed at a specified speed value; while keeping the temperature, bus voltage and speed of the motor under test unchanged, the d-axis voltage and q-axis voltage of the motor under test during steady-state operation under multiple current conditions are tested and recorded, and the current condition is determined based on the d-axis current and the q-axis current; based on the d-axis voltage and q-axis voltage under different current conditions, the corresponding permanent magnet flux is calculated; based on the permanent magnet flux under different current conditions, the corresponding q-axis inductance and d-axis inductance are calculated.

[0185] The target angle determination unit 300 is used to determine the target angle based on the electrical parameters and the motor parameters; the target angle is used to represent the angle between the constant torque direction and the voltage decreasing direction of the motor.

[0186] Optionally, the electrical parameters include q-axis current and d-axis current; the motor parameters include q-axis inductance, d-axis inductance and permanent magnet flux; the target angle determination unit 300 is specifically used to: substitute the q-axis current, d-axis current, q-axis inductance, d-axis inductance and permanent magnet flux into the constant torque direction expression to obtain a first parameter and a second parameter; the first parameter represents the direction of change of the d-axis current on the constant torque curve of the motor, and the second parameter represents the direction of change of the q-axis current on the constant torque curve; determine the q-axis voltage and d-axis voltage of the motor; substitute the q-axis voltage, d-axis voltage, q-axis inductance and d-axis inductance into the voltage decreasing direction expression to obtain a third parameter and a fourth parameter; the third parameter represents the direction of change of the d-axis voltage on the voltage limit ellipse of the motor, and the fourth parameter represents the direction of change of the q-axis voltage on the voltage limit ellipse; substitute the first parameter, the second parameter, the third parameter and the fourth parameter into the vector angle formula to obtain the target angle.

[0187] The magnetic field weakening region determining unit 400 is configured to determine the magnetic field weakening region in which the motor is located based on the target angle.

[0188] Optionally, the weakening magnetic region determination unit 400 is specifically used to: if the target angle is less than the specified angle, determine that the weakening magnetic region where the motor is located is the weakening magnetic region 1; if the target angle is greater than or equal to the specified angle, determine that the weakening magnetic region where the motor is located is the weakening magnetic region 2.

[0189] The electrical parameter correction unit 500 is used to determine the corresponding electrical parameter correction value based on the weak magnetic region where the motor is located, and correct the electrical parameter to control the output torque of the motor.

[0190] Optionally, the electrical parameter correction unit 500 is specifically used to: when the weak magnetic area where the motor is located is the weak magnetic area 1, determine the q-axis current correction value and the d-axis current correction value based on the first parameter, the second parameter and the target pressure difference; the target pressure difference includes the voltage difference between the output voltage of the current controller and the output voltage limit of the inverter; based on the q-axis current correction value and the d-axis current correction value, determine the electrical parameter correction value.

[0191] Optionally, the electrical parameter correction unit 500 is specifically used for: when the weak magnetic area in which the motor is located is the weak magnetic area zone 2, substituting the q-axis current, d-axis current, q-axis inductance, d-axis inductance and permanent magnet flux into the tangent direction expression of the maximum torque-voltage ratio curve to obtain the fifth parameter and the sixth parameter; the fifth parameter represents the direction of change of the d-axis current on the maximum torque-voltage ratio curve of the motor, and the sixth parameter represents the direction of change of the q-axis current on the maximum torque-voltage ratio curve; based on the fifth parameter, the sixth parameter and the target pressure difference, determining the q-axis current correction value and the d-axis current correction value; the target pressure difference includes the voltage difference between the output voltage of the current controller and the output voltage limit of the inverter; based on the q-axis current correction value and the d-axis current correction value, determining the electrical parameter correction value.

[0192] The voltage decoupling unit 600 is used to substitute the electrical parameters obtained from real-time monitoring and the corresponding motor parameters into the compensation voltage calculation formula to obtain the d-axis feedforward decoupling compensation voltage and the q-axis feedforward decoupling compensation voltage to compensate for the output voltage of the motor; the output voltage of the motor includes the d-axis voltage and the q-axis voltage, the d-axis feedforward decoupling compensation voltage is used to achieve the decoupling of the d-axis voltage, and the q-axis feedforward decoupling compensation voltage is used to achieve the decoupling of the q-axis voltage.

[0193] Each unit shown above takes into account the influence of motor parameters changing with current, queries the motor parameter lookup table in real time through real-time monitoring of the electrical parameters, updates the motor parameters in real time, and obtains electrical parameter correction values ​​to achieve effective correction of the motor's electrical parameters, thereby more accurately calculating and planning the working current trajectory of the motor in the weak magnetic field area, ensuring that the motor outputs torque as accurately as possible during the weak magnetic field acceleration process, and improving the torque control accuracy of the motor under weak magnetic field conditions.

[0194] This application also provides a computer-readable storage medium, see Figure 7 As shown, the computer-readable storage medium obtained by the processor 701 from the memory 702 includes a stored program, wherein the program executes the above-mentioned magnetic field weakening control method of the motor provided in the present application.

[0195] This application also provides a vehicle, see Figure 8 As shown, it includes: a current controller 801, a motor 802 and a bus 803. The current controller 801 is connected to the motor 802 via the bus 803. The current controller 801 is used to run a program, wherein the program executes the motor flux weakening control method provided by the present application.

[0196] Although several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of this application. Certain features described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination.

[0197] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the disclosure herein is not limited to technical solutions formed by specific combinations of the aforementioned technical features. It also encompasses other technical solutions formed by any combination of the aforementioned technical features or their equivalents, without departing from the aforementioned disclosure. For example, a technical solution formed by replacing the aforementioned features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for controlling a weak magnetic field of a motor, characterized in that: include: Based on a pre-established current lookup table, determining and inputting electrical parameters corresponding to a given reference torque of the motor into the motor; When the output voltage of the current controller of the motor exceeds the output voltage limit of the inverter of the motor, the corresponding motor parameters are determined based on the electrical parameters obtained by real-time monitoring and a pre-established motor parameter lookup table; Determining a target angle based on the electrical parameters and the motor parameters; wherein the target angle is used to represent the angle between the constant torque direction and the voltage decreasing direction of the motor; Determining a magnetic weakening region of the motor based on the target angle; Based on the weakening magnetic region in which the motor is located, a corresponding electrical parameter correction value is determined, and the electrical parameter is corrected to control the output torque of the motor.

2. The method according to claim 1, characterized in that The process of constructing the motor parameter lookup table includes: According to the rough calibration step of the motor parameters, a plurality of electrical parameter calibration values ​​and corresponding motor parameter calibration values ​​are obtained; the electrical parameter calibration values ​​include a q-axis current calibration value and a d-axis current calibration value; the motor parameter calibration values ​​include a q-axis inductance calibration value, a d-axis inductance calibration value and a permanent magnet flux calibration value; Constructing the motor parameter lookup table based on the plurality of electrical parameter calibration values ​​and the corresponding motor parameter calibration values; Among them, the rough calibration step of the motor parameters includes: pre-installing a pair of drag motors on a test bench; the pair of drag motors includes a drag motor and a measured motor, and the model of the measured motor is the same as that of the motor; controlling the drag motor to operate in a speed control mode, and the measured motor to operate in a d-axis and q-axis current control mode; controlling the bus voltage of the drag motor to be a specified voltage value, and fixing the speed to a specified speed value; while keeping the temperature, bus voltage and speed of the measured motor unchanged, testing and recording the d-axis voltage and q-axis voltage of the measured motor during steady-state operation under multiple current conditions, and the current condition is determined based on the d-axis current and the q-axis current; based on the d-axis voltage and q-axis voltage under different current conditions, calculating the corresponding permanent magnet flux; based on the permanent magnet flux under different current conditions, calculating the corresponding q-axis inductance and d-axis inductance.

3. The method according to claim 1, characterized in that The electrical parameters include q-axis current and d-axis current; the motor parameters include q-axis inductance, d-axis inductance, and permanent magnet flux; and determining a target angle based on the electrical parameters and the motor parameters includes: Substituting the q-axis current, the d-axis current, the q-axis inductance, the d-axis inductance, and the permanent magnet flux into a constant torque direction expression to obtain a first parameter and a second parameter; the first parameter represents a change direction of the d-axis current on the constant torque curve of the motor, and the second parameter represents a change direction of the q-axis current on the constant torque curve; Determining a q-axis voltage and a d-axis voltage of the motor; Substituting the q-axis voltage, the d-axis voltage, the q-axis inductance, and the d-axis inductance into a voltage decreasing direction expression to obtain a third parameter and a fourth parameter; the third parameter represents a change direction of the d-axis voltage on the voltage limit ellipse of the motor, and the fourth parameter represents a change direction of the q-axis voltage on the voltage limit ellipse; Substitute the first parameter, the second parameter, the third parameter, and the fourth parameter into the vector angle formula to obtain a target angle.

4. The method according to claim 1, wherein Determining a field weakening region of the motor based on the target angle includes: If the target angle is less than a specified angle, determining that the magnetic weakening region where the motor is located is a magnetic weakening region 1; If the target angle is greater than or equal to the specified angle, it is determined that the magnetic weakening region where the motor is located is the second magnetic weakening region.

5. The method according to claim 3, characterized in that Determining corresponding electrical parameter correction values ​​based on the field weakening region in which the motor is located includes: When the motor is in a magnetic weakening zone 1, determining a q-axis current correction value and a d-axis current correction value based on the first parameter, the second parameter, and a target voltage difference; the target voltage difference includes a voltage difference between an output voltage of the current controller and an output voltage limit of the inverter; An electrical parameter correction value is determined based on the q-axis current correction value and the d-axis current correction value.

6. The method according to claim 3, characterized in that Determining corresponding electrical parameter correction values ​​based on the field weakening region in which the motor is located includes: When the weak magnetic region in which the motor is located is the weak magnetic region 2, the q-axis current, the d-axis current, the q-axis inductance, the d-axis inductance, and the permanent magnet flux are substituted into the tangent direction expression of the maximum torque-voltage ratio curve to obtain a fifth parameter and a sixth parameter; the fifth parameter represents the direction of change of the d-axis current on the maximum torque-voltage ratio curve of the motor, and the sixth parameter represents the direction of change of the q-axis current on the maximum torque-voltage ratio curve; determining a q-axis current correction value and a d-axis current correction value based on the fifth parameter, the sixth parameter, and a target voltage difference; the target voltage difference comprising a voltage difference between an output voltage of the current controller and an output voltage limit of the inverter; An electrical parameter correction value is determined based on the q-axis current correction value and the d-axis current correction value.

7. The method according to claim 1, characterized in that The method further comprises: The electrical parameters obtained by real-time monitoring and the corresponding motor parameters are substituted into the compensation voltage calculation formula to obtain the d-axis feedforward decoupling compensation voltage and the q-axis feedforward decoupling compensation voltage to compensate for the output voltage of the motor; the output voltage of the motor includes the d-axis voltage and the q-axis voltage, the d-axis feedforward decoupling compensation voltage is used to achieve the decoupling of the d-axis voltage, and the q-axis feedforward decoupling compensation voltage is used to achieve the decoupling of the q-axis voltage.

8. A weak magnetic field control device for a motor, characterized in that: include: an electrical parameter monitoring unit, configured to determine and input into the motor an electrical parameter corresponding to a given reference torque of the motor based on a pre-established current lookup table; a motor parameter monitoring unit, configured to determine corresponding motor parameters based on electrical parameters obtained through real-time monitoring and a pre-established motor parameter lookup table when the output voltage of the motor's current controller exceeds the output voltage limit of the motor's inverter; a target angle determination unit, configured to determine a target angle based on the electrical parameters and the motor parameters; the target angle being used to represent the angle between the constant torque direction and the voltage decreasing direction of the motor; a magnetic field weakening region determining unit, configured to determine a magnetic field weakening region in which the motor is located based on the target angle; The electrical parameter correction unit is used to determine the corresponding electrical parameter correction value based on the weak magnetic area where the motor is located, and correct the electrical parameter to control the output torque of the motor.

9. A storage medium, characterized in that: The storage medium includes a stored program, wherein the program is executed by a processor to execute the magnetic field weakening control method of the motor according to any one of claims 1 to 7.

10. A vehicle, characterized in that: include: current controllers, motors, and buses; The current controller is connected to the motor via the bus; The current controller is used to run a program, wherein the program, when run by the current controller, executes the magnetic field weakening control method of the motor according to any one of claims 1 to 7.

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