Feedback field weakening control method and system of surface-mounted permanent magnet synchronous motor

Abstract

The invention discloses a feedback field weakening control method and system for a surface-mounted permanent magnet synchronous motor, and the method comprises the steps: collecting a rotation speed feedback value of a motor, and controlling the operation of the motor through employing a maximum torque current ratio if the rotation speed feedback value is smaller than a rated rotation speed; calculating a first flux-weakening rotating speed according to the real-time load rate and the bus voltage fluctuation, and if a rotating speed feedback value of the motor is greater than the first flux-weakening rotating speed, entering a first flux-weakening mode: calculating a difference value between an output voltage amplitude and the bus voltage, generating a d-axis current compensation value, and performing load compensation and rotating speed compensation on the d-axis current compensation value to obtain a d-axis current given value; the maximum value of the q-axis current is calculated, given voltage values of the d-axis and the q-axis are generated, and the motor is driven to operate; and calculating a second flux-weakening rotating speed according to the q-axis current maximum value and the voltage margin, and if the rotating speed feedback value of the motor is greater than the second flux-weakening rotating speed, entering a second flux-weakening mode: further limiting the q-axis current maximum value through a current limit circle and a voltage limit circle on the basis of the first flux-weakening mode.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and particularly to a feedback field-weakening control method and system for a surface-mounted permanent magnet synchronous motor. Background Art

[0002] A permanent magnet synchronous motor (PMSM) is a high-efficiency motor based on the principles of electromagnetic induction and synchronous operation, and is widely used in fields such as industrial automation, electric vehicles, aerospace, and household appliances. The rotor of the PMSM uses high-performance permanent magnet materials, which can generate a constant magnetic field without additional excitation, and interacts with the current in the stator winding to achieve electromagnetic torque output. Its synchronous operation characteristics ensure that the rotor and the stator rotating magnetic field maintain the same angular velocity, thus having significant advantages such as high power density, high efficiency, low noise, and excellent dynamic response. However, with the continuous improvement of application requirements, the PMSM still faces many technical challenges in aspects such as expanding the speed regulation range, enhancing the field-weakening ability, improving the operating efficiency, and improving the system robustness, which has become an important direction for the research and innovation of motor control technology.

[0003] Field-weakening control is a technology for expanding the speed range of permanent magnet synchronous motors, and is widely used in scenarios that require ultra-high-speed operation, such as electric vehicles and industrial servo systems. Below the base speed, the motor works with the flux linkage and torque current to output torque; but above the base speed, the back electromotive force will gradually approach the rated voltage limit of the motor as the speed increases, making it difficult to further increase the speed. Field-weakening control effectively weakens the permanent magnet flux linkage by introducing a direct-axis demagnetizing component into the stator current, thereby reducing the back electromotive force and allowing the motor to operate at a higher speed within the voltage limit. This method requires precise control of the stator current to ensure the stability of operation in the field-weakening region, while taking into account efficiency and safety, and is an important technical means for the PMSM to achieve high-performance operation.

[0004] There are mainly two traditional field-weakening methods: voltage regulator field-weakening and lead angle field-weakening. The voltage regulator field-weakening method can dynamically adjust the d-axis current according to the saturation of the voltages on the dq axes, but this method only considers the d-axis current in the dynamic situation, resulting in uncontrollable total current. The lead angle field-weakening method dynamically adjusts the currents on the dq axes while keeping the total current constant, but the value of the lead angle in this method is , and it is impossible to reach the negative q-axis current, and the calculation of the torque current and the field-weakening current together is not conducive to the refined control of the torque. Summary of the Invention

[0005] The present invention provides a feedback field-weakening control method and system for a surface-mounted permanent magnet synchronous motor, which solves the problem that existing field-weakening methods are difficult to meet the requirements of both field-weakening and torque control under dynamic working conditions and high-precision control requirements.

[0006] To solve the above technical problems, the present invention provides a feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor, including the following steps: Collect the speed feedback value of the surface-mounted permanent magnet synchronous motor. If the speed feedback value is less than the rated speed of the motor, calculate the q-axis current reference value according to the given speed and the speed feedback value , and set the d-axis current reference value . The current controller generates and based on and , and drives the motor to operate; Calculate the first field-weakening speed according to the real-time load rate of the motor and the bus voltage fluctuation. If the speed feedback value of the motor is greater than the first field-weakening speed, enter the first field-weakening mode: calculate the voltage difference between the output voltage amplitude of the motor and the bus voltage, and generate a d-axis current compensation value according to the voltage difference ; perform load compensation and speed compensation on to obtain the d-axis current reference value . Calculate the q-axis current according to the total current constraint, and use the calculated q-axis current as the q-axis current limit . The current controller generates the voltage reference values of the d-axis and q-axis based on and , and drives the motor to operate; Calculate the second field-weakening speed according to the maximum value of the q-axis current and the voltage margin. If the speed feedback value of the motor is greater than the second field-weakening speed, enter the second field-weakening mode: on the basis of the first field-weakening mode, further limit the q-axis current through the current limit circle and the voltage limit circle.

[0007] Preferably, the expression for calculating the q-axis current reference value according to the desired speed and the speed feedback value is: ; ; In the above formula, 、 are the parameters of the speed regulator; is the speed difference of the motor; is the desired speed of the motor, is the feedback speed of the motor; is thej The rotational speed difference of the motor during the next integration is the current integration count

[0008] Preferably, the current controller generates and The expressions for and are as follows ; ; ; ; In the formula , are the current differences on the dq axes respectively , are the actual dq-axis currents of the motor feedback by the sensor respectively 、 are the PI parameters of the current regulator is the current integration count , are the current differences on the dq axes during the j th integration respectively

[0009] Preferably, the expression for calculating the first field-weakening rotational speed is ; ; In the formula is the first field-weakening rotational speed is the rated rotational speed of the motor is the load correction coefficient is the load ratio is the real-time q-axis current is the rated q-axis current is the voltage fluctuation correction coefficient is the real-time bus voltage is the rated bus voltage

[0010] Preferably, the expressions for load compensation and rotational speed compensation for are ; ; = ; In the formula is the load compensation coefficient is the load ratio is the real-time q-axis current; is the rated q-axis current; is the speed compensation coefficient; is the speed deviation; is the real-time speed of the motor; is the rated speed of the motor.

[0011] Preferably, the expression for calculating the second field-weakening speed is: ; In the formula, is the second field-weakening speed; is the demarcation speed of the motor from the constant power region to the power-down region; is the current distribution coefficient; is the real-time q-axis current; is the maximum value of the q-axis current calculated from the current limit circle; is the voltage margin correction coefficient; is the voltage difference; is the rated bus voltage.

[0012] Preferably, the expression for calculating the output voltage amplitude is: ; In the formula, is the output voltage amplitude.

[0013] Preferably, the expression for the total current constraint is: ; In the formula, is the total current; is the d-axis current; is the q-axis current.

[0014] Preferably, the expression for further restricting the q-axis current through the current limit circle and the voltage limit circle is: ; ; ; In the above formula, is the maximum value of the q-axis current calculated from the current limit circle; is the rated current of the motor; is the maximum value of the q-axis current calculated from the voltage limit circle; is the bus voltage; is the current electrical angular velocity of the motor; is the inductance of the motor; is the permanent magnet flux linkage of the motor; is the maximum value of the q-axis current.

[0015] The present invention also provides a feedback field-weakening control system for a surface-mounted permanent magnet synchronous motor, which is implemented based on the above-mentioned feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor, and includes: a data acquisition module, a field-weakening judgment module, a speed control module, a first field-weakening control module, a second field-weakening control module, and a motor drive module; The data acquisition module: real-time collects the operating parameters of the motor, including the motor speed, d-axis current, q-axis current, and bus voltage; The field-weakening judgment module: dynamically calculates the first field-weakening speed and the second field-weakening speed according to parameters such as the real-time load rate and bus voltage fluctuation. If the current speed of the motor exceeds the first field-weakening speed, the first field-weakening control module is used to control the motor. If the current speed exceeds the second field-weakening speed, the second field-weakening control module is used to control the motor. Otherwise, the speed control module is used to control the motor; The speed control module: calculates the desired torque of the motor according to the given speed and the feedback speed, outputs the given value of the q-axis current, and keeps the given value of the d-axis current at 0 when operating below the base speed to achieve maximum torque per ampere control; The first field-weakening control module: calculates the difference between the output voltage amplitude and the bus voltage, generates the d-axis current compensation value through a voltage PI regulator, performs load compensation and speed compensation on the d-axis current compensation value to obtain the final given value of the d-axis current, and calculates the limit value of the q-axis current according to the total current constraint to limit the q-axis current; The second field-weakening control module: further limits the q-axis current based on the first field-weakening control module through the current limit circle and the voltage limit circle to ensure that the total current gradually decreases as the speed increases; The motor drive module: generates the given values of the d-axis and q-axis voltages according to the given values of the d-axis and q-axis currents, converts the given values of the d-axis and q-axis voltages into three-phase voltage signals to drive the motor to operate.

[0016] The advantages of the present invention at least include: 1. Dynamically calculates the field-weakening trigger speed through parameters such as the real-time load rate, bus voltage fluctuation, and q-axis current, improving the flexibility and adaptability of field-weakening control, ensuring that the motor can operate efficiently under different load and voltage conditions, and avoiding premature or delayed trigger problems caused by fixed thresholds; 2. Divides the control strategy into three stages: base speed, first field-weakening, and second field-weakening, gradually enhancing the field-weakening intensity to meet the requirements of different speed intervals, maintaining the maximum torque output below the base speed, expanding the speed range through hierarchical field-weakening in the high-speed interval, and at the same time ensuring that the total current is controllable to avoid current out-of-control. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the method flow chart of the embodiment of the present invention; Figure 2 This is the system framework diagram of the embodiment of the present invention. Specific embodiments

[0018] Next, in conjunction with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] As Figure 1 shown, the embodiment of the present invention provides a feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor, including the following steps: Collect the speed feedback value of the surface-mounted permanent magnet synchronous motor. When the speed feedback value is less than the rated speed of the motor, enter the base speed operation mode: Calculate the q-axis current reference value according to the given speed and the speed feedback value : ; ; In the above formula, 、 is the parameter of the speed regulator; is the speed difference of the motor; is the desired speed of the motor, is the feedback speed of the motor; is the j th speed difference of the motor during the th integration;

[0020] Since the control object is a surface-mounted permanent magnet synchronous motor, when the d-axis current is zero, the control is the maximum torque per ampere control. Therefore, let the d-axis current reference value . Substitute , and the system feedback values , into the current controller to generate the motor drive voltages and to drive the motor to operate.

[0021] The current controller generates and according to and , and the expressions are: ; ; ; ; In the formula, and are the current differences of the dq axes respectively; and are the actual dq-axis currents of the motor fed back by the sensor respectively; 、 are the PI parameters of the current regulator; is the current integral number; and are respectively the current differences of the dq axes at the j th integration.

[0022] Calculate the first field-weakening speed according to the real-time load rate of the motor and the bus voltage fluctuation. When the speed feedback value of the motor is greater than the first field-weakening speed, enter the first field-weakening mode.

[0023] The calculation expression of the first field-weakening speed is as follows: ; ; In the formula, is the first field-weakening speed; is the rated speed of the motor; is the load correction coefficient, which is used to balance the influence of load change on the current; is the load rate; is the real-time q-axis current; is the rated q-axis current; is the voltage fluctuation correction coefficient; is the real-time bus voltage; is the rated bus voltage.

[0024] By dynamically adjusting the first field-weakening speed, when the load rate increases, increase the dynamic threshold of the first field-weakening speed of the motor and delay entering the first field-weakening mode to ensure the stability of torque output; when the bus voltage is lower than the rated value, reduce the dynamic threshold of the first field-weakening speed of the motor and trigger field weakening in advance to compensate for the insufficient voltage margin.

[0025] The load correction coefficient is obtained through experimental calibration, including the following steps: Step S1: Operate the motor below the rated speed, gradually increase the load, and record the q-axis current and the load rate .

[0026] Step S2: Gradually increase the motor speed above the rated speed, observe the field-weakening trigger points of the motor under different loads, and record the motor speed at the time of field-weakening trigger , load rate and bus voltage .

[0027] Step S3: According to the experimental data, analyze the influence of the load rate on the field-weakening starting speed , and determine the initial value of the load correction coefficient by fitting the experimental data.

[0028] Step S4: Under different load and speed conditions, verify the rationality of , and adjust according to the verification results to ensure that the field-weakening trigger speed can maintain stability and response speed under different loads.

[0029] When the motor operates in the first field-weakening mode, calculate the voltage difference between the output voltage amplitude of the motor and the bus voltage, and generate a d-axis current compensation value according to the voltage difference : ; In the formula, , are the PI parameters of the voltage PI regulator; is the voltage difference; is the current integration times; is the voltage difference at the jth integration.

[0030] Among them, the calculation expression of the output voltage amplitude is:[[]] .

[0031] Perform load compensation and speed compensation on to obtain the d-axis current given value : ; = ; In the formula, is the rated q-axis current; is the speed compensation coefficient, which is used to expand the high-speed field-weakening range; is the speed deviation; is the real-time speed of the motor; is the rated speed of the motor.

[0032] According to the principle of constant total current, after calculating , according to Calculate the current value of the q-axis As the output current limit of the speed loop. The current controller is based on and Generate the voltage reference values of the d-axis and q-axis 、 , to drive the motor to run: ; ; ; ; In the formula, 、 Are the current differences of the dq axes respectively; 、 Are the actual dq axis currents of the motor feedback by the sensor respectively; 、 Are the PI parameters of the current regulator; Is the current integration times; 、 Are respectively the j th integration current differences of the dq axes.

[0033] Calculate the second field weakening speed according to the maximum q-axis current and voltage margin. When the speed feedback value of the motor is greater than the second field weakening speed, enter the second field weakening mode.

[0034] Among them, the calculation expression of the second field weakening speed is: ; In the formula, Is the second field weakening speed; Is the demarcation speed of the motor from the constant power area to the power reduction area, and its value is determined by the motor characteristic curve; Is the current distribution coefficient, used to balance torque and field weakening requirements; Is the maximum q-axis current calculated from the current limit circle; Is the voltage margin correction coefficient.

[0035] By dynamically adjusting the second field weakening speed, when the proportion of the q-axis current is higher, increase the second field weakening speed of the motor to give priority to ensuring torque output; when the voltage margin is larger, increase the second field weakening speed of the motor to expand the speed range.

[0036] According to the limitations of the current limit circle and voltage limit circle, the total current Decreases with the increase of speed. Therefore, after calculating the d-axis current reference value on the basis of the first field weakening mode, according to Calculate the maximum value of the q-axis current at this time , further restrict the q-axis current to ensure the stable controllability of the total current: ; ; ; In the above formula, is the maximum value of the q-axis current calculated according to the current limit circle; is the rated current of the motor; is the maximum value of the q-axis current calculated according to the voltage limit circle; is the bus voltage; is the current electrical angular velocity of the motor; is the inductance of the motor; is the permanent magnet flux linkage of the motor; is the maximum value of the q-axis current.

[0037] The method of the embodiment of the present invention integrates the advantages of voltage regulator field weakening and lead angle field weakening. While the motor speed is gradually increasing, the demagnetizing current is actively increased to reduce the stator air-gap magnetic field of the motor, so as to reach a higher speed. During the operation, the trigger speed of the field weakening mode can be adjusted in real time according to the load rate and the bus voltage fluctuation.

[0038] As Figure 2 shown, the embodiment of the present invention also provides a feedback field weakening control system for a surface-mounted permanent magnet synchronous motor, which is implemented based on the above-mentioned feedback field weakening control method for a surface-mounted permanent magnet synchronous motor, and includes: a data acquisition module, a field weakening judgment module, a speed control module, a first field weakening control module, a second field weakening control module, and a motor drive module.

[0039] Data acquisition module: Real-time collect the operating parameters of the motor, including motor speed, d-axis current, q-axis current, and bus voltage.

[0040] Field weakening judgment module: Dynamically calculate the first field weakening speed and the second field weakening speed according to parameters such as real-time load rate and bus voltage fluctuation. If the current speed of the motor exceeds the first field weakening speed, the first field weakening control module is used to control the motor. If the current speed exceeds the second field weakening speed, the second field weakening control module is used to control the motor. Otherwise, the speed control module is used to control the motor.

[0041] Speed control module: Calculate the desired torque of the motor according to the given speed and the feedback speed, and output the given value of the q-axis current. When operating below the base speed, keep the given value of the d-axis current at 0 to achieve maximum torque per ampere control.

[0042] The first field-weakening control module: calculates the difference between the output voltage amplitude and the bus voltage, generates the d-axis current compensation value through a voltage PI regulator, performs load compensation and speed compensation on the d-axis current compensation value to obtain the final d-axis current reference value, and calculates the q-axis current limit value according to the total current constraint to limit the q-axis current.

[0043] The second field-weakening control module: based on the first field-weakening control module, further limits the q-axis current through the current limit circle and voltage limit circle to ensure that the total current gradually decreases as the speed increases.

[0044] The motor drive module: generates the d-axis and q-axis voltage reference values according to the d-axis and q-axis current reference values, converts the d-axis and q-axis voltage reference values into three-phase voltage signals to drive the motor to operate.

[0045] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. Only the preferred embodiments of the present invention are expressed. The description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the present invention. As long as the combination of these technical features does not conflict, it should be considered as within the scope described in this specification.

[0046] It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor, characterized in that It includes the following steps: Collect the speed feedback value of the surface-mounted permanent magnet synchronous motor. If the speed feedback value is less than the rated speed of the motor, calculate the q-axis current reference value according to the given speed and the speed feedback value , and set the d-axis current reference value . The current controller generates and to and , and drive the motor to run; Calculate the first field-weakening speed according to the real-time load rate of the motor and the bus voltage fluctuation. If the speed feedback value of the motor is greater than the first field-weakening speed, enter the first field-weakening mode: calculate the voltage difference between the output voltage amplitude of the motor and the bus voltage, and generate a d-axis current compensation value according to the voltage difference ; Perform load compensation and speed compensation to obtain the d-axis current reference value , calculate the q-axis current according to the total current constraint, and use the calculated q-axis current as the q-axis current limit , The current controller generates the voltage setpoints for the d-axis and q-axis based on and to drive the motor to operate; 、 ​ Calculate the second field-weakening speed according to the maximum q-axis current and voltage margin. If the speed feedback value of the motor is greater than the second field-weakening speed, enter the second field-weakening mode: On the basis of the first field-weakening mode, further limit the q-axis current through the current limit circle and voltage limit circle.

2. The feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor according to claim 1, characterized in that: Calculating the q-axis current set value based on the desired speed and the speed feedback value is expressed as: ； ； In the above formula, 、 are the parameters of the speed regulator; is the speed difference of the motor; is the desired speed of the motor, is the feedback speed of the motor; is the j th speed difference of the motor during the th integration; is the current integration times.

3. The feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor according to claim 1, wherein: The current controller generates and with the expressions of and as follows: ； ； ； ； Wherein, and are the current differences of the dq axes respectively; and are the actual dq-axis currents of the motor feedback by the sensor respectively; 、 are the PI parameters of the current regulator; is the current integration times; and are the current differences of the dq axes at the j th integration respectively.

4. The feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor according to claim 1, wherein: The expression for calculating the first field-weakening speed is: ； ； Wherein, is the first field-weakening speed; is the rated speed of the motor; is the load correction factor; is the load rate; is the real-time q-axis current; is the rated q-axis current; is the voltage fluctuation correction factor; is the real-time bus voltage; is the rated bus voltage.

5. The feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor according to claim 1, wherein: The pair of The expression for load compensation and speed compensation is as follows: ； ； = ； Wherein, is the load compensation factor; is the load rate; is the real-time q-axis current; is the rated q-axis current; is the speed compensation factor; is the speed deviation; is the real-time speed of the motor; is the rated speed of the motor.

6. The feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor according to claim 1, wherein: The expression for calculating the second field-weakening speed is: ； Wherein, is the second field-weakening speed; is the demarcation speed of the motor from the constant power region to the power reduction region; is the current distribution coefficient; is the real-time q-axis current; is the maximum value of the q-axis current calculated from the current limit circle; is the voltage margin correction coefficient; is the voltage difference; is the rated bus voltage.

7. A feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor according to claim 1, characterized in that: The expression for calculating the output voltage amplitude is: ； In the formula, is the output voltage amplitude.

8. A feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor according to claim 1, characterized in that: The expression for the total current constraint is: ； Wherein, is the total current; is the d-axis current; is the q-axis current.

9. The feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor according to claim 1, wherein: The expression for further limiting the q-axis current through the current limit circle and voltage limit circle is: ； ； ； In the above formula, is the maximum value of the q-axis current calculated according to the current limit circle; is the rated current of the motor; is the maximum value of the q-axis current calculated according to the voltage limit circle; is the bus voltage; is the current electrical angular velocity of the motor; is the inductance of the motor; is the permanent magnet flux linkage of the motor; is the maximum value of the q-axis current.

10. A feedback field-weakening control system for a surface-mounted permanent magnet synchronous motor, which is implemented based on the feedback field-weakening control method for a surface-mounted permanent magnet synchronous motor according to any one of claims 1 to 9, characterized in that It includes: A data acquisition module, a field-weakening judgment module, a speed control module, a first field-weakening control module, a second field-weakening control module, and a motor drive module; The data acquisition module: Real-time collects the operating parameters of the motor, including motor speed, d-axis current, q-axis current, and bus voltage; The field-weakening judgment module: Dynamically calculates the first field-weakening speed and the second field-weakening speed according to parameters such as the real-time load rate and bus voltage fluctuation. If the current speed of the motor exceeds the first field-weakening speed, use the first field-weakening control module to control the motor. If the current speed exceeds the second field-weakening speed, use the second field-weakening control module to control the motor. Otherwise, use the speed control module to control the motor; The speed control module: Calculates the desired torque of the motor according to the given speed and feedback speed, outputs the q-axis current given value, and keeps the d-axis current given value at 0 when operating below the base speed to achieve maximum torque per ampere control; The first field-weakening control module: Calculates the difference between the output voltage amplitude and the bus voltage, generates the d-axis current compensation value through a voltage PI regulator, performs load compensation and speed compensation on the d-axis current compensation value to obtain the final d-axis current given value, and calculates the q-axis current limit value according to the total current constraint to limit the q-axis current; The second field-weakening control module: On the basis of the first field-weakening control module, further limits the q-axis current through the current limit circle and voltage limit circle to ensure that the total current gradually decreases as the speed increases; The motor drive module: Generates the d-axis and q-axis voltage given values according to the d-axis and q-axis current given values, converts the d-axis and q-axis voltage given values into three-phase voltage signals to drive the motor to operate.

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