A Field Weakening Control Method Based on Rotor Position Angle Adaptation

Abstract

A field weakening control method based on rotor position angle adaptation includes the following steps: S1, the motor controller collects motor speed, motor torque, stator current, angular velocity of the motor in its natural coordinate system, and DC bus voltage of the motor controller in real time, and sets the threshold range of voltage deviation [ΔU]. min ,ΔU max S2, determine the current operating condition of the motor based on the motor speed and motor torque; S3, determine whether the voltage deviation between the DC bus voltage and the back electromotive force meets the requirements. If it meets the requirements, directly output the current requested direct-axis and quadrature-axis currents of the motor; if it does not meet the requirements, proceed to step S4; S4, perform adaptive control on the rotor position angle to make the voltage deviation between the DC bus voltage and the back electromotive force within the set threshold range; S5, redistribute the direct-axis and quadrature-axis currents of the motor based on the rotor position angle obtained after adaptive control; S6, the motor controller outputs the redistributed direct-axis and quadrature-axis currents.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a field weakening control method based on rotor position angle adaptation. Background Technology

[0002] Permanent magnet synchronous motors have advantages such as wide speed range, high power density, and high working efficiency. Permanent magnet synchronous motor drive systems can output large torque at low speeds and achieve constant power speed regulation at high speeds, and are widely used in the field of electric vehicles.

[0003] Permanent magnet synchronous motors (PMSMs) often employ field weakening speed control during high-speed, constant-power operation. During this phase, as the motor speed increases, the inverter output voltage reaches its limit, potentially leading to motor runaway in saturation. Therefore, field weakening speed enhancement is necessary. In practice, lookup tables or formulas are commonly used. However, the values ​​in lookup tables are pre-set by calibration engineers and remain fixed. Since the skill level of calibration engineers varies, the accuracy of the preset parameters in the tables cannot be guaranteed. Therefore, lookup tables often result in poor control precision and ineffective field weakening speed enhancement. Formulas, on the other hand, rely on mathematical formulas. In engineering applications, the effectiveness of field weakening speed enhancement depends on the parameters and calculations. Errors in parameter measurement or calculation can cause problems in the control process. Therefore, neither lookup tables nor formulas can guarantee the effectiveness of field weakening speed enhancement. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a field weakening control method based on rotor position angle adaptation. This method enables the rotor position angle to always adaptively remain within a set range and redistributes the direct-axis and quadrature-axis current components, thereby ensuring stable operation of the motor in the field weakening zone.

[0005] The technical solution of this invention is: a field weakening control method based on rotor position angle adaptation, the steps of which are as follows:

[0006] S1, the motor controller collects motor speed, motor torque, stator current, and angular velocity in the motor's natural coordinate system in real time, and collects the DC bus voltage of the motor controller in real time through a voltage sensor, and sets the threshold range [ΔU] for the voltage deviation between the DC bus voltage and the back electromotive force. min , ΔU max ];

[0007] S2, the motor controller determines the current operating condition of the motor based on the motor speed and motor torque;

[0008] S3: The motor controller determines whether the voltage deviation between the DC bus voltage and the back electromotive force meets the requirements. If the requirements are met, the motor directly outputs the current requested direct-axis and quadrature-axis currents. If the requirements are not met, proceed to step S4.

[0009] S4, adaptively controls the rotor position angle to keep the voltage deviation between the DC bus voltage and the back electromotive force within the set threshold range.

[0010] S5, based on the rotor position angle obtained after adaptive control, redistributes the direct-axis and quadrature-axis currents of the motor;

[0011] S6, the motor controller outputs the redistributed direct-axis and quadrature-axis currents to other modules.

[0012] Further, in step S2, the motor operating state is determined as follows: ① When the motor speed n≥0 and the motor torque T≥0, the motor is in electric operation mode; ② When the motor speed n<0 and the motor torque T<0, the motor is in electric operation mode; ③ When the motor speed n≥0 and the motor torque T<0, the motor is in generator operation mode; ④ When the motor speed n<0 and the motor torque T>0, the motor is in generator operation mode.

[0013] Furthermore, S3 determines whether the voltage deviation meets the requirements by following these steps.

[0014] S3-1, calculate the voltage deviation using the following formula.

[0015]

[0016] In the formula, U dc ω is the DC bus voltage. e For electrical angular velocity, Ψ f For rotor permanent magnet flux linkage;

[0017] S3-2, if the voltage deviation ΔU>0, then the requirement is met, and the controller directly outputs the current requested direct-axis and quadrature-axis currents of the motor;

[0018] S3-3, if the voltage deviation ΔU < 0, then the requirement is not met, proceed to step S4.

[0019] Furthermore, step S4 involves adaptive control of the rotor position angle according to the following steps.

[0020] S4-1, When the motor is in motoring mode, increase the rotor position angle θ according to the principle of equal gradient, and compare the adjusted ΔU with the minimum threshold ΔU. min Compare, if ΔU < ΔU min Then continue to increase the rotor position angle θ until ΔU ≥ ΔU min Then compare ΔU with the maximum threshold ΔUmax Compare, if ΔU > ΔU max Then, the rotor position angle θ is reduced according to the principle of equal gradient until ΔU≤ΔU max The rotor position angle θ at this time is written into the NVM memory for storage;

[0021] S4-2, When the motor is in generating mode, reduce the rotor position angle θ according to the principle of equal gradient, and compare the adjusted ΔU with the minimum threshold ΔU. min Compare, if ΔU < ΔU min Then continue to decrease the rotor position angle θ until ΔU ≥ ΔU min Then compare ΔU with the maximum threshold ΔU max Compare, if ΔU > ΔU max Then, increase the rotor position angle θ according to the principle of equal gradient until ΔU≤ΔU max The rotor position angle θ at this time is written into the NVM memory for storage.

[0022] Furthermore, the equal gradient principle means increasing or decreasing the rotor position angle θ by 0.1°.

[0023] Furthermore, in step S5, the direct-axis and quadrature-axis currents are redistributed according to the following formula:

[0024]

[0025] In the formula, I s For stator current, I d For the quadrature-axis current component, I q θ represents the direct-axis current component, and θ is the rotor position angle.

[0026] Furthermore, based on the current limiting circle, the direct-axis and quadrature-axis current components are limited using the following formula:

[0027]

[0028]

[0029] In the formula, I s For stator current, I d For the quadrature-axis current component, I q This represents the direct-axis current component.

[0030] Furthermore, the electrical angular velocity is the product of the angular velocity in the motor's natural coordinate system and the number of pole pairs of the motor.

[0031] The beneficial effects of adopting the above technical solution are as follows:

[0032] 1. This invention can quickly and accurately adapt the rotor position angle to a set range, and redistribute the direct-axis and quadrature-axis currents according to the adaptively adjusted rotor position angle, so as to ensure that the voltage deviation can be maintained within a reasonable range when the motor is running in the weak magnetic region, and prevent the motor controller from going out of control.

[0033] 2. The present invention includes a limiting module to limit the direct-axis and quadrature-axis current components, thereby avoiding the risk of overcurrent due to the direct-axis and quadrature-axis current values ​​exceeding the limits.

[0034] 3. This invention is not affected by differences in motor parameters and can be applied to field weakening control of all permanent magnet synchronous motors.

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0036] Figure 1 This is a flowchart of the algorithm of the present invention;

[0037] Figure 2 This is a flowchart of the rotor position angle adaptive control process of the present invention;

[0038] Figure 3 This is a block diagram of the current component limiting strategy for the direct axis and quadrature axis of the present invention. Detailed Implementation

[0039] See Figures 1 to 3 An embodiment of a field weakening control method based on rotor position angle adaptation includes the following steps:

[0040] S1, the motor controller collects motor speed, motor torque, stator current, and angular velocity in the motor's natural coordinate system in real time, and collects the DC bus voltage of the motor controller in real time through a voltage sensor, as well as setting a threshold range [ΔU] for the voltage deviation between the DC bus voltage and the back electromotive force of the permanent magnet based on engineering experience. min , ΔU max In this embodiment, the motor is a permanent magnet synchronous motor.

[0041] S2, the motor controller determines the current operating condition of the motor based on the motor speed and motor torque:

[0042] ① When the motor speed n≥0 and the motor torque T≥0, the motor is in electric operation mode; ② When the motor speed n<0 and the motor torque T<0, the motor is in electric operation mode; ③ When the motor speed n≥0 and the motor torque T<0, the motor is in generator operation mode; ④ When the motor speed n<0 and the motor torque T>0, the motor is in generator operation mode.

[0043] S3: The motor controller determines whether the voltage deviation between the DC bus voltage and the back electromotive force of the permanent magnet meets the requirements. If the requirements are met, the motor directly outputs the current requested direct-axis and quadrature-axis currents. If the requirements are not met, proceed to step S4.

[0044] S3-1, calculate the voltage deviation using the following formula.

[0045]

[0046] In the formula, U dc This is the DC bus voltage;

[0047] ω e The electrical angular velocity is the product of the angular velocity in the motor's natural coordinate system and the number of pole pairs of the motor.

[0048] Ψ f For rotor permanent magnet flux linkage;

[0049] S3-2, if the voltage deviation ΔU>0, then the requirement is met. At this time, the motor is running in normal condition, and the controller directly outputs the direct axis and quadrature axis currents currently requested by the motor.

[0050] S3-3, if the voltage deviation ΔU < 0, the requirement is not met. At this time, the DC bus voltage of the motor controller is too low, which can easily cause damage to the motor hardware. It is necessary to perform field weakening control on the motor and proceed to step S4 to perform adaptive control of the rotor position angle.

[0051] S4, adaptively controls the rotor position angle to keep the voltage deviation between the DC bus voltage and the back electromotive force within the set threshold range.

[0052] Step S4 performs adaptive control of the rotor position angle θ according to the following steps. The rotor position angle θ can be obtained based on the calculation relationship between the stator current and the direct axis and quadrature axis currents collected in real time, or it can be obtained through other modules.

[0053] S4-1, When the motor is in motoring mode, the rotor position angle θ is increased according to the principle of equal gradient, so that the voltage deviation ΔU increases with the increase of the rotor position angle, and the adjusted ΔU is compared with the minimum threshold ΔU. min Compare, if ΔU < ΔU min Then continue to increase the rotor position angle θ until ΔU ≥ ΔU min Then compare ΔU with the maximum threshold ΔU max Compare, if ΔU > ΔU max Then, the rotor position angle θ is reduced according to the principle of equal gradient until ΔU≤ΔU max Adjust the difference between the DC bus voltage and the back electromotive force within the threshold range [ΔU]. min , ΔUmax Between ], the rotor position angle θ at this time is then written into the NVM memory for storage;

[0054] S4-2, When the motor is in generating mode, reduce the rotor position angle θ according to the principle of equal gradient, and compare the adjusted ΔU with the minimum threshold ΔU. min Compare, if ΔU < ΔU min Then continue to decrease the rotor position angle θ until ΔU ≥ ΔU min Then compare ΔU with the maximum threshold ΔU max Compare, if ΔU > ΔU max Then, increase the rotor position angle θ according to the principle of equal gradient until ΔU≤ΔU max The rotor position angle θ at this time is written into the NVM memory for storage;

[0055] The equal gradient principle is used to increase or decrease the rotor position angle θ by equal increments. The smaller the adjustment amount each time, the more precise the adaptive control. In this embodiment, 0.1° is used as the adjustment amount to increase or decrease the rotor position angle θ by increments.

[0056] S5. Based on the rotor position angle obtained after adaptive control, the direct-axis and quadrature-axis currents of the motor are redistributed according to the following formula:

[0057]

[0058] In the formula, I s For stator current, I d For the quadrature-axis current component, I q θ represents the direct-axis current component, and θ is the rotor position angle.

[0059] S6, the motor controller outputs the redistributed direct-axis and quadrature-axis currents to other modules, and limits the direct-axis and quadrature-axis current components according to the following formula based on the current limit circle.

[0060]

[0061]

[0062] In the formula, I s For stator current, I d For the quadrature-axis current component, I q This represents the direct-axis current component.

[0063] In actual operation, the motor in this embodiment needs to meet the voltage limit circle and current limit circle restrictions:

[0064]

[0065] In the formula, U limTo limit the voltage, it can be calculated using the motor's design parameters; U d For the direct-axis voltage component, U q The quadrature-axis voltage component can be calculated from the direct-axis and quadrature-axis voltage equations, respectively.

[0066]

[0067] In the above formula, I lim To limit the current, it can be calculated using the motor's design parameters; I d For the direct-axis current component, I q The quadrature-axis current component can be obtained from the acquired phase current I. a I b I c Obtained through coordinate transformation.

[0068] This invention is unaffected by differences in motor parameters and is applicable to field weakening control of all permanent magnet synchronous motors. Furthermore, by adaptively controlling the rotor position angle, it can quickly and accurately find a suitable rotor position angle and redistribute the right- and right-axis current components based on this angle. This ensures that the voltage deviation margin remains within a reasonable range when the motor is operating in the field weakening region, preventing the motor controller from malfunctioning. In addition, this invention includes right- and right-axis current limiting modules. By limiting the right- and right-axis current reference values ​​according to the current limit circle, it ensures that the current reference value will not exceed the limit under different operating conditions, thereby avoiding the risk of overcurrent.

Claims

1. A field weakening control method based on rotor position angle adaptation, characterized in that... The steps are as follows: S1, the motor controller collects motor speed, motor torque, stator current, and angular velocity in the motor's natural coordinate system in real time, and collects the DC bus voltage of the motor controller in real time through a voltage sensor, and sets the threshold range [ΔU] for the voltage deviation between the DC bus voltage and the back electromotive force. min , ΔU max ]; S2, the motor controller determines the current operating condition of the motor based on the motor speed and motor torque; S3: The motor controller determines whether the voltage deviation between the DC bus voltage and the back electromotive force meets the requirements. If the requirements are met, the motor directly outputs the current requested direct-axis and quadrature-axis currents. If the requirements are not met, proceed to step S4. S4, adaptively controls the rotor position angle to keep the voltage deviation between the DC bus voltage and the back electromotive force within the set threshold range. Adaptive control of the rotor position angle is performed using the following steps. S4-1, When the motor is in motoring mode, increase the rotor position angle θ according to the principle of equal gradient, and compare the adjusted voltage deviation ΔU with the minimum threshold ΔU. min Compare, if ΔU < ΔU min Then continue to increase the rotor position angle θ until ΔU ≥ ΔU min Then compare ΔU with the maximum threshold ΔU max Compare, if ΔU > ΔU max Then, the rotor position angle θ is reduced according to the principle of equal gradient until ΔU≤ΔU max， Write the rotor position angle θ at this time into the NVM memory for storage; S4-2, When the motor is in generating mode, reduce the rotor position angle θ according to the principle of equal gradient, and compare the adjusted voltage deviation ΔU with the minimum threshold ΔU. min Compare, if ΔU < ΔU min Then continue to decrease the rotor position angle θ until ΔU ≥ ΔU min Then compare ΔU with the maximum threshold ΔU max Compare, if ΔU > ΔU max Then, increase the rotor position angle θ according to the principle of equal gradient until ΔU≤ΔU max， Write the rotor position angle θ at this time into the NVM memory for storage; S5, based on the rotor position angle obtained after adaptive control, redistribute the direct-axis and quadrature-axis currents of the motor; S6, the motor controller outputs the redistributed direct-axis and quadrature-axis currents to other modules.

2. The field weakening control method based on rotor position angle adaptation according to claim 1, characterized in that: Step S2: Determining the motor's operating state: ① When the motor speed n≥0 and the motor torque T≥0, the motor is in electric operation mode; ② When the motor speed n<0 and the motor torque T<0, the motor is in electric operation mode; ③ When the motor speed n≥0 and the motor torque T<0, the motor is in generator operation mode; ④ When the motor speed n<0 and the motor torque T>0, the motor is in generator operation mode.

3. The field weakening control method based on rotor position angle adaptation according to claim 1, characterized in that: S3 determines whether the voltage deviation meets the requirements by following these steps. S3-1, calculate the voltage deviation using the following formula. ； In the formula, U dc ω is the DC bus voltage. e For electrical angular velocity, Ψ f For rotor permanent magnet flux linkage; S3-2, if the voltage deviation ΔU>0, then the requirement is met, and the controller directly outputs the current requested direct-axis and quadrature-axis currents of the motor; S3-3, if the voltage deviation ΔU < 0, then the requirement is not met, proceed to step S4.

4. The field weakening control method based on rotor position angle adaptation according to claim 1, characterized in that: The equal gradient principle is to increase or decrease the rotor position angle θ by 0.1°.

5. The field weakening control method based on rotor position angle adaptation according to claim 1, characterized in that: In step S5, the direct-axis and quadrature-axis currents are redistributed according to the following formula. ； In the formula, I s For stator current, I d For the quadrature-axis current component, I q θ represents the direct-axis current component, and θ is the rotor position angle.

6. The field weakening control method based on rotor position angle adaptation according to claim 1, characterized in that: The current components along the direct and quadrature axes are limited according to the current limiting circle using the following formula. ； ； In the formula, I s For stator current, I d For the quadrature-axis current component, I q This represents the direct-axis current component.

7. The field weakening control method based on rotor position angle adaptation according to claim 3, characterized in that: The electrical angular velocity is the product of the angular velocity in the motor's natural coordinate system and the number of pole pairs of the motor.

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