Permanent magnet synchronous motor rotor angle estimation method

Abstract

The invention relates to the technical field of motor control, in particular to a permanent magnet synchronous motor rotor angle estimation method, which comprises the following steps of: obtaining a state observer for estimating back electromotive force based on a permanent magnet synchronous motor; constructing a self-adaptive resonance estimator based on the state observer, and embedding the self-adaptive resonance estimator into the state observer to obtain a self-adaptive resonance state observer; performing angle information compensation on the traditional phase-locked loop to obtain an enhanced phase-locked loop; estimating the back electromotive force of the permanent magnet synchronous motor by using the obtained self-adaptive resonance state observer; and inputting the back electromotive force into the enhanced phase-locked loop, and estimating the rotor angle of the permanent magnet synchronous motor. According to the method, the adaptive resonance estimator and the enhanced phase-locked loop are constructed to replace a traditional back electromotive force estimator and a cascaded orthogonal phase-locked loop structure, and the method is used for rapidly extracting position and speed information so as to improve the dynamic performance of the permanent magnet synchronous motor under complex working conditions and the position estimation performance of the rotor.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and in particular relates to a method for estimating the rotor angle of a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in household appliances and industrial applications due to their high power density, high reliability, and low cost. Typically, rotor angle information is obtained using angle sensors such as encoders or resolvers. However, installing mechanical sensors increases installation and maintenance costs and reduces system reliability. To overcome these issues, academia and industry have conducted extensive and in-depth research on angle sensorless control. In the medium- and high-speed operating range of motors, methods based on motor mathematical models, such as back-EMF estimation, are often used. These methods typically consist of a back-EMF estimator and a cascaded angle / speed extractor, which extracts rotor speed and angle information from the estimated back-EMF. In actual motor operation, to cope with more complex operating conditions, motors may experience sudden acceleration and deceleration or large load torque disturbances across a wide speed range. In these situations, traditional angle sensorless methods reduce the performance of rotor angle estimation and tracking of actual motor speed changes. They are unable to respond quickly to speed changes, resulting in inaccurate speed and angle estimates, which in turn affects motor accuracy. Summary of the Invention

[0003] In view of this, the present invention aims to provide a permanent magnet synchronous motor rotor angle estimation method, by constructing an adaptive resonant state observer to accurately extract the back electromotive force of the motor, and adopting an enhanced orthogonal phase-locked loop to improve the dynamic performance of the phase-locked loop, so that the rotor angle estimation error converges to zero during the acceleration and deceleration process of the motor, thereby improving the estimation accuracy of the back electromotive force and the rotor angle and speed estimation performance.

[0004] To achieve the above object, the technical solution created by the present invention is implemented as follows: A method for estimating a rotor angle of a permanent magnet synchronous motor, comprising: S1: Based on the permanent magnet synchronous motor to be analyzed, a state observer for estimating the back electromotive force is obtained; S2: Based on the state observer obtained in step S1, an adaptive resonance estimator is constructed, and the adaptive resonance estimator is embedded in the state observer to obtain an adaptive resonance state observer; S3: Compensate the traditional phase-locked loop for angle information to obtain an enhanced phase-locked loop; S4: using the adaptive resonant state observer obtained in step S2, estimating the back electromotive force of the permanent magnet synchronous motor; inputting the back electromotive force into the enhanced phase-locked loop to estimate the rotor angle of the permanent magnet synchronous motor.

[0005] Furthermore, in step S1 , the motor input and the known disturbance are added to the voltage equation of the permanent magnet synchronous motor to obtain a state observer.

[0006] Furthermore, the voltage equation is: ; Among them, i α and i β They represent the stator currents of the α-axis and β-axis in the permanent magnet synchronous motor, u α and u β They represent the stator voltages of the α-axis and β-axis, E α and E β They represent the actual back electromotive force of the α-axis and β-axis respectively, and R and L represent the resistance and inductance of the stator in the permanent magnet synchronous motor respectively.

[0007] Furthermore, the motor input is: bu0=u αβ / L; Where u0 represents the motor input, b represents the control gain of the permanent magnet synchronous motor, and u αβ =[u α ,u β ] T ; Known interferences are: F(x,t)=Ri αβ / L; Where F(x,t) represents known interference, i αβ =[i α ,i β ] T .

[0008] Furthermore, the back EMF is taken as the unknown disturbance to be estimated, and the back EMF is expanded into a new state variable: d(t)=-E αβ / L; Among them, d(t) represents the state variable, E αβ =[E α ,E β ] T , E α and E β Represent the actual back electromotive force of α-axis and β-axis respectively; Substituting the motor input, known disturbance, and state variables into the voltage equation, the state observer is obtained as: ; in, , and denote the estimated stator currents of the α-axis and β-axis respectively, , and They represent the estimated back electromotive force of the α-axis and β-axis estimated by the state observer, , represents the error between the actual value of the stator current of the α axis and the estimated stator current value, represents the error between the actual value and the estimated stator current value of the β-axis, and β1 and β2 represent the gains of the state observer.

[0009] Furthermore, in step S2, the adaptive resonant state observer is: ; in, , and They represent the estimated back electromotive force of the α-axis and β-axis estimated by the adaptive resonant state observer, and Q represents the adaptive resonant estimator, which is: ; Among them, ω c represents the bandwidth of the adaptive resonance estimator, ω0 represents the bandwidth of the state observer, ω e represents the actual rotor speed, and q represents the adaptive phase compensation function, which is obtained by the following formula: ; Wherein, a represents the phase compensation coefficient.

[0010] Furthermore, in step S3, the expression of the traditional phase-locked loop is: ; Among them, k i Indicates the integral coefficient of the traditional phase-locked loop, k p represents the proportional coefficient of the traditional phase-locked loop, represents the conventional rotor estimated angle estimated by the conventional phase-locked loop, represents the estimated rotor speed, represents the traditional angle error between the actual rotor angle and the traditional rotor estimated angle; After compensating the traditional phase-locked loop for angle information, the enhanced phase-locked loop is obtained as follows: ; in, represents the enhanced rotor estimated angle estimated by the enhanced phase-locked loop, represents the enhanced angle error between the actual rotor angle and the enhanced rotor estimated angle, k, m, and n represent the adjustable coefficients in the enhanced phase-locked loop, represents the back electromotive force error of the permanent magnet synchronous motor, and They represent the estimated back electromotive force of the α-axis and β-axis estimated by the adaptive resonance estimator, respectively.

[0011] Furthermore, the estimated back EMF of the α-axis for: ; Among them, f represents the permanent magnet flux in the permanent magnet synchronous motor, θ e Indicates the actual rotor angle; Estimated back EMF of β axis for: ; The back-EMF error is input into an enhanced phase-locked loop to estimate the rotor angle.

[0012] Furthermore, the back EMF error is: .

[0013] Furthermore, the method further comprises: S5: Differentiate the rotor angle to obtain the estimated rotor speed of the permanent magnet synchronous motor.

[0014] Compared with the prior art, the present invention can achieve the following beneficial effects: In the permanent magnet synchronous motor rotor angle estimation method created by the present invention, the actual equivalent back electromotive force is further tracked by constructing an adaptive resonant state observer, the back electromotive force phase error is reduced, and the estimation accuracy is improved; in addition, after the present invention improves the traditional phase-locked loop to compensate for the angle information, the enhanced phase-locked loop obtained can make the estimated rotor position error converge to zero during the rapid acceleration and deceleration of the motor, and can quickly respond to speed changes, which helps to improve the dynamic performance of the positionless drive system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings: Figure 1 A flow chart of a method for estimating the rotor angle of a permanent magnet synchronous motor according to an embodiment of the present invention; Figure 2 This is a control framework diagram of the permanent magnet synchronous motor rotor angle estimation method according to an embodiment of the present invention; Figure 3 Schematic diagram of Bode diagrams of different bandwidths for the adaptive resonant state observer according to an embodiment of the present invention; Figure 4A schematic diagram of an adaptive resonant state observer according to an embodiment of the present invention; Figure 5 A schematic diagram of an enhanced phase-locked loop according to an embodiment of the present invention; Figure 6 A comparison chart of the method provided by the present invention and the traditional method for tracking different speeds; Figure 7 The figure is a comparison diagram of the rotor position error curve estimated by the method of the present invention and the traditional method during the motor speed change process. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0017] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or angles based on the positions or angles shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second" and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0019] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0020] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0021] like Figure 1 and Figure 2 As shown, the permanent magnet synchronous motor rotor angle estimation method described in the embodiment of the present invention includes: S1: Based on the permanent magnet synchronous motor to be analyzed, a state observer for estimating the back electromotive force is obtained.

[0022] In the permanent magnet synchronous motor to be analyzed in the embodiment of the present invention, Figure 2 As shown, SVPWM stands for space vector pulse width modulation.

[0023] The speed controller in the permanent magnet synchronous motor control system is mainly used to receive the desired electrical angular velocity , and according to the desired rotor electrical angular velocity Estimated rotor speed The error between the two generates the control current and , used to adjust the current of the q-axis and d-axis in the permanent magnet synchronous motor. The current controller receives the control current and and the three-phase current i detected by the rotor of the permanent magnet synchronous motor a 、i b and i c The actual current i obtained by Clark transformation qi and i di For comparison, the current controller outputs the control voltage and Used to adjust the voltage of the q-axis and d-axis in the permanent magnet synchronous motor and control the voltage and After Park transformation, the control voltage output by the current controller is converted into a PWM signal suitable for the inverter through space vector pulse width modulation, namely PWM1, PWM2, PWM3, PWM4, PWM5 and PWM6 in the figure, which are used to control the three-phase current of the permanent magnet synchronous motor, thereby achieving control of the motor speed. In this control process, the embodiment of the present invention mainly improves the estimation accuracy of the back electromotive force and the system convergence speed through an adaptive resonant state observer, and introduces a composite integral compensation link in the phase-locked loop control to reduce the rotor position estimation error during acceleration and deceleration of the speed ramp signal, thereby obtaining a high-precision enhanced rotor estimation angle. , and then get the estimated rotor speed , in order to achieve high-precision closed-loop control of the permanent magnet synchronous motor and improve the performance of the motor control system. Specifically, the specific process of the method provided in the embodiment of the present invention is as follows: In some embodiments, the motor input and known disturbance are added to the voltage equation of the permanent magnet synchronous motor to obtain a state observer. Specifically, the voltage equation of the permanent magnet synchronous motor is: ; Among them, i α and i β They represent the stator currents of the α-axis and β-axis in the permanent magnet synchronous motor, u α and u β They represent the stator voltages of the α-axis and β-axis, E α and E β They represent the actual back electromotive force of the α-axis and β-axis respectively, and R and L represent the resistance and inductance of the stator in the permanent magnet synchronous motor respectively.

[0024] The motor input is: bu0=u αβ / L; Where u0 represents the motor input and b represents the control gain of the permanent magnet synchronous motor.

[0025] The interference is: F(x,t)=Ri αβ / L; Where F(x,t) represents the known interference, i αβ =[i α ,i β ] T .

[0026] Take the back EMF as the unknown disturbance to be estimated and expand the back EMF into a new state variable: d(t)=-E αβ / L; Among them, d(t) represents the state variable, E αβ =[E α ,E β ] T , E α and E β They represent the actual back electromotive force of the α-axis and β-axis respectively.

[0027] After the motor input, known disturbance, and state variables are brought into the voltage equation of the permanent magnet synchronous motor, the resulting state observer is: ; in, , and denote the estimated stator currents of the α-axis and β-axis respectively, , and They represent the estimated back electromotive force of the α-axis and β-axis estimated by the state observer, , represents the error between the actual value of the stator current of the α axis and the estimated stator current value, represents the error between the actual value and the estimated stator current value of the β-axis, and β1 and β2 represent the gains of the state observer.

[0028] S2: Based on the state observer obtained in step S1, an adaptive resonance estimator is constructed, and the adaptive resonance estimator is embedded in the state observer to obtain an adaptive resonance state observer.

[0029] In some embodiments, based on the bandwidth of the state observer and the actual rotor speed, the adaptive phase compensation function of the adaptive resonance estimator is determined by the following equation: ; Where q represents the adaptive phase compensation function, ω0 represents the bandwidth of the state observer, and ω e represents the actual rotor speed, a represents the phase compensation coefficient. In the embodiment of the present invention, the phase compensation coefficient a is set to 0.28, that is, the adaptive phase compensation function in the embodiment of the present invention is: .

[0030] According to the obtained adaptive phase compensation function q, the adaptive resonance estimator is determined as: ; Where Q represents the adaptive resonance estimator, ω c represents the bandwidth of the adaptive resonance estimator, ω c The value range of ω is relatively wide. c =1000rad / s, bandwidth ω c It can be adjusted according to the actual Bode diagram of the adaptive resonant state observer, such as Figure 3 As shown, ω c The larger the value, the smaller the phase lag of the designed observer is, and the more susceptible it is to noise and irrelevant high-frequency interference. c The smaller the value, the more severe the phase lag, but it can filter out some high-frequency noise and enhance the system's anti-interference ability. Choose an appropriate bandwidth value based on the above performance compromise.

[0031] The adaptive resonance estimator is embedded in the state observer, as Figure 4 The adaptive resonant state observer shown is specifically: ; in, , and They represent the estimated back electromotive force of the α-axis and the β-axis estimated by the adaptive resonant state observer, respectively. In some embodiments, the estimated back electromotive force of the α-axis and the β-axis are: ; ; in, and denote the estimated back electromotive force of α-axis and β-axis, Ψ f represents the permanent magnet flux in the permanent magnet synchronous motor, θ e Indicates the actual rotor angle.

[0032] S3: Perform angle information compensation on the traditional phase-locked loop to obtain an enhanced phase-locked loop.

[0033] Among them, the traditional phase-locked loop is: ; Among them, k i Indicates the integral coefficient of the traditional phase-locked loop, k p represents the proportional coefficient of the traditional phase-locked loop, represents the conventional rotor estimated angle estimated by the conventional phase-locked loop, represents the traditional angle error between the actual rotor angle and the traditional rotor estimated angle, i.e. In a conventional phase-locked loop, the back-EMF error between the estimated back-EMFs of the α-axis and the β-axis is given by: ; in, Represents the back electromotive force error of the permanent magnet synchronous motor obtained in the traditional phase-locked loop. When the angle error is small enough, that is, When , we can further get: ; Based on the above ideas, the traditional phase-locked loop is compensated for the angle information, and the following is obtained: Figure 5 The enhanced phase-locked loop shown is specifically: Back EMF Error Resulted in Enhanced Phase-Locked Loop for: ; in, represents the enhanced rotor estimated angle estimated by the enhanced phase-locked loop, represents the enhanced angle error between the actual rotor angle and the enhanced rotor estimated angle, i.e. , let the enhanced angle error Small enough, that is When , we get: ; Then we get the following enhanced phase-locked loop: ; Wherein, k, m, and n represent adjustable coefficients in the enhanced phase-locked loop.

[0034] The parameters k, m, and n are adjusted according to the following: For the designed enhanced phase-locked loop, the enhanced rotor estimated angle is derived and the actual rotor angle θ e The transfer function G between EPLL for: ; Among them, (2s 2 +ms+n) and (s 2 +k p s+k i ) are equivalent to two second-order systems (2s 2 +4ξ1ω n1 s+2ω n1 2 ) and (s 2 +2ξ2ω n2 s+ω n2 2 ), that is, let m=4ξ1ω n1 , n=2ω n1 2 , k p =2ξ2ω n2 , and k i =ω n2 2 , ξ1 and ξ2 represent the damping coefficients of the two second-order systems, ω n1 and ω n2 denote the natural frequencies of the two second-order systems, ξ1 and ξ2, and ω n1 and ω n2 , according to the adjustment method of the second-order system, in the embodiment of the present invention, ξ1∈(0.5,1), ξ2∈(0.5,1), ω n1 =260rad / s,ω n2 =260rad / s.

[0035] S4: using the adaptive resonant state observer obtained in step S2, estimating the back electromotive force of the permanent magnet synchronous motor; inputting the back electromotive force into the enhanced phase-locked loop to estimate the rotor angle of the permanent magnet synchronous motor.

[0036] In some embodiments, the method further comprises: S5: Differentiate the rotor angle to obtain an estimated rotor speed of the permanent magnet synchronous motor. In the embodiment of the present invention, specifically: .

[0037] This process occurs in the enhanced phase-locked loop. It can be understood that the enhanced phase-locked loop estimates the rotor angle based on the input estimated back electromotive force, and obtains the estimated rotor speed according to the above formula. It can be further understood that the mathematical model of the enhanced phase-locked loop provided by the present invention is: .

[0038] To demonstrate the effectiveness of the permanent magnet synchronous motor rotor angle estimation method provided by the present invention, the embodiment of the present invention also provides a traditional permanent magnet synchronous motor rotor angle estimation method, that is, combining a traditional extended state observer with a phase-locked loop, and comparing the traditional method with the method provided by the present invention. It should be noted that in the embodiment of the present invention, the parameters of the two methods are set in the same way, that is, in the two methods, the parameters in the speed controller are both k p1 =1 and k i1 =15, the parameters in the current controller are all k p2 =2 and k i2 =360, the coefficients of the observer in both methods are β1=2000, β2=1000000. The coefficients of the phase-locked loop in both methods are k i =1000 and k p =50.

[0039] After conducting simulation experiments on the two methods under the same conditions, we obtained the following Figure 6 and Figure 7 The results comparison chart. Figure 6 As shown in FIG, the method proposed in the present invention can track the actual speed to reach a stable state faster than the traditional method, and the speed fluctuation after reaching the stable state is smaller, which is beneficial to improving the dynamic performance of the position sensorless control system; Figure 7 As shown in the figure, the rotor estimation error of the proposed method is significantly smaller than that of the traditional method, both in the stable state at different speeds and during the speed increase and decrease process. This demonstrates the superiority of the permanent magnet synchronous motor rotor position estimation method based on the adaptive resonant state observer and the enhanced phase-locked loop. It can be seen that the method provided by the present invention can effectively improve the estimation accuracy of back-EMF and the performance of rotor position and speed estimation.

[0040] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved. This is not limited herein.

[0041] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A method for estimating the rotor angle of a permanent magnet synchronous motor, characterized in that: include: S1: Based on the permanent magnet synchronous motor to be analyzed, a state observer for estimating the back electromotive force is obtained; S2: Based on the state observer obtained in step S1, construct an adaptive resonance estimator, and embed the adaptive resonance estimator into the state observer to obtain an adaptive resonance state observer; S3: Perform angle information compensation on the traditional phase-locked loop to obtain an enhanced phase-locked loop; S4: using the adaptive resonant state observer obtained in step S2, estimating the back electromotive force of the permanent magnet synchronous motor; inputting the back electromotive force into the enhanced phase-locked loop to estimate the rotor angle of the permanent magnet synchronous motor.

2. The method for estimating the rotor angle of a permanent magnet synchronous motor according to claim 1, wherein: In step S1 , the motor input and known disturbance are added to the voltage equation of the permanent magnet synchronous motor to obtain the state observer.

3. The method for estimating the rotor angle of a permanent magnet synchronous motor according to claim 2, wherein: The voltage equation is: ； Among them, i α and i β They represent the stator currents of the α-axis and β-axis in the permanent magnet synchronous motor, u α and u β represent the stator voltages of the α-axis and the β-axis, E α and E β represent the actual back electromotive force of the α-axis and the β-axis respectively, and R and L represent the resistance and inductance of the stator in the permanent magnet synchronous motor respectively.

4. The method for estimating the rotor angle of a permanent magnet synchronous motor according to claim 3, wherein: The motor input is: bu0=u αβ / L; Wherein, u0 represents the motor input, b represents the control gain of the permanent magnet synchronous motor, u αβ =[u α ,u β ] T ; The known interferences are: F(x,t)=Ri αβ / L; Wherein, F(x,t) represents the known interference, i αβ =[i α ,i β ] T .

5. The method for estimating the rotor angle of a permanent magnet synchronous motor according to claim 4, wherein: The back EMF is taken as the unknown disturbance to be estimated and expanded into a new state variable as: d(t)=-E αβ / L; Wherein, d(t) represents the state variable, E αβ =[E α ,E β ] T , E α and E β Represent the actual back electromotive force of α-axis and β-axis respectively; Substituting the motor input, the known disturbance, and the state variable into the voltage equation, the state observer is obtained as: ； in, , and denote the estimated stator currents of the α-axis and the β-axis respectively, , and denote the estimated back electromotive force of the α-axis and the β-axis estimated by the state observer, respectively, , represents the error between the actual value and the estimated stator current value of the α-axis, represents the error between the actual value and the estimated stator current value of the β-axis, and β1 and β2 represent the gains of the state observer.

6. The method for estimating the rotor angle of a permanent magnet synchronous motor according to claim 5, wherein: In step S2, the adaptive resonant state observer is: ； in, , and They represent the estimated back electromotive force of the α-axis and the β-axis estimated by the adaptive resonant state observer, and Q represents the adaptive resonant estimator, which is: ； Among them, ω c represents the bandwidth of the adaptive resonance estimator, ω0 represents the bandwidth of the state observer, ω e represents the actual rotor speed, and q represents the adaptive phase compensation function, which is obtained by the following formula: ； Wherein, a represents the phase compensation coefficient.

7. The method for estimating the rotor angle of a permanent magnet synchronous motor according to claim 6, wherein: In step S3, the expression of the traditional phase-locked loop is: ； Among them, k i represents the integral coefficient of the conventional phase-locked loop, k p represents the proportional coefficient of the conventional phase-locked loop, represents the conventional rotor estimated angle estimated by the conventional phase-locked loop, represents the estimated rotor speed, represents a conventional angle error between the actual rotor angle and the conventional rotor estimated angle; After compensating the angle information of the conventional phase-locked loop, the enhanced phase-locked loop is obtained as follows: ； in, represents the enhanced rotor estimated angle estimated by the enhanced phase-locked loop, represents the enhanced angle error between the actual rotor angle and the enhanced rotor estimated angle, k, m and n represent adjustable coefficients in the enhanced phase-locked loop, represents the back electromotive force error of the permanent magnet synchronous motor, and , and , respectively, represent estimated back electromotive forces of the α-axis and the β-axis estimated by the adaptive resonance estimator.

8. The method for estimating the rotor angle of a permanent magnet synchronous motor according to claim 7, wherein: The estimated back EMF of the α-axis for: ； Among them, f represents the permanent magnet flux in the permanent magnet synchronous motor, θ e represents the actual rotor angle; The estimated back EMF of the β-axis for: ； The back electromotive force error is input into the enhanced phase-locked loop to estimate the rotor angle.

9. The method for estimating the rotor angle of a permanent magnet synchronous motor according to claim 8, wherein: The back EMF error is: 。 10. The method for estimating the rotor angle of a permanent magnet synchronous motor according to claim 1, wherein: The method also includes: S5: Differentiate the rotor angle to obtain an estimated rotor speed of the permanent magnet synchronous motor.

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