Sensorless control angle acquisition method for permanent magnet synchronous motor

Abstract

The invention discloses a method for acquiring a sensorless control angle of a permanent magnet synchronous motor. The method comprises the following steps: step 1, acquiring parameters of a target motor under a two-phase static coordinate system; 2, constructing a sliding mode controller and a stator current error equation; 3, obtaining an extended counter electromotive force estimation value according to the step 2; step 4, filtering the extended back electromotive force estimation value through SOGI, and then performing normalization processing; and step 5, adding a phase-locked loop of a sign function to the extended back electromotive force estimation value processed in the step 4 to obtain a rotor angle estimation value. According to the invention, the extended back electromotive force is filtered by using the SOGI, and the phase shift error is not caused while the noise is filtered, so that the input of the forward and reverse rotation to the phase-locked loop is the same, thereby eliminating the influence of the forward and reverse rotation on the phase-locked loop.

Description

Technical Field

[0001] The invention relates to the technical field of permanent magnet synchronous motor control, and in particular to a sensorless control angle acquisition method for a permanent magnet synchronous motor based on an improved phase-locked loop. Background Art

[0002] As a commonly used AC motor, permanent magnet synchronous motor has various advantages in industrial applications and household appliances due to its small size, simple structure, high power and low loss. For permanent magnet synchronous motor, high-performance control requires accurate speed and position information to achieve closed-loop control.

[0003] Among the control methods based on back-EMF analysis angle, there is a method that introduces a phase-locked loop into a sensorless control system and uses the phase-locked loop to identify speed and position. This method has attracted much attention due to its simple structure and good performance. However, as a second-order system, the phase-locked loop cannot accurately track the frequency ramp signal generated when facing the acceleration and deceleration conditions of the motor, and may even lose lock. In addition, due to the influence of speed, the forward and reverse rotation of the motor will also affect the accuracy of the phase-locked loop output angle.

[0004] At present, some technologies have been made public to try to solve the above technical problems:

[0005] For example, a Chinese patent with publication number CN115021625B discloses a position resolution circuit, method, and control circuit and system for a permanent magnet synchronous motor. The position resolution circuit includes: a signal processing module configured to perform deviation correction on the measurement signal and output a sampling signal containing the position information of the outer rotor of the permanent magnet synchronous motor; an analog-to-digital conversion module configured to convert the sampling signal into a digital signal; and a resolution module configured to resolve the digital signal to output the angle information and speed information of the outer rotor. However, its phase-locked loop structure is a traditional orthogonal phase-locked loop, which is difficult to adapt to the motor speed change condition.

[0006] Another example is a Chinese patent with publication number CN109245649A, which discloses a method and system for calculating the motor flux phase and speed based on a phase-locked loop, wherein the method includes: obtaining the motor flux and in the two-phase stationary coordinate system of the motor through the motor model, and constructing the motor flux vector based on and; constructing a unit rotation vector based on the phase-locked angle; calculating the cross product of the unit rotation vector and the flux vector; performing PI operation on to calculate the motor phase-locked angular velocity; integrating the phase-locked angular velocity to calculate the motor phase-locked angle. However, its phase-locked result is greatly affected by speed fluctuations.

[0007] Another example is a Chinese patent with publication number CN116865609A, which discloses a sensorless control system and method for a linear motor based on a three-type phase-locked loop, including a sliding mode observer, a three-type phase-locked loop, a conversion module and a modulation module; the sliding mode observer is used to estimate two back electromotive forces according to the stator voltage and stator current acquired in a two-phase stationary coordinate system; the three-type phase-locked loop is used to calculate the error signal according to the estimated two back electromotive forces, and eliminate the error after filtering according to a predetermined transfer function to obtain the motor electrical angle; the conversion module is used to calculate the stator target voltage according to the motor electrical angle and the stator target current; the modulation module is used to generate an inverter modulation signal according to the stator target voltage to control the linear motor. The present invention solves the problem of position tracking when the motor changes speed by adopting a three-type phase-locked loop, but the single-loop structure is significantly affected by the rotation speed, and the phase-locked loop will produce obvious errors when the back electromotive force input causes the motor to rotate forward and reverse. Summary of the invention

[0008] In view of the deficiencies in the prior art, the present invention provides a sensorless control angle acquisition method for a permanent magnet synchronous motor to solve the technical problems in the prior art that the second-order phase-locked loop signal frequency changes rapidly and the phase error is large during forward and reverse switching, and the input signal noise is large and oscillation instability is easily generated.

[0009] The present invention provides a method for obtaining a sensorless control angle of a permanent magnet synchronous motor, comprising the following steps:

[0010] Step 1: Obtain the parameters of the target motor in the two-phase stationary coordinate system;

[0011] Step 2: Construct sliding mode controller and stator current error equation;

[0012] Step 3: Obtain the extended back-EMF estimate according to step 2;

[0013] Step 4: Filter the extended back-EMF estimate through SOGI and then normalize it;

[0014] Step 5: Obtain the rotor angle estimate by adding a phase-locked loop with a sign function to the extended back-EMF estimate processed in step 4.

[0015] Furthermore, in step 2, the sliding mode control law of the sliding mode controller is:

[0016]

[0017] In the formula, is the current observation error; e α 、e β Expanding the back EMF for the motor.

[0018] Furthermore, in step 2, the stator current error equation is:

[0019]

[0020] In the formula, ω e is the rotor electrical angular velocity; is the current observation error; L d , L q is the stator inductance.

[0021] Furthermore, in step 3, the estimated value of the extended back electromotive force obtained is:

[0022]

[0023] Furthermore, in step 4, the transfer function of SOGI is:

[0024]

[0025] In the formula, G SOGI is the transfer function of SOGI; ξ is the damping coefficient; ω0 is the center frequency of SOGI; s is the complex variable in Laplace transform.

[0026] Furthermore, in step 4, the center frequency ω0 of SOGI is set to:

[0027]

[0028] In the formula, To expand the back EMF estimation value; ψ f is the permanent magnet flux.

[0029] Furthermore, in step 5, the phase-locked loop adding the sign function is specifically:

[0030] Add a sign function to the error signal and the error compensation signal, where

[0031] The error signal formula with the sign function added is:

[0032]

[0033] Where, e is the error signal; θ is the actual angle of the motor; To estimate the angle; is the estimated value of the extended back-EMF after SOGI filtering; Estimated speed.

[0034] The error compensation signal formula with the sign function added is:

[0035]

[0036] Where, e′ is the error compensation signal; θ is the actual angle of the motor; To estimate the angle; is the estimated value of the extended back EMF after SOGI filtering.

[0037] Furthermore, in step 5, the specific setting of the sign function is:

[0038]

[0039] In the formula, Estimated speed.

[0040] Furthermore, in step 5, when the motor rotates forward, the error signal formula is:

[0041] The error compensation signal formula is:

[0042]

[0043] When the motor reverses, the error signal formula is:

[0044] The error compensation signal formula is:

[0045]

[0046] Where, e is the error signal; e′ is the error compensation signal; θ is the actual angle of the motor; To estimate the angle.

[0047] Furthermore, in step 5, the estimated value of the rotor angle obtained is:

[0048]

[0049] Where Δθ is the error between the actual angle and the estimated angle; θ is the actual angle of the motor; To estimate the angle; is the estimated angle after compensation.

[0050] Beneficial effects of the present invention:

[0051] 1. The present invention utilizes SOGI to filter the extended back electromotive force, thereby filtering out noise without causing phase shift error, making the input of the phase-locked loop the same for both forward and reverse rotations, thereby eliminating the influence of forward and reverse rotations on the phase-locked loop.

[0052] 2. The present invention provides an implementation method for improving the phase-locked loop. By introducing a sign function to rewrite the error and error compensation, the influence of the motor's forward and reverse rotation is eliminated, and a compensation loop is constructed, which significantly improves the accuracy of position estimation and can theoretically perform zero-error tracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the present invention in any way. In the accompanying drawings:

[0054] Figure 1 It is a block diagram of the implementation method of the sensorless control angle acquisition method of the permanent magnet synchronous motor proposed in the present invention;

[0055] Figure 2 This is a diagram showing the filtering effect of the low-pass filter used in the traditional method on the estimated value of the extended back-electromotive force;

[0056] Figure 3 It is a diagram showing the filtering effect of SOGI proposed in the present invention on the estimated value of extended back electromotive force;

[0057] Figure 4 It is the actual angle and estimated angle obtained by the traditional method under the motor acceleration condition;

[0058] Figure 5 are the actual angle and estimated angle obtained by the method of the present invention under the motor acceleration condition;

[0059] Figure 6 It is the actual angle and estimated angle obtained by the traditional method under the forward and reverse switching conditions of the motor;

[0060] Figure 7 These are the actual angle and estimated angle obtained by the method of the present invention under the forward and reverse switching conditions of the motor. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0062] The present invention is further illustrated below in conjunction with specific embodiments. Those skilled in the art should understand that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention, and modifications to various equivalent forms of the present invention fall within the scope defined by the appended claims of this application.

[0063] like Figure 1 As shown, the present invention provides a method for obtaining a sensorless control angle of a permanent magnet synchronous motor, comprising the following steps:

[0064] Step 1: Get the real-time stator voltage u through the sampling module and the calculation modulea 、u b 、u c and the stator current i a 、i b 、i c , the motor voltage u in the two-phase stationary coordinate system is obtained by formula (1): α 、u β and current i α 、i β ;

[0065] Get the target motor stator resistance R s 、Permanent magnet flux ψ f , stator inductance L d , L q ,

[0066]

[0067] Step 2: Construct a sliding mode controller, where the sliding mode control law is:

[0068]

[0069] In the formula, is the current observation error; e α , eβ is the extended back electromotive force of the motor;

[0070] Construct the stator current error equation:

[0071] First, according to step 1, we can get the current state equation:

[0072]

[0073] According to step 1, the current estimation equation is obtained:

[0074]

[0075] Finally, subtract formula (2) and formula (3) to get the current error equation:

[0076]

[0077] In the formula, ω e is the rotor electrical angular velocity.

[0078] Step 3: Get the extended back EMF estimate based on step 2

[0079]

[0080] Step 4: Filter the extended back EMF estimate through the speed-adapted SOGI and then normalize it. The transfer function of SOGI is:

[0081]

[0082] In the formula, G SOGI is the transfer function of SOGI; ξ is the damping coefficient; ω0 is the center frequency of SOGI; s is the complex variable in Laplace transform.

[0083] The center frequency ω0 of SOGI is set as:

[0084]

[0085] In the formula, To expand the back EMF estimation value; ψ f is the permanent magnet flux;

[0086] The normalization formula is:

[0087]

[0088] Step 5: Obtain the rotor angle estimate by adding a phase-locked loop with a sign function to the extended back-EMF estimate processed in step 4, where:

[0089] The error signal formula with the sign function added is:

[0090]

[0091] Where, e is the error signal; θ is the actual angle of the motor; To estimate the angle; is the estimated value of the extended back-EMF after SOGI filtering; is the estimated rotation speed;

[0092] The error compensation signal formula with the sign function added is:

[0093]

[0094] Where, e′ is the error compensation signal; θ is the actual angle of the motor; To estimate the angle; is the estimated value of the extended back-EMF after SOGI filtering;

[0095] The sign function in the error signal formula and the error compensation signal formula is set as:

[0096]

[0097] In the formula, is the estimated rotation speed;

[0098] Combining the set sign function, error signal formula (4) and error compensation signal formula (5), when the motor rotates forward, the error signal formula is:

[0099]

[0100] The error compensation signal formula is:

[0101]

[0102] When the motor reverses, the error signal formula is:

[0103]

[0104] The error compensation signal formula is:

[0105]

[0106] Where, e is the error signal; e′ is the error compensation signal; θ is the actual angle of the motor; To estimate the angle;

[0107] The error signal obtained to distinguish between positive and reverse rotation is adjusted by PI to obtain the estimated speed The estimated rotation speed is integrated to obtain the estimated angle

[0108] The error compensation signal is passed through a low-pass filter to obtain the angle error compensation.

[0109] The estimated angle is compensated according to the obtained angle error compensation to obtain the final estimated angle:

[0110]

[0111] The following is the simulation process of the present invention:

[0112] In the simulation environment of MATLAB / Simulink, the motor parameters are: stator resistance Rs = 3.875Ω, dq axis inductance L = 0.85mH, pole pair number pn = 4, rotor permanent magnet flux ψ f =0.175wb.

[0113] like Figure 2 As shown in FIG. 1 , it is a diagram showing the filtering effect of the low-pass filter used in the traditional method on the estimated value of the extended back electromotive force, such as Figure 3 The figure shows the filtering effect of SOGI proposed in the present invention on the estimated value of extended back electromotive force. Figure 2 and Figure 3It can be clearly found that the waveform of the back electromotive force estimation value after filtering by the SOGI filtering structure proposed in the present invention is smoother.

[0114] Figure 4 and Figure 5 They are respectively the actual angle and the estimated angle under the condition that the motor speed gradually accelerates from 400r / min to 1400r / min under the MATLAB / Simulink environment using the traditional method of applying the orthogonal phase-locked loop angle acquisition method and the permanent magnet synchronous motor sensorless control angle acquisition method in the embodiment of the present invention. Under the traditional method, there is an obvious error between the estimated angle and the actual angle, and a good fit cannot be made. The angle acquisition method proposed in the present invention can make the estimated angle always follow the actual angle.

[0115] Figure 6 and Figure 7 They are respectively the actual angle and the estimated angle under the forward and reverse switching conditions of the motor in the MATLAB / Simulink environment using the traditional method of applying the orthogonal phase-locked loop angle acquisition method and the permanent magnet synchronous motor sensorless control angle acquisition method in the embodiment of the present invention. It can be seen that when applying the traditional method, the angle tracking of the motor fails after reversal, while the angle acquisition method proposed in the present invention can make the estimated angle always follow the actual angle.

[0116] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for acquiring a sensorless control angle of a permanent magnet synchronous motor, characterized in that: The steps include: Step 1: Obtain the parameters of the target motor in the two-phase stationary coordinate system; Step 2: Construct sliding mode controller and stator current error equation; Step 3: Obtain the extended back-EMF estimate according to step 2; Step 4: Filter the extended back-EMF estimate through SOGI and then normalize it; Step 5: Obtain the rotor angle estimate by adding a phase-locked loop with a sign function to the extended back-EMF estimate processed in step 4.

2. The method for acquiring the sensorless control angle of a permanent magnet synchronous motor according to claim 1, characterized in that: In step 2, the sliding mode control law of the sliding mode controller is: In the formula, is the current observation error; e α 、e β Expanding the back EMF for the motor.

3. The sensorless control angle acquisition method for a permanent magnet synchronous motor according to claim 1, characterized in that: In step 2, the stator current error equation is: In the formula, ω e is the rotor electrical angular velocity; is the current observation error; L d , L q is the stator inductance.

4. The method for acquiring sensorless control angle of a permanent magnet synchronous motor according to claim 1, characterized in that: In step 3, the estimated value of the extended back electromotive force is obtained as follows:

5. The sensorless control angle acquisition method for a permanent magnet synchronous motor according to claim 1, characterized in that: In step 4, the transfer function of SOGI is: In the formula, G SOGI is the transfer function of SOGI; ξ is the damping coefficient; ω0 is the center frequency of SOGI; s is a complex variable in Laplace transform.

6. The method for acquiring the sensorless control angle of a permanent magnet synchronous motor according to claim 5, characterized in that: In step 4, the center frequency ω0 of SOGI is set to: In the formula, To expand the back EMF estimation value; ψ f is the permanent magnet flux.

7. The method for acquiring sensorless control angle of a permanent magnet synchronous motor according to claim 1, characterized in that: In step 5, the phase-locked loop with the sign function added is specifically: Add a sign function to the error signal and the error compensation signal, where The error signal formula with the sign function added is: Where, e is the error signal; θ is the actual angle of the motor; To estimate the angle; is the estimated value of the extended back-EMF after SOGI filtering; Estimated speed. The error compensation signal formula with the sign function added is: Where, e′ is the error compensation signal; θ is the actual angle of the motor; To estimate the angle; is the estimated value of the extended back EMF after SOGI filtering.

8. The method for acquiring sensorless control angle of a permanent magnet synchronous motor according to claim 7, characterized in that: In step 5, the specific setting of the symbol function is: In the formula, Estimated speed.

9. The method for acquiring sensorless control angle of a permanent magnet synchronous motor according to claim 8, characterized in that: In step 5, when the motor rotates forward, the error signal formula is: The error compensation signal formula is: When the motor reverses, the error signal formula is: The error compensation signal formula is: Where, e is the error signal; e′ is the error compensation signal; θ is the actual angle of the motor; To estimate the angle.

10. The method for acquiring sensorless control angle of a permanent magnet synchronous motor according to claim 9, characterized in that: In step 5, the estimated value of the rotor angle is obtained as follows: Where Δθ is the error between the actual angle and the estimated angle; θ is the actual angle of the motor; To estimate the angle; is the estimated angle after compensation.

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