Wide-speed-range sensorless control method for permanent magnet synchronous motor

Abstract

The invention discloses a wide-speed-domain position-sensorless control method for a permanent magnet synchronous motor, and the method comprises the steps: building an extended state observer of the permanent magnet synchronous motor, and obtaining the counter electromotive force of the motor through the extended state observer; a self-adaptive vector filter is adopted to filter out higher harmonics in the back electromotive force obtained by the extended state observer, estimated back electromotive force is obtained, the obtained estimated back electromotive force serves as input, position information contained in the estimated back electromotive force is demodulated through a phase-locked loop position observer, and the rotating speed and the position angle of the motor are obtained; and controlling the permanent magnet synchronous motor according to the obtained rotating speed and position angle. The position observer is used for extracting position information from the rotor back electromotive force, a mechanical position sensor is omitted, the system structure is simplified, cost is reduced, the self-adaptive vector filter is used for filtering harmonic waves for estimating the back electromotive force, and estimation errors of the rotating speed and the position angle of the motor are reduced. And the high efficiency and the stability of position-sensorless control of the motor in a wide speed range are improved.

Description

Technical Field

[0001] The invention relates to permanent magnet synchronous motor drive control, and in particular to a wide speed range position sensorless control method for a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors have the advantages of high power density, reliable operation, and wide speed regulation range. In order to achieve high-performance control of permanent magnet synchronous motors, the motor rotor position information is indispensable. However, mechanical position sensors increase hardware costs, reduce the reliability of the drive system, and increase the system volume, which limits its application. The back-EMF method is an effective position sensorless control scheme. However, the performance of this method in speed and position angle estimation during transient operation is poor. Back-EMF observers with fixed parameters often cannot maintain consistent estimation accuracy over a wide frequency range. Therefore, it is of great practical significance to study the back-EMF method with simple structure and low total harmonic distortion to improve the wide speed range position sensorless control performance.

[0003] In order to realize the position sensorless control of permanent magnet synchronous motor in wide speed range, in the prior art, for example, Chinese patent application with application number 2023105661141 discloses a permanent magnet synchronous motor speed control method based on adaptive sliding mode reaching law, the designed exponential integral sliding mode surface can effectively reduce the integral saturation effect, and the adaptive gain sliding mode reaching law with bounded convergence time can automatically adjust the size of the reaching law gain according to the system state, effectively reducing the time and jitter for the system state to reach the sliding mode surface. Although the structure of this method is relatively simple, the model parameters are complex and difficult to adjust. For example, Chinese patent application with application number 2013101408719 discloses an adaptive notch filter signal processing device and method based on the minimum mean square algorithm for eliminating the sixth rotor pulsation error in the model method of medium and high speed position sensorless permanent magnet synchronous motor control technology. The method obtains equivalent back electromotive force information through the model method, and then adjusts the adaptive notch filter based on the minimum mean square algorithm. The influence of the sixth pulsation error of the rotor position observation value is effectively suppressed, and the estimation accuracy of the motor rotor position angle is improved. However, this method will produce time delay and reduce the transient performance of the permanent magnet synchronous motor position sensorless control system. Summary of the invention

[0004] Purpose of the invention: In view of the above shortcomings, the present invention provides a position sensorless control method for a permanent magnet synchronous motor over a wide speed range, which takes into account the estimation performance of the motor speed and position during transient operation, while reducing the higher harmonics of the back electromotive force.

[0005] Technical solution: To solve the above problems, the present invention adopts a wide speed range position sensorless control method of a permanent magnet synchronous motor, comprising the following steps:

[0006] Step 1: Establish an extended state observer of the permanent magnet synchronous motor and use the extended state observer to obtain the back electromotive force of the permanent magnet synchronous motor;

[0007] Step 2: Use an adaptive vector filter to filter out the high-order harmonics in the back-EMF obtained by the extended state observer to obtain the estimated back-EMF of the permanent magnet synchronous motor:

[0008]

[0009] in, represents the estimated back EMF of the permanent magnet synchronous motor α axis at the kth instant filtered out, represents the estimated back EMF of the permanent magnet synchronous motor β axis at the kth instant filtered out, It represents the back electromotive force filtered out at the k-1th instant on the α axis of the permanent magnet synchronous motor. It represents the back electromotive force filtered out at the k-1th instant on the β axis of the permanent magnet synchronous motor. represents the observed speed value, T s Indicates the sampling frequency;

[0010] Step 3: Using the estimated back electromotive force as input, the phase-locked loop position observer is used to demodulate the position information contained in the estimated back electromotive force to obtain the speed and position angle of the permanent magnet synchronous motor;

[0011] Step 4: Control the permanent magnet synchronous motor according to the obtained speed and position angle.

[0012] Furthermore, the extended state observer established in step 1 is:

[0013]

[0014] Among them, ε 1 represents the estimation error, z 1 represents the estimated value of stator current, z 2 represents the lumped disturbance estimate, i αβ represents the stator current, b represents the unknown input gain, u 0 represents the control input, β 1 and β 2 is the feedback gain of the extended state observer;

[0015] Obtaining the Back Electromotive Force of a Permanent Magnet Synchronous Motor Using an Extended State Observer for:

[0016]

[0017] Among them, L s represents the stator inductance.

[0018] Furthermore, the feedback gain of the extended state observer is selected with reference to the bandwidth method as follows:

[0019]

[0020] Among them, ω 0 is the bandwidth of the extended state observer;

[0021] The bandwidth of the extended state observer is optimized as follows:

[0022]

[0023] Among them, ψ f represents the rotor flux of the permanent magnet, ε max represents the maximum acceptable value of the estimation error, ω 0min represents the minimum bandwidth of the extended state observer, ω 0max It represents the maximum value of the bandwidth of the extended state observer.

[0024] Furthermore, the discrete transfer function of the adaptive vector filter is:

[0025]

[0026] Among them, k f represents the filter coefficient, ω f represents the center frequency of the adaptive vector filter, j represents an imaginary number, i.e. j 2 =-1, z represents the signal delay time.

[0027] Furthermore, the amplitude-frequency characteristic and phase-frequency characteristic of the adaptive vector filter are:

[0028]

[0029] Where ω represents the frequency of the input signal.

[0030] Furthermore, the specific steps of using the phase-locked loop position observer to demodulate and estimate the position information contained in the back electromotive force to obtain the position angle of the permanent magnet synchronous motor in step 3 are: using the estimated back electromotive force as an input signal, automatically synchronizing the output signal with the input signal through closed-loop regulation, thereby indirectly extracting the phase information of the input signal, obtaining the angle error through the phase information, and then adjusting the angle error through a proportional-integral controller to estimate the baseband signal, and integrating the baseband signal to obtain the estimated position angle of the permanent magnet synchronous motor.

[0031] Furthermore, after compensating the phase lag of the extended state observer, the final estimated position angle of the permanent magnet synchronous motor is obtained. for:

[0032]

[0033] in, Represents the estimated position angle obtained by integrating the baseband signal.

[0034] Furthermore, the specific steps of step 4 are: using the estimated speed of the permanent magnet synchronous motor as feedback, comparing it with the given speed, and obtaining the current given value i through the proportional integral controller d * and i q * At the same time, the three-phase current of the permanent magnet synchronous motor obtained by sampling is transformed into the coordinate to obtain the current i of the dq axis d and i q , with a given current i d * and i q * After the proportional-integral controller and the inverse Park transformation, the voltage u is obtained. α and u β , output to the space vector pulse width modulator to synthesize PWM wave, output to the three-phase inverter, and finally establish a double closed-loop permanent magnet synchronous motor speed control system with speed as the outer loop and current as the inner loop.

[0035] Beneficial effects: Compared with the prior art, the present invention has the significant advantage of using a position observer to extract position information from the rotor back electromotive force, eliminating the need for a mechanical position sensor, reducing system costs and simplifying the hardware structure of the system, and using an adaptive vector filter to filter out the harmonics of the estimated back electromotive force, thereby reducing the estimated error of the motor speed and position angle. The adaptive bandwidth tuning scheme can tune the parameters of the extended state observer online, thereby improving the back electromotive force estimation performance of the motor in a wide speed range, and improving the efficiency and stability of the position sensorless control of the permanent magnet synchronous motor in a wide speed range. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is an overall block diagram of the position sensorless control of the permanent magnet synchronous motor of the present invention.

[0037] Figure 2 It is a schematic block diagram of the extended state observer in the present invention.

[0038] Figure 3 It is a schematic block diagram of the adaptive vector filter in the present invention.

[0039] Figure 4 It is a schematic diagram comparing the real position angle and the estimated position angle in the present invention.

[0040] Figure 5 It is a schematic diagram of the position error of the permanent magnet synchronous motor in the present invention.

[0041] Figure 6 It is a schematic diagram comparing the actual rotation speed and the estimated rotation speed in the present invention.

[0042] Figure 7 It is a schematic diagram of the speed error of the permanent magnet synchronous motor in the present invention. DETAILED DESCRIPTION

[0043] like Figure 1 As shown, in this embodiment, a position sensorless control method for a permanent magnet synchronous motor with a wide speed range includes the following steps:

[0044] Step 1: Establish an extended state observer of the permanent magnet synchronous motor and use the extended state observer to obtain the back electromotive force of the permanent magnet synchronous motor.

[0045] Design of extended state observer: According to the voltage equation of the motor αβ axis, the lumped disturbance (internal state and unknown external disturbance) is expanded into a new state, and then the extended state observer is constructed.

[0046] The voltage equation of the αβ axis of the permanent magnet synchronous motor can be expressed as

[0047]

[0048] Among them, u α 、u β and i α 、i β Represent the stator voltage and current on the α and β axes respectively, R s and L s They represent stator resistance and inductance respectively, e α and e β is the back electromotive force, defined as follows:

[0049]

[0050] Among them, ψ f is the rotor flux of the permanent magnet, ω e and θ e They represent the electrical angular velocity and the electrical rotor position respectively.

[0051] In practical applications, the motor voltage and current are considered as the input of the system, and the back EMF is considered as the unknown disturbance. Following the main idea of ​​the state observer, the system input and the lumped disturbance can be expressed as:

[0052]

[0053] Then the corresponding extended state observer is established as follows:

[0054]

[0055] Among them, z 1and z 2 denote the estimated value of stator current and the estimated value of lumped disturbance respectively, ε 1 represents the estimation error, β 1 and β 2 The observer gains are selected to be the same on the αβ axis.

[0056] The structure diagram of the extended state observer is as follows: Figure 2 As shown, when the observer is stable, the estimates of the stator current and the lumped disturbance will converge. Then, the estimate of the back EMF can be obtained as follows:

[0057]

[0058] The bandwidth of the extended state observer is adaptively adjusted according to the motor speed. The transfer function of the estimated error and the estimated lumped disturbance in the frequency domain is:

[0059]

[0060] It can be seen from the above formula that the transfer function is independent of the parameters of the system dynamics model. Therefore, the gain β of the extended state observer is 1 and β 2 It can be adjusted independently of system parameters, ensuring high robustness of disturbance estimation.

[0061] In order to facilitate parameter adjustment and theoretical analysis, the scale and bandwidth parameterization method is adopted. The gain parameterization is as follows:

[0062]

[0063] Among them, ω 0 is a constant representing the bandwidth of the observer. 0 The fixed ω value helps to improve the response rate, but it will increase the observer's sensitivity to noise. When the permanent magnet synchronous motor needs to switch frequently between different operating speeds, the fixed ω 0 Obviously, it does not meet the conditions for providing consistent estimation accuracy. Therefore, the adaptive bandwidth tuning scheme of the extended state observer can be designed as follows:

[0064]

[0065] Among them, ε max Defined as the maximum acceptable value of the estimation error, it should be determined based on the desired performance criteria. 0min and ω 0max The bandwidth is limited within a safe range to ensure system stability.

[0066] Step 2: Use an adaptive vector filter to filter out the high-order harmonics in the back-EMF obtained by the extended state observer to obtain the estimated back-EMF of the permanent magnet synchronous motor.

[0067] The adaptive vector filter will bring amplitude attenuation or phase shift to the target component, but will suppress other components of the input signal, so it is selected as a pre-filter to filter out the harmonic components of the estimated back EMF. The integrator is discretized using the reverse Euler formula, and the discrete transfer function of the adaptive vector filter can be expressed as:

[0068]

[0069] where ω f is the center frequency of the filter, T s is the sampling frequency, k f is the filter coefficient, j represents an imaginary number, that is, j 2 =-1, z represents the time of signal delay. Then, the amplitude-frequency characteristic and phase-frequency characteristic of the adaptive vector filter can be derived as follows:

[0070]

[0071] As can be seen from the above formula, as the frequency of the baseband signal increases, it will lead to amplitude amplification and phase shift. Feedback delay will cause the filtering performance to degrade, resulting in phase shift of the extracted back EMF, which will further lead to position estimation deviation.

[0072] If the predicted value of the filtered back EMF one control cycle ahead can be obtained and used for feedback, the influence of feedback delay can be eliminated. Therefore, a prediction-based compensation term is connected in series in the forward loop of the adaptive vector filter, such as Figure 3 As shown. The back EMF filtered out at the kth instant can be predicted by the back EMF filtered out at the k-1th instant

[0073]

[0074] Therefore, the feedback delay can be compensated without any complicated calculation.Since the improved adaptive vector filter with feedback delay compensation can extract the fundamental signal from the estimated back EMF without amplitude and phase shift, the position estimation deviation caused by the fundamental back EMF extraction deviation can be eliminated.

[0075] Step 3: Take the estimated back electromotive force as input, use the phase-locked loop position observer to demodulate the position information contained in the estimated back electromotive force, and obtain the speed and position angle of the permanent magnet synchronous motor.

[0076] The phase-locked loop can extract speed and position angle information from the estimated back EMF. It contains a phase detector, a loop filter, and a voltage-controlled oscillator. First, the output signal is automatically synchronized with the input signal through closed-loop regulation, thereby indirectly extracting the phase information of the input signal, and then the error is adjusted through a proportional-integral controller to estimate the fundamental frequency signal, and the fundamental frequency is integrated to obtain the estimated rotor position. Therefore, an orthogonal phase-locked loop using back EMF normalization can provide consistent performance through normalization even if the back EMF amplitude changes at different motor speeds.

[0077] In steady-state operation, the phase lag of the phase-locked loop can be ignored because any error on the forward path of the phase-locked loop will be eliminated in time through closed-loop regulation. Therefore, the estimated position can accurately track the phase of the estimated back EMF. However, the phase lag of the extended state observer cannot be ignored. The transfer function of the lumped disturbance estimation is similar to a low-pass filter. In this case, the estimated back EMF will lag behind the actual back EMF, and the estimated position will also lag behind the actual position. By compensating for the phase lag caused by the observer, the estimated motor position angle is finally obtained as:

[0078]

[0079] Step 4: Control the permanent magnet synchronous motor according to the obtained speed and position angle.

[0080] After comparing the estimated motor speed obtained in the previous step with the given speed, the current given value i is obtained through the proportional integral controller. q * At the same time, the three-phase current of the permanent magnet synchronous motor is sampled, and the current of the dq axis is obtained after coordinate transformation. The current feedback value i d and i q With the current given value i d * and i q * After the difference is made, the voltage u is obtained after the proportional integral controller and the inverse Park transformation. α and u β Then, the PWM wave is synthesized by space vector pulse width modulation and output to the three-phase inverter. Finally, a double closed-loop permanent magnet synchronous motor vector control system with speed as the outer loop and current as the inner loop is established.

[0081] Figure 4 and Figure 5 The figures are the actual speed and estimated speed comparison diagram of the permanent magnet synchronous motor and the speed error diagram. It can be seen from the figure that the estimated speed of the motor can follow the given speed well, and the speed error is small.

[0082] Figure 6 and Figure 7The figure shows the comparison of the actual position angle and the estimated position angle of the permanent magnet synchronous motor and the position error diagram. It can be seen from the figure that the estimated position angle and the actual position angle of the motor in the proposed method are basically consistent, the position error is small, and the position estimation effect is good.

Claims

1. A method for controlling a permanent magnet synchronous motor over a wide speed range without position sensor, characterized in that: The following steps are involved: Step 1: Establish an extended state observer of the permanent magnet synchronous motor and use the extended state observer to obtain the back electromotive force of the permanent magnet synchronous motor; Step 2: Use an adaptive vector filter to filter out the high-order harmonics in the back-EMF obtained by the extended state observer to obtain the estimated back-EMF of the permanent magnet synchronous motor: in, represents the estimated back EMF of the permanent magnet synchronous motor α axis at the kth instant filtered out, represents the estimated back EMF of the permanent magnet synchronous motor β axis at the kth instant filtered out, It represents the back electromotive force filtered out at the k-1th instant on the α axis of the permanent magnet synchronous motor. It represents the back electromotive force filtered out at the k-1th instant on the β axis of the permanent magnet synchronous motor. represents the observed speed value, T s Indicates the sampling frequency; Step 3: Using the estimated back electromotive force as input, the phase-locked loop position observer is used to demodulate the position information contained in the estimated back electromotive force to obtain the speed and position angle of the permanent magnet synchronous motor; Step 4: Control the permanent magnet synchronous motor according to the obtained speed and position angle.

2. The method for controlling a permanent magnet synchronous motor over a wide speed range without position sensor according to claim 1, characterized in that: The extended state observer established in step 1 is: Where ε1 represents the estimation error, z1 represents the estimated value of the stator current, z2 represents the estimated value of the lumped disturbance, and i αβ represents the stator current, b represents the unknown input gain, u0 represents the control input, β1 and β2 are the feedback gains of the extended state observer, the αβ axis represents the two-phase stationary coordinate system, and the dq axis represents the two-phase rotating coordinate system. Obtaining the Back Electromotive Force of a Permanent Magnet Synchronous Motor Using an Extended State Observer for: Among them, L s represents the stator inductance.

3. The method for controlling a permanent magnet synchronous motor over a wide speed range without a position sensor according to claim 2, characterized in that: The feedback gain of the extended state observer is selected according to the bandwidth method as follows: Where ω0 is the bandwidth of the extended state observer; The bandwidth of the extended state observer is optimized as follows: Among them, ψ f represents the rotor flux of the permanent magnet, ε max represents the maximum acceptable value of the estimation error, ω 0min represents the minimum bandwidth of the extended state observer, ω 0max It represents the maximum value of the bandwidth of the extended state observer.

4. The method for controlling a permanent magnet synchronous motor over a wide speed range without position sensor according to claim 2, characterized in that: The discrete transfer function of the adaptive vector filter is: Among them, k f represents the filter coefficient, ω f represents the center frequency of the adaptive vector filter, j represents an imaginary number, i.e. j 2 =-1, z represents the signal delay time.

5. The method for controlling a permanent magnet synchronous motor over a wide speed range without position sensor according to claim 4, characterized in that: The amplitude-frequency characteristic and phase-frequency characteristic of the adaptive vector filter are: Where ω represents the frequency of the input signal.

6. The method for controlling a permanent magnet synchronous motor over a wide speed range without position sensor according to claim 2, characterized in that: The specific steps of using the phase-locked loop position observer to demodulate and estimate the position information contained in the back electromotive force to obtain the position angle of the permanent magnet synchronous motor in step 3 are: using the estimated back electromotive force as an input signal, automatically synchronizing the output signal with the input signal through closed-loop regulation, thereby indirectly extracting the phase information of the input signal, obtaining the angle error through the phase information, and then adjusting the angle error through a proportional-integral controller to estimate the baseband signal, and integrating the baseband signal to obtain the estimated position angle of the permanent magnet synchronous motor.

7. The method for controlling a permanent magnet synchronous motor over a wide speed range without position sensor according to claim 6, characterized in that: After compensating the phase lag of the extended state observer, the final estimated position angle of the permanent magnet synchronous motor is obtained. for: in, Represents the estimated position angle obtained by integrating the baseband signal.

8. The method for controlling a permanent magnet synchronous motor over a wide speed range without position sensors according to claim 7, characterized in that: The specific steps of step 4 are: using the estimated speed of the permanent magnet synchronous motor as feedback, comparing it with the given speed, and obtaining the current given value i through the proportional integral controller. d * and i q * At the same time, the three-phase current of the permanent magnet synchronous motor obtained by sampling is transformed into the coordinate to obtain the current i of the dq axis d and i q , with a given current i d * and i q * After the proportional-integral controller and the inverse Park transformation, the voltage u is obtained. α and u β , output to the space vector pulse width modulator to synthesize PWM wave, output to the three-phase inverter, and finally establish a double closed-loop permanent magnet synchronous motor speed control system with speed as the outer loop and current as the inner loop.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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