Research On The Built-in Permanent Magnet Synchronous Motor Sensorless Control System Based On High-frequency Voltage Injection Method

In the Interior Permanent Magnet Synchronous Machine(IPMSM)drive system,in order to realize Field-Oriented Control(FOC),the permanent magnet rotor position must be effectively detected in real time.The commonly used permanent magnet rotor position acquisition method is detected by a mechanical position sensor installed on the motor.This method not only increases the cost and volume of the system,but also the signal is susceptible to large current electromagnetic interference during transmission,reducing the robustness of the system.Therefore,many experts and scholars at home and abroad have done a lot of research work on the FOC strategy of position sensorless.High-performance position-free speed sensor technology has become a hot research topic in the field of electronic control.In many products with position sensorless technology,the Back Electromotive Force(BEMF)is mainly used to identify the rotor position of the permanent magnet.The method is characterized in that the BEMF is proportional to the speed,namely,When the motor is at medium and high speed,the back-EMF of the motor that has a large amplitude can only be effectively extracted.However,at low speed or zero speed,because the BEMF amplitude is small,the useful signal-to-noise ratio is very low,and it is difficult to be effectively extracted.Therefore,when such a method works below the low speed of the motor,the position and speed of the permanent magnet rotor cannot be effectively detected.In this paper,using the salient pole effect of IPMSM,by injecting a high-frequency sinusoidal voltage signal into the synchronous rotating(d-q)coordinate system and the signal excitation to generate a high-frequency current signal containing the positional deviation information of the permanent magnet rotor.Then,processing the estimated deviation in the high-frequency current signal,the rotor position and speed of the IPMSM at low speed can be obtained.The research content of this paper mainly includes:(1)Analysis of research status.The FOC strategy of PMSM position-sensorless is reviewed,and the research status at home and abroad is summarized.The FOC strategies of various position-sensorless are analyzed and compared.Finally,the strategy of obtaining the position of permanent magnet rotor by high frequency signal injection method is proposed.(2)Basic control theory analysis and derivation.The equivalent physical model of IPMSM in d-q coordinate system is established,and the equivalent mathematical model in d-q coordinate system is derived.The idea of FOC strategy is expounded,and the coordinate transformation equation for implementing FOC strategy is derived.Several common control strategies are described.After comparative analysis,this paper uses the control method of i_d=0to cooperate with FOC to realize the decoupling of stator current.(3)Principle analysis and implementation of position sensorless vector control.A high-frequency sinusoidal voltage signal is input to the d-axis in the d-q coordinate system,and a mathematical model of the high-frequency response current containing the estimated position deviation of the permanent magnet rotor is derived and analyzed.According to the mathematical model of high-frequency response current,the demodulation and estimation deviation of the q-axis high-frequency current signal are extracted,thereby obtaining the permanent magnet position estimation deviation information,and using the phase-locked loop strategy to eliminate the estimation deviation and converge to the actual position of permanent magnet rotor.Using the principle of nonlinear magnetization,the N-pole direction of the permanent magnet rotor is identified by integrating the positive and negative half-axis of the direct-axis high-frequency response current.Finally,the algorithm model is built by MATLAB2016 simulation platform to verify the algorithm.(4)Optimize the design.The position sensorless strategy based on high frequency injection is mainly used in low speed applications.Due to the existence of dead time,the phase current zero-crossing clamping phenomenon under low speed conditions is very obvious,which is easy to cause torque ripple.The first-order low-pass digital filter is used to filter the current feedback signal of the dq axis coordinate system.Filter out the higher harmonic current in the dq axis coordinate system,but when the DC feedback signal of the d-q axis coordinate system changes,after filtering by the first-order low-pass filter,it will inevitably cause the attenuation of its amplitude,which makes the feedback signal distorted and easily cause system oscillation.Aiming at the above two problems,the dead zone compensation strategy and the variable step size adaptive Finite Impulse Response(FIR)feedforward filtering algorithm optimization control system are proposed respectively.