Research On Control Strategy For Full Speed Range Start And Operation Of Sensorless Permanent Magnet Synchronous Motor

The Permanent Magnet Synchronous Machine(PMSM)has been widely used in home appliances,medical equipment,electric vehicles,and aerospace due to its superior control performance.As the performance requirements increase,people are paying more attention to the speed control performance of PMSMs.Compared with DC motors,PMSMs have a simpler structure because they do not have commutators or brushes.Compared with asynchronous motors,PMSMs have no excitation device,which reduces the damage rate of the motor body while improving efficiency,making them economically effective.However,the use of sensors often increases costs and system complexity.Therefore,sensorless methods have become a highly regarded solution technology.This thesis studies the start-up and operation control of PMSMs at full speed range based on sensorless methods.The main work includes:Firstly,introduce the basic structure and mathematical model of PMSM,and provide the mathematical models of PMSM in different coordinate systems and the principles and methods of coordinate transformation between coordinate systems.Then,conduct an in-depth analysis of commonly used vector control strategies for permanent magnet synchronous motors,compare their advantages and disadvantages,and choose the id=0 vector control strategy.Secondly,to achieve sensorless control in the high-speed range of PMSMs,this thesis studies the model reference adaptive control method,which identifies the motor model by observing the motor state and performance parameters.The advantage is that it can improve system robustness and accuracy,but the disadvantage is that multiple parameters change during high-speed operation,resulting in poor identification effects and control problems.Thus,a double adjustable model reference adaptive method was improved on this basis and combined with a sliding mode current observer for speed estimation control.Realizing fast and accurate identification of multiple parameters online while maintaining high-precision control without affecting the high-speed operation of the PMSM system effectively improves efficiency and dynamic tracking performanceThirdly,to achieve sensorless control in the zero-low-speed range of PMSMs,research was conducted on related technologies such as pulse injection method.This method detects the rotor position of the synchronous motor by adding a high-frequency PWM pulse signal in the zero-low-speed range.Its advantage is simplicity and low cost,but the disadvantage is that it generates vibrations and noise in the middle and high-speed range,and requires high demands on the controller to adjust the high-frequency signal.Therefore,a new highfrequency current injection method was proposed and applied to the detection of rotor position during motor start-up,improving the precision of operation control.Finally,from the perspective of sensorless control methods for PMSMs,this thesis analyzes and integrates the two control methods of high-speed and zero-low-speed ranges,respectively,to achieve full-speed control.A composite control based on weighted switching method is established,which effectively combines the good dynamic tracking performance of the model reference adaptive control method in the high-speed range and the high-precision control of the pulse injection method in the zero-low-speed range.The intermediate speed range where the two methods transition is controlled by the weighted method.The advantages are the ability to achieve full-speed control while reducing noise interference and computational burden.Multiple control strategies are integrated and weighted according to the characteristics of PMSM operation at different speed ranges,ultimately overcoming the limitation of a single sensorless control method not being suitable for the full speed range.