Research On Sensorless Control Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor has become the main driving motor in industry because of its high efficiency,strong overload capacity and no slip between stator and rotor.In recent years,it has been widely used in medical equipment,automation equipment,new energy vehicles and other fields.But with the continuous development of modern industry,people have higher and higher requirements for motors.In order to improve the control quality of permanent magnet synchronous motor,it is necessary to obtain accurate actual rotor position and actual speed of the motor.Although mechanical sensors can be used for direct measurement,installing sensors in the motor will cause some problems.It not only increases the manufacturing cost of the motor,but also has many disadvantages of the mechanical sensor,resulting in all certain limitations of the use field of the motor.Therefore,sensorless control of the motor has become a good solution.In this thesis,the sensorless control technology of permanent magnet synchronous motor will be deeply studied.The work of the article is as follows:First,a sensorless control strategy based on improved sliding mode observer is proposed in the medium and high speed domain.First of all,for the traditional sliding mode observer,the system chattering phenomenon is obvious,and there are a large number of high order harmonic signals in the output anti-EMF signal.Therefore,an improved sliding mode observer is designed in this paper.Firstly,based on the traditional constant speed approach law,a new variable speed approach law is proposed and designed as the sliding mode control law of the improved sliding mode observer.Secondly,due to the nonlinearity of the inverter,there are a large number of harmonics in the back EMF estimation.In this paper,an adaptive synchronous filter is designed to filter the harmonics contained in the back electromotive force,so as to improve the estimation accuracy of rotor position and speed.The simulation results show that the improved sliding mode observer is better.Secondly,in the low speed region,the sensorless control strategy of pulse high-frequency voltage injection method is used.In this thesis,firstly,the pulse high-frequency voltage injection method is designed,and the workflow of rotor initial position judgment is described in detail.The experimental results verify that the control scheme can accurately obtain the rotor information estimation accuracy,and improve the control quality of low-speed permanent magnet synchronous motor.Third,through the design of smooth switching strategy,the two control methods applicable to different speed ranges can be combined,and finally the sensorless control of the full speed domain permanent magnet synchronous motor is realized.The simulation results show that the handoff strategy has good handoff effect.