Research On Control Of Permanent Magnet Synchronous Motor With Speed Sensorless In Full Speed Range

In recent years,electric vehicles in China have been vigorously promoted.Permanent Magnet Synchronous Motor(PMSM)is widely used in the traction system of electric vehicles because of its small size,high speed and high output torque.In order to achieve accurate control of the output speed and torque of the electric vehicle traction system,the traditional method is to obtain the closed-loop vector control of current and speed by obtaining the rotational speed and position information through a mechanical sensor such as a rotary transformer.The installation of mechanical sensors not only increases the size of the motor,but is also detrimental to the mounting arrangement of the motor.At the same time,the complex driving environment of electric vehicles reduces the reliability of mechanical sensors.In face of problems caused by mechanical sensors,sensorless control technology can be used to obtain motor rotor speed and position information.At present,PMSM sensorless control technology has become a hot research topic.Aiming at the disadvantages of mechanical sensors,this paper designs a speed sensorless control method for PMSM in full speed range,and verifies it in MATLAB simulation.In order to facilitate the speed control of the motor,this paper analyzes the mathematical model of PMSM in different coordinate systems,adopts the maximum torque current ratio and weak magnetic speed-up control strategy,realizes PMSM wide-range speed regulation and large output torque.Aiming at the rotor speed and rotor position estimation of PMSM speed sensorless control system,this paper first analyzes the basic principle of Model Reference Adaptive System(MRAS)and constructs a suitable reference model and adjustable model.Based on the Popov’s superstability theorem,the appropriate adaptive law of speed estimation is derived.The simulation results show that the MRAS method has a better estimation effect on the PMSM medium and high speed,but is poor on the PMSM low speed section.Aiming at the problem of poor estimation of rotor speed and rotor position at low speed section for MRAS method,this paper uses the pulse high frequency voltage injection method to improve.Firstly,the basic principle of pulse high frequency voltage injection method is expounded.The influencing factors of high frequency injection signal are analyzed,and a suitable rotor position information extraction method is constructed.The simulation results show that the pulse high frequency voltage injection method has a better estimation effect on the PMSMlow-speed section,but is poor on the PMSM medium and high speed section.Finally,in order to realize the PMSM speed sensorless control in the full speed range,the weighted average switching composite control method is adopted in this paper.The simulation results show that the method combines the advantages of low-speed pulse high frequency voltage injection method and the advantages of medium and high-speed MRAS method.The simulation results show that the PMSM sensorless speed estimation is better in the full speed range.