Research On Speed Sensorless Control System Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM)has the advantages of light weight,high power factor,and large starting torque.It is widely used in the fields of military and national defense,household appliances and electric vehicles,so it has market value for the research and optimization of PMSM control system.Core of high-performance vector control of PMSM is to obtain the rotor position of the motor.However,due to the influence of factors such as accuracy,cost and environmental adaptability,the application of position/speed sensor is limited.Therefore,this thesis analyzes the principle and structure of PMSM vector control system in detail,and on this basis,conducts an in-depth study on the speed/rotor position estimation in the full speed domain of the speed sensorless control system.Current speed sensorless control strategy is roughly divided into fundamental wave model mathematical method and high frequency injection method.In the former,traditional sliding mode observer designs the back EMF control law through the constant velocity approaching law.Due to the variable structure and fixed gain,high-frequency chattering is unavoidable and aggravates the problem of system speed and torque ripple under the PI controller.For this reason,this thesis designs a new approaching law based on the traditional sliding mode observer.New reaching law integrates the structural characteristics of exponential and power reaching law.Sgn function is selected as the switching function,and the adaptive sliding mode gain is designed according to the characteristics of speed and torque changes.At the same time,a second-order sliding mode controller is designed in the current control loop to suppress the input thrust,improve the current loop output waveform,and significantly reduce the system speed and torque ripple.Above-mentioned improved sliding mode observer is difficult to extract the useful signalto-noise ratio during the motor start-up phase,the estimated back EMF is too low,and there is a problem of inaccurate rotor position estimation.In the zero-low-speed phase of the motor,the current high-frequency method is often used for rotor position detection,but the rotating highfrequency injection method is difficult to apply to surface-mounted PMSM due to the semidifference inductance.For this reason,based on the virtual pulsation high frequency injection method,this thesis designs a new type of rotor position observer for surface-mounted and interior PMSM rotor position and speed estimation.New position observer uses a second order generalized integrator to replace the high-order filter to reduce the phase shift delay,heterodyne method is used to isolate the rotor position estimation error and position error tracking method is used to estimate the rotor position.New position observer solves the problem of inaccurate estimation of the rotor position when the motor is started by the improved sliding mode observer.In order to take advantage of the superiority of the two observers in different speed domains,a composite rotor position observer is designed,and the linear weighting method is used to switch between the two observers.In order to meet the needs of the experiment,new reaching law is applied to the discrete sliding mode observer and the improved sliding mode observer is replaced.Effectiveness of the scheme is verified through Matlab/Simulink simulation and real-time simulation system based on d SPACE1007.Simulation and experimental results show that the control strategy proposed in the thesis is effective.