Designation Of Startup And Low-speed Control Strategy Of Sensorless Switched Reluctance Motors

Compared to conventional motors,switched reluctance motors(SRM)have many advantages.However,due to position sensors,these advantages are diminished.Therefore,in recent years,the research on the startup and low speed control strategies of the sensorless switched reluctance motor,especially multi-phase pulse injection method and high-frequence pulse injection method,have received extensive attention in the industry.However,the multiphase pulse injection method may cause movement in initially position of the rotor,and the angle estimaion error may occur in the region where the phase inductance value is similar.At the same time,the idle phase high-frequency pulse injection method may cause error for the commutation angle detection,and the abnormal state of response current may affect stability of motor operation.Aiming at the above problems,this thesis improves the multi-phase pulse injection method and the idle phase high-frequency pulse injection method,and designs a high precision position startup and low-speed control strategy in sensorless SRM.Firstly,this thesis expounds the basic principles of SRM and multi-phase pulse injection method and high-frequence pulse injection method,analyzing the source of angle estimation error.The analysis results show that the main source of angle estimation error is current sampling error and magnetic saturation of air gap.Then,proposing specific solutions:(1)By establishing a model of the torque generated by the injection pulse,the maximum injection width that keeps the rotor stationary is derived,and the injection pulse is width-modulated,thereby ensuring the rotor to keep still during the detection period of the initial position.(2)Through the hysteresis detection of the response current,combined with the open-loop starting method,the angle estimation error caused by the current sampling error is eliminated,thereby realizing the non-reverse startup in the full angle range.(3)Using the freewheeling working state to detect the winding current,current in windings is sampled before the pulse injection pulse,to avoid the residual current in the winding causing the abnormal state of the response current.Finally,based on MATLAB/Simulink,the simulation model is built.Based on 6/4 pole SRM,the actual measurement platform is built,verifing the feasibility of the control strategy.The measured results show that the sensorless SRM control strategy implemented in this thesis can make the non-reverse startup in the full angle cycle.The speed range of the motor is 500r/min~1583r/min,and the maximum output torque of the motor is 1.3N·m,the rated power is 1040 W,and the estimation error of the commutation point is 1.71°,which achieves design requirements.