Research On Position Sensorless Control Of Switched Reluctance Motor

Switched reluctance motor(SR motor)has the advantages of flexible control strategy,small starting current,large starting torque,wide speed adjustment range and so on.The rotor position angle is the main basis to decide control logic and to estimate speed.The position sensors are used to detect the rotor position angle in the traditional switched reluctance motor drive system(SRD).Due to the existence of the position sensor,the reliability of the SRD is weakened,which hinders its further promotion and application.Therefore,the research on position sensorless control of SRM has become an important issue.The operating principle and electromagnetic characteristics of SR motor are analyzed in this paper.The electromagnetic field analysis of the experimental prototype motor is performed on the finite element analysis software of FEMM.According to the results of finite element analysis,a nonlinear model of the experimental prototype motor is built in the simulation environment of MATLAB/Simulink.On that basis,the simulation of experimental prototype motor under the strategy of double-closed-loop is made.The current,torque and speed response are analyzed under different loads and speeds,which proves the stability of the SRD designed in this paper.The common position sensorless control strategies for SR motor is studied,including the method of simplified flux and the method of high frequency pulse injection.Traditional high frequency pulse injection method,namely the method of non-conducting phase comparison,needs to inject the detection pulse in the minimum inductance region,which can only be commutated at the maximum value of the inductor,weaking the output of the motor.The traditional high frequency pulse injection method is improved and a new method is proposed in this paper.The method of new current threshold sets the current threshold at the intersection of the two-phase inductance curves,which can improve the accuracy of position detection,where the rate of inductance change is large,which solve the problem that the non-conduction phase comparison method can only inject the detection pulse in the minimum inductance interval and cannot be normally energized,energizing winding at the natural commutation point.Meanwhile,the new method shortens the pulse injection time,reduces switching losses,and improves the control performance of the high frequency pulse injection method.The position sensorless SRD based on single chip microcomputer of STM32 is designed in this paper.The design of hardware includes the circuit of current detection,the circuit of power conversion and the circuit of power drive.To solve the problem of voltage glitch caused by PWM chopping,a new circuit of response current peak detection is designed,which can reduce the interference of voltage glitch to the detection of peak current response.The design of position sensor control software and position sensorless control software is completed in this paper.The experiments on double-closed-loop control strategy with position sensor and the method of new current threshold position sensorless control strategy are carried out on experimental prototype motor.By analyzing the experimental results,the feasibility of position sensorless control strategy based on the method of new current threshold is verified...