Research On Sensorless Technology Of SRM Based On High Frequency Pulse Injection Method

SRM is a new kind of motor which developed in recent years,it has the advantages of simple structure,ease of control,wide speed range and high system reliability.However,SRM need special position sensors to obtain the initial position when starting,the dependence of external encoder limit its application during commutation.The study of sensorless technology can improve the integration and reliability of the system,reduce the hardware cost of the system.Therefore,it is of great significance to study the sensorless technology.This paper first introduces the theoretical basis,principle of operation and mathematical model of SRM.According to the voltage equation of SRM and the characteristic of each parameter during starting,the initial position determination for rotor of SRM without hall position sensor is studied,and an initial position determination algorithm of SRM without position sensor based on phase-by-phase injection of high-frequency pulse method is proposed.Before starting,the three-phase winding are injected with voltage pulse,and the initial position of the rotor is determined by comparing the response current of the three-phase winding.the Accuracy of the initial determination position obtained by high frequency pulse algorithm is twice higher compared with hall sensor.In this paper,the principle of sensorless operation by high frequency pulse injection for SRM is studied.After the initial on-phase is determined according to the initial position,high-frequency pulse voltage is injected into the latter non-on-phase,and the motor’s phase-changing point is determined by comparing the response current of the non-on-phase with the peak current,so as to realize the alternating on-phase of the motor and complete the phase changing process of the motor.A dynamic threshold current comparison is added on this basis compared with the traditional current threshold method,this way can eliminate the misleading communication signal in the inductance drop zone and avoid missing the commutation point due to the change of speed,and it improve the accuracy of the system’s commutation operation.When the motor is loaded,there are some problems such as large running current and long continuous current which are easy to generate negative torque.The advance angle is adjusted according to the working current of the load,and the maximum degree of optimization can minimize the time when the operating current reaches the given current,maximize the torque work,and improve the waveform of the continuous current stage to avoid the generation of negative torque.When the motor is loaded,there are some problems,such as large running current and long duration of continuous current which are easy to generate negative torque.The method of changing the current threshold to adjust the Turn on angle is proposed,which optimize the torque and perfect the waveform of current to avoid the negative torque.Finally,the relevant programs and algorithms for the three control and optimization methods were written on the experimental platform of the 12/8 pole 0.2kw three-phase switched reluctance motor control system,and the experimental verification of the control algorithms proposed in this paper were carried out.