Sensorless Control Of Switched Reluctance Motor Considering Inductance Saturation

Switched Reluctance Motor(SRM)has the benefits of uncomplicated structure,high reliability and low cost compared with traditional permanent magnet Motor,and has been applied more and more in industrial production,electric vehicle,aerospace and other fields.The operation of SRM needs to obtain the rotor position information to realize the sequential switching of phase current,and the position sensor not only increases the system cost,but also reduces the reliability of system.Therefore,in recent years,foreign and domestic scholars and research institutions have launched researchs on sensorless control strategies for SRM to improve the operational reliability of this kind of motor.Based on the sensorless control of SRM,this paper mainly studies the sensorless control after the phase winding enters the magnetic saturation state when the SRM operates under heavy load conditions,and solves the problem that the control precision without position sensor is influenced by the reduction of the number of pulses injected in the non-conductive section when the motor operates at high speed.Firstly,this paper expounds the basic principle of injecting high-frequency voltage pulse into the winding in the non-conductive section of the current to obtain the full cycle inductance of the winding,analyzes the full cycle inductance,and explains the basic principle of estimating the rotor position angle according to the inductance intersection.Then,considering the offset of inductance intersection due to inductance saturation phase during heavy load operation,the traditional method of using winding current to fit and compensate inductance intersection is improved.It is proposed to use load torque to fit and compensate inductance intersection online.The rotor position information can be updated eight times in a mechanical cycle,and the integral cumulative error is eliminated.The sensorless control accuracy of SRM under heavy load operation is improved,and a simulation model based on MATLAB/Simulink is established to validate the availability of the proposed sensorless control strategies for SRM.In allusion to the trouble that the amount of injection pulses in a single cycle affects the accuracy of position free control when SRM runs at high speed,a variable frequency injection voltage pulse method based on inductance threshold is proposed in this paper.The injection voltage pulse frequency is increased to 1.5 times when the phase inductance is less than the set threshold,which further improves the position sensorless control accuracy.On this basis,a simulation model based on MATLAB/Simulink is estalished to validate the availability of the proposed variable frequency injection voltage pulse method based on inductance threshold.Finally,taking a four phase 8/6-pole SRM as the prototype and the DSP chip based on TMS320F28335 as the control core,the laboratorial platform is set up.At the same time,the peripheral hardware circuit debugging and sensorless control programs are completed,and the sensorless control strategies for SRM proposed in this paper is experimentally verified.The experimental results show that when the motor runs under heavy load,the estimation error of posion angle for rotor can be effectively reduced by using the sensorless control method proposed in this paper,and the variable frequency voltage pulse injection method based on inductance threshold can further reduce the estimation error of rotor at high speed,which validates the availability of strategies presented in this paper.The research work launched in this paper provides theoretical basis and reference value for sensorless control of SRM under heavy load conditions.