Research On Sensorless Control For Switched Reluctance Motor Drives Based On Inductance Threshold Method

Switched reluctance motor has features of simple structure,strong tolerance,flexible control,etc.It has been widely concerned by scholars and research institutions at home and abroad.In recent years,it has been applied in areas of domestic appliances,electric vehicles and aeronautics and astronautics.The detection of the rotor position is the premise of the operation of the switched reluctance motor.The current method is to obtain the rotor position information by means of the position sensor.However,the installation of the position sensor not only increases the size and cost of the motor,but also the position sensor is prone to failure in a harsh environment.Therefore,research on the sensorless control is of great valueFor the identification of full-cycle inductance,a full-cycle inductance calculation method based on current slope difference is studied in this paper.The method adopts chopping or PWM control in the conduction interval,and high frequency pulses are injected in the non-conduction interval,and calculates the full-cycle inductance information by measuring the positive and negative slope difference of phase current.This method avoids the influence of back EMF and winding voltage drop on inductance estimation and can be applied to a series of position sensorless control algorithms based on full-cycle inductance.At the same time,for the different driving methods of the motor,the calculation effect of the full-cycle inductance is compared,and the simulation and experiment are used to verifyWhen the conduction phase current exceeds the current saturation limit or the current is in the freewheeling phase,the unsaturated inductance information cannot be directly obtained by the above method.Therefore,a low-speed position sensorless control based on the idle phase inductance two thresholds method is studied in this paper.The method compares the idle phase unsaturated inductance with two preset inductance thresholds to obtain a turn-on signal of one phase and a turn-off signal of the other phase,so that the motor can be operated under the control of the sensorless control with the load.At the same time,a dynamic inductance threshold method is proposed.By establishing the mathematical model of the angle and inductance,the dynamic adjustment of the motor turn-on and turn-off angle can be realized.Aiming at the control strategy of the static start of the motor,a rotor initial position detection method is proposed,which can realize the static start of the motor at any position Finally,based on the commutation pulse estimated by the above-mentioned inductance threshold method,a method for calculating the motor speed and rotor position angle by using the estimated pulse is studied.The above methods are verified by simulation and experimentIn view of the influence on motor performance,when high frequency pulses are injected in the idle phase,two different injection methods are studied based on the idle phase full-injection high frequency pulses method.When the idle phase inductance drops to the set inductance threshold,the two measures of stopping the pulse injection and increasing the injected pulse frequency respectively can effectively reduce the peak value of the response current.The above three methods are analyzed and compared by simulation and experiment,and the correctness of the two methods is verified.Aiming at the high-speed operation phase of the motor,a rotor position estimation method based on the inductance top threshold method is studied.The estimated pulse is obtained by intersecting the inductance threshold with the unsaturated region at the top of the inductance to calculate the motor speed and rotor position.At the same time,a method of realizing low-speed and medium-high speed algorithm switching of motor using estimated pulse is studied.The sensorless control of the motor in the full speed range can be completed Finally,the feasibility of the method is verified by simulation.