Research On Torque Ripple Suppression Of Switched Reluctance Motor DITC Based On Multilevel Circuit

Switched Reluctance Motor(SRM)is a simple structure motor with no rare earth material.Good robustness and wide speed range make it suitable for harsh environment such as high temperature,and it's gradually replacing traditional motor.Reliability of the drive system is the key to SRM speed regulation.Scholars at home and abroad have carried out many studies,but the problem of large instantaneous torque ripple of motor is still the main obstacle to limit the application of SRM in more range and give full play to its advantages.This paper analyzes the causes of torque ripple and summarizes the methods of suppressing torque ripple at home and abroad.Among them,the traditional control strategy of SRM is average torque control,which will inevitably lead to torque ripple because of its double convex structure.The Direct Instantaneous Torque Control(DITC)directly obtain the reference voltage required of the winding by comparing the instruction torque with the instantaneous torque,which can simplify the structure of the control system and significantly reduce the torque ripple.Therefore,this paper mainly focuses on the DITC system of the SRM.The traditional power circuit of motor mainly refers to asymmetric half-bridge power circuit,which has poor DITC dynamic response ability.At the same time,the voltage at both ends of the winding is limited by the DC power supply voltage during excitation and demagnetization.Therefore,a new multi-level power circuit is proposed in this paper.which not only has the rapid excitation and demmagnetization function,can stabilize the output torque within a certain range,effectively inhibit the torque pulse of SRM,but also has the advantages of simple structure,low capacity requirements for switching devices and independent operation,suitable for any phase number motor,and expands the working voltage range and improves the dynamic response capacity of SRM.At the same time,a method of selecting the boost capacitance of the power circuit based on load size is proposed,and the feasibility of the method is verified by experiments.In the DITC system of SRM,the delayed loop threshold also has a great influence on the torque pulsation,so the traditional DITC strategy is improved,and the DITC strategy based on the adopted multi-level power circuit is formulated.This paper analyzes the influence of block threshold on the torque pulse,explores the influence of switching frequency,system sampling frequency,load and speed on the general law of block threshold change,and proposes the online optimization scheme based on the least squares model.This paper simulates a SRM prototype with 1.5 k W three phase 12/8 pole,and designs an experimental platform for the SRM speed regulation system based on the proposed power circuit.Finally,the effectiveness and superiority of the proposed power circuit and control strategy in suppressing torque ripple and improving dynamic performance under low speed operation,high speed operation and load mutation are verified by experiments.