Research On Power Converter And Torque Ripple Suppression Of Bearingless Switched Reluctance Motor

Switched reluctance motor(SRM)is the structure of double salient pole,with the advantages of simple structure and high stability,which has been widely used in aerospace,electric vehicle and other fields.Bearingless switched reluctance motor(BSRM)combines bearingless technology and SRM,making BSRM have the functions of both levitation and rotation,which not only reduces the friction loss but also improves the service life of the motor.However,due to the strong coupling between torque and levitation force and the problem of large torque ripple,the performance and further promotion of BSRM is affected.To solve the coupling between BSRM torque and levitation force,12/8 bearingless switched reluctance motor with wider rotor teeth(BSRMWR)was proposed,the particularity of its structure realizes the natural decoupling between torque and levitation force.Although 12/8 BSRMWR achieves the decoupling between torque and levitation force,the structure of double salient pole and the pulsed power supply mode have not changed.Aiming at this problem,this paper mainly studies methods to reduce BSRMWR torque ripple from two aspects:control method and power converter.Firstly,the working principle of 12/8 single-winding BSRMWR is introduced,according to Maxwell tensor method,the mathematical model of motor torque and levitation force is derived,simplifies the mathematical model of levitation force additionally.The motor’s torque and levitation force characteristic curve table is constructed,which provides a theoretical basis for subsequent motor control.Secondly,aiming at the problem of large fluctuations in motor torque and levitation force under traditional current chopping control method,a direct instantaneous torque and direct levitation force control method(DITC&DFC)is studied.Explains its basic principle in detail and gives its control block diagram.This control method takes the instantaneous torque and the instantaneous levitation force of the motor as the directly controlled object,which eliminates the traditional current loop,and does not affect the decoupling between the BSRMWR torque and levitation force.It is verified by simulation that the control method can effectively reduce the torque ripple and levitation force fluctuation.However,due to the limitations of the asymmetric half bridge power converter,the motor still has a certain torque ripple during the commutation period.Then,in order to improve the slow excitation and demagnetization of motor windings when using the asymmetric half bridge power converter,a new power converter suitable for single-winding BSRM is studied.The basic working principle of the new power converter is analyzed,and the DITC&DFC control method is reformulated according to its working characteristics.Simulation verifies that the new power converter can further suppress the torque ripple of the motor while ensuring the stable levitation of the motor,and the dynamic performance is good.Finally,the hardware and software parts of the 12/8 BSRMWR experimental platform are briefly introduced,according to the above experimental platform,the non-load experiment of the motor is carried out,and successfully realizes the stable levitation of the motor under the condition of adopting the new power converter,which preliminary verifies the feasibility of the new power converter.