The Research On Control Strategy Of Bearingless Switched Reluctance Motor Based On Direct Control

The stator of switched reluctance motor(SRM)is a motor developed in modern times.It is widely used in industry due to its simple structure and low cost.Magnetic levitation technology can make the motor rotor detach from the bearing and levitate in the air,which greatly expands the speed range of the motor.Combining magnetic levitation technology with SRM,a bearingless switched reluctance motor(BSRM)was born.However,Under the existing control strategies,an indirect control strategy is used regardless of torque or levitation force,which results in large torque and levitation force ripples.From the perspective of direct control,this paper studies the direct control strategies based on the torque and the displacement.Firstly,for the levitation displacement control of BSRM,a direct displacement control strategy(DDC)is studied.This control method learns from the idea of magnetic bearings,abandoning the levitation current calculation in the traditional current control and achieving the control characteristics completely separated from the online calculation.So the rotor displacement is directly controlled.Then the stability of the control system is analyzed by the transfer function,and the parameters of the regulator are determined.Finally,the effectiveness of the control strategy is verified by simulations and experiments.Secondly,for torque and levitation force control of BSRM,a vector optimization control strategy based on direct torque control and direct force control(DTC&DFC)is studied.This control strategy removes the magnetic-linkage loop to improve the torque-ampere ratio.Then the voltage vector table is optimized to reduce the torque ripple,which increases some new vectors and achieves direct control of torque.In addition,due to the strong nonlinear characteristics of magnetic field,the model predictive control(MPC)is introduced into it.Finally,Three control methods are compared by simulations and experiments.It is verified that the control characteristics of the two improved methods is better than that of traditional DTC&DFC.Finally,in order to further the feasibility of the direct control idea when applied to fault-tolerant operation control of bearingless motors,a fault-tolerant compensation strategy based on direct instantaneous torque control and direct force control(DITC&DFC)was studied.The influence on the force of the levitation winding under open and short-circuit conditions was analyzed,and the method of levitation force compensation was studied.Based on this strategy,the simulation and experimental platforms are built.It is verified that in the case of winding failure,the rotor can still achieve the stable levitation after the compensation strategy is introduced.