Research On Control Method About Permanent Magnet Assisted-Switched Reluctance Motors

The switched reluctance motor has the advantages of simple structure,low cost and high reliability,and is widely used in aerospace,oil exploitation,power tools and other fields.Permanent magnet-assisted switched reluctance motors(PMa-SRM)adds permanent magnets to the stator poles of SRM,thus improving the power density.However,similar to SRM,the stator-rotor double salient pole structure,magnetic Louis saturation and the control mode of phase winding switching conduction are easy to produce large torque ripple,which affects the further application of this type of reluctance motor.In this paper,an improved control method to reduce torque ripple is studied.The main contents are as follows:Firstly,taking the three-phase 6/20 PMa-SRM as the research object,the structure and working principle of the motor are introduced,and the linear,quasi-linear and nonlinear mathematical models are established,and their advantages and disadvantages are compared.With the help of finite element analysis software,the nonlinear torque and flux linkage of the motor are obtained,and the more accurate winding current is derived through current interpolation.A high-precision nonlinear model is established in Simulink,which provides a basis for the simulation and verification of the follow-up control methods.Secondly,the reason for the large torque ripple of conventional direct instantaneous torque control method is analyzed,and a direct instantaneous torque control method based on turn-on angle optimization is given.An improved generalized regression neural network model is established,and the turn-on angle is adaptively selected according to the speed and load,and the turn-on angle is optimized.According to the characteristics of inductance change rate in the two-phase exchange region,the two-phase exchange region is subdivided into two regions,and a hysteresis control method suitable for inductance characteristics is designed for each region.The simulation results show that compared with the conventional direct instantaneous torque control method,the improved control method has better torque ripple suppression effect,and the torque ripple is maintained at 12.4%,when the motor operates at 800r/min and 5N·m.Then,the conventional torque sharing function control method is introduced,and the shortcomings of the conventional torque sharing function are analyzed according to the inductance and torque characteristics of the motor,and a non-uniform torque sharing function control method with adaptive overlapping angle is proposed.Based on the analyzing the inductance and torque characteristics of the motor,this method divides the conduction region into new zones,and puts forward the corresponding non-uniform torque sharing function in each new zone.Then,using the proposed function optimization algorithm and the adaptive algorithm of overlapping angle,the torque sharing function and overlap angle can be automatically adjusted under different speeds and load torques.Thirdly,an non-uniform torque sharing function control method with adaptive overlapping angle is proposed,which solves the problems of large peak current and copper loss in the direct instantaneous torque control method based on turn-on angle optimization.According to the characteristics of overlapping angle,the two-phase exchange region is subdivided into two regions,and the corresponding non-uniform torque sharing function is planned for each region.The overlapping angle and torque sharing function are adjusted according to different speeds and loads.The simulation results show that this method can restrain the torque ripple and reduce peak current and copper consumption.The torque ripple is kept at 20.8%,the peak current is reduced by 4.35 A and the copper loss is 8.87 A,when the motor operates at 1200r/min and5N·m.Finally,a prototype platform of PMa-SRM is built and verified by experiments.Hardware circuits,such as power converters,driving circuits,current and position detection,and subroutines,such as speed detection,CAN communication and lookup table algorithms,are designed and manufactured.The conventional and improved direct instantaneous torque control methods,conventional and overlapping angle adaptive torque sharing function method are compared and analyzed respectively.