Torque Ripple Suppression Strategries For Permanent Magnet Synchronous Motor Based On Improved Predictive Control

Permanent magnet synchronous motor traditional single-vector predictive torque control only acts one set of switching states in each control period.Because of the limited number of discrete voltage vectors that the two-level inverter can provide,the system torque control accuracy is relatively low.The traditional dual-vector predictive torque control with duty ratio modulation can reduce the torque ripple to a certain extent compared with tsingle-vector predictive torque control.However,due to the fixed direction of the selected action vectors,there is still a large torque ripple,and the duty ratio needs to be calculated online.In order to solve the problem of large torque ripple in traditional single-vector and dual-vector predictive torque control of PMSM,this paper focuses on changing the switch time and expanding the finite control set with generalized dual-vector.In the traditional single-vector predictive torque control strategy,the inverter switching time is fixed at the beginning or end of the control period,which leads to large torque ripple.This paper proposes to shift the switching time to the inside of the control period.By designing a set of synthetic vectors based on variable switching points,the candidate voltage vector and duty ratio are directly determined according to the distribution characteristics of all synthetic vectors in the set and the spatial positional relationship of the desired voltage vector.Then the action vector can be selected by value function to realize the variable switching point predictive torque control(VSP-PTC)of PMSM.Besides,the VSP-PTC just shifts the switching time,and will not increase the switching times of the switching state in each control period,so it will not cause a higher switching frequency.In the traditional dual-vector predictive torque control with duty ratio modulation,the direction of the selected action vector is fixed,resulting in large torque ripple.Besides,the duty ratio needs to be calculated online.In this paper,the generalized dual-vector is used to extend the finite control set,and a dual-vector predictive torque control strategy without online duty ratio calculation for PMSM is proposed.From the perspective of the extended finite control set,a synthetic vector is generated by the combination of two basic vectors is acted on one control period.The aim is to improve the accuracy of motor steady state control and reduce the torque ripple.At the same time,an alternative voltage vector table containing duty ratio information is constructed off-line to avoid on-line calculation.Finally,the two control strategies proposed in this paper are experimentally studied on the experimental platform of PMSM control system fed by two-level voltage source inverter.The validity and feasibility of the two control strategies proposed in this paper are verified under different conditions.