Research On Direct Torque Control In Permanent Magnet Synchronous Motor For Electric Vehicle

The direct torque control(DTC)technology takes the stator flux and torque as control variables directly,and it has strong robustness against motor parameters,simple structure and quick dynamic response,it has become a high-performance control scheme.In this paper,permanent magnet synchronous motor(PMSM)DTC system used in electric vehicles is studied.Combined with zero voltage vector and predictive control,this paper focuses on selection strategy of voltage vector,which has a certain significance to application of DTC in electric vehicles.In this paper,switching table based PMSM DTC system is analyzed,and effects of zero voltage vector are analyzed.The amplitude of stator flux and torque are decreased when applying zero voltage vector,conventional switching table using zero voltage vector is given based on effects of zero voltage vector.Due to two different switching states of zero voltage vector,switching state selection strategy of zero voltage vector is proposed,novel switching table using zero voltage vector is given based on the strategy.Combined with the merits of nonzero voltage vector and zero voltage vector,adaptive variable voltage vector switching table is given.Simulation results show three given switching tables are correct.Compared to conventional and novel switching table used zero voltage vector,system has quicker dynamic response using adaptive variable voltage vector switching table.Compared to conventional DTC switching table,torque error of system is decreased using three given switching tables,and system has favorable steady performance.Compared to conventional DTC switching table,the switching times and mean switching frequency of system are decreased using three given switching tables,and switching loss is decreased,meanwhile,compared to conventional switching table used zero voltage vector,the switching times of system has a further reduction applying novel switching table using zero voltage vector.Compared to conventional DTC switching table,the harmonic content in the stator current of system is at a lower level using three given switching tables.Finally,the effect of the voltage vector on the stator flux and torque is analyzed in this paper,the voltage vector selection strategy is proposed based on predictive control.Simulation results show that compared to conventional DTC switching table,the voltage vector selection strategy based on predictive control reduce the torque error and stator flux error,and value of cost function is decreased,the control effect of proposed voltage vector selection strategy based on predictive is better.