Study Of Direct Torque Control For Dual Three-Phase Permanent Magnet Synchronous Motor

Compared with the conventional three-phase motor variable frequency and variable speed system, multi-phase permanent magnet synchronous motor(PMSM) system has the advantages of large power output with low voltage, and high reliability, which make it have a broad application prospect in industrial, military etc., and get a high degree of attention in the electric drive fields. Direct Torque Control(DTC) has become another accepted advanced control method after Field Oriented Control(FOC) due to its compact system structure, quick response, and good dynamic and static behaviors, but for dual three-phase PMSM drive system, DTC is not so perfect because of its disadvantages of serious torque and flux ripples. To solve this problem, the space vector pulse width modulation(SVPWM) algorithm of DTC for dual three-phase PMSM is proposed and studied.Firstly, the structure, characteristics and mathematical model of dual three-phase PMSM are briefly introduced, as well as the theory of coordinate transformation. Then the basic principles and implementation methods of the dual three-phase PMSM direct torque control system are discussed in detail.Secondly, based on the above theories, the simulation model of dual three-phase PMSM direct torque control system is established in MATLAB/Simulink environment. The simulation results verify the effectiveness of the direct torque control strategy applied to the dual three-phase PMSM, and show that it has fast response, good performances, as well as the existence of torque and flux ripple defects.Finally, to solve the problem of torque ripples produced by the traditional dual three-phase PMSM direct torque control system, the SVPWM, a novel method which based on the zero-sequence balancing space vector was proposed. In this method flux and torque hysteresis controllers and switching vector table module in the traditional DTC are not used, and replaced by the SVPWM. Simulation results show that this method keeps the quick response of the traditional dual three-phase PMSM DTC strategy, and at the same time, reduces the torque and flux ripple, improves the static and dynamic performance of the system.