Direct Torque Control Of Permanent Magnet Synchronous Motor And Its Improved Algorithm

Permanent Magnet Synchronous Motor(PMSM) has been widely used in manyfields for its advantages of small size, high efficiency, simple structure and low noise. Inorder to further improve performance of PMSM, it is necessary to do further research ofits control strategy. Therefore, this paper mainly studied the direct torque control(DTC)strategy and its improved algorithm of PMSM.DTC is another important control strategy of AC speed regulating after the vectorcontrol strategy, its main idea is selecting the appropriate space vector of stator voltageaccording to the requirements of the torque and flux directly. Compared with vectorcontrol strategy, DTC has advantages of simple structure, good dynamic and strongrobustness to parameter change, it was mainly used in induction motors in earlier days,the application of DTC in PMSM remains to be further research. This paper firstintroduced the characteristics, present situation and development trend of the controlstrategy of PMSM, then derived the mathematical model of PMSM and the traditionalDTC was analyzed in theory. Beside, a new flux observer based on error feedback wasproposed and the problem of DC bias of the flux was solved. Meanwhile, the PMSMDTC system was simulated by Matlab/Simulink tools and the theoretical analysis resultswas verified.Both simulation and theoretical analysis indicated that the PMSM DTC systemexist torque and flux ripple and instability of switching frequency. To solve theseproblems, the space vector pulse width modulation (SVPWM) technology wasintroduced into the traditional DTC in this paper and put forward the PMSM SVM-DTCsystem which fundamentally solve the problems existing in the traditional DTC, Thenthe PMSM SVM-DTC system was simulated by Matlab/Simulink tools and thesimulation results indicated its superiority compared with the traditional DTC system.Finally, Both the hardware platform based on TMS320F2812and IPM of thePMSM speed regulation system and the softwares of traditional DTC and SVM-DTCwere designed. The DTC and open-loop SVM-DTC for PMSM was implemented,meanwhile, the experiment results were consistent with the theoretical analysis andsimulation results，which will be a solid foundation for further studies.