Direct Torque Control Of Fault Tolerant Permanent Magnet Motor

Electric actuation system is characterized by simple structure, fast response, flexible control, low energy consumption, easy for automatic management, etc., so in many cases, the power actuation system will gradually replace the hydraulic and mechanical actuation systems. The motors used in the traditional actuation systems do not have the fault-tolerant capabilities, which may leads to disasters in the harsh environments and results in personnel and economic losses.Due to the fault tolerance and high reliability of Fault-tolerant Permanent Magnet Motor (FTPM), it has been received extensively attention in aerospace, submarines and electric vehicles and other special areas and becomes a hot research topic. However, the study on the FTPM and its control technology has just started. Further, the study on six-phase FTPM control method based on dynamical model is just blank. The constant explorations on the FTPM control method have substantially theoretical and practical significance.Based on the in-depth study of the coordinate transformation principles, this article aims to transform the mathematical model of six-phase FTPM from a six-phase stationary coordination system to a two-phase rotating coordinate system so as to achieve the decoupling of the motel. Then, a six-phase FTPM model is built on the Matlab/Simulink tool box. After thoroughly acquiring the advantages of direct torque control(DTC) control method and H-type inverter, they are employed to the control of the six-phase FTPM and a DTC control system of simulation model is built for the six-phase FTPM. Finally, simulation study on four different cases of motor is performed, namely, running without open circuit, one and two-phase open circuit simultaneously, three-phase open circuit simultaneously and three-phase open circuit asynchronously. Simulation results demonstrated that when the above faults occurred, by regulating the phase current automatically, the torque ripple is very small, the speed is stable and the flux is circular.In comparison to the traditional control method of FTPM, the developed DTC control method assures that stability of the whole system without any added hardware entities and adjustment of control strategy. Therefore, it contributes to the reduced system cost, the simplified system structure, the accelerated system response, and the enhanced system stability. This paper lays a foundation on the study of FTPM based on dynamical model, and further provides some important technical parameters and theoretical basis.