Simulation Study Of Direct Torque Control For A Five-Phase Fault-Tolerant Permanent Magnet Motor Drive

The reliability of the adjustable speed drive is important for the applications like military, aerospace and automobile industry. Fault tolerant motor drives and its control system become an area of interest to increase reliability of the motor drive system. This thesis investigated the Direct Torque Control (DTC) system for a five-phase Fault-Tolerant Permanent Magnet (FTPM) motor drive.The mathematical model of a five-phase Permanent Magnet (PM) motor drive is established based on three-phase PM motor modelling. Each phase of the motor winding is wound around a single tooth and each slot is only placed by one winding to reduce the magnetic and thermal interaction between phases. The separate H-bridge inverter is used to drive each phase of the motor winding. No neutral point is needed for this type of inverter and as a result the distribution of the total space voltage vector based on FTPM motor drive is quite different from that of full-bridge drive motor. Thus, the available voltage vectors are firstly needed to be discussed. Then the sets of voltage vectors for healthy normal condition and one-phase open-circuit condition are chosen. The largest magnitude vectors are selected for healthy condition and the voltage vectors start with zero are selected for one-phase open-circuit condition. Based on these two sets of vectors, the fault control strategies of DTC for a five-phase FTPM motor drive is proposed under healthy and one-phase open-circuit fault condition.To verify the availability of the proposed control strategy, MATLAB/Simulink is used to build the simulation model for DTC of five-phase FTPM motor drive in this thesis. The proposed control strategy is tested at high speed and low speed. According to simulation results, the motor can operate under one-phase open-circuit condition with acceptable variation in current, torque and speed.