A tolerated fault direct torque control for six-phase permanent magnet synchronous motor with one opened phase based on fictitious variables

The strong ability of controlling torque and tolerated fault operation are demanded for multiphase permanent magnet synchronous motor drive system applied in such as locomotive traction, shipping-push, and so on. A tolerated fault direct torque control (DTC) strategy is proposed for six-phase symmetrical winding shifted-phase 60 degree permanent magnet synchronous motor in this paper. Firstly, the relationship between the flux linkage and torque based on the restructured fictitious variables is researched under the condition of one opened phase. Secondly, the optimal control strategy of fictitious flux linkage, torque and zero-sequence current error is proposed with different switching combination of five-phase invert bridge according to the fictitious voltage vector on αβ plane used to convert the mechanic-electric energy and zero-sequence voltage vector on z1z2 plane. The experimental results show that the presented DTC has fast response of torque, the five-phase stator currents are sinusoidal and the magnitudes of five-phase current are the same. © 2015 Chinese Society for Electrical Engineering.