Six-phase Space Vector PWM Based on Stator Single Phase Open-circuit Fault

The torque pulsation and speed pulsation of a six-phase induction machine with double Y-connected windings shifted by 30° increase after single phase of the stator winding is open-circuit. In order to reduce the pulsations, a method of six-phase space vector pulse width modulation (SVPWM) with fault-tolerance was proposed. The star point of the open-circuit winding group was connected to the mid-point of dc-link. The 32 column matrices representing 32 stator winding voltages were mapped to the d-q plane and z1-z2 plane by using a new five-dimensional orthogonal matrix, and then 32 basic vectors were obtained. By using an optimal model, six auxiliary vectors and a equivalent null vector were constructed, the magnitudes of which were all zero in the z1-z2 plane. By using the auxiliary vectors and equivalent null vector, a reference vector was synthesized, the zero magnitude of which in the z1-z2 plane can suppress the harmonic voltages, and the circular trajectory of which in the d-q plane can make the torque smooth. Simulation and experimental results show that the torque pulsation range and the speed pulsation range of the proposed method with fault-tolerance are 30% and 25% that of the classical method without fault-tolerance, respectively. So the phase-deficient operation performance of the system is improved. © 2019 Chin. Soc. for Elec. Eng.