Hybrid Mode Control of an Asymmetric Dual Three-Phase Synchronous Motor Under Single-Phase Open Fault

This paper proposes hybrid mode control for an asymmetric dual three-phase synchronous motor (ADTP-SM) with separated neutral points in a single-phase open-fault situation. The fault-tolerant control is classified into the maximum torque mode and minimum loss mode. For an arbitrary phase with an open fault, the combination of phase currents for operation in each mode is derived by mathematical analysis. In maximum torque mode operation, a rotational coordinate transformation is proposed to minimize the performance variance according to the speed. In minimum loss mode operation, a stationary coordinate transformation is proposed to control the harmonics of the phase currents. This stationary coordinate transformation can be applied to arbitrary-phase open-fault situations. In addition, the performances with and without harmonic control are compared and analyzed, and the smoothness of the mode conversion is also analyzed. The validity of the proposed coordinate transformations is verified through experiments at various speeds.