Control Strategy for Multiphase Drives With Minimum Losses in the Full Torque Operation Range Under Single Open-Phase Fault

Fault tolerance is an advantageous characteristic of multiphase machines when compared with three-phase ones. During open-phase fault, the current references need to be adapted to provide ripple-free torque. As a consequence of this modification, the postfault phase currents might be larger than the rated current. Such a situation leads to overheating, and to preserve the integrity of the system, some limits are set to the postfault phase currents. Two main strategies have been proposed for the postfault situation: maximum torque (MT) and minimum losses (ML). The MT strategy allows us to obtain the widest torque operation range (TOR) in the postfault situation but does not minimize the stator winding losses; conversely, the ML strategy provides the minimum stator winding losses for each torque value, at the expense of reducing the TOR. Thus, the solutions proposed so far do not achieve minimum stator winding losses in the entire (that of the MT strategy) TOR. This paper presents the full-range minimum losses (FRML) postfault control strategy, which minimizes the losses in the whole TOR, for multiphase machines with sinusoidally distributed windings under single open-phase fault. The FRML strategy is evaluated for different types of machines, phase numbers, and winding arrangements. Experimental results are provided.