General Open-Phase Fault-Tolerant Online Current-Reference Generation for Maximum Torque Range and Minimum Copper Loss With Phase-Current-Peak Limitation for n-Phase PMSMs With Nonsinusoidal Back-EMF

Multiphase permanent-magnet synchronous machines (PMSMs) with nonsinusoidal back-electromotive force (back-EMF) offer high fault tolerance and torque density. Most current-reference generation methods either minimize stator copper loss (SCL) or maximize achievable torque. Optimization of both goals is accomplished by the full-torque-range minimum-loss (FRML) strategies, but so far just for sinusoidal back-EMF. Moreover, many methods are only suitable for healthy conditions or specific machines, harmonics, or open-phase-fault (OPF) scenarios. This paper proposes an online FRML current-reference generation for n-phase PMSMs with nonsinusoidal back-EMF. When the torque reference is feasible without violating the phase-current-peak limit, minimum SCL per torque is attained while maximizing the achievable ripple-free torque value (i.e., FRML). For higher torque references, the instantaneous torque deviation is minimized. This FRML method is suitable for any n, harmonics, and healthy/OPF conditions. Experimental results performed with a six-phase PMSM are provided.