Optimized Current Trajectory Tracking Control of a Five-Phase Induction Machine Under Asymmetrical Current Limits

The fault-tolerant ability is a significant advantage of multiphase machines over the three-phase ones. Parallel connections of stator windings or converter legs are preferred to enhance the power rating or drive performance. Open-circuit faults on parallel branches are reflected as the derating of current limits for the corresponding phases, and fault-tolerant strategies are required to keep the phase currents within asymmetrical current limits. This article analyzes the optimal phase current trajectories of a five-phase induction machine under three different faulty scenarios in parallel situations and then proposes the offline optimized current trajectory tracking (OCTT) fault-tolerant strategy, which can reach the maximum achievable fault-tolerant power while guaranteeing optimized ohmic losses over the full power range. Furthermore, based on the generalized symmetrical components theory, an extended rotor field-oriented control (RFOC) is proposed to realize the OCTT mode in field-oriented control. Experimental results confirm the efficiency improvement of the OCTT mode in the full-power-range operation and verify the asymmetrical current trajectory tracking ability of the extended RFOC.