Single Open-Phase Fault Tolerant Control of Salient Dual Three-Phase PMSMs With Maximized Torque to Total Loss Ratio Considering Peak Phase Current Limit

For dual three-phase permanent magnet synchronous machines (DT-PMSMs) under open-phase fault, the fault tolerant currents are often unbalanced to generate smooth torque, which results in the peak current and copper loss of certain phases and per phase loss being significantly larger than healthy conditions. This can limit the maximum attainable torque and lead to overheating issue of the phases with larger currents. However, this is not fully addressed especially for salient PMSM. This article studies open-phase fault tolerant control (FTC) of salient DT-PMSM by considering the peak phase current limit to reduce the maximum per phase loss and improve the ratio of torque to total loss (TTL), resulting in improved maximum attainable torque. Analyses are first conducted to show the motivation. The proposed FTC aims to maximize the ratio of TTL and minimize peak phase current and fault-induced ripples without introducing phase current harmonics. Moreover, the current distribution affecting reluctance torque is optimized to improve the maximum torque considering saliency. Analytical solutions are derived to achieve better computation-efficiency. Compared with existing methods, the proposed approach can achieve better TTL ratio, maximum per phase loss, peak/rms phase current and maximum attainable torque, which is validated with experiments and comparisons.