Open-Phase Fault-Tolerant Pole Transition Control of an Asynchronous Variable-Pole Machine Using Harmonic Plane Decomposition

Automotive applications are revisiting the use of induction machines (IMs) as magnet-free propulsive solutions due to their intrinsic robustness and reliability. Special multiphase configurations are under investigation to reduce the losses further and fulfill the stringent energy-efficiency and compactness requirements of the automotive industry. One of these configurations is known as variable-pole machines (VPMs), which allows the number of magnetic pole pairs to change on the fly. These machines can stretch the torque-speed operating region, exploit the maximum torque capability, and exhibit competitive efficiency. Although fault tolerance has been widely explored for multiphase machines, the same cannot be said for VPMs, because, until recently, complete models to describe their dynamics under any condition, including magnetic pole changing and fault occurrences, were unavailable. This article presents a post-fault control strategy for VPMs with an open-phase fault (OPF), which can operate during pole changing and address the issue of fault-tolerant operation. The effectiveness of the control system is verified by experimental tests carried out with an 18-phase variable-pole IM prototype.