Global Fault-Tolerant Control Technique for Multiphase Permanent-Magnet Machines

In this paper, a global fault-tolerant control (FTC) technique is proposed for multiphase permanent-magnet (PM) machine drives. The goal of the proposed FTC is to find a general closed-form solution for healthy phase currents under steady-state post fault conditions. Healthy phase currents are found through an optimization problem to produce ripple-free output torque with minimum ohmic losses. A comprehensive FTC approach should be able to provide fault-tolerant currents for multiphase machines with any number of phases. In addition, it needs to find currents based on fault type (open-circuit/short-circuit), fault locations [phase(s) and/or line(s)], connection of stator windings, and even different control objectives. An important feature of the proposed method is its flexibility and simplicity in dealing with all possible fault conditions. The proposed method is a great tool to evaluate fault-tolerant capability of different drive systems in terms of maximum available ripple-free torque and copper losses. Due to its simplicity and flexibility, it is also well-suited for real-time implementation. A five-phase PM machine is used as an example to investigate the validity of the proposed solutions through finite-element analysis and experimental tests.