Open-circuit fault tolerant control of five-phase permanent magnet motors with third-harmonic back-EMF

In this work, an optimal open-circuit fault-tolerant control strategy is proposed for five-phase permanent magnet (PM) motors with trapezoidal back-EMF, containing fundamental and strong third harmonic components. A new solution based on the instantaneous power balance theory is presented to obtain the optimal stator excitation currents under single phase open-circuit fault. The solution is derived by applying a novel concept, introduced in this work, which correlates the currents in the stator healthy phases based on their spatial symmetry. The presented solution minimizes the stator ohmic loss and the torque pulsation while producing the required output torque to continue the machine operation under fault condition. Details derivation is presented to obtain a closed form solution. It is found that only fundamental current component is sufficient for the fault-tolerant control of the machine with minimum stator ohmic loss. Simulation and experimental results of a five-phase PM machine are presented to verify the validity of the proposed solution.