Enhancing Six-Phase PMSMs Performance Recovery Post Open-Circuit Fault via Specific Harmonic Injection

A fault-tolerant control scheme based on harmonic injection is proposed for dual three-phase permanent magnet synchronous motor (DTP-PMSM) drive systems to address opencircuit faults. The scheme aims to maximize torque output and minimize copper losses following a fault, thereby improving system performance while maintaining reliable operation. The key objective is to optimize the system's fault-tolerant operation to ensure that the torque output is as close as possible to its pre-fault value, while simultaneously reducing the losses that typically occur during such faults. Initially, the constraint on the d-axis magnetic kinetic potential is removed, ensuring that the output torque remains unchanged before and after the fault. An expression for the d-axis harmonic current injection after the fault is then derived. Next, to achieve decoupling of the harmonic and fundamental subspaces during fault-tolerant operation, the current reference in the harmonic subspace is determined through a simple linear operation. Finally, by treating unit copper consumption and unit torque output as optimization objectives, the rational d-axis harmonic current injection coefficient is derived, along with the reference expressions for the phase and harmonic subspace currents. This scheme is applicable not only to single-phase open-circuit faults in DTP-PMSM systems but also to two-phase open-circuit faults in motors. Experimental results demonstrate that the proposed fault-tolerant strategy enables the system to achieve 73.4% of the maximum torque output capability with only 1.414 p.u. copper loss after a singlephase open-circuit fault, thus validating the effectiveness and superiority of the proposed control scheme in minimizing losses and preserving torque output as much as possible post-fault.