A Novel SVPWM Fault-Tolerant Strategy for Torque Ripple Reduction of Seven-Phase Induction Machines Under Single-Phase Open-Circuit Fault

The development of multiphase drives has taken on an accelerated pace in the last decades, and fault-tolerance has been the subject of many classic studies. Traditional space vector pulsewidth modulation (SVPWM) would cause significant torque ripple in the case of open-circuit fault, which in turn degrades the fault-tolerant performance of multiphase machines. This work proposes a novel SVPWM fault-tolerant strategy for seven-phase induction machine under a single-phase open-circuit fault. A deeper insight has been provided into the reconstruction of voltage vectors without using reference current, ensuring the generality for various fault-tolerant principles. Subsequently, an eight-sector-based sector division method is proposed, and five specific nonzero voltage vectors and two zero-voltage vectors in each sector are determined to be candidates. Without confliction of switching state, the symmetric modulation module can still be utilized, which will minimize the modifications after fault occurrence. Besides, the close-loop control for harmonic planes can be fulfilled. Finally, experimental results have demonstrated the effectiveness of the proposed SVPWM fault-tolerant approach under both steady and transient states.