An improved space vector modulation strategy for three-level five-phase neutral-point-clamped inverters

Switched inverters generate fast rates of change of common-mode voltage and are an unwanted side-effect in variable speed drive systems operated with PWM inverters. Whilst techniques have been reported that theoretically eliminate the common-more voltage, when the dead-time effects and the practical transient performance of semiconductors are considered, a common-mode voltage is still generated, even though these proposed techniques sacrifice dc-link utilization and switching loss. In this paper, a switching strategy is proposed for the three-level five-phase neutral-point-clamped inverter, which reduces the common-mode voltage as far practically possible and eliminates vectors in the d₂q₂ plane. The proposed method maintains the same linear modulation range as the conventional space vector modulation technique but utilises fewer switching actions in one carrier period. Moreover, its complexity is reduced lowering the computational overhead. The proposed method is verified in both simulation and experiments on a prototype of five-phase neutral-point-clamped inverter.