Research on Low Power Factor Modulation Strategy of Three-Level Inverter

This paper addresses the persistent challenges of neutral point voltage (NPV) fluctuation and two-level switching transitions in three-level active neutral-point-clamped (3L-ANPC) inverters, which limit their broader application despite advantages like low harmonic distortion and reduced device stress over conventional two-level topologies. Building upon virtual space vector pulse width modulation (VSVPWM) and discontinuous PWM (DPWM) principles, a novel enhanced dual-modulating-wave-based virtual space vector PWM (E_DVSVPWM) strategy is proposed. The core innovation involves a refined modulating wave decomposition approach incorporating controlled zero-sequence voltage injection. This enables dynamic neutral current balancing for NPV stabilization while optimizing switching patterns: DPWM is strategically applied in specific sectors to minimize switching actions, and distinct P/N-type vector sequences are selectively employed in other sectors to significantly reduce switching frequency compared to standard VSVPWM. Crucially, a synchronous modulation scheme with carefully defined sector transition rules is integrated to eliminate hazardous two-level switching transitions during major sector crossings. Simulation results comprehensively validate that the proposed E_DVSVPWM strategy effectively suppresses NPV fluctuations across diverse modulation indices and power factors while concurrently reducing switching losses, offering a robust solution for improving 3L-ANPC inverter performance.