A Simplified Space Vector Pulse Width Modulation Strategy for NPC Six-Phase Three-Level Inverter Considering Neutral-Point Potential Balancing

Abstract

A neutral-point clamped (NPC) six-phase three-level inverter has excellent applicability in high-power drives because of its high reliability and robust fault tolerance. This paper proposes a simplified space vector pulse width modulation (SVPWM) strategy with vector simplification and virtual vector synthesis to improve its multi-objective constrained control performance, e.g., numerous and redundant switching states, harmonic current suppression and neutral-point potential balancing. Firstly, 729 output voltage vectors are simplified to 48 vectors based on the harmonic current suppression and neutral-point potential unbalancing analysis. Then, 12 virtual vectors are constructed based on the principle of synthesizing zero-amplitude vectors in the harmonic subspace, and an adjustable factor $k$ has been introduced during the construction to realize the dynamic adjustment between DC-link voltage utilization and control efficiency of the neutral-point potential balancing. Finally, these 12 virtual vectors are applied for the simplified SVPWM. Comparative experiments have been carried out to verify the effectiveness and feasibility of the proposed SVPWM strategy.

Keywords

• NPC six-phase three-level inverter
• simplified SVPWM
• harmonic current suppression
• neutral-point potential balancing
• vector simplification
• virtual vectors