A neutral-point potential balancing algorithm for three-level NPC inverters using analytically injected zero-sequence voltage

摘要

Based on the zero-sequence component of the reference voltages, this paper comprehensively analyzes the neutral-point variation and balancing control for three-level neutral-point-clamped inverter. An analytical method is proposed to accurately calculate the injected zero-sequence voltage for NP balancing. Based on the analytical analysis, the limitation of NP balancing control is revealed and the NP-fully-controllable region is presented. A real-time NP balancing algorithm is proposed as well. The feasibility of the proposed method is verified using simulation results for a 6kV/1800kVA medium voltage drive.