An Improved VSVPWM Strategy of Considering Neutral-point Potential Balancing in Three-level NPC Converter

摘要

Neutral-point (NP)-clamped three-level converter is a widely used topology in the research fields of the multilevel converters, which suffers from the NP voltage drift as its main technical drawback. In theory, it is based on the fact that the virtual space vector modulation approach could completely control the balance of neutral-point potential, so this paper introduces a improved control strategy of neutral-point potential balancing in three-level converter, which combines the space vector modulation approach based on virtual vectors with the algorithm of modifying small vectors pairs' distribution time accurately. Relative to the traditional proposed algorithm of setting voltage tolerance range to modify small vectors pairs' distribution time, the performance of algorithm of capacitor charge balancing is better and its accuracy of control is more precise. The feasibility of the proposed control approach has been verified via experiment results.