A simplified Space-Vector modulation algorithm for four-leg NPC converters

Abstract

To interface generation sources and loads to fourwire distribution networks it is important to use power converters and modulation methods, which provide high performance, flexibility, and reliability. To achieve these goals, this paper proposes a simple and efficient space vector modulation (SVM) algorithm in alpha beta gamma coordinates for neutral point clamped (NPC) converters. The proposed SVM method reduces a 3-D (alpha beta gamma) search amongst modulating vectors into a simple 2-D (alpha beta) problem. Moreover, the algorithm provides full utilization of the dc-link voltage and full utilization of the redundant vectors, and it can be applied to any other four-leg converter topology. The proposed SVM has been successfully validated using a 6-kW three-level four-leg NPC converter, achieving control over the voltages of the dc-link capacitors and a simple definition of the switching patterns for shaping the frequency spectrum.