Realization of a Nine – Level Cascaded NPC/H-Bridge PWM Inverter using Phase-Shifted Carrier PWM Technique

摘要

Cascaded H-bridge inverter has been researched for the past two decades, but there are no explicit guidelines on how one can realize a cascaded neutral-point-clamped (NPC) / Hbridge inverter. Past research has also concentrated on realizing a five level NPC/H-Bridge inverter. This fails to address the principle of realizing a general cascaded n- level NPC/H-Bridge PWM inverter. This paper proposes an improved topology for achieving a Nine - Level cascaded neutral-point-clamped (NPC) H-bridge inverter with reduced harmonic content. This new proposed topology requires a lesser number of separate dc sources as compared to conventional cascaded H-bridge inverter. The whole system is considered as having four cascaded three level legs having two positive and two negative legs. By properly phase shifting the modulating wave and carriers, a nine level output is achieved. A theoretical harmonic analysis of the proposed inverter is carried out based on double Fourier principle. The theoretical results are verified through MATLAB simulation.