Hybrid three-phase multilevel inverter based ON NPC cascaded to half-bridge cells

Abstract

This work presents a novel hybrid three-phase multilevel inverter that employs a three-phase Neutral Point Clamped converter and single-phase Half-Bridge cells in a particular cascade connection. Its cascaded structure allows its application in medium-voltage applications with low voltage semiconductors. The inverter operation is analyzed and can lead to a 5, 7 or 9 level structure. A hybrid modulation scheme for the operation with five levels at the output phase voltage is proposed, which leads to unidirectional power flow in all dc sources and, thus, eases the implementation. The proposed structure and modulation scheme are analyzed and explained in details and simulation and experimental results are provided to verify the presented analysis.