Single-Source Three-Phase Multilevel Inverter Assembled by Three-Phase Two-Level Inverter and Two Single-Phase Cascaded H-Bridge Inverters

Abstract

Multilevel inverters (MLIs) with reduced number of switching devices and dc sources have compact size, reduced cost, and higher efficiency. This article proposes a transformer-based single-source MLI with reduced number of components and small size transformers. The proposed topology is a hybrid three-phase MLI assembled by a conventional three-phase two-level inverter (TTI) and two single-phase cascaded H-bridge inverters (CHBIs). The proposed MLI has a low ratio of number of active switches to number of output voltage levels. In order to use only one dc source, the CHBIs are cascaded with the TTI through transformers. An individual nearest level modulation (NLM) has been developed to control voltage of this inverter. Moreover, power distribution between its modules is analyzed. The total power of the transformers is 28% of the inverter rated power. Simulation and experimental results of a 13-kVA prototype verify the efficiency of the proposed arrangement.