Systematic Synthesis and Derivation of Multilevel Converters Using Common Topological Structures With Unified Matrix Models

Abstract

Multilevel converters (MLCs) have been increasingly adopted in both low-power low-voltage systems and high-power high-voltage applications. In recent years, many new topologies have been proposed, and a few of them have been successfully implemented in industry. While searching for new topologies, synthesis and derivation principles of multilevel topologies are critical for converter design. In this article, a generalized synthesizing approach of multilevel topologies is proposed and analyzed with the considerations of the voltage source, current source, and matrix-type MLCs. Based on the proposed method, the topological relationship among these three types MLCs is revealed through the stage-based common circuit structure. In addition to the graphic-based approach, a mathematical approach is proposed for representing the MLC topologies in this work. The matrix-based model is utilized to unify and verify the derivation and simplification process in a systematic way through many MLC examples in this article. Finally, demonstration examples are presented to show how the proposed principles can be used to derive new topologies covering five-level to nine-level converters. With the ever-increasing research efforts on MLCs, it is hoped that this article can provide a new approach that inspires the development of more interesting and practical MLC topologies for various applications.