A Modular Cascaded Multilevel Converter With High Configurability: Design, Analysis, and Optimization Study

This article introduces a new modular cascaded multilevel inverter (MLI) that is composed of a cascaded connection of submodules (SMs). The combination of basic cells (BCs) with polarity changer H-bridge produces the SMs, which is the basis of the introduced inverter. Due to its high modularity, the proposed inverter can be extended to reach higher voltage levels. Hence, two extensions are suggested: 1) extension based on cascading more BCs within each SM and 2) extension based on cascading more SMs. Using a set of algorithms, the magnitude of dc voltage sources is determined to synthesize the proper ac-side voltage waveform. Furthermore, the proposed topology is optimized in different ways to achieve the desired purposes, such as maximizing the number of voltage levels, minimizing the number of switches and dc sources, and providing the least total standing voltage on the switches. Therefore, in each of the mentioned optimization goals, the optimal structure is obtained. A prototype of the presented MLI is defined and its performance is verified through several simulation studies in MATLAB/Simulink and experimental tests. Besides, a comprehensive comparison is made with the best performance of the existing alternatives to demonstrate the merits and superiorities of the proposed MLI.