Comparison and evaluation of sub-module configurations in modular multilevel converters

The application and research interest over modular multilevel converters (MMCs) has grown significantly over the last couple of years. The term MMC has been expanded to include all converters built on the series connection of sub-modules (SMs) as a basic building block forming converter arms and phase-legs. A review of the current literature reveals an abundance of SM configurations ranging from SMs derived from the well-known multilevel converter topologies to novel configurations targeted to niche MMC applications. This paper provides a comprehensive review of the current SM configuration state and a comparative evaluation based on complexity of configuration, voltage balancing and component count. It also provides an evaluation of switching and conduction losses for the devices within each SM, identifying those SMs that are more suitable to general MMC applications.