Modular multi-level converter topologies: Present status and key challenges

Modular multilevel converter (MMC) is an emerging technology for various applications including high voltage dc transmission and wind energy conversion systems. Submodule based MMC architecture dominates over other converters topologies, due to various technological as well as economic advantages. This paper presents a comprehensive review of MMC topology and its submodules. Different types of submodule architectures are discussed to provide an overview of evolving technology. Different submodules are grouped in accordance to their output terminal voltage levels. The key issues and challenges are also highlighted.