Modular Multilevel Converter Sub-modules for HVDC Applications

The flexibility offered to the modular multilevel converter (MMC) by its sub-module (SM) based structure has led to the development of multiple SM circuit configurations that provide a diverse range of functionalities. This paper provides a comprehensive and up-to-date overview of MMC SM configurations, identifying suitable SMs for HVDC systems and classifying them based on various properties aimed at high-level characteristics of each SM. By developing multiple MMC models with different SMs and considering practical aspects of converter operation in HVDC systems, the paper also provides a preliminary comparison of MMC losses across 27 different SMs.