Recent Advancements in Submodule Topologies and Applications of MMC

Modular multilevel converter (MMC) is a promising topology for medium- and high-power conversion systems. In recent years, it has been prominent over other power converters because of its exceptional features, including modularity and flexibility to adapt any voltage level, remarkable harmonic performance, no dc-link capacitors, transformerless operation, absence of ac-side filters, and capacitive nature of phase legs. However, there are some challenges, for instance, submodule (SM) capacitor voltage balancing, output current control, circulating current control, minimization of SM capacitor voltage ripple, dc-side faults, and efficient SM topologies that have been addressed by the research studies over time. In this article, we focus on the recent advancements in SM structures and their capability to overcome the faults, reduction in switching losses, decrease in voltage sensor count, and minimization of SM capacitor voltage ripple and provide the quick restoration of SM capacitor voltages after the removal of faults. Finally, the applications and development prospects of MMC are discussed in detail.