Impact of pole-to-pole DC voltage on energy requirement of FB YY-MMC

The aim of this paper is to investigate the impact of pole-to-pole DC voltage on the energy requirements of a modular multilevel converter with full-bridge submodules (FB-MMC). With focus on energy-storage equipped FB-MMCs, the relation between the pole-to-pole voltage and the peak-to-peak energy variations in the MMC’s arms is derived. Unlike MMC with half-bridge (HB) submodules (SM), in a FB-MMC the pole-to-pole DC voltage can be selected independently of the AC voltage; this allows for reduced energy requirements as well as lower number of FB SMs and capacitors for the same converter ratings. Furthermore, the impact of the converter’s circulating current on the MMC’s energy requirements is investigated. A guideline for the converter design is provided. Theoretical findings are validated via time-domain simulations.