On energy storage requirements in alternate arm converters and modular multilevel converters

In this paper, a comparison of the energy storage requirements is performed for the modular multilevel converter (MMC) with half-bridge and full-bridge submodules as well as for the alternate arm converter (AAC). Concerning the AAC, the operational mode with overlap period is taken into account and an analytical relation between the overlap angle and the modulation index is presented. This ensures that the net energy exchange for the converter arms is zero over each half cycle.