Extended Balancing and Dimensioning of Capacitors in MMC Double Submodules

The Double-Zero Submodule in Double Connection (DZDCSM) is one of the most promising submodule topologies for future Modular Multilevel Converter (MMC) applications. Internal paralleling of semiconductors and capacitors in the DZDCSM during the time spans of high load currents results in low losses and reduced energy pulsation. Furthermore, full controllability of the capacitors enables their critical balancing in a passive and lossless manner. This paper presents an analytical investigation of the internal balancing process as well as the energy pulsation reduction in the full operating range of the MMC utilizing the DZDCSM. A simulation, applying the nearest level modulation and a basic sorting algorithm, verifies the general energy pulsation reduction in comparison to a conventional Full-Bridge Submodule (FBSM).