Comparative study of variant topologies for MMC

On the base of the MMC principle, this work considers different topologies of sub module (or elementary converter) which make the High Voltage AC/DC converter more flexible and easy suitable respect to different voltage and current levels. A topological study is consolidated and extended on three different topologies proposed as elementary converter and their employment for the MMC structure is treated. For each cell, topology advantages and limits are discussed in terms of current and voltage. Under SPWM modulation conditions, an analytical approach for the power losses evaluation is proposed for the three topologies used in the MMC structure. A comparison on the efficiency is proposed by fixing the DC voltage and the operating power. By considering the basic topology of the MMC (composed by elementary cells) also an evaluation of the power losses is performed by considering the staircase modulation which is becoming more and more diffused especially for a high number of levels.