Dual active bridge assisted modular multilevel converter allowing low frequency output

Abstract

The modular multilevel converter(MMC) is one of the most attractive converter topologies for high or medium voltage power system. In this paper, a combination of modular multilevel converter and dual active bridge(DAB) is discussed. The DAB assisted MMC(MMC-DAB) is capable of low frequency output with elimination of capacitor voltage fluctuations in submodules. This paper analyzes the MMC-DAB structure and its control strategy. A MMC-DAB simulation model is built in the PSCAD/EMTDC software environment. The effectiveness of the MMC-DAB topology is verified by simulation results.