A novel comprehensive control scheme of modular multilevel converter-based power electronic transformer

In this paper, the modular multilevel converter-based power electronic transformer (MMC-based PET) is studied. This topology is suitable for high voltage and large power capacity situations, such as DC power distribution network. Only one medium frequency transformer is used in the PET structure, reducing the size and weight. A series inductor is added to the DC side of MMC which can improve the characteristics of the topology. By analyzing the structure of MMC stage, a comprehensive control scheme is proposed. Based on the small signal model of output stage, a phase shift closed-loop control scheme is designed for output stage. The control schemes of MMC stage and output stage are independent of each other. A Simulink model is built in Matlab, and the simulation results verify the effectiveness of the topology and the proposed control scheme.