Medium-voltage DC grid connection using modular multilevel converter

In recent years medium voltage direct-current (MVDC) grids have gained significant attention. This paper presents a new isolated modular multilevel converter (MMC)-based dc/dc converter for connecting such networks. The proposed converter can connect DC grids with different voltage levels and control power flow among them. The proposed isolated dc/dc converter has fewer components compared to conventional isolated MMC-based dc/dc converter. A major challenge in MMC-based dc/dc converters is balancing capacitor voltages in each arm and phase. To this end, a closed loop control is proposed. Simulation results using Matlab/SIMULINK is provided to demonstrate the dynamic response under step changes of reference powers.