Switching-Cycle Capacitor Voltage Control for the Modular Multilevel DC/DC Converters

This paper presents a Switching-Cycle Capacitor Voltage Control (SCCVC) scheme that can be used in realizing the capacitor voltage balancing Modular Multilevel DC/DC Converters (MMDC). The capacitor voltage will follow the reference in every switching cycle by controlling the average currents that flow through the capacitors to zero. With the new control scheme, the MMDC can directly convert energy in between HVDC and MVDC or between MVDC and LVDC, avoiding the intermediate AC stage with high power density. The MMDC family can be promising alternatives for the MVDC distribution inside the city or any other DC grids interconnections.