Modular multi-level DC-DC converter for high-power and high-voltage applications

A transformer-less DC-DC Modular Multi-level Converter (DC-DC-MMC) topology based on H-bridge cells is proposed in this paper. The suggested DC-DC-MMC can be used to either control the power flow in a HVdc grid or interconnect HVdc lines with different voltage levels. Branch energy and current control loops are presented as well as a cell capacitor voltage balancing strategy. Finally, the operation of the converter is validated by means of PSCAD simulations. Results for the operation of the DC-DC-MMC controlling the power flow between two HVdc grids with different voltage levels are presented.