A High-Power High-Ratio DC-DC Converter with DC Fault Blocking Capability

This paper proposes a non-isolated medium-voltage DC-DC converter with high step-up ratio. It aims to interconnect the low-voltage (LV) generation units and medium-voltage (MV) power-collecting grid in DC renewable system. The proposed DC-DC converter is composed by a switch network and a few cells. The switch network alternatively configures the cells in parallel connection for charging from low-voltage input side (V_L) and in series connection for discharging to high-voltage output side (V_H). This helps step up the low generation-unit voltage to power-collecting-grid level. Meanwhile, the embedded cells in converter possess voltage adjusting ability, which enables the immediate change of output voltage. As compared to other megawatt-class non-isolated DC-DC converter, the proposal not only achieve high step-up ratio, but also integrates the capabilities of output voltage modulation and DC fault blocking. The feasibility of the proposed DC-DC converter is verified by simulations performed in MATLAB/SIMULINK.