A High Step-up Modular Isolated DC-DC Converter for Large Capacity Photovoltaic Generation System integrated into MVDC Grids

Nowadays, the research and design of the DC-DC conversion system has become more and more popular in the application of photovoltaic generation into the medium voltage DC (MVDC) grids. A novel high power modular isolated DC-DC converter with high step-up ratio is proposed as a module of the DC-DC conversion system in this paper. Based on the input parallel and output series (IPOS) connections of the proposed modular converters, the system is easy to achieve high capacity and high voltage. A two-stage structure is employed in the proposed converter. The interleaved boost topology is applied to the front-stage, which realizes MPPT for PV arrays with low input current ripples. The full-bridge LLC topology is employed as the back-stage, which lowers power losses by the implementation of soft-switching. The voltage gain of the proposed converter is derived in detail. The theoretical analysis and control strategy are studied in depth. Simulation and experiment verify the feasibility and effectiveness of the proposed converter.