A High Step-Up DC-DC Converter Integrated With Modified Sepic Network

Nonisolated high step-up soft-switching dc-dc converter is suitable for dc microgrid system because of its simple and high efficiency. This article proposes a single-switch high step-up dc-dc converter, which integrates a coupled-inductor based modified Sepic network. It achieves ZVS turnon transition without adding extra devices, just with appropriate designed parameters. The proposed converter provides high voltage gain with appropriate converter parameters, provides ZVS/ZCS turnon transition of switch and ZCS turnoff of diodes, obtains continuous input current and balanced voltage of capacitors. The ZVS/ZCS transition of the switch and diodes caused by the resonance of leakage inductor of the coupled-inductor and capacitor improves electromagnetic compatibility (EMC) and efficiency. The balanced voltage of capacitors results from multilevel structure is beneficial to capacitors selection. The steady-state operation principle and comparison of the similar topologies have been analyzed in detail. The properties of the converter are verified by designing a 500 W prototype in the laboratory. The efficiency reaches 95.17% at half power and the efficiency at a rated power is 92.99%. The typical experimental waveforms of the proposed converter agree well with the theoretical analysis.