A Cascaded High Step-up DC-DC Converter with Single Switch for Microsource Applications

Abstract— This paper proposes a new high step-up DC-DC converter designed especially for regulating the DC interface between various microsources and a DC-AC inverter to electricity grid. The figuration of proposed converter is a quadratic boost converter with the coupled inductor in the second boost converter. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switch. Additionally, the energy stored in the leakage inductor of the coupled-inductor can be recycled to the output capacitor. The operating principles and steady-state analyses of continuous-conduction mode and boundary-conduction mode are discussed in detail. To verify the performance of the proposed converter, a 280W prototype sample is implemented with an input-voltage range of 20 ~ 40 V and output voltage of up to 400 V. The upmost efficiency of 93.3% is reached with high line input; on the other hand, the full-load efficiency remains at 89.3% during low line input. Index Terms – microgrid, microsource, high step-up voltage gain, single switch, boost-flyback converter, coupled-inductor.