An Isolated Multi-Input ZCS DC-DC Front-End-Converter Based Multilevel Inverter for the Integration of Renewable Energy Sources

A new isolated current-fed zero-current switched (ZCS) front-end dc/dc converter based multilevel inverter is proposed for multi-input applications. The proposed front-end converter with only two controllable switches integrates two different renewable energy sources, resulting in an advantageous compact structure and low conduction losses. The ZCS turn-OFF is achieved in both the controllable switches with the proposed modulation scheme. The converter maintains ZCS turn-OFF under a wide load, as well as input voltage variations by employing frequency modulation along with a variable duty ratio technique. Simple structure, soft switching, high gain, and automatic load regulation make the converter structure novel for simultaneous power management in multi-input renewable energy applications. Converter operation and design guidelines have been outlined. A laboratory prototype of the proposed converter is developed and tested at 300-W power level. Simulations and experimental results demonstrate the robust performance of the converter under load, as well as input source voltage variations.