Abstract
DC nanogrids have become a subject of interest inrecent years due to the increase of renewable energy sources with energy storage systems. Hybrid AC/DC systems with different DCbuses are an interesting solution to efficiently supply different AC and DC loads. In this paper, a high efficiency bidirectional converter to interlink a 400V DC bus with a 48V DC bus ispresented. The proposed converter is based on a LLC resonant converter operating as a DC transformer at a fixed frequency and duty cycle without any complex control strategy. A clearand simplified design procedure for high efficiency operation and optimal self-load regulation is presented. To verify the converter operation, a 1kW prototype has been implemented, featuring on maximum efficiency of 96:7% and a self-regulated output voltage with 3% of maximum offset from the nominal voltage.