Capacitively Isolated Multicell Dc-Dc Transformer for Future Dc Distribution System

This paper proposes a new capacitively isolated multicell dc–dc transformer (dcx). The proposed dcx consists of dc–dc cell converters with pairs of isolation capacitors that substitute for high frequency transformers. The capacitively isolated cell converter achieves higher efficiency compared with the conventional inductively isolated dc–dc converter because of no transformers. The multicell approach also accomplishes the various voltage transformation ratios based on the input–series–and–output–parallel and input–parallel–and–output–series connections of the cell converters, overcoming the drawback of the capacively isolated converter with the fixed voltage transformation ratio. The analysis of the isolation voltage–sharing across the capacitors was conducted to show the feasibility of the proposed multicell dcx. The prototype of the 96 V–24 V, 200 W dcx using two 48 V–24 V, 100 W capacitively isolated dc–dc cell converters was also fabricated to confirm the validity of the analysis. The proposed approach contributes to the achievement of highly efficient and scalable power converters to realize future low–carbon societies.

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