Analytical modelling and efficiency optimisation of bidirectional CLLC, LLC, and DAB converters for wireless power transfer

Bidirectional CLLC, LLC and dual active bridge (DAB) converters are promising contenders for bidirectional wireless power transfer (WPT) across an air gap of a WPT transformer. The choice between these three converter topologies is generally not obvious and depends e.g. on the WPT transformer’s installation space, air gap length, and resulting coupling factor.Hence, the most suitable converter topology can be identified by means of a system efficiency optimisation, for which exact, analytical and computationally efficient models are beneficial. This paper introduces such new analytical models and corresponding efficiency optimisations for the three considered converters with actively controlled rectification.Optimisation results for an exemplary WPT transformer with two distinct air gap lengths are presented and discussed. On the basis of the calculated results, the most suitable converter for the considered transformer is obtained.