Design and Modeling of CLLC Converter for Bidirectional on-Board Charger

With the proposal of double carbon goals in various countries around the world, the development of new energy vehicles has received more and more attention as one of the important measures to reduce carbon emissions, and battery electric vehicles are the main research and application direction. In order to alleviate the impact of the influx of a large number of electric vehicles on the existing power grid, the construction of a flexible V2G system has become a future development trend, and the bidirectional on-board charger is an indispensable device. Combined with this application background, this article designs a CLLC converter for the bidirectional on-board charger which has fully symmetrical parameters. Based on the three-stage charging strategy of lithium-ion batteries, the platform characteristics of lithium-ion batteries are transformed into converter parameters, ensuring higher efficiency during the charging process. The small-signal model of the converter is established and verified, and the closed-loop PFM control is realized. Finally, a planar transformer with integrated leakage inductor is designed and a 1.2 kW experimental prototype is built.