2022 IEEE 3rd China International Youth Conference on Electrical Engineering (CIYCEE 2022)

       With the development of electric vehicles, LLC converter for bidirectional energy transmission has received more and more attention. In order to achieve bidirectional boost operation, the L-LLC converter is applied. However, the forward operation efficiency of L-LLC converter is reduced compared to the traditional LLC converter due to the addition of an extra inductor. This paper proposes an improved bidirectional variable structure LLC (VS-LLC) resonant converter to improve forward operation efficiency. Compared with L-LLC converter, the VS-LLC converter improves the efficiency in forward mode by changing the resonant network. The working principle of the proposed converter is introduced, and the parameters of a VS-LLC converter are designed. Bidirectional boost operation and soft switching capabilities of VS-LLC converter are validated by the simulation results. The comparison results show that VS-LLC converter has higher efficiency than L-LLC converter in forward mode, and the backward operation efficiency of two converters is approximate.

efficiency; LLC; soft switching; variable structure