Bidirectional LCLL Resonant Converter with Wide Output Voltage Range

A new bidirectional LCLL-type resonant dc-dc converter (LCLL-BDC) is proposed in this article, which features a wide output voltage range for both ports, thus achieving zero-voltage switching (ZVS) at the input side and zero-current switching (ZCS) at the output side. The snubberless converter is similar to the type-11 LLC-type resonant converter, with the exception of an additional inductor. The auxiliary inductor allows for the converter to achieve a wide voltage range power transfer, thus addressing the inability of the LLC-type converter to be boosted in the reverse mode. The equivalent model and the steady-state operation are presented in this article. Moreover, the design methodology for the resonant network was derived for the LCLL-BDC. A 1-kW prototype, which interfaces two batteries of different energy systems, was developed to verify the validity and applicability of the proposed converter. The input and output voltage range was found to be 80-120 V, and the highest efficiencies for the bidirectional operational modes exceeded 96%.