Backward Step-Up Control Strategy for Bidirectional LLC Resonant Converter

Jingkai Niu, Xuezhi Wu, Yue Wang, Long Jing, Weige Zhang and Yibin Tong
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Jingkai Niu: National Active Distribution Network Technology Research Center, Beijing Jiaotong University, Beijing 100044, China
Xuezhi Wu: National Active Distribution Network Technology Research Center, Beijing Jiaotong University, Beijing 100044, China
Yue Wang: National Active Distribution Network Technology Research Center, Beijing Jiaotong University, Beijing 100044, China
Long Jing: National Active Distribution Network Technology Research Center, Beijing Jiaotong University, Beijing 100044, China
Weige Zhang: National Active Distribution Network Technology Research Center, Beijing Jiaotong University, Beijing 100044, China
Yibin Tong: National Active Distribution Network Technology Research Center, Beijing Jiaotong University, Beijing 100044, China

Energies, 2022, vol. 15, issue 12, 1-15

Abstract: An LLC resonant converter has the advantages of simple structure and soft switching. It can enable bidirectional power transmission, but it is difficult to realize a normalized gain greater than one under backward mode (backward step-up mode). Cascaded dc/dc converters or topological changes can solve this problem, but additional switches and components are required and losses are added. Without changing the LLC resonant converter’s basic topology, this paper proposes a variable duty-cycle control strategy of primary side switches for backward step-up mode. Using variable duty-cycle control, the LC resonant tank can be charged, and then the backward step-up mode can be realized. Soft switching characteristics of some primary side switches and all secondary side switches are guaranteed. In this study, the working principle of an LLC resonant converter under bidirectional control strategy was analyzed, and the backward step-up control was analyzed in detail. The voltage gain and the boundary of continuous conduction mode (CCM) and discontinuous conduction mode (DCM) were derived. A synchronous rectification method related to the backward step-up control is proposed. The control strategy was verified by experiments.

Keywords: LLC resonant converter; backward step-up mode; control strategy; voltage gain; synchronous rectification (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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