| Title |
Analysis of Backward Mode for LLC-based Bidirectional Batteries Charger |
| Authors |
생차야(Chhaya Seng) ; 서정진(Joungjin Seo) ; 차한주(Hanju Cha) |
| DOI |
https://doi.org/10.5370/KIEE.2023.72.7.820 |
| Keywords |
Bidirectional battery charger; LLC resonant converter; Backward mode; energy storage system (ESS). |
| Abstract |
This paper proposes a bidirectional dc-dc converter for the energy storage systems (ESS) that operate in forward and backward mode power direction between the DC bus of the PV system and batteries. A bidirectional dc-dc converter with LLC resonant method has the advantage of simple structure and soft switching. In the forward direction, the LLC resonant converter can realize a normalized gain greater than one or less than one and can operate to reach soft switching zero voltage switching (ZVS), and zero current switching (ZCS) in light load and heavy load at the resonant point. However, in the backward direction only a normalized gain of less than one can be achieved. Since the operation modes of the LLC converter are different between forward and backward modes, the operated switching frequency is also different. Without changing the LLC resonant converter’s basic topology, the backward mode of the LLC converter can be achieving soft switching by operating in a specific switching frequency below the resonant. The backward mode of the LLC converter study in this paper is operated at 0.9 value of normalized switching frequency in order to achieve soft switching ZCS with an easy control method. The backward mode of the LLC resonant converter was analyzed in this paper and verified soft switching by simulation and experiment. |