부산대학교 도서관

To address the wide voltage conversion requirements in the field of battery charging, the LCL resonant tank adopting pulse frequency modulation is investigated utilizing the time-domain model (TDM) in this article. LCL exhibits similar soft switching characteristics and enhanced voltage gain regulation capability with a simpler resonant tank than the existing classic CLLC . The operating principles, mode distribution, and power transfer properties of LCL during bidirectional operations are presented and analyzed in detail utilizing TDM. By incorporating TDM, the low accuracy deficiency of the first harmonic approximation for wide voltage applications is completely eliminated, and the implementation of full-range zero-voltage switching (ZVS) with time-domain accuracy becomes feasible. An LCL resonant parameters optimization method that is capable of providing the required voltage gain and guaranteeing the achievement of ZVS with reduced reactive power under desired load conditions during bidirectional operations is proposed. Finally, the revealed experimental results from a 1-kW prototype validated the correctness of the TDM theoretical analysis and the effectiveness of the proposed optimization method. The optimized prototype achieves the designed 1.8× voltage gain within a narrow switching frequency range of 88.7–120 kHz and a peak efficiency of 97.306%.