Hybrid-Three-Level Current-Fed Series-Resonant Isolated DC-DC Converter and its Optimization Modulation Strategy

In this article, a hybrid three-level current-fed series-resonant isolated bidirectional dc–dc converter is proposed, containing an interleaved parallel bidirectional buck/boost converter at the low-voltage side and a half-bridge three-level converter at the high-voltage side. The operation principles and characteristics of the proposed converter are thoroughly analyzed with the duty-cycle plus dual phase-shift control. The relationship between the general case of three independent control variables and the transfer power is derived. Then, a modulation strategy optimization algorithm by taking the minimum root mean square (rms) value of the resonant current as the objective function is presented. Under the optimal operation point, the converter operates efficiently with the minimum rms value of the resonant current and accordingly increases the efficiency. The detailed experimental results verify the correctness and feasibility of the proposed converter and modulation strategy.