High-Efficiency Bidirectional Three-Level Series-Resonant Converter With Buck-Boost Capacity for High-Output Voltage Applications

To improve the efficiency and power density of electronic vehicles, battery packs with higher voltage levels have been gradually adopted. This change poses new challenges for conventional battery charger designs based on two-level topologies and low-voltage rating switches. Therefore, in this article, a bidirectional buck-boost three-level series-resonant converter (BBTL-SRC) for high-output voltage applications is proposed. The voltage stress of switches is reduced to only half of the output voltage, so the low-voltage rating switches with lower losses and costs can be used. In addition, the phase shift and pulsewidth modulation strategies are designed to realize buck and boost conversion. All switches can achieve zero-voltage switching, and the reactive current in resonant tank decreases significantly. Hence, the switching and conduction losses are reduced and efficiency is optimized. The operation principles and characteristics are analyzed in detail, and design considerations are provided. A 3.3-kW, 600-840-V output prototype is built and tested. The experimental results verify the effectiveness of the proposed BBTL-SRC.