A Family of Novel Active Auxiliary Circuit‐Based ZVS Three‐Level Bidirectional Buck/Boost Converters for Wide‐Load‐Range Efficiency Improvement

ABSTRACT Three‐level bidirectional buck/boost converters (TLBBBCs) have been widely adopted in renewable energy systems and grid‐tied storage. Still, their efficiency at high switching frequencies remains limited by switching losses. So, this paper introduces a fundamental innovation, which is a novel active auxiliary circuit. The novel active auxiliary circuit enables the generation of bidirectional, discrete triangular‐wave currents. These triangular‐wave currents can create zero‐voltage switching (ZVS) conditions for all main switches, significantly reducing overall switching losses across wide load ranges. First, building upon this core innovation, a family of novel ZVS TLBBBC topologies is systematically derived, so that engineers can choose an optimal one according to actual requirements. Then, Topology 1 and Topology 4 are selected as representative cases. Their operating principles, circuit characteristics, and conditions for maintaining soft‐switching are explored in depth, providing detailed guidance for the design process of practical applications. Finally, to confirm the analytical study's effectiveness, the experimental results of two representative proof‐of‐concept model circuits are presented. Experimental results demonstrate that the topologies proposed in this paper can all maintain an excellent efficiency of over 96% within the load range from 20% to 100% and achieve efficiency improvements of up to 2.96% (Topology 1) and 2.62% (Topology 4) under full‐load operation.