Soft-Switching Control Method of Interleaved Three-Level Boost Converter in near-CRM for Fuel Cells

High power DC-DC converters with high efficiency, small size and low current ripple are required in fuel cells locomotives. Combining the advantages of three-level technology low switching voltage stress and interleaving technology small total inductor current ripple, this paper proposes a soft-switching control method of two-phase interleaved three-level Boost converter. The proposed converter is mainly characterized by the novel soft-switching method with fewer auxiliary devices (the small power switches and resonant capacitors). This paper mainly analyzes the inductor current ripple and the current ripple cancellation rule. Then the variable switching frequency control scheme based on current ripple prediction is proposed to make the converter operate in near critical conduction mode (near-CRM). Finally, a two-phase interleaved three-level Boost converter is tested to experimentally verify the proposed soft-switching control method.