Hybrid Input-Series–Output-Series Modular DC–DC Converter Constituted by Resonant and Nonresonant Dual Active Bridge Modules

Possessing the capability to handle high voltage, the bidirectional input-series–output-series (ISOS) modular dc–dc converter is suitable for use in dc grids. Regarding topology selection of the constituent modules, the open-loop controlled series-resonant dual active bridge (SR-DAB) converter exhibits superior efficiency performance and the advantage of simple control. However, it has no regulation capability. Aimed to reap the advantages of SR-DAB and achieve flexible control, this article presents a hybrid ISOS converter composed of SR-DAB and nonresonant phase-shift controlled dual active bridge (PS-DAB) modules. The SR-DAB modules process most of the power to ensure high-efficiency conversion, whereas the PS-DAB is responsible for flexible control. At the output stage of the ISOS system, embedded nonisolated resonant dual active half-bridge (NR-DAHB) converters are integrated between every two adjacent modules without adding any switches. The transformer property of the open-loop controlled SR-DAB and NR-DAHB circuits facilitates natural voltage sharing at both the input and output sides. The hardware experiment has been conducted to verify the operating principles and performance of the proposed ISOS system.