A Multiple Modular Isolated DC/DC Converter With Bidirectional Fault Handling and Efficient Energy Conversion for DC Distribution Network

The isolated bidirectional dc/dc converter (IBdc) plays an important role in dc buses connection, voltage conversion, electrical isolation, and bidirectional power transmission for dc distribution networks. In this article, a multiple modular IBdc scheme based on hybrid dual-active-bridge (HDAB) for medium-voltage and high-voltage dc distribution network is proposed. In proposed HDAB, the switches in upper position of full-bridge are replaced by the half-bridge submodules, and the proposed HDAB maintains the advantages of conventional DAB and achieves bidirectional fault handling capability, avoiding the application of large dc-link capacitors and dc circuit breakers, thus reducing the volume and construction cost. Besides, a high-frequency-link (HFL) voltage regulation strategy is also proposed in this article, adjusting the HFL voltages in HDAB to match HFL transformer voltage ratio adaptively, thus improving the efficiency and applicability of IBdc under the fluctuation of power flow and dc bus voltage. The topology, operation principle, control structure, and corresponding bidirectional fault handling and HFL voltage regulation strategy of the proposed IBdc scheme are investigated. The experimental results verify correctness and effectiveness of proposed scheme and control strategy, promoting the adaptability and practicality for both IBdc and dc distribution network.