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In this study, a new two-input isolated boost dc-dc converter based on a distributed multi-transformer structure, which is suitable for hybrid renewable energy systems is investigated and designed. With a novel transformer winding-connecting strategy, the two-input ports can be decoupled completely, so the proposed converter can draw the power from the two different dc sources, which have low output voltage, and transfer it to the dc bus, which has high voltage, separately or simultaneously. The detailed operation principles of the proposed converter have been analysed in the dual-input mode and the single-input mode, respectively. The main advantage of the proposed topology is that the four transformers and the secondary rectifiers are fully utilised whether the converter is connected with two-input power sources or only one input. Although the four transformers are employed, the nominal powers of each transformer and rectifier are both reduced by four times. Furthermore, some special issues on converter design, such as increasing number of the input ports, the magnetic integration and the ground loop decoupling are discussed. A 2-kW prototype was built and tested. Experiments on the converter-s steady-state and transient operations verified the validity of the analysis and design.