Research On A Double-input DC-DC Converter With Bootstrap Boost Topology

Development and utilization of the renewable energy is one of the effectivesolutions to solve the energy crisis problems and the envirmental pollution. With noneed of electric isolation between input-source and the load, hybrid renewable powersystem composed of multi-input converter without transformers is growing popularbecause of its simpler circuit, lower cost, higher efficiency, unnecessary transformerdesign and other advantages.From the way of connection between input-source and DC-link, a boost convertercan be used in the tranditional design. But large inductance, slow dynamic responseand EMI are obvious, which are serious problems for the system. With combination ofthe bootstrap circuit and multi-input converter, a novel double-input DC-DC converterusing step-up capacitors is proposed in this paper. The aim of the proposed topology isto improve dynamic performance, simplify magnetic design and enhance reliability.Specifically, a capacitor of large capacitance could be interfaced with the port ofrenewable energy source in parallel. When the renewable energy generator is poweredoff, it should quit from system immediately. At the same time, the back-up source canconnect the capacitor in parallel by constructed auxiliary circuit. Thus, the port’svoltage and the overall syetem keep stable. From another point of view, voltage ratingof the back-up source can be reduced with the help of the bootstrap capacitor.Operation principle and input-output voltage relationship are explained in detailand the corresponding energy management control strategy requiring to make the mostutilization of renewable energy for the hybrid power system is presented in this paper.In addition, charge-discharge features of the bootstrap mode is analyzed and chargingloss is calculated mathematically, and whose results serve as the theoretical referenceof the system’s parameters design.Small signal models of the whole renewable energy generation system composedof double-input DC-DC converter and the associated close-loop control design aredeveloped. Moreover, simulation confirms the correctness of the power management control strategy. A200W prototype with TMS320LF2407A and EPM7128STC100-7has been built and tested successfully for mode transition and efficiency assessment inthe lab. As a result, the experimental measurements are demonstrated to verify thefeasibility of the proposed topology.