| Summary: | 碩士 === 國立成功大學 === 電機工程學系 === 104 === In this thesis, a novel high step-up DC-DC converter with ZVZCS is proposed based on several existing coupled-inductor and switching-capacitor topologies. According to the characteristics of renewable energy sources, these kinds of converters are usually required to have a high conversion ratio, high efficiency and large power capacity. Therefore, the interleaving and active-clamp techniques are introduced.
During steady-state operating modes of the proposed converter, the leakage inductor of the coupled inductors resonates with two switching capacitors. Under different resonant frequencies, ZVS turn-on and ZCS turn-off can be realized for certain power switches and rectifying diodes, respectively. Therefore, the switching loss and reverse recovery problems are alleviated, which improves the efficiency of the converter. Thanks to the interleaving mechanism and more switches, the turn ratio of each coupled inductor can be reduced dramatically, along with less current stress in the primary-side winding. Therefore, the power capacity can be improved significantly.
Before experiment, steady-state performance including the voltage conversion ratio is derived and compared with existing ones. In addition, the mode boundary map for distinguishing soft-switching modes is depicted and verified by the software simulation. Finally, a prototype with 24 V input voltage, 400 V output voltage and 800 W output power using controller TMDSDOCK28035 is implemented in the laboratory to verify the feasibility of the proposed converter.
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