| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 106 === A bi-directional variable-structure DC-DC converter with high voltage conversion ratio and wide voltage range is proposed in this thesis. The proposed bi-directional DC-DC converter can be operated in six different circuit structures according to the input and output voltage levels. The circuit configuration of proposed bi-directional DC-DC converter can be divided into terminals A and B. Defining the power flowing from terminal A to terminal B as buck mode, the proposed converter can be operated in single buck, interleaved buck and dual buck structures. On the contrary, defining the power flowing from terminal B to terminal A as boost mode, the proposed converter can be operated in single boost, interleaved boost and dual boost structures. The loss formulas are also derived to identify the optimal efficiency switching points for different circuit structures at different voltage ranges. Due to the duality of proposed bi-directional DC-DC converter, a universal bi-directional DC-DC converter is also proposed in this thesis by cascading two proposed converters. Wider voltage range and step-up and step-down voltages at terminals A and B can therefore be achieved. A prototype for the proposed bi-directional DC-DC converter with a rated voltage of 200V at terminal A, a rated voltage between 25V and 150V at terminal B and a rated current of between 1A and 10A at terminal B is designed and implemented in this thesis. A prototype with a rated input voltage of 200V and a rated output voltage between 25V and 750V is also implemented for the proposed universal bi-directional DC-DC converter. Experimental results show and compare the waveforms of driving signals of switches and inductor currents and conversion efficiencies under different voltage levels and different circuit structures. The validity of proposed universal bi-directional DC-DC converter is also verified. From the simulation and experimental results of conversion efficiency, the optimal efficiency switching points for different circuit structures under different voltage and current levels can be determined. Experimental results also indicate that a maximum conversion efficiency of 98.81% can be achieved for the proposed bi-directional variable-structure DC-DC converter.
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