Abstract
In view of the rapid growth of fuel-cells applications, a high voltage gain converter is essential as an efficient interface between the loads and the fuel cells. Naturally, one can use a transformer to achieve the high voltage gain as well as provide electrical isolation. However, a high turn-ratio transformer always accompanies high leakage inductance which results in low efficiency and high electric stress of devices. This situation becomes even worse for high power rating case. In light of these dilemmas, a novel isolated four-phase DC converter base on flat matrix transformer is proposed in this thesis to solve the above problems for high power application. Basically, the contributions of this thesis may be summarized as follows. First, a correct equivalent circuit model is proposed for the adopted flat matrix transformers with very low leakage inductance (almost unity coupling coefficient) and with possible fraction-turn windings. Then, based on the proposed model matrix transformers can be integrated with other circuit components to obtain a system model convenient for simulation with a commercial software such PSpice. Second, the sharing characteristic of flat matrix transformers is analyzed and verified. Third, a novel isolated four-phase DC converter is proposed for high power high voltage-gain applications. By using a new interleaved control to together with a new transformer interconnection configuration, the converter output voltage can reach 3n, n being the transformer turn-ratio, times the input voltage and the output voltage-ripple frequency is increased to 8 times the switching frequency. As a results, the size of the output filter and the turn-ratio of the transformer can be reduced. Finally, a prototype is also constructed by using a high speed digital signal processor, namely TMS320F2812 to verify the feasibility of the proposed converter.