| Energy is not only the basis for human survival, but also socio-economic basis for sustainable development. But now, mankind faces increasingly energy crisis and environmental pollution. Photovoltaic power generation, wind power generation, and fuel cell power generation are the main researching direction in the field of new energy. Fuel cells are widely concerned because they have the advantages of high efficiency, clean, pollution-free, high power density and not restricted by different region. Fuel cells have broad application in fuel cell power station, electronic vehicle, portable power, aerospace and other field. Because the output characteristics of fuel cell is low voltage and high current, the output voltage of one single fuel cell is only 0.7V, they must be used in series. When fuel cell stack are cascaded by too many cells to obtain higher output voltage, it will easily make the whole battery stack not work if one cell of the battery stack doesn't work. Besides,the output voltage of the fuel cells is varied when the load is changed. Therefore it needs a DC/DC converter in practical application. The DC/DC converter must have has the ability of meeting the widely input voltage range, the ability of boosting the input voltage with high ratio, the ability of reducing the input current ripple and fast dynamic response capability.At present, the fuel cell DC/DC converters include two class, isolated and non-isolated. Each class includes many types. After analyzing the advantage and disadvantage of these converters, in this paper we construct two converter topologys, improved cascade Boost converter and switch capacitor interleaved Boost converter, base on the advantage of the switch capacitor in boosting the output voltage. All main switches and all diodes voltage stress is very low when the duty ratio is more than 0.5, the input current ripple is very small in the switch capacitor interleaved Boost converter. Moreover, the currents in two inductors are proportioned.This paper has the following components:â‘ Outlines the principles of fuel cells, types, applications, analysis the static and dynamic output characteristics, and gives a simplified equivalent circuit.â‘¡After analyzing the state of fuel cell DC/DC converter, improved cascade Boost converter and switch capacitor interleaved Boost converter have been proposed on the basis of cascade structure, switch capacitor and interleaving theory. Steady-state results of two new topologys are derived, and compared with the conversional converter.â‘¢The small signal circuit model and the transfer functions of the switch capacitor interleaved Boost converter have been derived. After analyzing of transfer functions of the converter, we choose the averaged current control to design the control circuit.â‘£Using the actual parameters of fuel cell products, a switch capacitor interleaved Boost converter is designed, including main circuit and control circuit, by simulation software. The simulation results verify the advantages of the new topology. At last, the experimentation of a low power prototype of switch capacitor interleaved Boost converter is designed to verify the correctness of theoretical analysis and simulation. |
