Study On DC-DC Power Converter For Fuel Cells

GREEN power(renewable power) becomes increasingly more important due to global pollution problems.Fuel cell is a kind of electrochemistry electricity generating device that is out of noise and pollution.It is an advanced energy transfer device hardly letting out N-O compound.Fuel cell is widely used in any place that is in need of the energy sources and power.With the increasing quantity of cars in China, the contradiction between the feed and need of the traditional fuel increasingly stands out because of the lack of the oil resource.The air pollution caused by cars becomes worse and worse.Electro motion car that is motivated by fuel cell is the most efficient and practical measure to solve these problems.However,because of the generation of unstable direct current,the weak output characteristic and the unsatisfact dynamic performance,it can't adapt to a single-handed power source directly.Therefore,fuel cell must be equipped with a Power Control Unit(PCU) to produce standard DC or AC power through regulation,control and management of the output.With the development of fuel cell products and technology,the researches on the power electronics supply base on fuel cell has showed the significance nowadays.Considering the advantage of the fuel cell,this paper researches a two-step DC-DC converter with low voltage input,low cost,low pollution and high efficiency. The converter can improve the feature of the fuel cell and provide the basic for invertion.This thesis introduce the work principle and characteristic of fuel cell first, illustrate the importance of using fuel cell in China,and describe the background of the thesis and its importance,then give the work the author have done.Secondly,the thesis gives a global description of the DC-DC converter which is fit for the high efficiency fuel cell system,and give an analysis of the work principle of the circuit we choose.Then,the thesis makes an analysis on the Soft-switching which is the key point for the Full-bridge topology,meanwhile the thesis gives the hardware design,including the Digital control circuit for Boost and phase-shift control,drive circuit,protection circuit for Full Bridge Phase Shift.Fourthly,it introduces the function and the realization of all the software modules as the initialization and the main program,A/D sampling,PWM signal generating,velocity feedback and the PI control,as well as the program flow according to the requirement of the software design.Finally,the paper simulates the Boost for fuel cell with the MATLAB/SIMULINK,and analyses the result.