Study Of Fuel-cell Model And Power System

Fuel cells are devices capable of converting chemical energy into heat and dc electric energy by means of the oxidation of a fuel, usually hydrogen. For some time they have been considered as alternative power converters both for transportation and for stationary power generation. Since such a system generates electric energy as long as is supplied continuously from outside, it can also be considered a generating system similar to conventional generating systems.Fuel cells have the following advantages over conventional generating systems: low environmental pollution; highly efficient power generation; diversity of fuels; reusability of exhaust heat; modularity; faster installation. Recent worldwide clean-air movements have greatly increased the importance of fuel cell development. Development of various types of fuel-cell systems has also been stimulated by this new trend. Therefore, we expected fuel cells to be used extensively in the future.The fuel cells existent problems and the background of this thesis are summarized in the first chapter. The necessity of development fuel cell generation technology in China's power system is verified, and technical line for developing fuel cell generation is put forward.In chapter 2, a description of what a fuel cell is, how it works, efferent applications of fuel cells, and different types of fuel cells are given.The fuel cells models are presented in chapter 3. Based on the balance conditions in fuel cells stack, the dynamic performance is analyzed. The dynamic model is developed with a set of correlation equations of voltage, fuel utilization, current density and other variables involved in the operating course, which are some partialdifferential equations with variable coefficients. From the disturbance of the load, the relationships between these variable are discussed. The simulation results show good agreement with the experimental data, which proves that the analysis and the model are correct. The results are helpful to definition of the control method and the flow field, as well as the selection of cell materials.Chapter 4 develops a generic dynamic model for a grid-connected fuel-cell plant based on MATLAB/SIMULINK. The model is defined by a small number of parameters and is suitable for planning studies. The steady state power generation characteristics of the plant are derived and analyzed. Two major loops for voltage and power control are incorporated. This chapter also presents an application of the proposed model to the study of distributed generation for a utility that employs fuel cells and gas turbine plants.In chapter 5, the principle of molten carbonate fuel cell power system is introduced. The development of the system, such as the improvement of cell components including electrodes and electrolyte, the fuel processing, the heat recovery, the power conditioning and grid interconnection, the control system and the combine generation. In addition, the capacity and market of fuel-cell plant are also described.