Study On Pemfc Hybrid System And Fuel Gas Pressure Nonlinear Control

As a renewable enegy source, the proton exchange membrane fuel cell is widely regarded as one of the most promising energy sources because of its high enegy efficiency, extremely low emission of oxides of nitrogen and environment friendly. The hybrid system of fuel cell and other power sourse is widely applied recently. Based on the development of fuel cell hybrid bicycle, it is known that large deviations between anode and cathode gas pressures can cause severe membrane damage. A control scheme is presented to prevent membrane damage by achieving optimal anode and cathode gas flow rates in this thesis.Firstly, the characteristics and classifications of the fuel cells are summarized. A brief overview is conducted on the important elements and the principle of PEMFC, as well as the framework and control strategy of fuel cell hybrid system. Then, the fuel cell and ultra-capacitor hybrid bicycle system including the hybrid control strategy is designed and accomplished both in hardware and software. The fuel cell hybrid bicycle is tested both in lab and on the road, the test results shows that the hybrid system designed is suitable to the bicycle system.For further study of the nonlinear control of PEMFC gas pressure, a dynamic PEMFC model is proposed as a nonlinear, multiple-input multiplep-output system based on the energy conservation equation, PEMFC experiential equations and the state equations of PEMFC internal gas partial pressures in this thesis. Finally, a PEMFC control system based directly on the nonlinear dynamic fuel cell model is established by the concepts of differential geometry based feedback linearization and generic model control theory. During the control design, anode and cathode gas inlet flow rates are defined as the control variables, and the pressures of anode and cathode gases are appropriately defined as the control objectives. The MATLAB/SIMULINk simulation results show it is feasible that the control strategy proposed in this thesis keeps the anode and cathode gas pressures stable nearby the desired value so that the fuel cell stack can be protected by minimizing the deviaton between the anode and cathode gas pressures under large load varieties.