Simulation And Control Of Intermediate Temperature Planar Solid Oxide Fuel Cell Stack

Energy crisis and environmental problems like climate change have become main challenges to the world in 21st century, therefore clean and efficient fuel cell technology is of great importance for us to face the challenges. Solid oxide fuel cell (SOFC) is research focus as the most efficient one in many types of fuel cell, and it can use natural gas as fuel when hydrogen is not available, so it has promising application in distributed generation (DG) and combined heat and power generation (CHP). And intermediate temperature planar SOFC is a trend because its advantages reached by compromising between cost and performance.Though SOFC is still being researched as a relatively new field, modeling and control are necessary for system optimization, performance improvement and mitigating degradation. In this thesis, many methods such as electrochemical analysis have been used for modeling SOFC stack and system, and nonlinear identification method is introduced to simulate steady state and dynamic performance under MATLAB/Simulink environment, the results show consistency with numerical analysis.And control relevant model of SOFC system is set up on the basis of above works. According to the nonlinear, high dimensional and strong coupling characteristics of SOFC system, a new idea of control strategy which separate temperature control and fuel utilization control from voltage control is proposed. Furthermore, a SOFC-ultracapacitor hybrid system is designed to solve the intrinsic problem of large time delay and tight constraints. Simulation shows this hybrid system can evidently slow down the sudden change caused by load change, and it is very effective to improve quality of power supply and longevity of fuel cell.