The high efficiency cooperative control of power and temperature of a stand-alone solid oxide fuel cell system with an air bypass valve

In this paper, a temperature feed-forward and power feedback control strategy based on open-loop optimal operation path and constrained generalized predictive control algorithm is proposed to address the competitive relations among power tracking, temperature constraints and high system efficiency of an independent solid oxide fuel cell (SOFC) system. Firstly, optimal operation points (OOPs) for different output powers are obtained by forcing temperature constraints and optimizing system efficiency based on a distributed SOFC system dynamic model. Then the thermo-electrical coupling characteristics of SOFC system are studied through static and dynamic analysis. As the temperature variation in the stack is slow, we can apply the thermal management relevant variables of OOPs to system immediately when the power changed, such as U, AR and BP, to suppress the potential system temperature fluctuation during power switching process. Due to the output power is directly determined by fuel flow rate, a constrained generalized predictive control algorithm based on online T-S fuzzy model (TS-CGPC) is utilized to regulate fuel flow rate to achieve fast load following with the consideration of input constraint. The simulation results indicate that the controller can drive the system achieves excellent load tracking capability while keeping system constraints safe with high system efficiency of 42%~53%, implying that the independent SOFC system can possess excellent performances by design an appropriate controller and this work set a solid foundation for the high efficiency and long operation life of SOFC.