Transient performance and control system design of solid oxide fuel cell / gas turbine hybrids

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Transient performance and control system design of solid oxide fuel cell / gas turbine hybrids

Kroll, Florian / Nielsen, Annette / Staudacher, Stephan

The presentation of a control strategy for the most important SOFC / gas turbine hybrid system maneuvers like start-up, shutdown or system-failures is one of the main issues of this paper. For a successful system simulation during different operational states, a coupled model of a gas turbine and a SOFC was combined with the proposed control system. To keep the model structure lean enough for real-time calculation, a non-linear lumped volume model with modular set up was chosen to achieve an accurate reflection of the dynamic effects. The control strategy takes into account the requirements of the gas turbine components but also necessitates safe operation of the SOFC. Specified boundary conditions are strictly to be considered within the control structure to ensure failure-free and safe operation during the entire operation range. In the presented hybrid cycle a possibility of bypassing both, the cold side of the recuperator and the cathode side of the SOFC is suggested. These two bypasses, which introduce two additional actuators to the system, allow the SOFC stack temperature to be kept in its limits more easily.