Transfer function development for SOFC/GT hybrid systems control using cold air bypass

• Fuel cell gas turbine hybrids present significant challenges in terms of system control because of the couplingof different time-scale phenomena. Hence, the importance of studying the integrated systemdynamics is critical. With the aim of safe operability and efficiency optimization, the cold air bypass valvewas considered an important actuator since it affects several key parameters and can be very effective incontrolling compressor surge. Two different tests were conducted using a cyber-physical approach. TheHybrid Performance (HyPer) facility couples gas turbine equipment with a cyber physical solid oxide fuelcell in which the hardware is driven by a numerical fuel cell model operating in real time. The tests wereperformed moving the cold air valve from the nominal position of 40% with a step of 15% up and down,while the system was in open loop, i.e. no control on turbine speed or inlet temperature. The effect of thevalve change on the system was analyzed and transfer functions were developed for several importantvariables such as cathode mass flow, total pressure drop and surge margin. Transfer functions can showthe response time of different system variables, and are used to characterize the dynamic response of theintegrated system. Opening the valve resulted in an immediate positive impact on pressure drop andsurge margin. A valve change also significantly affected fuel cell temperature, demonstrating that the coldair bypass can be used for thermal management of the cell.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

Nyckelord

SOFC

cyber-physical

transfer function

cathode airflow

Energy- and Environmental Engineering

energi- och miljöteknik

Publikations- och innehållstyp

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