Control strategy for a solid oxide fuel cell and gas turbine hybrid system

This paper presents a multi-loop control strategy for a SOFC/GT hybrid system. A detailed dynamic model of the system is presented and its part-load performance is studied. The control objectives are discussed, with the main issue being a fairly constant fuel cell temperature under all conditions. Based on the system configuration and part-load performance, input and output variables of the control system are detected. Control cycles are introduced and their design is discussed. The responses of the resulting system on load changes, external disturbances as well as malfunction and degradation incidents are investigated. The system is stable under all incidents. An error in fuel flow measurement or assumed fuel quality provokes a steady-state fuel cell temperature offset. For a degraded system, it may be advisable to readjust the control system to the new characteristics.