Control of the dual mode operation of generator/motor in SOFC/GT-based APU for extended dynamic capabilities

The integrated solid oxide fuel cell (SOFC)/gas turbine (GT) system is an appealing power generation solution for mobile applications from energy conversion efficiency point of view. The relatively poor dynamic capabilities of the SOFC/GT system, which are often the results of system characteristics and SOFC operation safety considerations, limit their widespread applications and must be enhanced to meet safe, efficient and fast load following requirements. To this end, the SOFC/GT system can be augmented by an energy storage unit (e.g., battery) and a dual operating generator/motor (G/M). This paper focuses on investigating the G/M dual mode operation and its implications on system transient performance and battery requirements. Active shaft load control is achieved to manage the load transients through: (a) pre-conditioning of the generator power for load step-up transients; (b) absorbing the excessive power by motoring operation for load step-down transients. By taking full advantage of the bi-directional operation of G/M, we show that better trade-offs between power tracking and thermal management can be achieved, power and energy requirements for the energy storage (battery) can be reduced, and overall system performance can be enhanced.

► SOFC/GT system augmented by battery and dual operating generator/motor (G/M).
► Pre-conditioning (of G/M load) strategy proposed for load step-up transients.
► Motoring operation to absorb the excessive power for load step-down transients.
► Enhanced system performance and loosened battery requirements by dual operating G/M.
► Better trade-offs between load following and thermal safety management achieved.