Load-Tracking Performance of an Autonomous SOFC-Based Hybrid Power Generation/Energy Storage System

This paper focuses on the load-tracking performance of an autonomous hybrid power generation/energy storage system (PG/ESS) with two solid-oxide fuel cells (SOFCs), a diesel-engine generator (DEG), a battery ESS (BESS), two dc-dc converters, and a dc-ac inverter. The system can sustain PG to supply suddenly changed loads, one of which is an emergency load that must have uninterruptible power supply. This paper proposes a control scheme using the output dc current of the SOFC or the current magnitude of the ac load to modulate the hydrogen-flow rate of the SOFC. The PG of the two SOFCs can be adequately coordinated with the generated power of the DEG, the stored/released energy of the BESS, and the output power of the dc-ac inverter to maintain both frequency and voltage of the connected loads at the desired values. Time-domain simulated results of the studied hybrid system under four studied cases are performed and analyzed to validate the good load-tracking characteristics of the proposed SOFC-based hybrid PG/ESS feeding time-varying loads.