Coordinated Control Strategies for Fuel Cell Power Plant in a Microgrid

Solid-oxide fuel cell (SOFC) power plant plays a vital role in a hybrid alternative energy based microgrid due to its reliability and flexibility in power supply. However, the control of SOFC is challenging in terms of providing a fast load tracking while maintaining the fuel utilization rate within a safe range. To this end, this paper builds two basic coordinated control strategies (CCS) for power management of SOFC-based microgrid. The first is “Fuel Cell follows Inverter” scheme, where fast tracking is preferred while SOFC may operate on the edge of the safety range. The second is “Inverter follows Fuel Cell” scheme, where high security is guaranteed by sacrificing performance in load tracking. To obtain a robust and simple scheme, energy balance principle is used in CCS such that PI controller is sufficient to fulfill the basic duties. Moreover, a simple supervisory control strategy is proposed for microgrid to provide a reasonable power reference for SOFC. The control system is designed and tuned based on an SOFC plant with inverter's average model. The efficiency of the proposed strategies is validated via a grid-connected SOFC/photovoltaic microgrid.