Optimal Load-Tracking Operation of Grid-Connected Solid Oxide Fuel Cells through Set Point Scheduling and Combined L1-MPC Control

• Main Authors: Siwei Han, Li Sun, Jiong Shen, Lei Pan, Kwang Y. Lee
• Format: Article
• Language: English
• Published: MDPI AG 2018-03-01
• Series: Energies
• Subjects: solid oxide fuel cells (SOFCs); grid-connected fuel cell; power control; set point scheduling; L1 adaptive control; Model Predictive Control (MPC)
• Online Access: http://www.mdpi.com/1996-1073/11/4/801

An optimal load-tracking operation strategy for a grid-connected tubular solid oxide fuel cell (SOFC) is studied based on the steady-state analysis of the system thermodynamics and electrochemistry. Control of the SOFC is achieved by a two-level hierarchical control system. In the upper level, optimal setpoints of output voltage and the current corresponding to unit load demand is obtained through a nonlinear optimization by minimizing the SOFC’s internal power waste. In the lower level, a combined L1-MPC control strategy is designed to achieve fast set point tracking under system nonlinearities, while maintaining a constant fuel utilization factor. To prevent fuel starvation during the transient state resulting from the output power surging, a fuel flow constraint is imposed on the MPC with direct electron balance calculation. The proposed control schemes are testified on the grid-connected SOFC model.