On control concepts to prevent fuel starvation in solid oxide fuel cells

Several methods to prevent fuel starvation in solid oxide fuel cells are developed and investigated. Fuel starvation can occur during transients, if fuel is consumed in the fuel cell faster than it can be supplied by the fuel processing and delivery system. It is demonstrated through simulation that fuel depletion can occur in the fuel cell if no corrective action is employed. Fuel starvation can be prevented by the use of rate limiters, reference governors, and modifications to the fuel-flow controller. The various methods to prevent fuel depletion within the fuel cell are developed and compared. Analysis indicates that reference governors can avoid hydrogen depletion with much less of an impact on transient load following capability than rate limiters. Hence, various reference governors ranging in level of fidelity were developed and compared for performance. It was further demonstrated that with knowledge of the fuel preprocessor response, it is possible to manipulate the fuel flow to minimize reformer flow dynamics, minimizing the need to govern the fuel cell transient capability.