Model-based control of an integrated fuel cell and fuel processor with exhaust heat recirculation

In this paper, we consider the dynamic and controlled operation of an integrated natural gas fuel processor system (FPS), a proton exchange membrane fuel cell (PEM-FC), and a catalytic burner (CB). The FC provides power based on the electrochemical reaction of hydrogen. The FPS generates the hydrogen from natural gas through catalytic partial oxidation (CPOX) and the CB provides the energy for preheating the FPS inlet flows by burning any excess hydrogen from the FC exhaust. The coupling of these three systems poses a challenging optimization and control problem. Optimization is performed to generate the air and fuel flow intake setpoints to the FPS for various load levels. The optimal flow setpoints are used in a static feedforward map that ensures maximum efficiency at steady state. Linear quadratic techniques are then used to develop a controller to mitigate hydrogen starvation in the fuel cell and regulate CPOX reactor temperatures. We show in simulations that the designed observer-based feedback controller, which relies on temperature measurements of two reactors, speeds up the transient response fourfold, as compared to the baseline when the static feedforward controller is employed.