Reliable Sliding Mode Approaches for the Temperature Control of Solid Oxide Fuel Cells with Input and Input Rate Constraints

Abstract High-temperature fuel cells are promising devices to generate both electric energy and process heat in a decentralized energy supply grid. On the one hand, fuel cells have a relatively high eficiency concerning conversion of chemical energy. On the other hand, as far as solid oxide fuel cells (SOFCs) are concerned, they can also operate with a large variety of gas mixtures, involving hydrogen, methane, carbon monoxide, and carbon dioxide. This results from the fact that SOFCs are capable to perform an internal gas reformation. However, the variability of the required electric power — to be provided by the SOFC — leads to the necessity to develop reliable, real-time capable control strategies. In contrast to linear stateof-the-art approaches, these procedures should be applicable within wide ranges of operating temperatures. Moreover, the controllers have to be designed in such a way that they are robust against uncertain parameters and external disturbances. Finally, they have to guarantee that upper bounds for the admissible cell temperature are guaranteed not to be violated. For these reasons, this paper presents extensions of interval-based sliding mode controllers employing a novel barrier Lyapunov function technique. These controllers provide a way to consider one-sided state constraints as well as input and input rate constraints.