Experimental Validation of a Sensitivity-Based Observer for Solid Oxide Fuel Cell Systems

Fuel cells can be used to convert the chemical energy of fuel directly into electric energy. The thermodynamic and electrochemical processes involved in such systems are described by a large variety of parameters affecting the system states. These are the temperatures inside the fuel cell stack as well as partial pressures of gases and the electrical voltage. In general, it is not possible to measure all internal system states, disturbances, and parameters. However, knowledge about these quantities is necessary to implement efficient control strategies. Therefore, a novel state and parameter estimation procedure is described in this paper. The goals are the identification of parameters at non-stationary operating points as well as the reconstruction of the internal states of fuel cell systems during the heat-up phase. Using a procedure for sensitivity analysis with a suitable performance criterion, system states and disturbances can be estimated in real-time on a test rig available at the Chair of Mechatronics, University of Rostock. Experimental results show the practical applicability of the above-mentioned method which can be generalized to systems with a variable spatial resolution.