A bond graph model-based evaluation of a control scheme to improve the dynamic performance of a solid oxide fuel cell

A control strategy for a solid oxide fuel cell (SOFC) is developed in this paper to maintain required cell operating conditions while ensuring good fuel efficiency and satisfying the constraints on the transient performance. To verify the controller performance, a zero-dimensional true bond graph model of an SOFC system is developed which makes use of a C-field for two gas species in order to model the cathode and anode channel gases. Moreover, an existing R-field model has been extended for modeling of forced convection of a mixture of two gas species. The coupling between the chemical, thermal, mechanical and the hydraulic domains, which is encountered in a fuel cell system, is represented in a unified manner by using true bond graphs. The fuel utilization (FU) and the air utilization (AU) are interpreted in terms of the partial pressures of the gases. The static characteristics of the fuel cell obtained are in good agreement with the data from the literature. The dynamic response of the fuel cell to step changes in load current is obtained. From the simulations it is shown that all the control objectives are achieved by the proposed control system.