Control structure design and dynamic modeling for a solid oxide fuel cell with direct internal reforming of methane

• The control structure design for SOFCs with direct internal reforming of methane is presented.
• The controllability property of the SOFC is analyzed based on a relative gain array.
• The fuel cell temperature is the active constraint that should be controlled at its optimal point.
• The flow rates of air and fuel are inputs to control the cell temperature and the concentration of fuel.

This paper presents the control structure design and controllability analysis for a solid oxide fuel cell (SOFC) operating on direct internal reforming of methane. A nonlinear dynamic, lumped parameter model of the SOFC used to analyze its steady-state and dynamic behavior is presented. To achieve an efficient control system, the control structure of the SOFC operated under optimal operating conditions is considered to identify good controlled variables. The obtained results are employed to investigate the controllability properties of the SOFC by considering a relative gain array (RGA). The results of the control structure design show that the fuel cell temperature is the active constraint that should be controlled at its optimal point and the good self-optimizing variable is found to be the fraction of methane at the outlet. Regarding the controllability analysis based on the RGA, the inlet molar flow rates of air and fuel are manipulated variables to control the cell temperature and the content of fuel, respectively. Performance of the SOFC control using a conventional control methodology with the designed control structure is studied.