The present paper discusses the dynamic behavior of a solid oxide fuel cell (SOFC) system under the load-following operation with adoption of four control schemes, conducting dynamic simulation. The dynamic modeling of the SOFC, which consists of a cell stack and reformer, was firstly carried out to predict the dynamic behavior to load change. Secondly, a control circuit model was implemented into the dynamic model. For the load-following operation, the SOFC DC power output, operating temperature, fuel utilization factor and steam-to-carbon ratio were employed as the controlled variables. The current density, air, fuel and steam flow rates were chosen for manipulated variables in the SOFC control schemes for the load-following operation. Feedback control methodology was adopted to achieve adequate operation of the SOFC. The dynamic simulation was conducted by assuming the rapid change of the power. The simulation results showed the capability of the multivariable control of the SOFC operation. The cell temperature control is quite important, however the direct measure of the cell temperature is difficult. In the proposed control scheme, the air temperature at the cathode outlet is employed as a controlled variable, and then the cell temperature can be indirectly adjusted with controlling the cathode outlet temperature.
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