Patent ID: 8492041

Claim:
A solid oxide fuel cell system comprising: a fuel cell module comprising multiple fuel cell units; a fuel supply device configured to supply fuel to the fuel cell module according to a fuel supply function which defines a relationship between a demand for output power from a the fuel cell module and an amount of fuel supply to the fuel cell module for meeting the demand for output power; an oxidation gas supply device configured to supply oxidation gas to the fuel cell module; and a controller programed to control the amount of fuel supply from the fuel supply device, the controller comprising a degradation determining circuit programed to determine degradation of the fuel cell module, and a fuel correction circuit programed to correct the fuel supply function to adjust the amount of fuel supply from the fuel supply device, based on a result of determination performed by the degradation determining circuit, wherein the fuel correction circuit is programed to execute, when the fuel cell module is determined to have degraded, one of (i) an increasing correction mode in which the fuel supply function is corrected to increase the amount of fuel supply to the fuel cell module so that a maximum rated output power of the fuel cell module is maintained, and (ii) a decreasing correction mode in which the fuel supply function is corrected to decrease the maximum rated output power so that the fuel supply amount is reduced, and the solid oxide fuel cell system has a mode selection device which selects the increasing correction mode or the decreasing correction mode.