FUEL CELL SYSTEM AND METHOD OF OPERATING THE SAME

A fuel cell system (100) includes: a reformer (1) configured to generate a hydrogen-containing gas through a reforming reaction by using a raw material and steam; a raw material supply device (2) configured to supply the raw material to the reformer; a steam supply device (3, 4) configured to supply the steam to the reformer; a temperature detector (5) configured to detect a temperature of the reformer; a fuel cell (7) configured to generate electric power by using the hydrogen-containing gas; a combustor (6) configured to combust the hydrogen-containing gas discharged from the fuel cell to heat the reformer; and a controller (10) configured to, while controlling the raw material supply device such that the temperature detected by the temperature detector becomes a target temperature, control the steam supply device such that a change rate of a steam supply amount to the reformer becomes less than a change rate of a raw material supply amount to the reformer.