Fuel cell system

A fuel cell system, comprising:

• a fuel cell configured to generate power using a fuel gas and an oxygen-containing gas;
• an oxygen-containing gas supply configured to supply the oxygen-containing gas to the fuel cell;
• a fuel supply configured to supply the fuel gas to the fuel cell;
• a power regulator configured to regulate supply of a current generated in the fuel cell to a load;
• and
• a controller configured to control at least one of the oxygen-containing gas supply or the fuel supply, and the power regulator,
• wherein the controller includes a plurality of relational expressions predefined and representing a relationship between a generation power level of the fuel cell and at least one of an air utilization or a fuel utilization,
• wherein the controller is configured to selects at least one of the plurality of relational expressions based on an increase rate of the current set by the power regulator, and
• wherein the controller is configured to control operation of the fuel cell system based on the selection of at least one of the plurality of relational expressions.