FUEL CELL SYSTEM AND METHOD OF CONTROLLING FUEL CELL SYSTEM

A fuel cell system according to the present invention includes: a hydrogen generator (2); a burner (3); an air supply device (6); a fuel cell (1); a condenser (4) configured to condense an exhaust reducing gas to recover condensed water, the exhaust reducing gas being discharged from the fuel cell (1); a condensed water tank (7) configured to store the condensed water recovered by the condenser (4); a water level detector (22) configured to detect a water level in the condensed water tank (7); a degasifier (9) configured to remove a carbonic acid component contained in the condensed water by using an exhaust oxidizing gas discharged from the fuel cell (1); a water conveyance passage (8) configured to connect the condensed water tank (7) and the degasifier (9) and including a water sealing structure (8A) at a portion thereof; a water level changing unit configured to change the water level in the condensed water tank (7); and a controller (15), and the controller (15) causes the water level changing unit to change the water level in the condensed water tank (7), and when the water level detector (22) has detected the change of the water level, the controller determines that the water level detector (22) is normally operating.