FUEL CELL SYSTEM AND FUEL CELL SYSTEM CONTROL METHOD

A fuel cell system includes a fuel cell stack and a battery that are connected to a high voltage line in parallel, a converter connected to the high voltage line and the battery while being located therebetween and configured to control a voltage at the high voltage line, and a controller, in a stop control mode of the fuel cell stack, when an error occurs in a drop control of an output voltage of the fuel cell stack, the controller dropping the voltage at the high voltage line under the output voltage of the fuel cell stack by the converter to drop the output voltage of the fuel cell stack.