Patent ID: 8906567

Claim:
A fuel cell system comprising: a fuel cell; a power storage unit that can be charged with electric power generated by the fuel cell; a power consuming device that consumes electric power from the fuel cell and from the power storage unit; a voltage conversion unit placed between the fuel cell and the power consuming device or between the power storage unit and the power consuming device; a signal generation unit programmed to generate an output command signal by superimposing a first sinusoidal wave signal onto an output target signal for the fuel cell; a calculation unit programmed to calculate frequency characteristics of a second sinusoidal wave superimposed onto an output value contained in an output signal output from the fuel cell according to the output command signal generated by the signal generation unit; and a judgment unit programmed to judge that a failure occurs in the voltage conversion unit if a value of the frequency characteristics calculated by the calculation unit is less than a lower limit threshold value of an allowable range established based on frequency characteristics of the first sinusoidal wave signal.