FUEL CELL SYSTEM, FUEL CELL CONTROL METHOD, AND FUEL CELL DETERMINATION METHOD

A fuel cell system includes: an input-amplitude-value obtain unit that obtains an amplitude value of an input value given to a fuel cell; an output-amplitude-value obtain unit that obtains an amplitude value of an output value output from the fuel cell; and an operation condition change unit that changes an operation condition of the fuel cell according to a comparison of an amplitude value of an input value obtained by the input-amplitude-value obtain unit and an amplitude value obtained by the output-amplitude-value obtain unit. Another fuel cell system includes: an input-amplitude-value obtain unit that obtains an amplitude value of an input value given to a fuel cell; an output-amplitude-value obtain unit that obtains an amplitude value of an output value output from the fuel cell; and a deterioration determination unit that determines deterioration of the fuel cell according to a comparison of an amplitude value of an input value obtained by the input-amplitude-value obtain unit and an amplitude value of an output value obtained by the output-amplitude-value obtain unit.