Patent ID: 8263275

Claim:
A fuel cell system including: a fuel cell; an electric accumulator interposed in a discharge path of the fuel cell and connected in parallel to the fuel cell; and a DC/DC voltage converting device connected between the electric accumulator and the fuel cell, the DC/DC voltage converting device having a reactor; wherein the fuel cell system includes a control unit, the control unit further comprising: a voltage instruction signal generating section for superimposing an impedance measuring signal on an output target voltage of the DC/DC voltage converting device and outputting the voltage to the DC/DC voltage converting device, when an impedance of the fuel cell is measured by using an AC impedance method; a state detection section for judging a state of a response characteristic of the DC/DC voltage converting device during the impedance measurement; a superimposed signal control section programmed to control an amplitude of the impedance measuring signal based on the state of the response characteristic of the DC/DC voltage converting device judged by the state detection section, a measuring device for measuring a reactor current of the DC/DC voltage converting device; and a first storage device for storing a response characteristic map to judge from the reactor current of the DC/DC voltage converting device whether or not the response characteristic of the DC/DC voltage converting device is in a stable state; wherein the state detecting section compares a measurement result of the measurement device with the response characteristic map to judge the stable state of the response characteristic; and the superimposed signal control section programmed to perform a control so that the amplitude of the impedance measuring signal in a case where the response characteristic of the DC/DC voltage converting device is in an unstable state is larger than that of the impedance measuring signal in a case where the response characteristic of the DC/DC voltage converting device is in the stable state.