Abstract: A fuel cell system includes a fuel cell stack in which a plurality of unit cells is stacked, a detection unit configured to detect a cell voltage of at least one of the unit cells, a converter configured to regulate an output current of the fuel cell stack, and a control device configured to control the converter. The control device executes current reduction processing for reducing the output current in a stepwise manner when the cell voltage detected by the detection unit is a negative voltage.

Abstract: A fuel cell system includes a fuel cell stack in which a plurality of unit cells is stacked, a detection unit configured to detect a cell voltage of at least one of the unit cells, a converter configured to regulate an output current of the fuel cell stack, and a control device configured to control the converter. The control device executes current reduction processing for reducing the output current in a stepwise manner when the cell voltage detected by the detection unit is a negative voltage.

Abstract: A fuel cell system includes a fuel cell stack in which a plurality of unit cells is stacked, a detection unit configured to detect a cell voltage of at least one of the unit cells, a converter configured to regulate an output current of the fuel cell stack, and a control device configured to control the converter. The control device executes current reduction processing for reducing the output current in a stepwise manner when the cell voltage detected by the detection unit is a negative voltage.

Abstract: A fuel cell has multiple cells, the multiple cells including a first cell having a first fuel gas flow path, and a second cell having a second fuel gas flow path and a sensor that measures a specific parameter value relating to a decrease in concentration of fuel gas in the second fuel gas flow path.

Abstract: A fuel cell stack includes: a first cell having a first fuel gas flow path; and a second cell having a second fuel gas flow path constructed to have a specific flow path structure having a higher potential for a decrease in concentration of a fuel gas than that of the first fuel gas flow path during power generation. A sensor is located on the second cell to detect a decrease in concentration of the fuel gas during power generation. In one exemplified structure, a groove formed on an anode separator of the second cell as the second fuel gas flow path has a restriction element to narrow the sectional area of flow passage. A hydrogen concentration sensor is located in a non-narrowed area in the downstream of the restriction element having a lower pressure level. Impurity gas discharge control discharges an anode off gas out of the fuel cell stack, in response to detection of a decrease in hydrogen concentration to or below a preset reference level by the hydrogen concentration sensor.