Fuel cell system

A fuel cell system comprising:

• a unit cell that generates electric power by an electrochemical reaction between a fuel gas supplied to an anode of the unit cell and an oxidant gas supplied to a cathode of the unit cell;
• a fuel cell that is formed with the unit cell;
• a voltage measurement portion that measures a voltage of the unit cell;
• a power generation control portion that restrains power generation of the fuel cell when the voltage of the unit cell is below a predetermined threshold voltage;
• an IR resistance measurement portion that measures an IR resistance of the unit cell;
• and
• a threshold voltage setting portion that sets the predetermined threshold voltage based on the IR resistance and a load current,
• wherein the threshold voltage setting portion stores map data that approximates current-voltage characteristics when the fuel gas is insufficiently supplied to the anode, and sets the predetermined threshold voltage based on the voltage with respect to the load current obtained from the map data and an IR loss calculated from the IR resistance and the load current.

A fuel cell system comprising:

• a unit cell that generates electric power by an electrochemical reaction between a fuel gas supplied to an anode of the unit cell and an oxidant gas supplied to a cathode of the unit cell;
• a fuel cell that is formed with the unit cell;
• a voltage measurement portion that measures a voltage of the unit cell;
• a power generation control portion that restrains power generation of the fuel cell when the voltage of the unit cell is below a predetermined threshold voltage;
• an IR resistance measurement portion that measures an IR resistance of the unit cell;
• and
• a threshold voltage setting portion that sets the predetermined threshold voltage based on the IR resistance and a load current,
• wherein the threshold voltage setting portion stores map data that approximates current-voltage characteristics at a plurality of cell temperatures when the fuel gas is insufficiently supplied to the anode, and sets the predetermined threshold voltage based on the voltage with respect to the load current and the cell temperature obtained from the map data and an IR loss calculated from the IR resistance and the load current.

A fuel cell system comprising:

• a unit cell that generates electric power by an electrochemical reaction between a fuel gas supplied to an anode of the unit cell and an oxidant gas supplied to a cathode of the unit cell;
• a fuel cell that is formed with the unit cell;
• a voltage measurement portion that measures a voltage of the unit cell;
• a time measuring portion that measures the time after the unit cell voltage has dropped below a predetermined threshold voltage and that determines if the elapsed time has exceeded a permissible time;
• a power generation control portion that restrains power generation of the fuel cell when the voltage of the unit cell is below the predetermined threshold voltage and the permissible time is exceeded;
• a cell temperature measurement portion that measures a temperature of the unit cell;
• a threshold voltage setting portion that sets the predetermined threshold voltage based on the measured temperature of the unit cell;
• and
• an oxidant gas supply control portion that insufficiently supplies the oxidant gas to the fuel cell with respect to a required amount of the oxidant gas from the load current,
• wherein the threshold voltage setting portion stores map data that predicts a temperature dependency of an IR resistance of the unit cell, and sets the predetermined threshold voltage based on an IR loss calculated from the load current and the IR resistance with respect to the cell temperature obtained from the map data.

A fuel cell system comprising:

• a unit cell that generates electric power by an electrochemical reaction between a fuel gas supplied to an anode of the unit cell and an oxidant gas supplied to a cathode of the unit cell;
• a fuel cell that is formed with the unit cell;
• an oxidant gas supply control portion that switches between a first supplying mode that sufficiently supplies the oxidant gas to the fuel cell in accordance with a required amount of the oxidant gas from the load current and a second supplying mode that insufficiently supplies the oxidant gas to the fuel cell in accordance with the required amount of the oxidant gas;
• a voltage measurement portion that measures a voltage of the unit cell;
• a power generation control portion that restrains power generation of the fuel cell when the voltage of the unit cell is below a predetermined threshold voltage;
• and
• a threshold voltage setting portion that sets the predetermined threshold voltage in accordance with the supplying mode of the oxidant gas.

A fuel cell system comprising:

• a unit cell that generates electric power by an electrochemical reaction between a fuel gas supplied to an anode of the unit cell and an oxidant gas supplied to a cathode of the unit cell;
• a fuel cell that is formed with the unit cell;
• a voltage measurement portion that measures a voltage of the unit cell;
• a unit cell voltage control portion that recovers the voltage of the unit cell when the voltage of the unit cell falls to a predetermined threshold voltage by reducing the load current of the fuel cell;
• an oxidant gas supply portion that supplies the oxidant gas to the fuel cell;
• an oxidant gas supply control portion that switches between an amount of the supply of the oxidant gas in accordance with a first power generation efficiency of the fuel cell and an amount of the supply of the oxidant gas in accordance with a second power generation efficiency that is lower than the first power generation efficiency;
• and
• a threshold voltage setting portion that sets the predetermined threshold voltage in accordance with the power generation efficiency of the fuel cell,
• wherein the predetermined threshold voltage for the second power generation efficiency is lower than the predetermined threshold voltage for the first power generation efficiency.