Fuel cell system and control method thereof

A fuel cell system comprising:

• a fuel cell stack having a fuel electrode and an oxidant electrode provided facing each other with an electrolyte membrane in between;
• a gas supply unit which supplies a fuel gas to the fuel electrode and supplies an oxidant gas to the oxidant electrode to cause the fuel cell stack to generate power;
• a circulation unit having a circulation passage to return an excess fuel gas, discharged from the fuel cell stack, to a fuel gas inlet port of the fuel cell stack;
• a gas discharge unit having an open/close valve which discharges a gas present on the fuel electrode from the circulation passage;
• and
• a control unit which calculates an integration value resulting from integration of a discharge gas flow rate from the open/close valve, which varies in accordance with a gas pressure of the fuel electrode and a temperature of the fuel gas, when the open/close valve is set in an open state, and controls the open/close valve in a closed state when the integration value becomes equal to or greater than a discharge threshold value.

A fuel cell system comprising:

• a fuel cell stack having a fuel electrode and an oxidant electrode provided facing each other with an electrolyte membrane in between;
• a gas supply unit which supplies a fuel gas to the fuel electrode and supplies an oxidant gas to the oxidant electrode to cause the fuel cell stack to generate power;
• a circulation unit having a circulation passage to return an excess fuel gas, discharged from the fuel cell stack to a fuel gas inlet port of the fuel cell stack;
• a gas discharge unit having an open/close valve which discharges a gas present on the fuel electrode from the circulation passage;
• and
• a control unit which controls an open/closed state of the open/close valve,
• wherein the control unit calculates an integration value resulting from integration of a value per unit time concerning a gas to be supplied to the fuel electrode, which varies in accordance with a gas pressure of the oxidant electrode and a temperature of the fuel cell stack, when the open/close valve is set in a closed state, and controls the open/close valve in an open state when the integration value becomes equal to or greater than an accumulation threshold value, and
• calculates an integration value resulting from integration of a discharge gas flow rate from the open/close valve, which varies in accordance with a gas pressure of the fuel electrode and a temperature of the fuel gas, when the open/close valve is set in an open state, controls the open/close valve in a closed state when the integration value becomes equal to or greater than a discharge threshold value, and sets an initial value of the integration value to be calculated in case of controlling the open/close valve in the open state lower as the temperature of the fuel cell stack when the open/close valve is operated to the closed state from the open state is higher.

A control method of a fuel cell system which comprises a fuel cell stack having a fuel electrode and an oxidant electrode provided facing each other with an electrolyte membrane in between, a gas supply unit which supplies a fuel gas to the fuel electrode and supplies an oxidant gas to the oxidant electrode to cause the fuel cell stack to generate power;

• a circulation unit having a circulation passage to return an excess fuel gas, discharged from the fuel cell stack, to a fuel gas inlet port of the fuel cell stack, and a gas discharge unit having an open/close valve which discharges a gas present on the fuel electrode from the circulation passage, comprising steps of:
• calculating an integration value resulting from integration of a discharge gas flow rate from the open/close valve, which varies in accordance with a gas pressure of the fuel electrode and a temperature of the fuel gas, when the open/close valve is set in an open state;
• and
• controlling the open/close valve in a closed state when the integration value becomes equal to or greater than a discharge threshold value.

A control method of a fuel cell system which comprises a fuel cell stack having a fuel electrode and an oxidant electrode provided facing each other with an electrolyte membrane in between, a gas supply unit which supplies a fuel gas to the fuel electrode and supplies an oxidant gas to the oxidant electrode to cause the fuel cell stack to generate power, a circulation unit having a circulation passage to return an excess fuel gas, discharged from the fuel cell stack, to a fuel gas inlet port of the fuel cell stack, a gas discharge unit having an open/close valve which discharges a gas present on the fuel electrode from the circulation passage, comprising steps of:

• calculating an integration value resulting from integration of a value per unit time concerning a gas to be supplied to the fuel electrode, which varies in accordance with a gas pressure of the oxidant electrode and a temperature of the fuel cell stack, when the open/close valve is set in a closed state;
• controlling the open/close valve in an open state when the integration value becomes equal to or greater than an accumulation threshold value;
• calculating an integration value resulting from integration of a discharge gas flow rate from the open/dose valve, which varies in accordance with a gas pressure of the fuel electrode and a temperature of the fuel gas, when the open/close valve is set in an open state;
• controlling the open/close valve in a closed state when the integration value becomes equal to or greater than a discharge threshold value;
• and
• setting an initial value of the integration value to be calculated in case of controlling the open/close valve in the open state lower as the temperature of the fuel cell stack when the open/close valve is operated to the closed state from the open state is higher.