Fuel cell system and control method thereof

A fuel cell system for generating electric power by supplying fuel gas to an anode of a fuel cell via a fuel gas supply flow path and supplying an oxygen-containing gas to a cathode of the fuel cell via an oxygen-containing gas supply flow path, the fuel cell system comprising:

• a fuel exhaust gas flow path configured to allow fuel exhaust gas discharged from the anode to flow therethrough;
• a gas-liquid separator into which the fuel exhaust gas flows via the fuel exhaust gas flow path, the gas-liquid separator being configured to separate the fuel exhaust gas into a gas and a liquid;
• a circulation flow path that is connected to the fuel gas supply flow path via a connecting section so as to cause a gas discharge port of the gas-liquid separator and the fuel gas supply flow path to be in communication with each other;
• a connecting flow path configured to cause a liquid discharge port of the gas-liquid separator to be in communication with the oxygen-containing gas supply flow path, via a drain valve;
• a distribution flow path configured to cause the fuel gas supply flow path or the circulation flow path to be in communication with the oxygen-containing gas supply flow path;
• and
• an opening and closing valve configured to open and close the distribution flow path.