Power generation stopping method for fuel cell system and fuel cell system

A fuel cell system comprising:

• a fuel cell to generate electric power via electrochemical reaction between fuel gas and oxidant gas;
• a fuel gas supplier to supply the fuel gas into the fuel cell;
• an oxidant gas supplier to supply the oxidant gas into the fuel cell;
• a coolant supplier to supply a coolant into the fuel cell;
• and
• circuitry configured to
• control the fuel cell to continue generating the electric power during a post running period after the fuel cell system is ordered to stop;
• control the coolant supplier to supply the coolant at a first flow rate to the fuel cell during the post running period until temperature of the fuel cell reaches a threshold temperature;
• and
• control the coolant supplier to supply the coolant to the fuel cell at a second flow rate larger than the first flow rate during the post running period after the temperature of the fuel cell has reached the threshold temperature.