FUEL CELL SYSTEM AND CONTROL METHOD THEREOF

A fuel cell system comprises a fuel cell stack (10), radiator (51), stack side cooling water passage (53s), radiator side cooling water passage (53r), bypass cooling water passage (53b), deionizer (55), stack side cooling water pump (56s), and radiator side cooling water pump (56r). The pumps (56s), (56r) are formed from rotary pumps able to change directions and amounts of cooling water discharged by changes of drive speeds. Drive speeds of the pumps are controlled to thereby control an amount of cooling water flowing through the radiator side cooling water passage, an amount of the cooling water flowing through the stack side cooling water passage, and a direction and an amount of the cooling water flowing through the bypass cooling water passage. The disclosure also relates to a method of control of the fuel cell system.