Condensate water drain control system and method for fuel cells

A condensate water drain control method for fuel cells, the condensate water drain control method comprising the steps of:

• determining, by a drain controller, whether a fuel supply valve is controlled such that pressure is maintained in a fuel supply line except for change as a result of discharge from the fuel supply line through a drain valve, wherein the fuel supply line is configured to recirculate fuel discharged from a fuel cell stack together with fuel introduced from the fuel supply valve so as to be supplied to the fuel cell stack;
• opening, by the drain controller, a drain valve located in an outlet of a water trap located in the fuel supply line, the water trap being configured to collect condensate water discharged from the fuel cell stack, the drain valve being configured to discharge condensate water stored in the water trap to an outside when opened;
• sensing, by the drain controller, discharge of fuel from the fuel supply line through the drain valve upon determining in the determining step that the pressure is maintained;
• differentiating a signal output from a fuel supply controller for controlling an opening degree of the fuel supply valve or calculating variation of an absolute value from a previous control value, by the drain controller;
• and
• controlling, by the drain controller, the fuel supply valve such that the pressure in the fuel supply line is maintained in a case in which the calculated differential value is maintained within a predetermined range for a period of time greater than or equal to a predetermined maintenance time;
• wherein the drain controller is further configured to sense that fuel has been discharged when a rate of change in the signal for controlling the opening degree of the fuel supply valve is greater than or equal to a predetermined rate of change.