Condensate water drain control system and method for fuel cells

Abstract

A condensate water drain control system for fuel cells includes a fuel cell stack configured to generate electric power through chemical reaction, a fuel supply line configured to recirculate fuel discharged from the fuel cell stack together with fuel introduced from a fuel supply valve, a water trap located in the fuel supply line, the water trap being configured to collect condensate water discharged from the fuel cell stack, a drain valve configured to discharge the condensate water stored in the water trap to the outside when opened, and a drain controller configured to determine whether the fuel supply valve is controlled such that pressure in the fuel supply line is maintained before the drain valve is opened and to sense discharge of fuel from the fuel supply line through the drain valve upon determining that the pressure is maintained.

What is claimed is: 
     
         1 . A condensate water drain control system for fuel cells, the condensate water drain control system comprising:
 a fuel cell stack configured to generate electric power through chemical reaction in the fuel cell stack;   a fuel supply line configured to recirculate fuel discharged from the fuel cell stack together with fuel introduced from a fuel supply valve so as to be supplied to the fuel cell stack;   a water trap located in the fuel supply line, the water trap being configured to collect condensate water discharged from the fuel cell stack;   a drain valve located in an outlet of the water trap, the drain valve being configured to discharge the condensate water stored in the water trap to an outside when opened; and   a drain controller configured to determine whether the fuel supply valve is controlled such that pressure in the fuel supply line is maintained before the drain valve is opened and to sense discharge of fuel from the fuel supply line through the drain valve upon determining that the pressure is maintained.   
     
     
         2 . The condensate water drain control system according to  claim 1 , wherein the drain controller determines whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained based on a change in pressure in the fuel supply line or a change in opening degree of the fuel supply valve in a state in which the drain valve is closed. 
     
     
         3 . The condensate water drain control system according to  claim 2 , further comprising:
 a pressure sensor configured to sense the pressure in the fuel supply line, wherein   the drain controller determines whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained based on a change in a pressure signal sensed by the pressure sensor.   
     
     
         4 . The condensate water drain control system according to  claim 2 , further comprising:
 a fuel tank configured to store fuel in the fuel tank; and   a fuel supply controller configured to control the opening degree of the fuel supply valve such that the pressure in the fuel supply line follows a target pressure, wherein   the drain controller determines whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained based on a change in a signal for controlling the opening degree of the fuel supply valve from the fuel supply controller.   
     
     
         5 . The condensate water drain control system according to  claim 4 , wherein the fuel supply controller fixes the target pressure in the fuel supply line in a case in which opening of the drain valve is required. 
     
     
         6 . The condensate water drain control system according to  claim 1 , further comprising a power controller configured to fix required current or required power of the fuel cell stack in a case in which opening of the drain valve is required. 
     
     
         7 . The condensate water drain control system according to  claim 6 , further comprising:
 a battery configured to be assist generation of electric power by the fuel cell stack while being charged or discharged by electric power generated by the fuel cell stack; and   a load connected to the fuel cell stack and the battery to receive electric power from the fuel cell stack or the battery,   wherein the power controller controls the required current or required power of the fuel cell stack based on required power of the load or a charge amount of the battery, and controls charging and discharging of the battery in order to satisfy the required power of the load in a case in which the required current or required power of the fuel cell stack is fixed.   
     
     
         8 . The condensate water drain control system according to  claim 1 , wherein the drain controller senses the discharge of fuel from the fuel supply line through the drain valve based on a change in pressure in the fuel supply line or a change in opening degree of the fuel supply valve in a state in which the drain valve is open. 
     
     
         9 . The condensate water drain control system according to  claim 1 , wherein:
 the drain valve is configured to have a purge function of purging fuel in the fuel supply line to the outside when opened, and   the drain controller measures a purge time from a point in time when the discharge of fuel from the fuel supply line through the drain valve is sensed to a point in time when the drain valve is closed.   
     
     
         10 . The condensate water drain control system according to  claim 1 , further comprising a concentration estimator configured to estimate an amount purged by opening of the drain valve and to estimate concentration of fuel in the fuel supply line through reflection of the estimated purge amount. 
     
     
         11 . 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, which 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; and   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.   
     
     
         12 . The condensate water drain control method according to  claim 11 , wherein the step of determining whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained comprises determining whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained based on a change in pressure in the fuel supply line or a change in opening degree of the fuel supply valve in a state in which the drain valve is closed. 
     
     
         13 . The condensate water drain control method according to  claim 11 , further comprising:
 determining whether opening of the drain valve is required before the step of determining whether the fuel supply valve is controlled such that the pressure in the fuel supply line is maintained; and   fixing a target pressure in the fuel supply line or fixing required current or required power of the fuel cell stack upon determining that opening of the drain valve is required.   
     
     
         14 . The condensate water drain control method according to  claim 11 , further comprising:
 measuring a purge time from a point in time when the discharge of fuel from the fuel supply line through the drain valve is sensed to a point in time when the drain valve is closed after the step of sensing the discharge of fuel;   estimating an amount purged by opening of the drain valve based on the measured purge time; and   estimating concentration of fuel in the fuel supply line through reflection of the estimated purge amount.   
     
     
         15 . A condensate water drain control system for fuel cells, the condensate water drain control system comprising:
 a fuel cell stack configured to generate electric power through chemical reaction in the fuel cell stack;   a fuel supply line configured to recirculate fuel discharged from the fuel cell stack together with fuel introduced from a fuel supply valve so as to be supplied to the fuel cell stack;   a water trap located in the fuel supply line, the water trap being configured to collect condensate water discharged from the fuel cell stack;   a drain valve located in an outlet of the water trap, the drain valve being configured to discharge the condensate water stored in the water trap to an outside when opened;   a drain controller configured to sense discharge of fuel from the fuel supply line through the drain valve; and   a fuel supply controller configured to control the fuel supply valve such that pressure in the fuel supply line is maintained when the drain valve is opened under control of the drain controller.