System and method for controlling temperature of fuel cell stack

A method for controlling a temperature of a fuel cell stack, comprising:

• performing a low output avoidance mode to allow a power converter to reduce a voltage upper bound of a bus terminal, when a cooling water outlet temperature is equal to or less than a preset third temperature while an output normal mode in which the voltage upper bound of the bus terminal between an output terminal of the fuel cell stack and the power converter has a predetermined value is performed;
• and
• performing the output normal mode when the cooling water outlet temperature is equal to or greater than a preset fourth temperature while the low output avoidance mode is performed,
• wherein the cooling water outlet temperature is a cooling water outlet temperature estimation value in a pump OFF mode which turns off a cooling water pump or operates the cooling water pump while reducing a rotation speed of the cooling water pump to be less than a preset reference rotation speed and is a sensing value of the cooling water outlet temperature in a pump normal mode which adjusts the rotation speed of the cooling water pump to be equal to or greater than the preset reference rotation speed and varies a revolutions per minute (rpm) based on the cooling water outlet temperature.

A method for controlling a temperature of a fuel cell stack, comprising:

• performing a pump OFF mode which turns off the cooling water pump or operates the cooling water pump while reducing the rotation speed of the cooling water pump to be less than the reference rotation speed, when a cooling water outlet temperature is equal to or less than a preset first temperature while a pump normal mode which adjusts a rotation speed of a cooling water pump to be equal to or greater than a preset reference rotation speed and varies revolutions per minute (rpm) based on the cooling water outlet temperature is performed;
• and
• performing a low output avoidance mode which allows a power converter to reduce a voltage upper bound of a bus terminal, when a cooling water outlet temperature calculation value is equal to or less than a preset third temperature while an output normal mode in which the voltage upper bound of the bus terminal between an output terminal of the fuel cell stack and the power converter has a predetermined value is performed,
• wherein the cooling water outlet temperature calculation value is a cooling water outlet temperature estimation value in the pump OFF mode and is a sensing value of the cooling water outlet temperature in the pump normal mode, and
• wherein the first temperature is equal to or greater than the third temperature.

A method for controlling a temperature of a fuel cell stack, comprising:

• performing a pump OFF mode which turns off a cooling water pump or operates the cooling water pump while reducing a rotation speed of the cooling water pump to be less than a preset reference rotation speed, when a cooling water outlet temperature is equal to or less than a preset first temperature and a heating value of the fuel cell stack is equal to or less than a preset first reference heating value while a pump normal mode which adjusts a rotation speed of the cooling water pump to be equal to or greater than a preset reference rotation speed and varies revolutions per minute (rpm) based on the cooling water outlet temperature is performed;
• and
• performing a low output avoidance mode which allows a power converter to reduce a voltage upper bound of a bus terminal, when a cooling water outlet temperature calculation value is equal to or less than a preset third temperature while an output normal mode in which the voltage upper bound of the bus terminal between an output terminal of the fuel cell stack and the power converter has a predetermined value is performed,
• wherein the first reference heating value is equal to or greater than a heating value of the fuel cell stack in the low output avoidance mode and the cooling water outlet temperature calculation value is a cooling water outlet temperature estimation value in the pump OFF mode and a sensing value of the cooling water outlet temperature in the pump normal mode.