Fuel cell system and method for limiting current thereof

A fuel cell system, comprising:

• a fuel cell having a plurality of cells;
• a cell monitor for detecting cell voltages of the cells;
• a deviation calculator for calculating a deviation between the lowest cell voltage in the detected cell voltages and a predetermined lowest-cell-voltage acceptable value;
• a PI computation section for calculating a current-limit value through PI compensation based on the calculated deviation;
• and
• a supply current calculator for calculating a supply current by subtracting the current-limit value from a system-request current requested by the system, wherein:
• the supply current calculator prohibits the subtraction of the current-limit value when the lowest cell voltage is equal to or higher than the lowest-cell-voltage acceptable value;
• and
• the PI compensation section sets different values between gains in the PI compensation when the lowest cell voltage is lower than the lowest-cell-voltage acceptable value and gains in the PI compensation when the lowest cell voltage is equal to or higher than the lowest-cell-voltage acceptable value.

A method for limiting a current in a fuel cell system that includes:

• a fuel cell having a plurality of cells;
• and a controller for computing a supply current to be supplied to a load based on a system-request power requested by a system, the method comprising steps, performed by the controller, of:
• computing the system-request power requested by the system;
• detecting the lowest cell voltage in the cells;
• judging whether or not the lowest cell voltage falls below a predetermined lowest-cell-voltage acceptable value;
• and
• performing, when the lowest cell voltage falls below the lowest-cell-voltage acceptable value, a compensation computation for limiting the supply current through a PI compensation using, as a reference value, a current value of the system-request current as of the time when the lowest cell voltage falls below the predetermined lowest-cell-voltage acceptable value,
• wherein values for gains in the PI compensation for limiting the supply current are different from values for gains in the PI compensation for restoring the supply current.