Method and arrangement for controlling fuel feed in the fuel cell system

A method for producing electricity in a high temperature fuel cell system, comprising:

• feeding fuel to the high temperature fuel cell system by providing information on the fuel;
• generating information on fuel utilization in the fuel cells and oxygen to carbon ratio (O/C ratio) in the fuel cell system process flow;
• controlling loading of the fuel cells;
• controlling the feeding of fuel by taking into account the fuel utilization information as process feedback information, and by implementing a constraint function taking control of O/C ratio by restricting a first control output when said O/C ratio deviates from an allowed range by falling below a minimum target value in the allowed range;
• and
• controlling loading of the fuel cells by implementing a constraint function taking control of fuel utilization by restricting a second control output when said fuel utilization deviates from an allowed range by exceeding a target value in the allowed range.

A high temperature fuel cell system for producing electricity with plural fuel cells, each fuel cell having an anode side, a cathode side, and an electrolyte between the anode side and the cathode side, the high temperature fuel cell system comprising:

• a feeder that feeds fuel to the fuel cells and for providing information on the fuel;
• a processor that generates information about fuel utilization in the fuel cells and oxygen to carbon ratio (O/C ratio) in the fuel cell system process;
• an active controller that controls a loading of the fuel cells;
• a first closed loop controller that controls said fuel feeding means by taking into account the fuel utilization information as process feedback information, and by implementing a constraint function taking control of O/C ratio by restricting output of the first controller when said O/C ratio deviates from an allowed range by falling below a minimum target value in the allowed range;
• and
• a second controller that controls the active controller by implementing a constraint function taking control of fuel utilization by restricting output of the second controller when said fuel utilization deviates from an allowed range by exceeding a target value in the allowed range.