Exemplary embodiments are directed to a fuel cell system that is fed fuel and provided information on the fed fuel. The system generates information about fuel utilization in the fuel cells and oxygen to carbon ratio (O/C ratio) in the fuel cell system process and includes features for controlling a loading of the fuel cells. The fuel cell system also includes a first closed loop controller for 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 output of the first controller when said O/C ratio deviates from an allowed range, and a second controller for controlling active fuel cell loading by implementing a constraint function taking control of fuel utilization restricting output of the second controller when said fuel utilization deviates from an allowed range.