Multivariable control of hydrogen concentration and fuel over-pressure in a polymer electrolyte membrane fuel cell with anode re-circulation

In this work, a multivariable control approach for maintaining the hydrogen concentration as well as the differential pressure between the anode and cathode compartments, known as the fuel over-pressure, in a polymer electrolyte membrane fuel cell (PEMFC) with anode re-circulation is explained. To achieve the control objectives and to meet the problem constraints, a model predictive control approach is used which utilizes two proportional control valves as actuators; one for the fuel over-pressure regulation, the pressure control valve, and the other for controlling the hydrogen concentration, the purge valve. A unique approach for dynamic purging is proposed. Using the pneumatic representation of the variables, the entire anode side of the PEMFC is modeled and experimentally verified for a 9-cell Ballard PEM fuel cell stack with anode re-circulation. Using the linearized model, the controller performance with regard to load current changes and nitrogen crossover flow has been evaluated through numerical simulations. The results show the effectiveness of the proposed control approach to satisfy the problem objectives.