Power efficient operation of a PEM fuel cell system using cathode pressure and excess ratio by nonlinear model predictive control

Polymer electrolyte membrane (PEM) fuel cell systems convert chemical energy from hydrogen into electrical power via a reaction with oxygen. Fuel cells are highly efficient, nearly noiseless, and locally emission-free. However, safe and efficient operation requires special system temperatures, mass flow rates of the reaction gases, and a particular excess ratio and gas pressure on the anode and cathode. All values are current dependent and must fall within specific ranges for both stationary and dynamic loads. This paper deals with modeling fuel cell peripherals and with model predictive control (MPC) of gas pressures. This nonlinear MPC handles all kinds of dynamic load changes, while maximizing power efficiency. All experiments were verified on a test bench with a 4,4kW PEM fuel cell.