Multi-variable Robust Control of Proton Exchange Membrane Fuel Cell Pressure Using Nonlinear Model

PEMFC is a nonlinear, multiple-input and output, and strongly coupled dynamic system. A nonlinear fuel cell system dynamic model that is suitable for control study is presented. In designing PEMFC control, the main focus is on the control of hydrogen and oxygen partial pressures which can avoid unwanted pressure fluctuation and prevent the membrane electrode assemblies (MEAs) from collapsing by minimizing the pressure difference between the anode and the cathode. According to ideal gas law, mass continuity is used to balance the partial pressure of four elements (Hydrogen, Oxygen, Nitrogen and water). A MIMO dynamic model that is appropriate for developing a nonlinear robust controller is proposed. The state feedback exact linearization (a well-known nonlinear approach) with the dynamic extension algorithm which is applied todesign the proposed H-infinity robust controller, based directly on the nonlinear dynamic PEMFC model. From the system point of view, partial pressure of PEMFC can be modeled as a two-input two-output system, where the inputs are control variable of anode and cathode, and the outputs are partial pressures of hydrogen and oxygen. The results show that, this nonlinear control model is robustness to step and pulse disturbance. In this model amplitude of alternative disturbances decreased from 10 atm to 0.25 atm. Also the pressure of each electrode tracks various input pressure profile with negligible steady-state error. On the other hand the electrode pressure does not depend on the variation of constrained electrical current profile by consumer in the PEM fuel cells.

Keywords:

PEM Fuel Cell , Robust Control , H-Infinity , State Feedback , Dynamic Extension