Thermal and Air Management of an Open Cathode PEM Fuel Cell using Sliding Mode Control

The paper presents a simplified nonlinear model for an open cathode proton exchange membrane fuel cell (PEMFC) and its control by using three different strategies. The model presented uses four state variables. The mass flow of oxygen, hydrogen flow, water and temperature were taken to be the critical dynamics in the system. The unknown parameters were estimated using the experimental data of a 1.2 kW PEMFC. The simplified model showed good agreement with experimental results. Control schemes were implemented to control the stack temperature of the PEMFC. The proportional (P) and proportional-integral (PI) Control performed well but had a poorer response compared to the sliding mode control (SMC) scheme. The study of the different control schemes reveals the dangers of singularly controlling either the oxygen excess ratio or the temperature. Results show the best control is achieved when the excess ratio is control through the reference temperature. The study also compares the parasitic losses from the fans caused by the different controllers. Overall the results provide a good insight into designing a robust control system for an open cathode PEMFC for faster response and greater durability.