Interaction between proton exchange membrane fuel cells and power converters for AC integration

New aspects about steady-state and transient behaviours are considered in the relationships among the model variables for fuel cell (FC) stacks that are of great interest in the scientific environment. In this way, the most important variables are voltage, current, power, heat from cooling system, membrane temperature and hydrogen pressure. The transient model aims at reproducing FC variations of its internal resistance under distinct current levels. This current effect modifies the time response during load turning on/off conditions. Results from a modified FC model are presented and comparisons with real data are made. Additionally, these results are included in an analysis about the electrical interaction between FCs and converters as a cause of great concern among power electronics designers. As the number of such converters has significantly increased in the last few years, FC generation systems are steadily calling attention for operational problems related to their efficiency, stability and durability when DC/DC converters are connected across its terminals. Therefore design proceedings of a DC/DC converter associated to ´T´ filters to avoid fast current transitions caused by converter connection across the FC stack terminals are included. To deliver the energy produced by the FC system to the grid, it is presented, also, an analysis of a DC-AC converter used to improve power quality when the FC is, simultaneously, supplying load and grid.