Two possible integration circuits were considered in this project: a buck converter circuit and a boost converter circuit.
While they donít offer some advantages of more complex DC to DC converters such as isolation and bi-directional power flow, they are very efficient and simple. They have a very low part count and are therefore also the cheapest solution. The properties of the fuel cell and battery bank must also be taken into consideration in designing the integration circuit. The battery bank voltage can never exceed a maximum value to prevent damage to the bank. Current ripples at frequencies lower than 100 KHz will damage or decrease the lifetime of PEM fuel cells. The current ripple comes from the voltage ripple on the battery bank, and is primarily due to the inverters that produce a 120 Hz ripple of significant magnitude. As other loads are added or removed from the battery bank other current ripples are also introduced. An important role of the DFCIC circuit was to be able to quickly respond to changes in the battery bank voltage to maintain a constant current through the fuel cell.
Both the BUCK and BOOST solutions would be adequate integration circuits, however, which circuit is superior? Both have an equal part count, and operate in a very similar fashion. It was decided that both circuits should be simulated and the design which best met the design criteria should be built.