An Efficiency Comparison of Fuel-Cell Hybrid Systems Based on the Versatile Buck–Boost Converter

This paper extends the use of the versatile buck-boost converter to power manage a parallel hybrid system topology as an alternative to the well-known serial hybrid (SH) topology and the most recent series-parallel hybrid (SPH) topology. These systems utilize a proton exchange membrane fuel cell as the primary source in combination with an auxiliary storage device (ASD), and the selected converter is in charge of the power management between the sources (fuel cell or ASD) and the load. Therefore, the converter has a very important role in the system since it is responsible of ensuring a dc-bus voltage regulation with a safe and reliable operation of the entire system while also guarantee a high power conversion efficiency. Hence, this is the third topology, where the coupled-inductor dc-dc buck-boost converter is studied to demonstrate and exploit its advantages such as noninverting voltage step-up and step-down, high efficiency, regulation of input and output currents and low ripple values, and the ability to change from input to output current regulation loop, suddenly and smoothly, and vice versa. In order to determine which topology (SH, PH, or SPH) exhibits the highest power conversion efficiency under a certain load profile, it is important to ensure a fair efficiency comparison that will only reflect the properties of the topology and not its individual components. Therefore, the same design criteria, the same control, and the same components were used for all the studied topologies. Simulation and experimental results have been validated on a 48-V 1200-W dc bus.