Current control in PEMFC hybrid system using DC/DC buck-boost converter

A hybrid fuel cell system includes a fuel cell unit, a battery and/or a super-capacitor. A super-capacitor is a passive element, it is easily grasp the SOC state, but battery is difficult to determine the exact SOC state causing break by excessive charging and discharging. In order to resolve this problem, the hybrid fuel cell system utilizes the bi-directional dc/dc converter for battery protection by managing the battery charging and discharging. As a bi-directional converter is necessary to increase overall performance in the fuel cell vehicle application to cope with fluctuating load, a dc/dc bi-directional converter is expensive and complicated to control. This study presents the simple dc/dc buck-boost converter topology in the fuel cell hybrid system which has small load variations.