Fuel cell and lithium iron phosphate battery hybrid powertrain with an ultracapacitor bank using direct parallel structure

In this study, a novel fuel cell-Li-ion battery hybrid powertrain using a direct parallel structure with an ultracapacitor bank is presented. In addition, a fuzzy logic controller is designed for the energy management of hybrid powertrain aimed at adjusting and stabilizing the DC bus voltage via a bidirectional DC/DC converter. To validate the Fuel cell-Li-ion battery-Ultracapacitor (FC-LIB-UC) hybrid powertrain and energy management strategies developed in this study, a test station powered by a 1 kW fuel cell system, a 2.8 kWh Li-ion battery pack and a 330 F/48.6 V ultracapacitor bank is designed and constructed on the basis of stand-alone module. Finally, an Urban Dynamometer Driving Schedule cycle is performed on this station and the experimental results show that: (i) the power distribution of FC system is narrowest and the power distribution of UC bank is widest during a cycle, and (ii) the FC system is controlled to satisfy the slow dynamic variation in this hybrid powertrain and the output of the LIB pack and UC bank is adjusted to meet fast dynamic load requirements. As a result, the proposed FC-LIB-UC hybrid powertrain can take full advantage of three kinds of energy sources.