Abstract
A laboratory-scale passive hybrid power system for transportation applications is constructed and tested in this study. The hybrid power system consists of a fuel cell stack connected with a diode, a lithium-ion battery pack connected with a DC/DC power converter and another diode. The power converter is employed to regulate the output voltage of the battery pack. The dynamic responses of current and voltage of the stack to the start-up and acceleration of the load are experimentally investigated at two different selected output voltages of the DC/DC converter in the battery line. The power sharing of each power source and efficiency are also analyzed and discussed. Experimental results show that the battery can compensate for the shortage of supplied power for the load demand during the start-up and acceleration. The lowest operating voltage of the fuel cell stack is limited by the regulated output voltage of the DC/DC converter. The major power loss in the hybrid power system is attributed to the diodes. The power train efficiency can be improved by lowering the ratio of forward voltage drop of the diode to the operating voltage of the fuel cell stack.
Highlights
Proton exchange membrane fuel cells (PEMFCs) are considered as one of potential power sources for transportation applications in the near future
The configuration in this study is aimed for transportation applications, in which the fuel cell stack supports for nominal power demand and lithium-ion batteries (LIBs) compensates for sudden power demand during the start-up and acceleration
The power scale in this study is miniature when compared with that in real transportation applications, this study demonstrates the feasibility of the passive fuel cell/battery hybrid power system
Summary
Proton exchange membrane fuel cells (PEMFCs) are considered as one of potential power sources for transportation applications in the near future. The dynamic response of a PEMFC to a step-increase in power demand is relatively slow and designed nominal power usually cannot meet the instantaneous requirements during start-up or acceleration. Lithium-ion batteries (LIBs) have the advantages of quick response and large C-rate discharging. The performance of a PEMFC can be improved when it is hybridized with secondary batteries. There are two types of fuel cell/battery hybrid power systems: active and passive systems. In an active power system, a DC/DC converter is installed between the fuel cell and the battery. Gao et al [1] experimentally compared two active hybrid power systems with different battery sizes in terms of specific power, power density, volume, and weight. Blackwelder et al [2]
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