The purpose of this thesis is to design hardware and a control strategy for a fuel cell/battery
hybrid power supply. Modern fuel cell/battery hybrid power supplies can have 2 DC/DC
converters: one converter for the battery and one for the fuel cell. The hardware for the
power supply proposed in this thesis consists of a single DC/DC buck converter at the
output terminals of the fuel cell. The battery does not have a DC/DC converter, and it is
therefore passive in the system. The use of one single converter is attractive, because it
reduces the cost of this power supply. This thesis proposes a method of controlling the fuel
cell's DC/DC buck converter to act as a current source instead of a voltage source. This
thesis will explain why using the fuel cell's buck converter to act as a current source is
most appropriate. The proposed design techniques for the buck converter are also based on
stiff systems theory.
Combining a fuel cell and a battery in one power supply allows exploitation of the
advantages of both devices and undermines their disadvantages. The fuel cell has a slow
dynamic response time, and the battery has a fast dynamic response time to fluctuations in
a load. A fuel cell has high energy density, and a battery has high power density. And the
performance of the hybrid power supply exploits these advantages of the fuel cell and the
battery. The controller designed in this thesis allows the fuel cell to operate in its most
efficient region: even under dynamic load conditions. The passive battery inherits all load
dynamic behavior, and it is therefore used for peaking power delivery, while the fuel cell
delivers base or average power. Simulations will be provided using MATLAB/Simulink based models. And the results
conclude that one can successfully control a hybrid fuel cell/battery power supply that
decouples fluctuations in a load from the fuel cell with extremely limited hardware. The
results also show that one can successfully control the fuel cell to operate in its most
efficient region.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-08-3259 |
| Date | 14 January 2010 |
| Creators | Smith, Richard C. |
| Contributors | Ehsani, Mehrdad |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis |
| Format | application/pdf |
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