MODELING, CONTROL, AND DESIGN OF HYBRID FUEL CELL VEHICLES

The Polymer Electrolyte Membrane Fuel Cell (PEMFC) has been projected to be the fuel cell of choice for future automotive applications. Among the challenging aspects of this application is maintaining highly efficient operation of the fuel cell. The key component of the PEMFC, the Nafion Membrane, can reach two critical states: drying and flooding. In drying, high resistance prevents normal operation of the fuel cell. In flooding, reactants are prevented from reaching reaction sites and there is a reduction of performance of the fuel cell. To address the first point, a spatially distributed along the plane membrane model was developed and tested with proportional-integral control of voltage and temperature. To analyze the occurrence of severe and frequent changes in power demand, a model aimed at mimicking the load expected in a fuel cell vehicle, including a DC motor, DC-DC converters and a rechargeable battery for peak-shaving and regenerative braking was developed. The model includes rotational and translational inertia as well as a simple wind resistance model for a vehicle. In contrast to simple lab-focused loads where load impendence is directly manipulated, the manipulated variable within this load is the DC-DC converter gain. Based on this model a control system architecture was developed consisting of a number of low level regulatory loops, a power distributor for peak-shaving and finally a high level loop for tracking vehicle speed. After understanding the load demands to a fuel cell vehicle with only a battery, the issue of multiple energy storage technologies is addressed. Designing a vehicle with these technologies poses an optimization problem. A high-level model of a fuel cell vehicle with two storage technologies, a battery and super-capacitor was developed. The model accounted for the constraints of each component and a drive cycle characterized the power demand. An economic-based optimization problem xv was posed whereas its objective was to minimize the capital cost of the system, while meeting power demand and keeping the technologies within their constraints. The result of the optimization provided a controller from which a high-level power coordination unit can be developed for the fuel cell vehicle.Ph.D. in Chemical Engineering, December 201