Two degree of freedom control concept for a hydrogen production unit in fuel cell based power plants

Fuel cell systems directly and efficiently convert chemical energy into electrical power with water as the only byproduct. Thereby, most fuel cell systems use hydrogen as chemical power source. As the storing of hydrogen in high pressure tanks is demanding, the aim is to produce hydrogen on site using a reformer which uses conventional fuels, such as methane or dimethyl ether, as energy source. In contrast to hydrogen, conventional fuels are readily available and thus infrastructural changes are not necessary in order to operate fuel cell systems in mobile applications or in domestic applications. As integrated fuel cell systems are complex technical systems, sophisticated control techniques are essential to the efficient operation in order to maximize efficiency in terms of energy consumption and in order to maximize robustness of the system against external disturbances. The present contribution focuses on the control of the hydrogen producing reforming unit. Using a spatially distributed dynamical model of the process, a two degree of freedom control strategy is proposed which enables precise control of the reformer. To show the applicability of the proposed control approach, experiments are conducted on an experimental plant and control results are presented.