Current management in a hybrid fuel cell power system: A model-predictive control approach

The problem of oxygen starvation in fuel cells coupled with air compressor saturation limits, is addressed in this paper. We propose using a hybrid configuration, in which a bank of ultracapacitors supplements the polymer electrolyte membrane fuel cell during fast current transients. Our objective is to avoid fuel cell oxygen starvation, prevent air compressor surge and choke, and simultaneously match an arbitrary level of current demand. We formulate the distribution of current demand between the fuel cell and the bank of ultracapacitors; in a model predictive control framework, which can handle multiple constraints of the hybrid system. Simulation results show that reactant deficit during sudden increase in stack current is reduced from 50% in stand-alone architecture to less than 1% in the hybrid configuration. In addition, the explicit constraint handling capability of the current management scheme prevents compressor surge and choke and maintains the state-of-charge of the ultracapacitor within feasible bounds.