A robust energy processing method for fuel cell systems supplying a time‐varying uncertain load

Abstract

Robustness and performance are key properties that can contribute to the widespread dissemination of fuel cell systems (FCSs) as power sources, and a precise output voltage can serve as a reliable criterion to evaluate these properties. In this paper, we propose to utilize intentional time delays as part of controllers to achieve proper output voltage regulation in an FCS. In the past few years, there has been a growing interest toward designing controllers with intentional delays to render improved responses and better noise attenuation capabilities in various classes of systems and this investigation extends the use of delay-based controllers to the application field of FCSs. A natural progression of this research, which to our knowledge has not been addressed, pertains to how such controllers perform in the presence of uncertainties, and whether or not these controllers can accommodate these uncertainties. In this research work, we present a solution to this open problem on a class of proportional integral retarded (PIR) controllers when controlling an FCS supplying a time-varying uncertain load. Through stability theory, the safe operation of the PIR controlled FCS is systematically guaranteed in spite of uncertain loads and input voltages. Specifically, based on Lyapunov methods and L 2 $$ {L}_2 $$ -gain analysis, we derive simple stability conditions to achieve robustness and H ∞ $$ {H}_{\infty } $$ performance. We show that utilizing only output voltage measurements the PIR controller can maintain the predictive features of a pure differentiator, but without its inherent noise amplification problems. Hence, low-pass filtering of signals or reconstruction of the states can be obviated. Compared with published control schemes for FCSs, the PIR controller is structurally simpler and practically realizable, and it is able to maintain robustness against uncertain loads and H ∞ $$ {H}_{\infty } $$ performance under exogenous signals without relying on disturbance estimators. Numerical simulations confirm the superiority of the PIR controller over benchmark proportional integral and proportional integral derivative controllers in terms of robustness, performance and noise attenuation capabilities.