Robust H∞ Delay-Based Control of a Fuel-Cell System with Time-Varying Norm-Bounded Uncertainties

Robustness and performance are key properties that can contribute to the widespread dissemination of Fuel-Cell Systems (FCS) 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 subject to norm-bounded time-varying uncertainties associated with the electrical load. For the nominal FCS, a derivative-dependent controller is first proposed and then approximated using artificial delays with the goal of obtaining a realizable controller. With the approximated controller at hand, a tuning strategy to optimize system's response is adopted and the closed-loop system is presented as an uncertain time-delay system for which we derive simple sufficient stability conditions, based on Lyapunov-Krasovskii methods, so as to achieve robustness with prescribed H-infinity performance guarantees.