Double PI-PBC for a Fuel Cell System with a Hybrid Energy Storage System

This paper describes a double proportional-integral passivity-based control design to coordinate the operation of a proton-exchange membrane fuel cell system supported by two energy storage devices, such as a supercapacitor and a battery. Considering the singular perturbation theory, a timescale separation is applied to decouple the current and voltage dynamics and synthesize two control loops: an inner current loop and an outer voltage loop. Both current and voltage dynamics are controlled by exploiting the passive properties of each subsystem through a simple proportional-integral action over the passive output. The overall control objectives are to ensure load and super-capacitor voltage regulation and smooth variations in fuel cell current despite variations in energy demand. Numerical results demonstrate the correct performance of the closed-loop system despite pulsating variations in energy demand.