Exploiting Monotonicity to Design an Adaptive PI Passivity-Based Controller for a Fuel-Cell System

TL;DR

This paper introduces an adaptive passivity-based PI controller for a fuel-cell power system that exploits monotonicity, ensuring voltage regulation despite load uncertainties, validated through experiments.

Contribution

The paper develops a novel adaptive control method leveraging monotonicity and hybrid estimation techniques for fuel-cell systems, enhancing robustness to parameter uncertainties.

Findings

Controller maintains voltage regulation under load variations.

Adaptive scheme effectively estimates system parameters online.

Experimental results confirm stability and robustness.

Abstract

We present a controller for a power electronic system composed of a fuel cell (FC) connected to a boost converter which feeds a resistive load. The controller aims to regulate the output voltage of the converter regardless of the uncertainty of the load. Leveraging the monotonicity feature of the fuel cell polarization curve we prove that the nonlinear system can be controlled by means of a passivity-based proportional-integral approach. We afterward extend the result to an adaptive version, allowing the controller to deal with parameter uncertainties, such as inductor parasitic resistance, load, and FC polarization curve parameters. This adaptive design is based on an indirect control approach with online parameter identification performed by a ``hybrid'' estimator which combines two techniques: the gradient-descent and immersion-and-invariance algorithms. The overall system is proved to be stable with the output voltage regulated to its reference. Experimental results validate our proposal under two real-life scenarios: pulsating load and output voltage reference changes.