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It is often assumed that the input voltage source of a switch-mode power supply is constant or shows negligible small variations. However, the last assumption is no longer valid when a fuel-cell stack is used as input source. A fuel-cell stack is characterised by low and unregulated DC output voltage, in addition, this voltage decreases in a non-linear fashion when the demanded current increases; henceforth, a suitable controller is required to cope the aforementioned issues. In this study, an average current-mode controller is designed using a combined model for a fuel-cell stack and a boost converter; moreover, a selection procedure for the controller gains ensuring system stability and output voltage regulation is developed. The proposed energy system uses a fuel-cell power module (polymer electrolyte membrane fuel cells) and a boost converter delivering a power of 900 W. Experimental results confirm the proposed controller performance for output voltage regulation via closed-loop gain measurements and step load changes. In addition, a comparison between open-and closed-loop measurements is made, where the controller robustness is tested for large load variations and fuel-cell stack output voltage changes as well.

In this paper, a passivity-based control (PBC) scheme for output voltage regulation in a fuel-cell/boost converter system is designed and validated through real-time numerical results. The proposed control scheme is designed as a current-mode control (CMC) scheme with an outer loop (voltage) for voltage regulation and an inner loop (current) for current reference tracking. The inner loop’s design considers the Euler–Lagrange (E-L) formulation to implement a standard PBC and the outer loop is implemented through a standard PI controller. Furthermore, an adaptive law based on immersion and invariance (I&I) theory is designed to enhance the closed-loop system behavior through asymptotic approximation of uncertain parameters such as load and inductor parasitic resistance. The closed-loop system is tested under two scenarios using real-time simulations, where precision and robustness are shown with respect to variations in the fuel cell voltage, load, and output voltage reference.

International audienceAn observer-based methodology for decentralized stabilization of large-scale linear time-invariant systems is presented. Each local controller is provided with available local measurements, it implements a deterministic observer to reconstruct the state of the other subsystems and uses—in a certainty-equivalent way—these estimates in the control law. The observers are designed following the principles of immersion and invariance. The class of systems to which the design is applicable is identified via a linear matrix inequality, from which the observer gains are obtained. It is shown that the use of immersion and invariance observers, instead of standard Luenberger's observers, enlarges the class of stabilizable systems. The applicability of the proposed method is illustrated with a transient stabilization controller for a two-machine power system

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