Large-Signal Stability Guarantees for a DC Microgrid with Nested Nonlinear Distributed Control: The Slow Communication Scenario

TL;DR

This paper presents a scalable control framework for DC microgrids that guarantees large-signal stability using nested nonlinear control loops, validated through simulations and small-signal analysis.

Contribution

It introduces a novel nested control scheme with stability guarantees for DC microgrids, combining Lyapunov and singular perturbation methods for global exponential stability.

Findings

Proven global exponential stability under time-scale separation.

Validated control strategy through simulations on standard microgrid models.

Provided practical guidelines for parameter setting and stability enhancement.

Abstract

The increasing integration of renewable energy sources into electrical grids necessitates a paradigm shift toward advanced control schemes that guarantee safe and stable operations with scalable properties. Accordingly, this paper investigates large-signal stability guarantees for cyber-physical DC microgrids employing a nonlinear distributed consensus-based control scheme to enable coordinated integration and management of distributed generation units within an expandable framework. The proposed control framework adopts nested control loops; inner (decentralized) and outer (distributed), specifically designed to simultaneously achieve uniform voltage containment within pre-specified limits, and proportional current sharing in steady state. Our scalable stability result relies on singular perturbation theory and Lyapunov arguments to prove global exponential stability when imposing a sufficient time-scale separation at the border between the nested control loops, while relying on some practical parameter-setting schemes. The effectiveness and versatility of the proposed control strategy are then validated through time-domain simulations performed on a case-specific low-voltage DC microgrid and the modified IEEE 33-bus radial distribution system. Moreover, a small-signal stability analysis is conducted to derive practical guidelines that enhance the applicability of the method.