Stability of a DC Microgrid with a Nonlinear Nested Control Framework: The Fast Communication Scenario

Abstract

As modern power systems continue to evolve into multi-agent, converter-dominated systems that demand reliable, stable, and optimal control architectures within an expandable framework, this paper investigates scalable stability guarantees of a promising nonlinear communication-reliant control framework for DC microgrids. Particularly, relying on nested control loops; inner decentralized(primary) and outer distributed(secondary), the control configurations are designed to simultaneously achieve proportional current sharing and voltage containment within pre-specified limits, at the converged steady state. By enforcing sufficient time-scale separation at the boarder between the control loops, the system admits a singular perturbation formulation, allowing global exponential stability (G.E.S.) to be established via Lyapunov arguments. Although the theoretical G.E.S. certificate is structurally scalable, the stability guarantees depends on a sufficiently large permanent leakage, introduced in the primary controller. Thus, the results of this paper emphasize the importance of appropriate practical tuning guidelines and electrical parameter selection. The effectiveness of the proposed method is validated through case studies on a low-voltage DC microgrid under load variations and topological changes (and communication time-delays), followed by a small-signal stability analysis.