Large-Signal Stability Analysis of Low-Inertia Dynamic Microgrids During Black-Start

Power Systems with high penetration of Distributed Energy Resources (DERs) can restore critical loads by forming microgrids (MGs). However, the transient response of inverter controls, network dynamics, and loads may cause instability in inverter-dominated zero-inertia systems, especially during service restoration. To address frequency and voltage deviations, a consensus-based distributed secondary control is proposed, while considering communication network time delays. This paper examines the impact of communication delay on MG operational stability during service restoration, employing large-signal stability analyses. A comprehensive nonlinear state-space model quantifies the stability region, and delay margins for stability are determined. The methodology is validated through PSCAD/EMTDC simulations on a modified IEEE-123 node feeder with 100% inverter-based resources.