Understanding Small-Signal Stability of Low-Inertia Systems

TLDR

Renewable generation integrated via power electronics has dramatically altered power system dynamics. The study investigates stability properties of low‑inertia power systems. The authors develop a high‑fidelity dynamic model of a generic low‑inertia system, incorporating full‑order control schemes for synchronous and converter‑based generators, detailed transmission line and load dynamics, and use modal analysis to identify vulnerable segments and assess timescale coupling and control interference. The work determines maximum permissible penetration levels of inverter‑based generation, identifies associated unstable modes and dynamics, and proposes ways to improve stability margins for different generation portfolios across benchmark systems.

Abstract

Large-scale integration of renewable generation, usually interfaced to the network through power electronics, has led to drastic changes in power system dynamics. This paper presents novel insights into stability properties of such systems. For that purpose, a high-fidelity dynamic model of a generic low-inertia power system has been developed. The full-order, state-of-the-art control schemes of both synchronous and converter-based generators are included, with the latter differentiating between grid-forming and grid-following mode of operation. Furthermore, the dynamics of transmission lines and loads are captured in the model. Using modal analysis techniques such as participation factors and parameter sensitivity, the most vulnerable segments of the system are determined and the adverse effects of timescale coupling and control interference are investigated. More precisely, this work characterizes the maximum permissible penetration levels of inverter-based generation as well as the nature of the associated unstable modes and the underlying dynamics. Finally, potential directions for improving the system stability margin under different generation portfolios are proposed for several benchmark systems.