SIaD-Tool: A Comprehensive Frequency-Domain Tool for Small-Signal Stability and Interaction Assessment in Modern Power Systems

TL;DR

SIaD-Tool addresses the challenge of assessing small-signal stability and interactions in modern power systems dominated by power-electronic resources. It introduces a flexible, open-source frequency-domain scanning framework that operates across multiple reference frames ($abc$, $0pn$, $dq0$) using both series voltage and parallel current perturbations, with a steady-state decoupling scheme to avoid mirror-frequency artifacts. The tool integrates four standardized stability assessments—Generalized Nyquist Criterion, impedance mode analysis, phase-margin stability, and passivity-based stability—and is validated on passive elements, grid-following and grid-forming converters, offshore wind plants, and the IEEE 9-bus system. By enabling reproducible, cross-platform impedance-based analyses and facilitating black-box system identification, SIaD-Tool supports robust stability screening and informed control design for modern grids.

Abstract

This paper presents SIaD-Tool, an open-source frequency-domain (FD) scanning solution for stability and interaction assessment in modern power systems. The tool enables multi-sequence identification in the abc, dq0, and 0pn frames and supports both series voltage and parallel current perturbation strategies. A novel perturbation scheme allows direct scanning in the target frame, simplifying the analysis of coupling effects and mirrored frequencies. SIaD-Tool is implemented on a multi-platform architecture, including MATLAB/Simulink and Python-PSCAD/EMTDC. Beyond system identification, it integrates automated stability evaluation through four standardized methods: Generalized Nyquist Criterion (GNC), modal impedance analysis, phase margin assessment, and passivity checks. Validation is carried out via extensive case studies involving passive elements, grid-following and grid-forming converters, offshore wind power plants, and the IEEE 9-bus system. Results confirm high accuracy, scalability, and robustness in detecting critical modes, interaction frequencies, oscillatory behavior, and stability margins.

Figures (19)

• Figure 1: SIaD-Tool architecture.
• Figure 2: Time-domain scanning strategies.
• Figure 3: General scanning scheme for passive elements.
• Figure 4: $abc$ frequency response of a series $RLC$ load.
• Figure 5: Frequency response of a PI section in the $dq$ frame.