A Dynamic Similarity Index for Assessing Voltage Source Behaviour in Power Systems

TL;DR

This paper introduces the Dynamic Similarity Index (DSI), a tool for assessing how inverter-based generators behave compared to ideal voltage sources, aiding manufacturers and operators in performance evaluation and system diagnosis.

Contribution

The paper develops the DSI as a novel, frequency-dependent metric for dynamic behavior comparison in power electronics-dominated systems, with practical applications for control evaluation and voltage vulnerability diagnosis.

Findings

DSI effectively compares inverter dynamics to ideal sources.

Validated DSI applications through Matlab Simulink simulations.

Enables targeted diagnosis of voltage stability issues.

Abstract

Due to the fundamental transition to a power electronic dominated power system, the increasing diversity of dynamic elements underscores the need to assess their similarity to mature electrical engineering models. This article addresses the concept of the Dynamic Similarity Index (DSI) for its use in, power electronics-dominated networks. The DSI is a multipurpose tool developed to be used by different stakeholders (e.g., converter manufacturers and system operators). Such an index is calculated per frequency, which serves to anticipate potential differences in particular frequency ranges of interest between the model under study and the reference model. Within the scope of this study, the dynamic similarity of inverter-based generators to an ideal voltage source behind an impedance is assessed, due to the relevance of this fundamental circuit in the representation of generation units in power system studies. The article presents two potential applications based on this mathematical framework. First, for manufacturers to evaluate control performance compared to a reference model and second, it enables operators to diagnose buses with voltage vulnerability based on a user-defined reference Short-Circuit Ratio (SCR) value. The DSI results for these two case studies are validated using Matlab Simulink simulations.