An Oscillatory Stability Criterion Based on the Unified <inline-formula> <tex-math notation="LaTeX">$dq$ </tex-math> </inline-formula>-Frame Impedance Network Model for Power Systems With High-Penetration Renewables

TLDR

Emerging oscillatory stability problems in high‑penetration renewable power systems arise from dynamic interactions between AC/DC grids and power‑electronic converters, and prior work has largely ignored the combined effects of many converters, generators, and HVDCs. This paper introduces a unified dq‑frame impedance network model that integrates converters, generators, and HVDCs into a practical system representation to fill that gap. By aggregating the model into a lumped impedance matrix, the authors propose a new oscillatory‑stability criterion based on the frequency characteristics of the matrix determinant and apply it to a real‑world high‑renewable system. The criterion’s effectiveness is confirmed through field measurements and electromagnetic transient simulations.

Abstract

Recent years have witnessed emerging oscillatory stability issues in power systems with high-penetration renewables. These issues are generally caused by the dynamic interaction between the AC/DC grid and power electronic converters used for the integration of renewables. Some previous studies have explored the issues with simplified system models containing only a few converters and idealized networks. However, the interactions between many converters and traditional generators/HVDCs have not been fully considered. To fill this gap, this paper first presents the concept of a unified dq frame impedance network model (INM), with which different converters as well as traditional generators/HVDCs can be incorporated to form an integrated s-domain model of a practical system. As the INM is aggregated into a lumped impedance matrix, a new criterion is then proposed to quantify the oscillatory stability, just by analyzing the frequency characteristics of the determinant of the matrix. Finally, the modeling method and the stability criterion are applied to a real-world system with a very high share of renewables and a realistic risk of oscillatory instability. Their effectiveness has been validated by both field measurements and electromagnetic transient simulations.