Gain and Phase: Decentralized Stability Conditions for Power Electronics-Dominated Power Systems

TL;DR

This paper introduces scalable decentralized stability conditions for multi-converter power systems, enabling efficient stability assessment of large-scale, heterogeneous systems without complex eigenvalue computations.

Contribution

It combines the small gain and small phase theorems to develop less conservative, scalable stability criteria applicable to diverse power system components.

Findings

The proposed conditions are less conservative than passivity-based methods.

They are computationally lighter and scalable for large systems.

Applicable to systems with grid-following, grid-forming converters, and synchronous generators.

Abstract

This paper proposes decentralized stability conditions for multi-converter systems based on the combination of the small gain theorem and the small phase theorem. Instead of directly computing the closed-loop dynamics, e.g., eigenvalues of the state-space matrix, or using the generalized Nyquist stability criterion, the proposed stability conditions are more scalable and computationally lighter, which aim at evaluating the closed-loop system stability by comparing the individual converter dynamics with the network dynamics in a decentralized and open-loop manner. Moreover, our approach can handle heterogeneous converters' dynamics and is suitable to analyze large-scale multi-converter power systems that contain grid-following (GFL), grid-forming (GFM) converters, and synchronous generators. Compared with other decentralized stability conditions, e.g., passivity-based stability conditions, the proposed conditions are significantly less conservative and can be generally satisfied in practice across the whole frequency range.