Complex-Frequency Synchronization of Converter-Based Power Systems

TL;DR

This paper introduces a complex-frequency framework to analyze the stability of converter-based power systems, providing new insights and practical solutions for phase-amplitude synchronization and stability issues.

Contribution

It proposes the concept of complex-frequency synchronization and analyzes stability of power systems with virtual oscillator-controlled converters using this novel approach.

Findings

Complex-frequency synchronization offers a new perspective on power system stability.

The analysis separates fast and slow dynamics for tractable stability assessment.

The approach links dVOC control with complex-power-frequency droop control.

Abstract

In this paper, we study phase-amplitude multivariable dynamics in converter-based power systems from a complex-frequency perspective. Complex frequency represents the rate of change of voltage amplitude and phase angle by its real and imaginary parts, respectively. This emerging notion is of significance as it accommodates the multivariable characteristics of power networks where active and reactive power are inherently coupled with both voltage amplitude and phase. We propose the notion of complex-frequency synchronization to study the phase-amplitude multivariable stability issue in a power system with dispatchable virtual oscillator-controlled (dVOC) converters. To achieve this, we separate the system into linear fast dynamics and approximately linear slow dynamics. The linearity property makes it tractable to analyze fast complex-frequency synchronization and slower voltage stabilization. From the perspective of complex frequency and complex-frequency synchronization, we provide novel insights into the equivalence of dVOC and complex-power-frequency droop control, stability analysis methods, and stability criteria. Our study offers a practical solution to address challenging stability issues in converter-based power systems.