A Unified Theory for Transient Synchronization Stability Analysis of Renewable Dominated Power Systems

TL;DR

This paper develops a unified theoretical framework for analyzing transient synchronization stability in renewable-dominated power systems, addressing the complexities introduced by converter dynamics and providing accurate stability assessment methods.

Contribution

It introduces a generalized swing equation and an improved equal-area criterion for stability analysis, unifying modeling and analysis of RDPS transient dynamics.

Findings

Critical clearing time calculation errors are about 1%.

Unified modeling approach for renewable device switching dynamics.

Effective stability assessment for large-scale renewable fields.

Abstract

The change of electric power generation - from synchronous generator (SG) to converter - is generally regarded as the second revolution of power system. Different from rotor swing of SG in traditional grids mainly described by the swing equation (SE), the converter dynamics plays an indispensable role in modern renewable dominated power systems (RDPS). The high complexity of the RDPS, including spatial large-scale, nonlinearity, multi-time-scale, and even sequential switching, prevents us from fully understanding its dynamics and assessing its transient stability under large disturbance. Here, a variety of transient switching mechanism models of renewable devices relying on wind or solar energies under low-voltage ride-through are established and unified, which can be perfectly described by a generalized swing equation (GSE) under parameter changes for switching dynamics. The GSE focusing on the dominant phase-locking loop dynamics is similar to the SE. Mainly relying on the mechanical equivalence and the energy conservative principle, a substantially improved equal-area criterion method is proposed. Based on this method, even for large-scale renewable fields, the calculation errors for the critical clearing time are only about 1%. This elegant nonlinear-dynamics-based approach establishes a unified theory including modelling and analysis for the RDPS transient dynamics.