Open Access

ARTICLE

Mechanism Analysis and Detection Methods of Voltage Fluctuation under Wide-Band Oscillation

Guofeng Zhuang¹, Xiuzhen Zhao², Xuemei Luo^3,*, Shibin Chen³, Xujun Zhang³
1 State Grid Gansu Electric Power Company, Lanzhou, China
2 State Grid Gansu Electric Power Company Extra High Voltage Branch, Lanzhou, China
3 Electric Power Research Institute of State Grid Gansu Electric Power Company, Lanzhou, China
* Corresponding Author: Xuemei Luo. Email:
(This article belongs to the Special Issue: Advances in Grid Integration and Electrical Engineering of Wind Energy Systems: Innovations, Challenges, and Applications)

Energy Engineering https://doi.org/10.32604/ee.2026.072999

Received 09 September 2025; Accepted 03 March 2026; Published online 19 May 2026

Abstract

This paper investigates voltage fluctuations in direct-drive wind farms induced by wide-band oscillations during grid integration. A sequence impedance model of the wind farm is established, incorporating key components such as direct-drive wind turbines, static var generators (SVGs), transformers, and transmission lines. Based on this model, positive- and negative-sequence impedance expressions are derived. The quantitative relationship among voltage fluctuation, system strength (short-circuit ratio, SCR), and power imbalance is formulated, leading to a comprehensive expression that highlights the influence of impedance mismatch between positive and negative sequences on wide-band oscillations. Simulation results confirm an approximately linear correlation between voltage fluctuation and power imbalance, and validate the inverse relationship between voltage fluctuation and system strength. Sensitivity analysis and modal participation factor analysis are further conducted to identify the voltage response characteristics under active and reactive power disturbances, revealing that capacitor voltage, q-axis current, and phase-locked loop (PLL) states are the dominant factors driving voltage fluctuations in the wide-band frequency domain. To mitigate these effects, a frequency-weighted adaptive virtual impedance shaping (FW-AVZ) method is proposed for both positive and negative sequences. The method effectively equalizes sequence impedances, improves phase margin, and suppresses voltage fluctuations across a wide frequency range. The findings provide theoretical insights and practical guidance for enhancing voltage stability in direct-drive wind farms under weak grid conditions.

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Keywords

Direct-drive wind farm; wide-band oscillation; voltage fluctuation; sequential impedance modeling; power imbalance

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