Novel Aerodynamic Damping Identification Method for Operating Wind Turbines

Chao Chen,Paul Fromme,Philippe Duffour

doi:10.1088/1742-6596/1222/1/012008

Chao Chen, Paul Fromme + Show 1 more

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https://doi.org/10.1088/1742-6596/1222/1/012008

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Abstract

This contribution introduces a novel method to determine the aerodynamic damping for operating wind turbines. Previous research typically estimated the modal damping ratios in the fore-aft and side-side directions as two decoupled degrees of freedom. This can result in misleading results, as the two directions are closely and unconventionally coupled through the wind-rotor interaction. This study proposes the identification of a novel type of aerodynamic damping matrix. This matrix arises from the linearization of the aerodynamic force resultant obtained from blade element momentum theory (blade modes not included). This linearized force is then applied to a beam finite element model of the tower with a lumped mass representing the rotor-nacelle assembly. This decoupled strategy efficiently describes the physics of the system including the coupling between the fore-aft and side-side motions. The identification of the damping matrix is shown to work for simulated wind time data.

Highlights

Damping is a key variable in wind turbine systems as it limits vibration amplitude around resonance [1] and significantly influences fatigue life [2]
To identify the aerodynamic damping, operational modal analysis (OMA), which uses the measured vibration responses caused by ambient excitation, is the preferred method since conventional experimental modal analysis requires controlled excitation, which is very difficult to achieve due to the large size of modern wind turbines
This paper proposes a new damping identification method which falls under the umbrella of OMA in the sense that it uses ambient wind excitation as an input

Summary

Introduction

Damping is a key variable in wind turbine systems as it limits vibration amplitude around resonance [1] and significantly influences fatigue life [2]. Wind turbine tower design is often governed by fatigue limit. A dynamic model with correctly identified damping is key for wind turbine design or assessing fatigue life and future maintenance needs. To identify the aerodynamic damping, operational modal analysis (OMA), which uses the measured vibration responses caused by ambient excitation, is the preferred method since conventional experimental modal analysis requires controlled excitation, which is very difficult to achieve due to the large size of modern wind turbines. Tcherniak et al [8] and Ozbek et al [9] highlighted some difficulties in using OMA in the context of wind turbines

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