Analysis of Wind-Turbine Main Bearing Loads Due to Constant Yaw Misalignments over a 20 Years Timespan

Martin Cardaun,Ralf Schelenz,Georg Jacobs,Björn Roscher

doi:10.3390/en12091768

Abstract

The compact design of modern wind farms means that turbines are located in the wake over a certain amount of time. This leads to reduced power and increased loads on the turbine in the wake. Currently, research has been dedicated to reduce or avoid these effects. One approach is wake-steering, where a yaw misalignment is introduced in the upstream wind turbine. Due to the intentional misalignment of upstream turbines, their wake flow can be forced around the downstream turbines, thus increasing park energy output. Such a control scheme reduces the turbulence seen by the downstream turbine but introduces additional load variation to the turbine that is misaligned. Within the scope of this investigation, a generic multi body simulation model is simulated for various yaw misalignments. The time series of the calculated loads are combined with the wind speed distribution of a reference site over 20 years to investigate the effects of yaw misalignments on the turbines main bearing loads. It is shown that damage equivalent loads increase with yaw misalignment within the range considered. Especially the vertical in-plane force, bending and tilt moment acting on the main bearing are sensitive to yaw misalignments. Furthermore, it is found that the change of load due to yaw misalignments is not symmetrical. The results of this investigation are a primary step and can be further combined with distributions of yaw misalignments for a study regarding specific load distributions and load cycles.

Highlights

Wind turbines are mainly clustered as wind farms
The work carried out in this paper showed the effects of yaw misalignment on loads for a generic
The work carried out in this paper showed the effects of yaw misalignment on loads for a generic turbine

Summary

Introduction

Wind turbines are mainly clustered as wind farms. Due to the limited space, the turbines are densely placed to obtain the full potential of the available space and to avoid unnecessary cabling costs especially at offshore sites. The increased turbulence intensity leads to greater loads on the drive train and its structural components [1] This results in accelerated damage accumulation and shortened maintenance intervals. As an initial classification of the occurring load changes and the detection of further effects, load calculations are carried out on a generic wind turbine model with flexible structural components For this purpose, a multi body simulation model of a 3 MW turbine with a rotor diameter of 126 m (C3 × 126 [15]) is simulated at Design Load Case 1.1 according to DIN EN 61400-1 (production operation) [16] with wind class 2B at multiple yaw misalignments. The findings could be taken into account in the design of the bearings, and on the other hand, the park regulation could be adapted to prevent an uneconomical accumulation of damage in favour of energy production

Simulation Model and Setup

Discussion

Conclusions