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

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.

A review of wind turbine main bearings: design, operation, modelling, damage mechanisms and fault detection

“…A commercially available multibody modelling software, Simpack, has been used to analyse MB loads at a number of operating points, while also exploring the effects of bearing clearance (Sethuraman et al, 2015). In Cardaun et al (2019) a Simpack model is used to investigate the impacts of yaw misalignments on WTMB loads in terms of fatigue life. The results indicate that misalignment increases the damage equivalent loads for the MB, but that the effect is not symmetrical and depends on the inflow direction.…”

“…This is likely due to the fact that historically the MB has not been reported as resulting in high rates of failure. For example, prominent and often-cited reliability studies (Carroll et al, 2016;Hahn et al, 2006;Wilkinson et al, 2011;Spinato et al, 2009) either neglect the MB entirely or appear to lump it in with other components under the heading of "drivetrain", "main shaft" or "other", obscuring contributions from the MB itself. These works are often simply reporting the information available to them, and so in turn it seems likely that the MB has not been prioritised in terms of logging failures and considering root cause.…”

Response to Reviewer 1

“…We also agree that more literature pertaining to wind turbine main bearings would strengthen this piece of work and this will be included in the updated manuscript. This will include [1][2][3][4][5][6], below, among others.…”

Response to Reviewer 2

“…We also agree that more literature pertaining to the modelling of wind turbine main bearings would strengthen this piece of work and this will be included in the updated manuscript. This will include ref [2][3][4][5][6][7] among others.…”