Determination of optimal wind turbine alignment into the wind and detection of alignment changes with SCADA data

Abstract

Abstract. Upwind horizontal axis wind turbines need to be aligned with the main wind direction to maximize energy yield.Attempts have been made to improve the yaw alignment with advanced measurement equipment but most of these techniques introduce additional costs and rely on alignment tolerances with the rotor axis or the true north.Turbines that are well aligned after commissioning, may suffer an alignment degradation during their operational lifetime. 10Such changes need to be detected as soon as possible to minimize power losses. The objective of this paper is to propose a three-step methodology to improve turbine alignment and detect changes during operational lifetime with standard nacelle metrology (met) mast instruments (here: two cup anemometer and one wind vane).In step one, a reference turbine and an external undisturbed reference wind signal, e.g. met mast or lidar are used to determine flow corrections for the nacelle wind direction instruments to obtain a turbine alignment with optimal power 15 production. Secondly a nacelle wind speed correction is enabling the application of the previous step without additional external measurement equipment.Step three is a monitoring application and allows to detect alignment changes on the wind direction measurement device by means of a flow equilibrium between the two anemometers behind the rotor.The three steps are demonstrated at two 2MW turbines together with a ground based lidar. A first order multi linear regression model gives sufficient correction of the flow distortion behind the rotor for our purposes and two wind vane 20 alignment changes are detected with an accuracy of ±1.4 ° within three days of operation after the change is introduced.We could show, that standard turbine equipment is able to align a turbine with sufficient accuracy and changes to its alignment can be detected in a reasonable short time which helps to minimize power losses.

Robust active wake control in consideration of wind direction variability and uncertainty

“…Such an offset has a clearly degrading effect on active yaw deflection control and should be reduced by proper calibration of the wind vane. For this purpose several practical procedures are available as for instance demonstrated by (Mittelmeier et al, 2017;Mittelmeier and Kühn, 2018). Without loss of generality we assume in our analysis that a wind direction bias is negligible.…”