A five-parameter wind field estimation method based on spherical upwind lidar measurements

Abstract

Turbine mounted scanning lidar systems of focussed continuous-wave type are taken into consideration to sense approaching wind fields. The quality of wind information depends on the lidar technology itself but also substantially on the scanning technique and reconstruction algorithm. In this paper a five-parameter wind field model comprising mean wind speed, vertical and horizontal linear shear and homogeneous direction angles is introduced. A corresponding parameter estimation method is developed based on the assumption of upwind lidar measurements scanned over spherical segments. As a main advantage of this method all relevant parameters, in terms of wind turbine control, can be provided. Moreover, the ability to distinguish between shear and skew potentially increases the quality of the resulting feedforward pitch angles when compared to three-parameter methods. It is shown that minimal three measurements, each in turn from two independent directions are necessary for the application of the algorithm, whereas simpler measurements, each taken from only one direction, are not sufficient.