Lidar arc scan uncertainty reduction through scanning geometry optimization
Lidar arc scan uncertainty reduction through scanning geometry optimization
复制标题
通过扫描几何优化减少激光雷达弧扫描不确定性
DOI：
10.5194/amt-9-1653-2016
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Gareth J. Brown
中科院分区：
文献类型：
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作者：
Hui Wang;R. Barthelmie;S. Pryor;Gareth J. Brown
抽象的。多普勒激光雷达经常以一种称为弧形扫描的模式运行，其中激光雷达波束以一个固定的仰角扫描整个扇区，并使用产生的测量结果来推导出n分钟水平平均风速(速度和方向)的估计。以前的研究表明，测量风速的不确定度源于湍流风速波动，并取决于扫描几何形状(弧距和弧向)。本文旨在为风能行业中的两个关键应用：风力机功率性能分析和年发电量预测提供最佳扫描几何的指导。我们给出了一个基于各向同性和冻结湍流假设的新的理论模式所得到的风速不确定度的定量分析，以及分别来自地形平坦的陆上、地形复杂的陆上和近海的三个站点的观测。理论模型和观测结果都表明，不确定度随湍流强度的变化而变化，使得10 分钟平均风速的相对标准误差约为湍流强度的30 %。通过将激光雷达波束与主导风向对准、增加弧距和降低每次弧扫的波束数，可以减少反演风速和推导出的风能估计值的不确定性。在湍流强度较高和/或风向变化较大的场地，应使用大弧度。
Abstract. Doppler lidars are frequently operated in a mode referred to as arc scans, wherein the lidar beam scans across a sector with a fixed elevation angle and the resulting measurements are used to derive an estimate of the n minute horizontal mean wind velocity (speed and direction). Previous studies have shown that the uncertainty in the measured wind speed originates from turbulent wind fluctuations and depends on the scan geometry (the arc span and the arc orientation). This paper is designed to provide guidance on optimal scan geometries for two key applications in the wind energy industry: wind turbine power performance analysis and annual energy production prediction. We present a quantitative analysis of the retrieved wind speed uncertainty derived using a theoretical model with the assumption of isotropic and frozen turbulence, and observations from three sites that are onshore with flat terrain, onshore with complex terrain and offshore, respectively. The results from both the theoretical model and observations show that the uncertainty is scaled with the turbulence intensity such that the relative standard error on the 10 min mean wind speed is about 30 % of the turbulence intensity. The uncertainty in both retrieved wind speeds and derived wind energy production estimates can be reduced by aligning lidar beams with the dominant wind direction, increasing the arc span and lowering the number of beams per arc scan. Large arc spans should be used at sites with high turbulence intensity and/or large wind direction variation.