内陆复杂风电场风速垂直外推模型研究

Study on Vertical Extrapolation Model of Wind Speed in Inland Complex Wind Farms

陆上风能资源评估中风电机组的轮毂高度大于测风塔高度,忽略大气稳定度影响与地表粗糙度变化,风切变指数受地面地形和地貌因素的影响,且在外推到轮毂高度处时,风速难以精确预测。综合考虑了Monin Obukhov相似理论与动力学粗糙度最小二乘法计算模型,建立一种基于大气热稳定性在中性条件下的拟合方法。首先,评估了风切变指数在不同地点的空间分布和与大气稳定度变化之间的相关影响;其次,以2个不同地貌下陆上风电场的实测数据为基础,与常用的综合切变外推轮毂高度风速的计算方案相比较,结果表明:风切变指数日变化与大气稳定性日变化存在一定的相关性,新型外推风速模型计算方法能更加准确地评估目标高度风速的垂直分布变化。

According to the evaluation of onshore wind energy resources,the hub height of the wind turbine is greater than the height of the wind tower.The influences of atmospheric stability and surface roughness changes are ignored,and the wind shear index is affected by ground topography and geomorphic factors.Moreover,the wind speed is difficult to predict accurately when increased to the hub height.Therefore,based on Monin Obukhov's similarity theory and the least squares calculation model of dynamic roughness,a fitting method based on atmospheric thermal stability under neutral conditions was established.Firstly the spatial distribution of wind shear index at different locations and its correlation with changes in atmospheric stability were evaluated.Secondly,based on the measured data of onshore wind farms with two different landforms,the proposed method was compared with the commonly used calculation scheme of wind speed at hub height using comprehensive shear extrapolation.The results show that the daily variation of wind shear index is correlated with that of atmospheric stability.The new calculation method of the extrapolated wind speed model can evaluate the vertical distribution of wind speed at target height more accurately.