基于幂律过程和改进参数估计方法的风电场风能评估

Wind Energy Assessment of Wind Farms Based on Power-law Process and Modified Parameter Estimation Method

研究垂直风切变环境下风电场的风速概率分布及可用度评估。利用幂律过程描述风切变,由标准高度数据生成拓展高度数值,阐释风速随高度变化的规律;假设2高度的风速均服从2参数Weibull分布,采用最小二乘法(least square,LS)和极大似然估计法(maximum likelihood estimation,MLE)求解模型参数,提出并应用改进极大似然估计方法;计算2高度风速分布和主要风能指标。基于实例,通过拟合优度分析及主要风能指标的对比,验证所提出方法的合理性和有效性。结果表明:极大似然估计法及改进方法优于最小二乘法;风切变导致不同高度风速分布变化,Weibull分布的柔性特点使其在模拟高层风速时更为准确。

The probability distribution of wind speed and availability assessment for wind farms were investigated considering the vertical wind shear,which was clarified by the power-law process precisely. Wind speed at extended height （60 m） was generated from that of reference height （10 m）, so as to interpret the discipline of wind shear. Assumed the wind speed submitted to the two-parameter Weibull distribution, the least square （LS） method and maximum likelihood estimation （MLE） method were used to estimate the parameters, to which a modified MLE method was proposed and applied. The distribution of wind speed at extended height and main wind energy characteristic indices were deduced. Analyzed the goodness-of-fit and compared the main indices, the rationality and effectiveness of the method were verified from the case study. It shows that MLE and modified MLE method are superior to LS method in the parameter estimation, and wind speed distribution at different height changes with wind shear, the Weibull distribution can describe the wind speed at extended height more accurately for its flexibility.