中文摘要：

风速概率分布特性是决定风电场功率输出的重要因素。常用的两参数威布尔函数在拟合较长周期风速时效果很好，然而在研究短周期或特殊时段风速概率分布后发现，其分布规律常为双峰或多峰分布，很难用传统方法准确逼近。对此，提出一种混合威布尔函数逼近特殊时段风速分布的方法，构造极大似然函数逼近风速实际分布并采用数论布点方法获得待求参数。结果显示，七参数混合威布尔函数显著提高了双峰型风速概率密度分布逼近的精度，而极大似然估计的加权处理，提高了关注风速段的拟合优度，达到了降低逼近误差的目的。

英文摘要：

Wind speed probability distribution is usually expressed by z-parameter Weibull difficult to approximate accurately the short term, distribution with two or more peaks. A mixed Weibull distribution function with seven parameters is proposed. A moment estimation method is used to get initial value of parameters first and then maximum likelihood estimation used to calculate parameters. It is also necessary to pay more attention to a special peak or some important wind speed ranges. The weighted maximum likelihood estimation is adopted to improve the estimation in these special ranges. Results show that the mixed Weibull distribution function has a much better approximation precision than the 2- parameter one. By controlling the overall error, the method can significantly improve the performance of approximation for important wind speed ranges.