CHARACTERISTICS OF THE OFFSHORE EXTREME WIND LOAD PARAMETERS FOR WIND TURBINES DURING STRONG TYPHOON HAGUPIT

Observational data of the severe typhoon Hagupit are obtained by a 3-dimensional ultrasonic anemometer which is installed on a 100-meter-high meteorological tower located at an islet off the coast of Guangdong.The characteristics of the extreme wind load parameters for offshore wind turbines under the influence of extreme winds at severe typhoon intensity are analyzed.By comparing the observed data with the results derived from the International Electrotechnical Commission （IEC） standard 61400-1,the applicability of the methods computing extreme wind load parameters in the IEC standard are investigated under typhoon conditions.The results are as follows.（1） The changes of both the offshore extreme gust wind speeds and the extreme wind directions render a ＂M＂ shape bi-modal distribution with peak values in the eyewall region of Hagupit.（2） There are significant differences of amplitudes of the observed extreme operating gust wind speeds and extreme wind direction from the results calculated from the IEC standard.（3） The amplitudes of both the extreme operating gust wind speeds and the extreme directions exceed the upper limits of the IEC standard for three standard classes of wind turbines,and the values calculated by IEC standard are much significantly larger than the measured ones.（4） The observed extreme operating gust wind speeds are consistent with the results calculated by the IEC standard when wind turbines are under full or partial workload or cut-off conditions,although the amplitude of extreme wind directions calculated in terms of the IEC standard is larger than that of direct measurements.Measured extreme operating gust wind speeds sometimes exceed the IEC design criteria.