Performance prediction of active pitch-regulated wind turbine with short duration variations in source wind

Short duration wind variations affect real time performance of active pitch-regulated wind turbines in two ways as evident from reported experimental and empirical studies. First the mean output power, which may be referred to as the short duration output power, differs significantly from the corresponding zero-turbulence value obtained with ideal source wind streamlines. Second, random variation of output around the mean value appears with a significant standard deviation; the normalised value of which is referred to as the short duration variability. In this paper, analytical interpretation of both metrics is presented under assumption of two-parameter Weibull statistics for short duration wind variations. Statistical estimates for the metrics are presented for conditions described by the well known IEC 61400-1 Standards. Finally the statistical estimation procedure is applied to a Vestas V90 3MW zero-turbulence output curve as an illustrative application example.