tailieunhanh - From Turbine to Wind Farms Technical Requirements and Spin-Off Products Part 10

Tham khảo tài liệu 'from turbine to wind farms technical requirements and spin-off products part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 124 From Turbine to Wind Farms - Technical Requirements and Spin-Off Products The former section has analyzed values logged with high time resolution each grid cycle 20 ms but the duration was relatively short a bit more than 10 minutes due to storage limitations in the recording system. Ten-minute records with 20 ms time resolution allow studying fluctuations with durations between some tenths of second up to one minute However this duration is insufficient for analyzing wind farm dynamics slower than Hz with acceptable uncertainty. 6. Case study comparison of PSD of a wind farm with respect to one of its turbines during a day In order to study the behaviour of fluctuations slower than one minute the next section will analyze the mean power of each second during a day. Daily records with one second time resolution allow to study the fluctuations with durations from a few seconds up to an hour. Overall the transition frequency from uncorrelated to correlated fluctuations is mild and in fact the ratio PSDfarm f PSDturtme f depends noticeably on atmospheric conditions and it varies from one wind farm to another. This is one of the reasons why the values of the coherence decay factors AOng and Aat may vary twofold among different sources. At higher frequencies the control and generator technology influences greatly the smoothness of the power delivery. At low frequencies and under rated power the variability is mainly due to the wind because any turbine tries to extract the maximum amount of power from the wind regardless of their technology. During full power generation the fluctuations have smaller amplitude and higher frequency. The case presented in this section corresponds to low mid wind speed since this range presents bigger fluctuations. The wind direction does not present big deviations during the day and the atmospheric conditions can be considered similar during all the day. For clarity the turbine and the farm is generating bellow rated power during