Posters

Abstract

Nacelle-mounted LiDARs are widely used in the feed-forward control of wind turbines. There are now more than 10,000 LiDARs on turbines and the LiDARs are showing great benefits in load reduction and power increase. Based on predicted rotor effective wind speed (REWS), turbines can pitch just before the wind changes. This protects wind turbines from extreme loads and reduces fatigue loads. Most LiDARs have a similar detection range and beam angle. These LiDARs can accurately describe the wind field of small turbines, but have limitations in describing large turbines, which are now the majority. The low accuracy of LiDAR REWS greatly reduces the effectiveness of using LiDAR and may even have an opposite effect on wind turbines. Wind shear is a key parameter for wind field monitoring, as large wind shear could reduce power generation and even lead to safety incidents. But it’s hard to evaluate the wind shear of the field in front of a large rotor especially when the air velocity is uneven. This requires increasing the number of measurement points and extending the detection plane. Pulsed Nacelle-Mounted LiDAR can measure wind speed from several focal points simultaneously. Based on this feature and Taylor's frozen hypothesis, data from multi-distance gates can be rearranged in the plane to get more accurate REWS. LiDAR REWS errors from multi-gate data are reduced by over 50% compared to single-gate data in the simulation. The angle and detective range of LiDAR beams also significantly influence the accuracy of LiDAR-REWS. In general, large angles and the long range of beams benefit the REWS accuracy of the large rotor and have the opposite influence on the small rotor. Rotor equivalent wind shear can also be calculated from these data and it shows a great relevance with rotor imbalance loads and blade clearance. LiDAR with a 300 m horizontal detection range and 15° vertical and horizontal beam angle gives a good result for a 240 m rotor diameter.