Increased Power Gains from Wake Steering Control Using Preview Wind Direction Information

Yaw controllers typically rely on measurements taken at the wind turbine, resulting in a slow reaction to wind direction changes and subsequent power losses due to misalignments. Delayed yaw action is especially problematic in wake steering operation, because it can result in power losses when the yaw misalignment angle deviates from the intended one due a changing wind direction. This study explores the use of preview wind direction information for wake steering control in a two-turbine setup with a wind speed in the partial load range. For these conditions and a simple yaw controller, results from an engineering model identify an optimum preview time of 90 s. These results are validated by forcing wind direction changes in a large-eddy simulation model. For a set of six simulations with large wind direction changes, the average power gain from wake steering increases from only 0.44% to 1.32%. For a second set of six simulations with smaller wind direction changes, the average power gain from wake steering increases from 1.24% to 1.85%. Low-frequency fluctuations are shown to have a larger impact on the performance of wake steering, and the effectiveness of preview control in particular, than high-frequency fluctuations. From these results it is concluded that wake steering can benefit from preview wind direction control, especially when the wind direction change is rapid.