Wake effects above rated wind speed. An overlooked contributor to high loads in wind farms

In this paper a new validation of the Dynamic Wake Meandering method for calculating wake effects on power and load levels on a turbine is presented based on load and power measurements on a turbine located in the Lillgrund wind farm. What is unique is the large set of measurements available, where the wake effects from multiple neighboring turbines in high wind speed conditions could be included. It appears that the DWM method gives accurate results in single wake situations as well as for multiwake situations below rated wind speed. However, the so far used method for superposition of multiple wakes above rated wind speed has led to non-conservative load predictions for high wind speeds. Therefore a new approach is presented and compared to both measurements and present practice in the IEC61400-1 standard.