Axial induction control design for a field test at Lillgrund wind farm

Lillgrund offshore wind farm near Copenhagen has been the subject of a number of research projects. The close turbine spacing makes it an interesting candidate for research into turbine wakes and wind farm control. As part of the EU TotalControl project, an axial induction controller has been designed for field testing at Lillgrund. The controller was designed using steady-state optimisations in DNV's LongSim code, which predicted a small but significant power gain along with a considerable reduction in fatigue loading. Some simplifications were introduced for ease of practical implementation on this particular site; the controller was initially optimised to improve the power output of one 7-turbine row, with the aim of extending to the whole wind farm if the first test was successful. The expected power gain was confirmed by running realistic, detailed time-domain simulations in LongSim, and independently corroborated using steady-state calculations with DTU's linear CFD code Fuga. The controller was implemented on site, and a toggle test was initiated on site in late December 2021, with the wind farm controller toggling between controlled and default states every 50 minutes. First results are expected early in 2022.