Full-scale validation of optimal axial induction control of a row of turbines at Lillgrund wind farm

We present a full-scale validation study of an optimal power open-loop wind farm control schedule (WFCS) using a full row of turbines (Row-A) at the Lillgrund offshore wind farm as the demonstration case. The derived WFCS is conditioned on the ambient wind speed and wind direction. The WFCS’s are developed using the DNV and DTU numerical models LongSim and Fuga. Prior to implementation, the developed optimal controllers are tested by comparing LongSim results, based on Fuga optimized input, with Fuga optimized results and vice versa. These models are very different in their nature — Fuga being a linearized RANS CFD solver, and LongSim being based on a range of engineering wake models and allowing for unsteady wind farm flow modelling — but nevertheless the overall computed Row-A power gains are reasonably similar. This gives confidence to the developed WFCS’s, even though the two models predict significantly different distributions of the power gains over wind speeds and directions. Based on the numerical analysis, simplified WFCS’s for implementation in the Row-A turbines are developed and tested against the more detailed optimized controller. The test predicts only a small reduction of performance enhancement of the simplified controller compared to the detailed controller, and on this basis it is decided to use the simplified controller for the full-scale turbine implementation. The test, toggling between base control and optimal control in 50-minute successive time slots, has been running since 09-05-2022 and is still ongoing. A huge amount of data is needed to obtain robust statistics for the comparison of measured and numerical data.