Wind energy is one of the most promising sources of renewable energy and has experienced a very rapid growth in the last 15 years. In order to maintain and sustain this growth wind energy needs to be competitive with the other sources of energy, especially with fossil fuels. A major factor keeping the competitiveness of wind energy is the sustained investment made on research and innovation. Active wake wind farm control is part of the research effort that aims to reduce the cost of producing wind energy; these new control strategies have the goal of reducing wind turbine wakes interactions in order to increase the power production and to minimize loads and fatigue. Literature shows good potential for these control strategies; however most of the studies have been made in a virtual environment through the use of computer simulations and as a consequence there is a lack of real field measurement data analysis that could confirm the potential of these strategies. The French National Research Agency SMARTEOLE project implemented two wind farm control strategies in an operating wind farm called La Sole du Moulin Vieux and owned by Engie Green in order to assess the effects that the applied innovative wind farm control strategies have on the blade loads, particularly in terms of blade fatigue. The two wind farm control strategies applied are the curtailment strategy and the yaw-control strategy. It needs to be noted that due to the high sensitivity of loads and fatigue to inflow conditions and due to the limited amount of data available the results observed should be considered as general trends very specific for this particular wind turbine set up and location. In the curtailment strategy the upstream turbine SMV6 loads decreased up to 33% (at 9 m/s) in the flapwise direction and up to 67% (at 8 m/s) in the edgewise direction. Fatigue loads decreased up to 22% (at 9 m/s) in the flapwise direction and up to 2% (at 9 m/s) in the edgewise direction. In the downstream turbine no clear trend has been detected due to the high uncertainty in the results. Most likely low amount of data and increased turbulence in the downstream turbine led to this uncertainty in the trends. In the yaw-control strategy loads showed a decrease up to 8% (at 9 m/s) in the flapwise direction loads and up to 72% (at 9 m/s) in the edgewise direction loads for the upstream turbine SMV6. Fatigue also decreased up to 19% (at 11 m/s) in the flapwise direction loads and up to 1.3% (at 10 m/s) in the edgewise direction for the upstream turbine. The downstream turbine SMV5 showed no significant reductions in the flapwise loads and fatigue when the whole wake was analyzed but, when the full-wake only was analyzed, a significant increase in loads and power produced, without any significant increase in fatigue loads have been observed. This underlines the potential of the yaw-controlled strategy to increase power production without significantly increasing fatigue.

Due to the limited availability of sites on both land and sea, there is a need to maximize the power density of wind farms whilst limiting the adverse wake effect between the wind turbines that cause power losses and/or increased load cases. The study focuses on analyzing the potential of combining yaw-based wake-steering and constant blade pitch control down-regulation to mitigate the detrimental wind turbine wake interactions. Data-driven surrogate models based upon polynomial chaos theory have been used to model the statistical distributions of the wind farm power production and short-term Damage Equivalent Loads (DEL) in function of the control inputs. The model calibration data has been generated for a range of control settings for two V27 wind turbines aligned with the wind direction through large eddy simulations using the flowsolver EllipSys3D and the aeroelastic code Flex5. A power-based optimization with DEL constraints has been performed and median power gains ranging from +1% to +3% have been observed at close spacings depending on the severity of the imposed constraints. It was identified that larger power gains corresponded to an increase in DEL. At larger spacings, the wind farm control strategies shows limited performance increases and revert to baseline operations.