Pressure-based lift estimation and its application to feedforward load control employing trailing-edge flaps

This experimental load control study presents results of an active trailing-edge flap feedforward controller for wind turbine applications. The controller input is derived from pressure-based lift estimation methods that rely either on a quasi-steady method, based on a three-hole probe, or on an unsteady method that is based on three selected surface pressure ports. Furthermore, a standard feedback controller, based on force balance measurements, is compared to the feedforward control. A Clark-Y airfoil is employed for the wing that is equipped with a trailing-edge flap of x/c=30% chordwise extension. Inflow disturbances are created by a two-dimensional active grid. The Reynolds number is Re=290 000, and reduced frequencies of k=0.07 up to k=0.32 are analyzed. Within the first part of the paper, the lift estimation methods are compared. The surface-pressure-based method shows generally more accurate results, whereas the three-hole probe estimate overpredicts the lift amplitudes with increasing frequencies. Nonetheless, employing the latter as input to the feedforward controller is more promising as a beneficial phase lead is introduced by this method. A successful load alleviation was achieved up to reduced frequencies of k=0.192.DFG, 218736457, Experimentelle Untersuchung von Strömungskontrollmethoden zur Lastkontrolle an Windkraftanlagen mittels einer Forschungswindkraftanlage im WindkanalDFG, 414044773, Open Access Publizieren 2021 - 2022 / Technische Universität Berli

Development and assessment of a method to determine the angle of attack on an operating wind turbine by matching onboard pressure measurements with panel method simulations

Wind Energy is substantially growing in recent years and is now one of the most competitive renewable energy sources on the market. To further foster the growth of this energy source, increasing effort is put into building accurate numerical models. Most models compute the loads acting on the turbine as a dependence of some sort to the angle of attack (AoA). Accurate AoA measurements would allow for comparison with experiments and would be of great benefit for the improvement of numerical models and the investigations of aerodynamic phenomena such as stall delay. However, the determination of the angle of attack during operation is troublesome to the present day. In addition to what was already mentioned, the AoA is key to evaluate loads acting on the wind turbine and assessing experiments, computational models, and aeroelastic models. This paper proposes a simple comparative method to estimate the AoA based on pressure distributions. The proposed method is tested using data from different numbers of pressure taps placed on the Berlin Research Turbine (BeRT) at the Hermann Föttinger Institut of the Technische Universität Berlin. The predicted results are in line with those from other methods while the operating conditions to which the model can be applied are improved