Wind tunnel testing of wake tracking methods using a model turbine and tailored inflow patterns resembling a meandering wake

Wind farm control can be enhanced by feedback information about the current flow situation in the farm. Especially for closed-loop wake-steering control, the position of a wind turbine's wake with respect to the next turbine is valuable. Depending on the context, e.g. installed sensory or required time- and wake position resolution, different methods for wake tracking exist. With increasing fidelity, not only time-averaged wakes but also instantaneous wake conditions are considered for control. In this work, two methods for the dynamic estimation of the wake centre position are experimentally tested. One of them is based on wind turbine blade loads, the other on a fixed-beam staring lidar. Both methods use an Extended Kalman Filter with a dynamic model that takes the meandering nature of a wind turbine wake into account. In the atmospheric boundary layer, turbulence patterns of multiple rotor diameters are driving the downstream meandering of the wake. In wind tunnel setups with large model turbines, these spatial scale ratios are hardly reachable, thus meandering conditions were difficult to reproduce up to now. In this work, the inflow conditions are generated in a wind tunnel with an active grid, which imprints both a wind speed deficit and additional turbulence in a meandering frame of reference. The paper describes the generation and characterization of such inflow, while not claiming for an exact representation of a meandering wake in an atmospheric boundary layer. Inflow conditions of different meandering dynamics are used and their impact on the tracking methods is analyzed. The experiments show that the generated inflow conditions both resemble a wake and induce an expected response of the model wind turbine of 1.8 m diameter. The results from the wake tracking methods match the available literature, thus indicate the potential of the setup for control-oriented experiments in the context of meandering wakes, turbine-turbine interaction and load alleviation.