An experimental analysis of wind and power fluctuations through time-resolved data of full scale wind turbines

Addressing short-term wind and wind turbine power fluctuations is fundamental in order to understand the nature of turbulence and of the mechanical loads to which wind turbines are subjected. This work is an experimental study of wind and power fluctuations at on onshore wind farm in Italy. Four wind turbines having 2 MW of rated power each are studied through time-resolved data. The sampling frequency is of the order of the Hz. This wind farm has been selected because there are two orders of magnitude of inter-turbine distance (3 and 7 rotor diameters) and therefore it is possible to study different levels of wake interactions recovery. The power curve at short time scales is studied and the inertia of the wind turbines, with respect to the wind fluctuations, is observed in the form of hysteresis of the power curve. Subsequently, the distribution of the wind and power variations is studied on several time scales and different features of the distributions are observed for downstream wind turbines with respect to upstream ones. The two-point statistics of power and wind-power is shown to be responsive to the wake regime to which wind turbines are subjected. This can suggest new approaches for wake control strategies.