Horizontal axis wind turbine yaw differential error reduction approach

Abstract

The core of Wind Power, considered as one of the most dynamically developed technologies, consists primarily of the Horizontal Axis Wind Turbines (HAWT) which have a known problem of yawing error, systematically evaluated in at least 3–4 degrees. This error is caused not only by the hysteresis of chasing the wind flow direction fluctuations by yaw system, but also by periodical wind flow deviation from the rotating blades. In this research the authors have proved the yawing error phenomenon by experimental observation and numerical simulation, and have found the analytic solution to significant reduction of yawing error.The experiment with the SWT-3.6-120 HAWT nacelle based weather vane has proved the periodical nature of wind flow oscillations caused by the rotating blades. The numerical Computational Fluid Dynamics (CFD) modeling of the wakes behind the rotating blades, on the base of the Navier-Stokes equations and k-ε turbulence model, has shown the similar picture on the nacelle top, which is considered as the input signal set for the weather vane and hence a yaw system. The periodical yawing error caused by the flow deviation was named as a “differential error” of yawing.The similarity of the experimental and modeling results allowed then using the Matlab Simulink software for functional modeling of the weather vane behavior with yawing error estimation and evaluation of the corresponding power reduction. Using the series of simulation experiments it was determined that the integration of compensator with the yaw control system would lead to considerable yaw differential error reduction and increase the output power at least on 3.37%. The developed approach may become a basic method for the built-in differential yaw error reduction algorithm for any and all HAWTs.