Experimental investigation of wind turbine wake and load dynamics during yaw maneuvers

Stefano Macrí,Annie Leroy,Sandrine Aubrun,Nicolas Girard

doi:10.5194/wes-6-585-2021

Abstract

Abstract. This article investigates the far wake response of a yawing upstream wind turbine and its impact on the global load variation in a downstream wind turbine. In order to represent misalignment and realignment scenarios, the upstream wind turbine was subjected to positive and negative yaw maneuvers. Yaw maneuvers could be used to voluntarily misalign wind turbines when wake steering control is targeted. The aim of this wind farm control strategy is to optimize the overall production of the wind farm and possibly its lifetime, by mitigating wake interactions. While wake flow and wind turbine load modifications during yaw maneuvers are usually described by quasi-static approaches, the present study aims at quantifying the main transient characteristics of these phenomena. Wind tunnel experiments were conducted in three different configurations, varying both scaling and flow conditions, in which the yaw maneuver was reproduced in a homogeneous turbulent flow at two different scales and in a more realistic flow such as a modeled atmospheric boundary layer. The effects of yaw control on the wake deviation were investigated by the use of stereo particle imaging velocimetry while the load variation on a downstream wind turbine was measured through an unsteady aerodynamic load balance. While overall results show a nondependence of the wake and load dynamics on the flow conditions and Reynolds scales, they highlight an influence of the yaw maneuver direction on their temporal dynamics.

Highlights

The rising market demand for wind energy, together with the need to reduce costs and maximize power yield, has led to an increase in wind farm density (Pao and Johnson, 2009) with a concomitant increase in wake interactions
The results concerning the influence of the static yaw angle applied to an upstream WT on its wake deviation, on the available wind power for a virtual downstream WT and on the actual thrust applied to a downstream WT, will be provided
The aerodynamic characterization of the wake of a wind turbine model and its effect on the load of a similar downstream wind turbine model consequent to a dynamic positive or negative yaw variation were experimentally studied for different incoming flow conditions, Reynolds scales and induction factors by using porous discs

Summary

Introduction

The rising market demand for wind energy, together with the need to reduce costs and maximize power yield, has led to an increase in wind farm density (Pao and Johnson, 2009) with a concomitant increase in wake interactions. A wind farm control strategy consists in controlling each wind turbine individually in order to reduce its wake effects on the nearest downstream turbines and maximize the total power production. The most common solutions investigated are twofold: induction control and yaw control The former is based on a power curtailment strategy, as reducing the power extraction of an upstream wind turbine leaves more kinetic energy available for a downstream one. The latter consists in wake steering: a wind turbine ( WT) is voluntarily misaligned with respect to the wind direction in order to deviate its wake from its nominal position and reduce wake effects on a downstream wind turbine. Some studies on the effects of yaw misalignment on wind turbine wakes, mainly based on quasi-

Objectives

Results

Conclusion