On the Robustness of Active Wake Control to Wind Turbine Downtime

Stoyan Kanev

doi:10.3390/en12163152

Abstract

Active wake control (AWC) is an operational strategy for wind farms that aims at reducing the negative effects of wakes behind wind turbines on the power production and mechanical loads at the wind turbines’ downstream. For a given wind direction, the strategy relies on collaborative control of the machines within each row of turbines that affect each other through their wakes. The vast amount of research performed during the last decade indicates that the potential upside of this technology on the annual energy production of a wind farm can be as high as a few percentage points. Although these predictions on the potential benefits are quite significant, they typically assume full availability of all turbines within a row operating under AWC. However, even though the availability of offshore wind turbines is nowadays quite high (as high as 95%, or even higher), the availability of a whole row of turbines is shown to be much lower (lower than 60% for a row of ten turbines). This paper studies the impact of turbine downtime on the power production increase from AWC, and concludes that the AWC is robust enough to be kept operational in the presence of turbines standing still.

Highlights

Within wind farms, wind turbines interact with each other through their wakes
active wake control (AWC) is a cooperative approach to operate wind farms that aims at maximizing the power production of the whole farm, while at the same time trying to reduce the fatigue loading on the wind turbines
Wake redirection is an approach to control the wakes in a wind farm, which is based on intentional yaw misalignment, i.e., yawing the rotors of the upstream wind turbines away from the wind

Summary

Introduction

The wakes feature reduced wind velocity and increased turbulence levels, and cause reduced power production and increased fatigue loading at downstream wind turbines. To reduce these negative effects on power and loads, the concept of active wake control (AWC) has been developed in the beginning of this century [1,2]. AWC is a cooperative approach to operate wind farms that aims at maximizing the power production of the whole farm, while at the same time trying to reduce the fatigue loading on the wind turbines. There are two main classes of AWC approaches, both of which share the common feature that upstream wind turbines will reduce their power capture to allow downstream turbines to produce more power. The second class of AWC methods, called wake redirection, is based on operating the upstream turbines with yaw misalignment in order to generate a transverse force on the air flow and steer the wakes away from downstream turbines [5,6]

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