Active load control techniques for wind turbines.

Abstract

This report provides an overview on the current state of wind turbine control and introduces a number of active techniques that could be potentially used for control of wind turbine blades. The focus is on research regarding active flow control (AFC) as it applies to wind turbine performance and loads. The techniques and concepts described here are often described as "smart structures" or "smart rotor control". This field is rapidly growing and there are numerous concepts currently being investigated around the world; some concepts already are focused on the wind energy industry and others are intended for use in other fields, but have the potential for wind turbine control. An AFC system can be broken into three categories: controls and sensors, actuators and devices, and the flow phenomena. This report focuses on the research involved with the actuators and devices and the generated flow phenomena caused by each device. 4 Disclaimer:Given the nature of research in a progressive field such as wind energy, it is very difficult to mention every potential AFC device and to report precisely on all of the past and up-to-date findings. If a device or research paper is not mentioned within, it is because it was not found during the literature survey. Publications up through 2007 were used in this report. 5

Powers Adjusting Wind Turbine Means Investigation

“…Pechlivanoglou and Eisele [9] investigated the operation of plasma actuators on wind turbine airfoils at a wide range of Reynolds numbers and found that the effect of all the investigated plasma actuators vanished at Re > 10 5 . The energy conversion efficiency is also another operational parameter which highly depends on the actuators design, and undergoes further investigation.…”

“…Pechlivanoglou and Eisele [9] investigated the operation of plasma actuators on wind turbine airfoils at a wide range of Reynolds numbers and found that the effect of all the investigated plasma actuators vanished at Re > 10…”

“…With respect to wind turbine applications, plasma actuators are under extensive research [9,11] and their applications in this field seem to be The DC surface corona discharge actuator consists of two wire electrodes mounted flush on the surface of a dielectric profile (Fig. 5a).…”

Dynamic Circulation Control for a Vertical Axis Wind Turbine using Virtual Solidity Matching

“…Wind turbine blade lift control mechanisms that ultimately control power capture have included pitch variation or feathering, trailing edge flaps, vortex-generators, and even plasma systems [3] [4] [7] [8] [9] [10]. During rotation of a VAWT, each blade experiences different flow conditions requiring individual control for maximum efficiency [11].…”

Improvement of Wind Turbine Blade Performance by Means of Rod Vortex Generators

“…As a consequence of the boundary layer separation, the air flow on the blade is detached leading to increased aerodynamic losses and noise generation (Wagner et al 2012). In order to reduce the flow separation, different flow control devices have been developed and implemented on the blades during the last few decades (Van Dam et al 2008). Several flow control devices, such as trailing edge flaps, microtabs, microflaps, plasma actuators, active flexible walls or vortex generators, have been proposed in literature (Van Dam et al 2007Andersen et al 2010;Johnson et al 2010;Nelson et al 2008;Gao et al 2015).…”