Integrated aeroelastic and control analysis of wind turbine blades equipped with microtabs

Abstract

Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.)Published in Renewable Energy 75 (2015) 102-114 Terence Macquart & Alireza Maheri 1 Integrated Aeroelastic and Control Analysis of Wind Turbine Blades Equipped with MicrotabsTerence Macquart and Alireza Maheri Faculty of Engineering and Environment, Northumbria University, UK AbstractThis paper presents the results of an investigation into the performance of different controllers in active load control of wind turbine blades equipped with microtabs. A bang-bang (BB) controller, a linear quadratic regulator (LQR) a proportional integral derivative (PID) and a sliding mode controller (SMC) are synthesised for load alleviation. The performance of the synthesised controllers in load alleviation is evaluated by employing WTAC (Wind Turbine Aeroelastic and Control), a wind turbine simulator incorporating an unsteady aerodynamic module, a structural analysis module and a control module. The variable-speed pitch-controlled NREL-5MW is adopted as the case study. Using frequency domain analysis it is shown that for the studied case all controllers have more or less the same performance at rejecting the first rotational frequency loads. It is also shown that all controllers are more effective at rejecting loads with lower frequencies. BB and PID controllers, although capable of rejecting low frequency loads, may cause amplification of loads with higher frequencies. Investigating the performance of four controllers at different wind speeds for the studied wind turbine, it is observed that the effectiveness of BB and PID controllers reduces with wind speed but on the other hand SMC and LQR perform better at higher wind speeds. Introducing a new parameter, life index, the performance of different controllers in terms of the actuation wear is investigated. It is shown that LQR cause less actuation wear compared to SMC, while having comparable performance in load alleviation.

Microtab Design and Implementation on a 5 MW Wind Turbine

“…Passive control techniques would represent an improvement in the turbine's efficiency and in loads reduction without external energy consumption. Active control techniques need an additional energy source to get the desired effect on the flow and, unlike microtabs and other passive devices, active flow control needs intricate algorithms to get the maximum benefit (see Becker et al [16] and Macquart et al [17]). Johnson et al [7] made an analysis and discussed fifteen different devices for wind turbine control.…”

A decoupling control strategy for wind turbine blades equipped with active flow controllers

“…In general, current research follows the idea that increasingly complex control architectures such as optimal, multi‐input multi‐output (MIMO) and predictive control systems will outperform classical controllers . However, issues related to the tuning, sensing and state estimation required for MIMO state‐based controllers are rarely considered . Furthermore, it is known that the efficiency and stability of complex model‐based control structures may be very sensitive to uncertainty .…”

“…The dynamic response of an aerodynamic surface subjected to external forcing is generally obtained by numerical approximation, for which finite element (FE) modelling is one of the dominant approaches. In this research, we use the FE model that we previously developed in Macquart and Maheri and which approximates the aeroelastic behaviour of wind turbine blades using beam elements. Since the large size of FE models is often cumbersome to work with, we use a modal reduction in order to reduce the FE model by conserving only the prime dynamics .…”

“…The external force, included into the vector D Ae , on each element is assumed to be a uniformly distributed time varying force. These include aerodynamic forces calculated by an aerodynamic blade element momentum code and gravitational and inertia forces . Since the aerodynamic effects of CSs are generally much greater than their impacts on structural properties, the structural properties are assumed to remain unchanged.…”

Fatigue Loads Mitigation on Horizontal Axis Wind Turbines Using Aerodynamic Devices. A Survey

“…Various journal articles have been published on active flow control using different aerodynamic devices. For example; micro-tabs [38][39][40][41][42][43], Rigid trailing edge flap [44,45], deformable trailing edge flap (DTEF) [14,24,[44][45][46][47][48][49][50][51][52] and morphing trailing edge [44,45,[53][54][55][56][57][58]. Upwind Offshore NREL 5MW wind turbine [59] has been used extensively to investigate reduction of load on multi megawatts turbine [14, 45, 49-52, 60, 61].…”