FUNDAMENTAL AND ADVANCED TOPICS IN WIND POWER Edited by Rupp Carriveau Fundamental and Advanced Topics in Wind Power Edited by Rupp Carriveau Published by InTech Janeza Trdine 9, 51000 Rijeka, Croatia Copyright © 2011 InTech All chapters are Open Access articles distributed under the Creative Commons Non Commercial Share Alike Attribution 3.0 license, which permits to copy, distribute, transmit, and adapt the work in any medium, so long as the original work is properly cited. After this work has been published by InTech, authors have the right to republish it, in whole or part, in any publication of which they are the author, and to make other personal use of the work. Any republication, referencing or personal use of the work must explicitly identify the original source. Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published articles. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book. Publishing Process Manager Davor Vidic Technical Editor Teodora Smiljanic Cover Designer Jan Hyrat Image Copyright Floris Slooff, 2010. Used under license from Shutterstock.com First published June, 2011 Printed in Croatia A free online edition of this book is available at www.intechopen.com Additional hard copies can be obtained from orders@intechweb.org Fundamental and Advanced Topics in Wind Power, Edited by Rupp Carriveau p. cm. ISBN 978-953-307-508-2 free online editions of InTech Books and Journals can be found at www.intechopen.com Contents Preface IX Part 1 Aerodynamics and Environmental Loading of Wind Turbines 1 Chapter 1 Aerodynamics of Wind Turbines 3 Emrah Kulunk Chapter 2 Wind Turbines Theory - The Betz Equation and Optimal Rotor Tip Speed Ratio 19 Magdi Ragheb and Adam M. Ragheb Chapter 3 Inboard Stall Delay Due to Rotation 39 Horia Dumitrescu and Vladimir Cardoş Chapter 4 Verification of Lightning Protection Measures 65 Søren Find Madsen Chapter 5 Extreme Winds in Kuwait Including the Effect of Climate Change 89 S. Neelamani and Layla Al-Awadi Part 2 Structural and Electromechanical Elements of Wind Power Conversion 113 Chapter 6 Efficient Modelling of Wind Turbine Foundations 115 Lars Andersen and Johan Clausen Chapter 7 Determination of Rotor Imbalances 175 Jenny Niebsch Chapter 8 Wind Turbine Gearbox Technologies 189 Adam M. Ragheb and Magdi Ragheb VI Contents Chapter 9 Monitoring and Damage Detection in Structural Parts of Wind Turbines 207 Andreas Friedmann, Dirk Mayer, Michael Koch and Thomas Siebel Chapter 10 Magnetic Suspension and Self-pitch for Vertical-axis Wind Turbines 233 Liu Shuqin Chapter 11 The Analysis and Modelling of a Self-excited Induction Generator Driven by a Variable Speed Wind Turbine 249 Ofualagba, G and Ubeku, E.U Chapter 12 Optimisation of the Association of Electric Generator and Static Converter for a Medium Power Wind Turbine 269 Daniel Matt, Philippe Enrici, Florian Dumas and Julien Jac Part 3 Wind Turbine Control and System Integration 289 Chapter 13 Advanced Control of Wind Turbines 291 Abdellatif Khamlichi, Brahim Ayyat, Mohammed Bezzazi and Carlos Vivas Chapter 14 A Complete Control Scheme for Variable Speed Stall Regulated Wind Turbines 309 Dimitris Bourlis Chapter 15 MPPT Control Methods in Wind Energy Conversion Systems 339 Jogendra Singh Thongam and Mohand Ouhrouche Chapter 16 Modelling and Environmental/Economic Power Dispatch of MicroGrid Using MultiObjective Genetic Algorithm Optimization 361 Faisal A. Mohamed and Heikki N. Koivo Chapter 17 Size Optimization of a Solar-wind Hybrid Energy System Using Two Simulation Based Optimization Techniques 379 Orhan Ekren and Banu Yetkin Ekren Chapter 18 Fuzzy Control of WT with DFIG for Integration into Micro-grids 399 Christina N. Papadimitriou and Nicholas A. Vovos Preface As the fastest growing source of energy in the world, wind has a very important role to play in the global energy mix. This becomes increasingly apparent as many countries begin to phase out traditional fossil fuels, while some re-evaluate their comfort level with nuclear power generation. The conversion of wind’s kinetic energy into another desired form dates back millennia. The years since have afforded some time for maturation of the technology. However, while many advances have been made in the last 40 years, challenges remain in the complex interdependent mechanisms that comprise wind energy production. The first of such challenges include the natural environment in which the industry operates. Climate change and its impact on wind patterns has become a variable of some consideration when examining long term wind energy outputs. More recently, the increasing density of wind park penetration has provoked some regions to contemplate how large scale energy extraction from the wind may eventually influence local microclimates. As wind parks become more widespread across the landscape, concerns are raised about the inevitable intersection with extreme weather that can bring with it destructive winds and lightning. Even under normal atmospheric conditions; from the fundamentals of the Betz equation to the intricate impact of turbulence on blade boundary layer separation, the wind environment and turbine aerodynamics continue to be active subjects of study. The mechanical conversion of wind loading into electricity is an ongoing concern for wind power producers. Frequently cited as a leading maintenance matter in utility scale commercial wind energy generation, mechanical transmissions and associated electric generator designs are recurrently being refined. The optimization of these individual components and their coupling will continue to be a factor in the economics of future wind power. The highly variable and cyclic loads on rotor, mechanical transmission, tower, and foundation all demand special fatigue design considerations. The potential for low frequency, high intensity loading events like extreme weather, create an even greater demand for a fuller appreciation of how the turbine ages structurally and mechanically over its service life. With appropriate wind resources secured, and proven structural and electromechanical designs in place, what remains is how to optimally control wind generators to provide X Preface the desired output for stakeholders. This may be a utility, small business, or household. The integration of wind turbines of varying scales into a larger system will be perhaps the most considerable challenge facing a growing industry. Wind power is now advanc- ing against a backdrop of energy grid evolution not seen since grids were instituted a century ago. Wind will be integrated with other renewable and legacy fossil generators, storage facilities, and a range of loads, into new micro and smart grid infrastructures. As the demand for energy increases in both the developed and developing worlds, so will also increase the variety of end applications for wind power. The complete picture of the energy grid of the future is far from totally defined. What is clear however, is the signifi- cant part that wind power will play. This text covers a spectrum of leading edge topics critical to the rapidly evolving wind power industry. The reader is introduced to the fundamentals of wind energy aerody- namics; then essential structural, mechanical, and electrical subjects are discussed. The book is composed of three sections that include the Aerodynamics and Environmental Loading of Wind Turbines, Structural and Electromechanical Elements of Wind Power Conversion, and Wind Turbine Control and System Integration. In addition to the fundamental rudiments illustrated, the reader will be exposed to specialized applied and advanced topics including magnetic suspension bearing systems, structural health monitoring, and the optimized integration of wind power into micro and smart grids. Rupp Carriveau Ph.D. P.Eng. Associate Professor Civil and Environmental Engineering University of Windsor [...]... (9) Substituting equation 7 into equation 8 gives the thrust on the disk in more explicit form 1 2 (10 ) ∞ Combining Eqn 3, 4 and 10 the velocity through the disk can be obtained as (11 ) ∞ 2 Defining the axial induction factor α as in Eqn 12 ∞ (12 ) ∞ gives Eqn 13 and 14 1 (13 ) 1 2 (14 ) To find the power output of the rotor Eqn 15 can be used (15 ) By substituting equation 10 into 15 gives the power output... Part 1 Aerodynamics and Environmental Loading of Wind Turbines 1 Aerodynamics of Wind Turbines Emrah Kulunk New Mexico Institute of Mining and Technology USA 1 Introduction A wind turbine is a device that extracts kinetic energy from the wind and converts it into mechanical energy Therefore wind turbine power production depends on the interaction between the rotor and the wind So the major... rotor in more explicit form 1 2 (16 ) ∞ Also substituting equations 13 and 14 into equation 15 gives 2 1 (17 ) Finally the performance parameters of a HAWT rotor (power coefficient C , thrust coefficient C , and the tip-speed ratio λ) can be expressed in dimensionless form which is given in Eqn 18 , 19 and 20 respectively 6 Fundamental and Advanced Topics in Wind Power 2 (18 ) ∞ 2 (19 ) ∞ (20) ∞ Substituting... the rotor becomes 1 2 ∞ 1 2 1 2 ∞ 1 2 ′ (27) Applying the Bernoulli’s equation between station 2 and 3 gives the pressure drop as 1 2 2 (28) Substituting this result into the equation 27 gives 1 2 2 (29) 8 Fundamental and Advanced Topics in Wind Power In station 4, the pressure gradient can be written as (30) Differentiating Eqn 29 relative to r and equating to equation 30 gives 1 2 ( 31) The equation... rotor performance and blade design Carrying the tip-loss factor through the calculations, the changes will be as following: 4 1 4 1 (75) (76) 15 Aerodynamics of Wind Turbines 1 (78) 4 1 (79) 4 4 (80) 1 ( 81) 4 1 1 4 8 1 1 1 (82) (83) The results for the span-wise variation of power extraction in the presence of tip-loss for a blade with uniform circulation on a three-bladed HAWT operating at a tip speed... given in Eqn 18 using Eqn 72 gives 14 Fundamental and Advanced Topics in Wind Power Using Eqn 60, 65 and 70 the power coefficient relation can be rearranged as (73) 2.4 .1 Tip losses At the tip of the turbine blade losses are introduced The ratio of the average value of tip loss factor to that at a blade position is given in Fig 6 As it is shown in the figure only near the tip the ratio begins to fall... equated to obtain the following expression (62) Also equating Eqn 40 and 60 in the same manner gives 13 Aerodynamics of Wind Turbines (63) By rearranging Eqn 63 and combining it with Eqn 50 (64) can be written In order to calculate the induction factors and ′, C can be set to zero Thus the induction factors can be determined independently from airfoil characteristics Subsequently, Eqn 62, 63 and 64 can... Roskilde, 20 01 Burton, T and Sharpe, D., Wind Energy Handbook John Wiley & Sons Ltd, ISBN 0-4 71- 489972, Chichester, 2006 Glauert, H., (19 35b) Windmills and Fans Aerodynamic theory (ed Durand, W F.) Julius Springer, Berlin, Germany Hau, E., Wind Turbines: Fundamentals, Technologies, Application, Economics Krailling, Springer, 2006 Hoerner, S F., (19 65) ‘Pressure drag on rotating bodies’ Fluid dynamic... Rotor Examining Fig 5, the following equations can be derived immediately (49) (50) ( 51) (52) (53) 12 Fundamental and Advanced Topics in Wind Power (54) If the rotor has B number of blades, Eqn 49, 51 and 52 can be rearranged (55) (56) The elemental torque can be written as dQ rdL which gives Eqn 57 (57) Also Eqn 58 can be derived by examining Fig 5 (58) The solidity ratio can be defined as (59) Finally,... in Wind Power 2 (18 ) ∞ 2 (19 ) ∞ (20) ∞ Substituting Eqn 17 into Eqn 18 , the power coefficient of the rotor can be rewritten as 4 1 ( 21) Also using the equations 10 , 13 and 17 the axial thrust on the disk can be rewritten as 2 1 (22) Finally substituting equation 22 into equation 19 gives the thrust coefficient of the rotor as 4 1 (23) 2.2 Rotating annular stream tube analysis Thus far the method is . Aerodynamics and Environmental Loading of Wind Turbines 1 Aerodynamics of Wind Turbines Emrah Kulunk New Mexico Institute of Mining and Technology USA 1. Introduction A wind turbine is a. that include the Aerodynamics and Environmental Loading of Wind Turbines, Structural and Electromechanical Elements of Wind Power Conversion, and Wind Turbine Control and System Integration. In.     ∞   2 (11 ) Defining the axial induction factor α as in Eqn 12   ∞    ∞ (12 ) gives Eqn 13 and 14 .     1  (13 )     1 2 (14 ) To find the power output