ELECTRICITY GENERATION USING WIND POWER

ELECTRICITY GENERATION USING WIND POWER

ELECTRICITY GENERATION USING WIND POWER William Shepherd University of Bradford, UK Li Zhang University of Leeds, UK World Scientific NEW JERSEY LONDON SINGAPORE BEIJING SHANGHAI HONG KONG TAIPEI CHENNAI

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Published by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. ELECTRICITY GENERATION USING WIND POWER Copyright 2011 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. Desk Editor: Tjan Kwang Wei ISBN-13 978-981-4304-13-9 ISBN-10 981-4304-13-1 Typeset by Stallion Press Email: enquiries@stallionpress.com Printed in Singapore.

Foreword and Acknowledgement This book is written for electrical engineers and students of electrical engineering. As a textbook it is pitched at the level of final-year undergraduates and postgraduates. There is no detailed coverage of the aeronautical and meteorological features of wind turbines. The book is not intended as a design handbook. Certain of the chapters contain end-of-chapter numerical problems, with the answers shown separately at the end of the book. Some of the material in chapters 2, 5, 6 and 7 is reworked from earlier publications by of one of the authors (WS). This material is acknowledged in appropriate places and the authors are grateful to the publishers of the earlier work for their permission to reproduce it. Bradford, England 2010 v

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Contents Foreword and Acknowledgement... v 1. The Development of Wind Converters 1 1.1 Nature and Origin of the Wind... 1 1.2 Development of Wind Converters... 3 References... 6 2. Theory of Wind Converters 7 2.1 Power and Energy Basis of Wind Converters... 7 2.1.1 Origin and properties of the wind... 7 2.1.2 Power and energy... 8 2.2 Theoretical Power Available in the Wind... 9 2.3 Theoretical Maximum Power Extractable from the Wind... 11 2.4 Practical Power Extractable from the Wind... 15 2.4.1 Power coefficient... 15 2.4.2 Torque versus rotational speed... 16 2.4.3 Shaft power versus rotational speed... 16 2.4.4 Tip-speed ratio (TSR)... 17 2.5 Mechanical Features of Wind Machines... 19 2.5.1 Axial thrust (Pressure)... 19 2.5.2 The Yaw effect... 20 2.5.3 Gyroscopic forces and vibrations... 20 2.5.4 Centrifugal forces... 22 2.5.5 Solidity factor... 22 vii

viii Electricity Generation Using Wind Power 2.5.6 Two rotor blades or three rotor blades?... 23 2.5.7 Shaft torque and power... 24 2.6 Fixed Rotational Speed or Variable Rotational Speed?... 26 2.6.1 Constant speed operation... 27 2.6.2 Variable speed operation... 28 2.7 Efficiency Considerations of Wind-Powered Electricity Generation... 29 2.8 Worked Numerical Examples on Wind-Turbine Operation... 31 2.9 Problems and Review Questions... 36 References... 38 3. Past and Present Wind-Energy Turbines 41 3.1 Nineteenth-Century Windmills... 41 3.2 Early Twentieth-Century Wind-Energy Turbines... 43 3.3 Later Twentieth-Century Wind-Energy Turbines... 48 3.4 Modern Large Wind Power Installations... 51 3.5 Worked Numerical Example... 59 3.6 Vertical Axis Wind Machines... 60 3.6.1 The Savonius design... 61 3.6.2 The Darrieus design... 62 3.6.3 Other forms of vertical axis machine... 63 References... 63 4. The Location and Siting of Wind Turbines 65 4.1 The Availability of Wind Supply... 65 4.1.1 Global survey... 65 4.1.2 Energy content of the wind... 66 4.1.3 Wind-energy supply in Europe... 68 4.1.4 Wind-energy supply in the USA... 74 4.2 Statistical Representation of Wind Speed... 79 4.3 Choice of Wind Turbine Sites... 84 4.3.1 Identification of suitable areas... 85 4.3.2 Selection of possible sites within the chosen area... 85

Contents ix 4.4 Effects of the Site Terrain... 87 4.5 Spacing Effects of Wind Farm Arrays... 89 4.6 Problems and Review Questions... 91 References... 92 5. Power Flow in Electrical Transmission and Distribution Systems 93 5.1 Basic Forms of Power Transmission Networks... 93 5.2 Current and Voltage Relationships... 95 5.3 Power Relationships in Sinusoidal Circuits... 99 5.3.1 Instantaneous power... 99 5.3.2 Average power and apparent power... 100 5.3.3 Power factor... 101 5.3.4 Reactive power... 103 5.4 Complex Power... 105 5.5 Real Power Flow and Reactive Power Flow in Electrical Power Systems... 109 5.5.1 General summary... 109 5.5.2 Summary from the perspective of the References consumer...... 111 111 6. Electrical Generator Machines in Wind-Energy Systems 113 6.1 DC Generators... 113 6.2 AC Generators... 114 6.3 Synchronous Machine Generators... 114 6.4 Three-Phase Induction Machine... 121 6.4.1 Three-phase induction motor... 122 6.4.2 Three-phase induction generator... 127 6.4.3 Different generation systems... 132 6.5 Analysis of Induction Generator in Terms of Complex Vector Representation... 136 6.5.1 Three-phase to d-q-0 space vector transformation... 140 6.6 Switched Reluctance Machines... 143 6.6.1 Switched reluctance motors... 143 6.6.2 Switched reluctance generator... 144

x Electricity Generation Using Wind Power 6.7 What Form of Generator is the Best Choice for Wind Generation Systems?... 145 References... 146 7. Power Electronic Converters in Wind-Energy Systems 147 7.1 Types of Semiconductor Switching Converters... 147 7.2 Three-Phase Controlled Bridge Rectifier... 148 7.3 Three-Phase Controlled Bridge Inverter Feeding an Infinite Bus... 154 7.3.1 Output voltage... 154 7.3.2 Real (average) power output... 158 7.3.3 Reactive power... 159 7.3.4 RMS output current... 160 7.3.5 Inverter power factor... 162 7.4 The Effect of AC System Reactance on Inverter Operation... 164 7.5 Three-Phase Cycloconverter Feeding an Infinite Bus... 165 7.6 Matrix Converter Feeding an Infinite Bus... 166 7.7 Worked Numerical Examples... 169 7.7.1 Three-phase bridge rectifier... 169 7.7.2 Three-phase bridge inverter feeding on infinite bus... 170 7.8 Commonly Used Forms of Power Electronic Drive in Wind-Energy Systems... 175 7.8.1 Fixed-speed and directly coupled cage induction generator... 175 7.8.2 Variable-speed and doubly fed induction generator... 176 7.8.3 Variable-speed and direct drive synchronous generator... 177 7.9 Problems and Review Questions... 178 7.9.1 Three-phase controlled bridge rectifier, with ideal supply, feeding a highly inductive load.. 178

Contents xi 7.9.2 Three-phase, full-wave, and controlled bridge inverter feeding an infinite bus... 179 References... 180 8. Integrating Wind Power Generation into an Electrical Power System 181 8.1 Electricity Distribution Systems... 182 8.2 Issues for Consideration Concerning the Integration of Wind-Energy Generation into an Electric Power System... 183 8.2.1 Energy credit... 184 8.2.2 Capacity credit... 187 8.2.3 Control and reliability... 188 8.3 The Effect of Integrated Wind Generation on Steady-State System Voltages... 190 8.4 The Effect of Integrated Wind Generation on Dynamic and Transient System Voltages... 193 8.4.1 Lightning strikes... 194 8.4.2 Voltage flicker... 194 8.4.3 Harmonics... 195 8.4.4 Self-excitation of induction generators... 200 References... 201 9. Environmental Aspects of Wind Energy 203 9.1 Reduction of Emissions... 203 9.1.1 World consumption of coal... 203 9.1.2 Open coal fires... 205 9.2 Effluents due to Coal Burning... 206 9.2.1 Sulphur oxides... 206 9.2.2 Nitrogen oxides... 207 9.2.3 Particulates... 208 9.2.4 Carbon dioxide... 209 9.3 Wind Turbine Noise... 209 9.3.1 Measurement of wind turbine aerodynamic noise... 212 9.3.2 Mechanical noise... 214

xii Electricity Generation Using Wind Power 9.4 Electromagnetic Interference from Wind Turbines... 215 9.4.1 Electromagnetic interference radiated from wind turbines... 215 9.4.2 Electromagnetic interference effects due to the rotating blades... 216 9.5 Effect of a Wind Turbine on Wildlife... 217 9.6 Visual Impact of Wind Turbines... 219 9.6.1 Individual response... 219 9.6.2 Shadow flicker... 219 9.7 Safety Aspects of Wind-Turbine Operation... 220 References... 220 10. Economic Aspects of Wind Power 223 10.1 Investment Aspects of Wind-Powered Electricity Generation... 223 10.1.1 Costs of the turbines and generators... 224 10.1.2 Costs of the turbine site, construction, and grid connection... 225 10.1.3 Operation and maintenance (O and M) costs.. 226 10.1.4 Turbine lifetime and depreciation rate... 227 10.1.5 Cost associated with the financing of wind farm building and operation... 228 10.1.6 Wind regime at the turbine site... 229 10.2 Comparative Costs of Generating Electricity from Different Fuel Sources... 230 References... 234 Answers to the End of Chapter Problems 237 Index 241