SIGNAL PROCESSING OF POWER QUALITY DISTURBANCES

Transcription

1 SIGNAL PROCESSING OF POWER QUALITY DISTURBANCES

2 IEEE Press 445 Hoes Lane Piscataway, NJ IEEE Press Editorial Board Mohamed E. El-Hawary, Editor-in-Chief M. Akay J. B. Anderson R. J. Baker J. E. Brewer T. G. Croda R. J. Herrick S. V. Kartalopoulos M. Montrose M. S. Newman F. M. B. Pereira C. Singh G. Zobrist Kenneth Moore, Director of IEEE Book and Information Catherine Faduska, Senior Acquisitions Editor, IEEE Press Jeanne Audino, Project Editor, IEEE Press IEEE Power Engineering Society, Sponsor PE-S Liasion to IEEE Press, Chanan Singh Books in the IEEE Press Series on Power Engineering Rating of Electric Power Cables in Unfavorable Thermal Environments George J. Anders Power System Protection P. M. Anderson Understanding Power Quality Problems: Voltage Sags and Interruptions Math H. J. Bollen Electric Power Applications of Fuzzy Systems Edited by M. E. El-Hawary Principles of Electrica Machines with Power Electronic Applications, Second Edition M. E. El-Hawary Pulse Width Modulation for Power Converters: Principles and Practice D. Grahame Holmes and Thomas Lipo Analysis of Electric Machinery and Drive Systems, Second Edition Paul C. Krause, Oleg Wasynczuk, and Scott D. Sudhoff Risk Assessment for Power Systems: Models, Methods, and Applications Wenyuan Li Optimization Principles: Practical Applications to the Operations and Markets of the Electric Power Industry Narayan S. Rau Electric Economics: Regulation and Deregulation Geoffrey Rothwell and Tomas Gomez Electric Power Systems: Analysis and Control Fabio Saccomanno Electrical Insulation for Rotating Machines: Design, Evaluation, Aging, Testing and Repair Greg Stone, Edward A. Boulter, Ian Culbert, and Hussein Dhirani

3 SIGNAL PROCESSING OF POWER QUALITY DISTURBANCES MATH H. J. BOLLEN IRENE YU-HUA GU IEEE PRESS SERIES ON POWER ENGINEERING MOHAMED E. EL-HAWARY, SERIES EDITOR IEEE PRESS A JOHN WILEY & SONS, INC., PUBLICATION

4 Copyright # 2006 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published by John Wiley & Sons, Inc. Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) , fax (978) , or on the web at Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) , fax (201) , or online at Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) , outside the United States at (317) or fax (317) Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at Library of Congress Cataloging-in-Publication Data is available. ISBN ISBN Printed in the United States of America

5 To my father and in memory of my mother (from Irene)

6 CONTENTS PREFACE ACKNOWLEDGMENTS xvii xix 1 INTRODUCTION Modern View of Power Systems / Power Quality / Interest in Power Quality / Definition of Power Quality / Events and Variations / Power Quality Monitoring / Signal Processing and Power Quality / Monitoring Process / Decomposition / Stationary and Nonstationary Signals / Machine Learning and Automatic Classification / Electromagnetic Compatibility Standards / Basic Principles / Stochastic Approach / Events and Variations / Three Phases / 25 vii

7 viii CONTENTS 1.5 Overview of Power Quality Standards / Compatibility Between Equipment and Supply / Normal Operation / Normal Events / Abnormal Events / Distributed Generation / Impact of Distributed Generation on Current and Voltage Quality / Tripping of Generator Units / Conclusions / About This Book / 37 2 ORIGIN OF POWER QUALITY VARIATIONS Voltage Frequency Variations / Power Balance / Power Frequency Control / Consequences of Frequency Variations / Measurement Examples / Voltage Magnitude Variations / Effect of Voltage Variations on Equipment / Calculation of Voltage Magnitude / Voltage Control Methods / Voltage Unbalance / Symmetrical Components / Interpretation of Symmetrical Components / Power Definitions in Symmetrical Components: Basic Expressions / The dq-transform / Origin of Unbalance / Consequences of Unbalance / Voltage Fluctuations and Light Flicker / Sources of Voltage Fluctuations / Description of Voltage Fluctuations / Light Flicker / Incandescent Lamps / Perception of Light Fluctuations / Flickercurve / Flickermeter Standard / 101

8 CONTENTS ix Flicker with Other Types of Lighting / Other Effects of Voltage Fluctuations / Waveform Distortion / Consequences of Waveform Distortion / Overview of Waveform Distortion / Harmonic Distortion / Sources of Waveform Distortion / Harmonic Propagation and Resonance / Summary and Conclusions / Voltage Frequency Variations / Voltage Magnitude Variations / Voltage Unbalance / Voltage Fluctuations and Flicker / Waveform Distortion / PROCESSING OF STATIONARY SIGNALS Overview of Methods / Parameters That Characterize Variations / Voltage Frequency Variations / Voltage Magnitude Variations / Waveform Distortion / Three-Phase Unbalance / Power Quality Indices / Total Harmonic Distortion / Crest Factor / Transformers: K-factor / Capacitor Banks / Motors and Generators / Telephone Interference Factor / Three-Phase Harmonic Measurements / Power and Power Factor / Frequency-Domain Analysis and Signal Transformation / Continuous and Discrete Fourier Series / Discrete Fourier Transform / Estimation of Harmonics and Interharmonics / Sinusoidal Models and High-Resolution Line Spectral Analysis / Multiple Signal Classification / 233

9 x CONTENTS Estimation of Signal Parameters via Rotational Invariance Techniques / Kalman Filters / Estimation of Broadband Spectrum / AR Models / ARMA Models / Summary and Conclusions / Frequency Variations / Voltage Magnitude Variations / Three-Phase Unbalance / Waveform Distortion / Methods for Spectral Analysis / General Issues / Further Reading / PROCESSING OF NONSTATIONARY SIGNALS Overview of Some Nonstationary Power Quality Data Analysis Methods / Non-Model-Based Methods / Model-Based Methods / Discrete STFT for Analyzing Time-Evolving Signal Components / Interpretation of STFT as Bank of Subband Filters with Equal Bandwidth / Time Resolution and Frequency Resolution / Selecting Center Frequencies of Bandpass Filters / Leakage and Selection of Windows / Discrete Wavelet Transforms for Time Scale Analysis of Disturbances / Structure of Multiscale Analysis and Synthesis Filter Banks / Conditions for Perfect Reconstruction / Orthogonal Two-Channel PR Filter Banks / Linear-Phase Two-Channel PR Filter Banks / Possibility for Two-Channel PR FIR Filter Banks with Both Linear-Phase and Orthogonality / Steps for Designing Two-Channel PR FIR Filter Banks / Discussion / Consideration in Power Quality Data Analysis: Choosing Wavelets or STFTs? / 296

10 CONTENTS xi 4.4 Block-Based Modeling / Why Divide Data into Blocks? / Divide Data into Fixed-Size Blocks / Block-Based AR Modeling / Sliding-Window MUSIC and ESPRIT / Models Directly Applicable to Nonstationary Data / Kalman Filters / Discussion: Sliding-Window ESPRIT/MUSIC Versus Kalman Filter / Summary and Conclusion / Further Reading / STATISTICS OF VARIATIONS From Features to System Indices / Time Aggregation / Need for Aggregation / IEC / Voltage and Current Steps / Very Short Variations / Flagging / Phase Aggregation / Characteristics Versus Time / Arc-Furnace Voltages and Currents / Voltage Frequency / Voltage Magnitude / Very Short Variations / Harmonic Distortion / Site Indices / General Overview / Frequency Variations / Voltage Variations / Very Short Variations / Voltage Unbalance / Voltage Fluctuations and Flicker / Voltage Distortion / Combined Indices / 381

11 xii CONTENTS 5.5 System Indices / General / Frequency Variations / Voltage Variations / Voltage Fluctuations / Unbalance / Distortion / Power Quality Objectives / Point of Common Coupling / Voltage Characteristics, Compatibility Levels, and Planning Levels / Voltage Characteristics EN / Compatibility Levels: IEC / Planning Levels: IEC / Current Distortion by Customers: IEC ; IEEE Standard 519 / Current Distortion by Equipment: IEC / Other Power Quality Objectives / Summary and Conclusions / ORIGIN OF POWER QUALITY EVENTS Interruptions / Terminology / Causes of Interruptions / Restoration and Voltage Recovery / Multiple Interruptions / Voltage Dips / Causes of Voltage Dips / Voltage-Dip Examples / Voltage Dips in Three Phases / Phase-Angle Jumps Associated with Voltage Dips / Voltage Recovery After a Fault / Transients / What Are Transients? / Lightning Transients / Normal Switching Transients / Abnormal Switching Transients / Examples of Voltage and Current Transients / 509

12 CONTENTS xiii 6.4 Summary and Conclusions / Interruptions / Voltage Dips / Transients / Other Events / TRIGGERING AND SEGMENTATION Overview of Existing Methods / Dips, Swells, and Interruptions / Transients / Other Proposed Methods / Basic Concepts of Triggering and Segmentation / Triggering Methods / Changes in rms or Waveforms / High-Pass Filters / Detecting Singular Points from Wavelet Transforms / Prominent Residuals from Models / Segmentation / Basic Idea for Segmentation of Disturbance Data / Using Residuals of Sinusoidal Models / Using Residuals of AR Models / Using Fundamental-Voltage Magnitude or rms Sequences / Using Time-Dependent Subband Components from Wavelets / Summary and Conclusions / CHARACTERIZATION OF POWER QUALITY EVENTS Voltage Magnitude Versus Time / rms Voltage / Half-Cycle rms / Alternative Magnitude Definitions / Phase Angle Versus Time / Three-Phase Characteristics Versus Time / Symmetrical-Component Method / Implementation of Symmetrical-Component Method / Six-Phase Algorithm / Performance of Two Algorithms / 604

13 xiv CONTENTS 8.4 Distortion During Event / Single-Event Indices: Interruptions / Single-Event Indices: Voltage Dips / Residual Voltage and Duration / Depth of a Voltage Dip / Definition of Reference Voltage / Sliding-Reference Voltage / Multiple-Threshold Setting / Uncertainty in Residual Voltage / Point on Wave / Phase-Angle Jump / Single-Index Methods / Single-Event Indices: Voltage Swells / Single-Event Indices Based on Three-Phase Characteristics / Additional Information from Dips and Interruptions / Transients / Extracting Transient Component / Transients: Single-Event Indices / Transients in Three Phases / Additional Information from Transients / Summary and Conclusions / EVENT CLASSIFICATION Overview of Machine Data Learning Methods for Event Classification / Typical Steps Used in Classification System / Feature Extraction / Feature Optimization / Selection of Topologies or Architectures for Classifiers / Supervised/Unsupervised Learning / Cross-Validation / Classification / Learning Machines Using Linear Discriminants / Learning and Classification Using Probability Distributions / Hypothesis Tests and Decision Trees / Neyman Pearson Approach / Bayesian Approach / 694

14 CONTENTS xv Bayesian Belief Networks / Example of Sequential Classification of Fault-Induced Voltage Dips / Learning and Classification Using Artificial Neural Networks / Multilayer Perceptron Classifiers / Radial-Basis Function Networks / Applications to Classification of Power System Disturbances / Learning and Classification Using Support Vector Machines / Why Use a Support Vector Machine for Classification? / SVMs and Generalization Error / Case 1: SVMs for Linearly Separable Patterns / Case 2: Soft-Margin SVMs for Linearly Nonseparable Patterns / Selecting Kernels for SVMs and Mercer s Condition / Implementation Issues and Practical Examples of SVMs / Example of Detecting Voltage Dips Due to Faults / Rule-Based Expert Systems for Classification of Power System Events / Structure and Rules of Expert Systems / Application of Expert Systems to Event Classification / Summary and Conclusions / EVENT STATISTICS Interruptions / Interruption Statistics / IEEE Standard 1366 / Transmission System Indices / Major Events / Voltage Dips: Site Indices / Residual Voltage and Duration Data / Scatter Plot / Density and Distribution Functions / Two-Dimensional Distributions / SARFI Indices / Single-Index Methods / Year-to-Year Variations / Comparison Between Phase Ground and Phase Phase Measurements / 771

15 xvi CONTENTS 10.3 Voltage Dips: Time Aggregation / Need for Time Aggregation / Time Between Events / Chains of Events for Four Different Sites / Impact on Site Indices / Voltage Dips: System Indices / Scatter Plots / Distribution Functions / Contour Charts / Seasonal Variations / Voltage-Dip Tables / Effect of Time Aggregation on Voltage-Dip Tables / SARFI Indices / Single-Index Methods / Summary and Conclusions / Interruptions / Voltage Dips / Time Aggregation / Stochastic Prediction Methods / Other Events / CONCLUSIONS Events and Variations / Power Quality Variations / Power Quality Events / Itemization of Power Quality / Signal-Processing Needs / Variations / Variations and Events / Events / Event Classification / 819 APPENDIX A IEC STANDARDS ON POWER QUALITY 821 APPENDIX B IEEE STANDARDS ON POWER QUALITY 825 BIBLIOGRAPHY 829 INDEX 849

16 PREFACE This book originated from a few occasional discussions several years ago between the authors on finding specific signal-processing tools for analyzing voltage disturbances. These simple discussions have led to a number of joined publications, several Masters of Science projects, three Ph.D. projects, and eventually this book. Looking back at this process it seems obvious to us that much can be gained by combining the knowledge in power system and signal processing and bridging the gaps between these two areas. This book covers two research areas: signal processing and power quality. The intended readers also include two classes: students and researchers with a power engineering background who wish to use signal-processing techniques for power system applications and students and researchers with a signal-processing background who wish to extend their research applications to power system disturbance analysis and diagnostics. This book may also serve as a general reference book for those who work in industry and are engaged in power quality monitoring and innovations. Especially, the more practical chapters (2, 5, 6, and 10) may appeal to many who are currently working in the power quality field. The first draft of this book originated in 2001 with the current structure taking shape during the summer of Since then it took another three years for the book to reach the state in which you find it now. The outside world did not stand still during these years and many new things happened in power quality, both in research and in the development of standards. Consequently, we were several times forced to rewrite parts and to add new material. We still feel that the book can be much more enriched but decided to leave it in its current form, considering among others the already large number of pages. We hope that the readers will pick up a few open subjects from the book and continue the work. The conclusion xvii

17 xviii PREFACE sections in this book contain some suggestions on the remaining issues that need to be resolved in the authors view. Finally, we will be very happy to receive feedback from the readers on the contents of this book. Our s are and If you find any mistake or unclarity or have any suggestion, please let us know. We cannot guarantee to answer everybody but you can be assured that your message will be read and it will mean a lot to us. Ludvika, Sweden Gothenburg, Sweden May 2006 MATH H. J. BOLLEN IRENE Y. H. GU

18 ACKNOWLEDGMENTS The authors would like to thank those who have contributed to the knowledge for the writing of this book. A main word of thanks goes to colleagues and students at Eindhoven University of Technology, Eindhoven, The Netherlands; University of Manchester Institute of Science and Technology (UMIST, currently part of University of Manchester), Manchester, United Kingdom; the University of Birmingham, Birmingham, United Kingdom; Chalmers University of Technology (Gothenburg, Sweden); STRI AB (Ludvika, Sweden); and Luleå University of Technology (Skellefteå, Sweden). Especially we would like to thank Emmanouil Styvaktakis for his contributions to bridging the gap between our research areas. The availability of data from real power system measurements has been an important condition for allowing us to write this book. Measurement data and other power system data and information were collected through the years. Even though not all of them were used for the material presented in this book, they all contributed to our further understanding of power quality monitoring and disturbance data analysis. Therefore we would like to thank all those that have contributed their measurement data through the years (in alphabetical order): Peter Axelberg (Unipower); Geert Borloo (Elia); Larry Conrad (Cinergy); Magnus Ericsson (Trinergi); Alistair Ferguson (Scottish Power); Zhengti Gu (Shanghai, China); Per Halvarsson (Trinergi and Dranetz BMI); Mats Häger (STRI); Daniel Karlsson (Sydkraft, currently at Gothia Power); Johan Lundquist (Chalmers, currently at Sycon); Mark McGranaghan (Electrotek, currently at EPRI Solutions); Larry Morgan (Duke Power); Robert Olofsson (Göteborg Energi, currently at Metrum, Sweden); Giovanna Postiglione (University of Naples, currently at FIAT Engineering); Christian Roxenius (Göteborg Energi); Dan Sabin (Electrotek); Ambra Sannino (Chalmers, currently at ABB); Helge Seljeseth (Sintef Energy Research); xix

19 xx ACKNOWLEDGMENTS Torbjörn Thiringer (Chalmers); Erik Thunberg (Svenska Kraftnät); and Mats Wahlberg (Skellefteå Kraft). The interesting discussions in a number of working groups and international cooperation projects also contributed to the material presented in this book. The authors especially acknowledge the contribution from fellow members in IEEE task force P1564 and CIGRE working group C4.07 (originally 36.07). Many thanks are due to the anonymous reviewers of this book for their valuable suggestions. Thanks are also due to Peter Willett (University of Connecticut, United States) for his encouragement and very useful suggestions, and to Mats Viberg (Chalmers, Sweden) for support. A special thanks also goes to Lars Moser (KvaLita, Sweden) for invaluable encouragement and support. A final thanks goes to Marilyn Catis and Anthony Vengraitis at IEEE Press for encouraging us to start writing this book and for the help through the whole writing process. M. H. J. B I. Y-H. G