Power Systems

More information about this series at http://www.springer.com/series/4622

Magdi S. Mahmoud • Fouad M. AL-Sunni

Control and Optimizationof Distributed GenerationSystems

123

Magdi S. MahmoudDepartment of Systems EngineeringKing Fahd University of Petroleumand Minerals

DhahranSaudi Arabia

Fouad M. AL-SunniDepartment of Systems EngineeringKing Fahd University of Petroleumand Minerals

DhahranSaudi Arabia

ISSN 1612-1287 ISSN 1860-4676 (electronic)Power SystemsISBN 978-3-319-16909-5 ISBN 978-3-319-16910-1 (eBook)DOI 10.1007/978-3-319-16910-1

Library of Congress Control Number: 2015934050

Mathematics Subject Classification: 93A10, 93A13, 93A14, 93A15, 93A30

Springer Cham Heidelberg New York Dordrecht London© Springer International Publishing Switzerland 2015This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or partof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmissionor information storage and retrieval, electronic adaptation, computer software, or by similar ordissimilar methodology now known or hereafter developed.The use of general descriptive names, registered names, trademarks, service marks, etc. in thispublication does not imply, even in the absence of a specific statement, that such names are exemptfrom the relevant protective laws and regulations and therefore free for general use.The publisher, the authors and the editors are safe to assume that the advice and information in thisbook are believed to be true and accurate at the date of publication. Neither the publisher nor theauthors or the editors give a warranty, express or implied, with respect to the material containedherein or for any errors or omissions that may have been made.

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In the Name of

the All-Compassionate, the All-Merciful.“And of knowledge, you (mankind)have been given only a little.”

To Our Families

Magdi S. Mahmoud, Fouad M. AL-SunniDhahran-Saudi Arabia, 2013

Preface

Distributed generation (DG) of electricity based on renewable energy sources suchas wind and solar is gaining more and more attention all over the world because ofever growing concerns on energy cost, energy security, and environmental issues.Although DG has a great potential for economic and environmental benefits, how toestablish efficient and reliable control over a large number of DG units is one of thefundamental problems to be solved in the near future. One promising solution tothis problem is the microgrid, which interconnects a group of DG units and loads ata distribution voltage level in a local area such as a university or a residentialcommunity. Microgrids are small-scale power systems that facilitate the integrationof distributed generators and can operate in both grid-connected and islandedmodes. In normal operation, the microgrid is connected to the main grid, and itsfrequency is dictated by the nominal frequency of the main grid. However, themicrogrid may disconnect from the main grid and go to the islanded operation dueto preplanned or unplanned events. Islanding process results in active powerunbalance between generation and consumption units which, in turn, may causefrequency instability.

Microgrids are established based on localized control and can operate in either agrid-connected mode or an islanded mode, which significantly reduces the com-plexity of DG unit control. In order to avoid high capital expenditure and lowreliability in microgrid operation, decentralized control is indispensable.

This book is essentially written for senior and first-year graduate studentsinterested in studying distributed energy systems and future power systems. Thedifferent chapters and sections are organized to treat three broad avenues, namelyarchitectures and integration, modeling and analysis, and communication andcontrol. The main perspective of these sections is to capture the main sources forexpanding the present electric power grid. Our goal is to capture the spectrum ofthis exponential transformation, and at the same time present the plethora of openproblems that this transformation poses for our control theory colleagues.

ix

The layout of the different chapters is as follows:

• The architectures and integration avenue opens the book with visionary ideas onsustainable architectures for power system operation and control under significantpenetration of highly variable renewable energy resources presented in Chap. 1.

• This is followed by a detailed discussion on the distribution generation plants andtheir dynamic models in Chap. 2.

• Chapter 3 addresses the problem of supply–demand in electric power grid.• Chapter 4 illustrates several practical control methods for microgrids.• Chapter 5 focuses on a technical survey of computational intelligence methods.• Chapter 6 provides a system of systems approach to the modeling, analysis, andcontrol/optimization of microgrids.

• Chapter 7 delves into novel networked control techniques for wide-area oscil-lation tracking in large-scale power systems.

• This is further elaborated in Chap. 8 to highlight the importance of distributedcontrol and processing as a major tool for wide-area monitoring research.

• In Chap. 9, a hierarchical structuring and control approach is introduced to modelthe dynamic mechanisms of cascading failures in geographically dispersed grids.

• The book in concluded by an Appendix to complement the math analysis of thebook.

Looked at in this light, this book deals with the basic concept, generation tech-nologies, impacts, operation, control and management aspects, and economic via-bility and market participation issues of microgrid and active distribution networksin a broad perspective.

Each chapter includes examples/simulation cases and a list of appropriateproblems at the end.

Throughout this book, the following terminologies, conventions, and notationshave been adopted. All of them are quite standard in the scientific media and onlyvary in form or character. Matrices, if their dimensions are not explicitly stated, areassumed to be compatible for algebraic operations. In symmetric block matrices orcomplex matrix expressions, we use the symbol � to represent a term that is inducedby symmetry.

x Preface

Acknowledgments

The book is mainly targeted at senior undergraduate or graduate-level students, atacademic and industrial researchers working in the field of electrical energy sys-tems, and also at engineers developing actual solutions for distributed generationsystems deploying communication networks. One can view this book as a goodbasis to teach a class on networked-control systems for distributed generationsystems.

The idea of writing the book arose and developed during extensive discussionswithin KFUPM, where we took full advantage of the supportive scientific envi-ronment. It is our great pleasure to acknowledge the financial funding afforded byDSR through project no. IN141019 and for providing overall support for researchactivities at KFUPM.

During the past years, we had the privilege of teaching various senior andgraduate courses at KFUPM (Saudi Arabia). The course notes, updated and orga-nized, were instrumental in generating different chapters of this book and valuablecomments and/or suggestions by graduate students were greatly helpful, particu-larly by those who attended the courses SCE 507, SCE 527, SCE 614, and SCE691 offered at the Systems Engineering Department over the period 2007–2013.

Heartfelt thanks are owed to our colleagues from all over the world who havehelped us, one way or another, in grasping the fundamental concepts of this excitingfield and in writing this book. Moreover, we deeply appreciate the efforts ofDr. Muhammad Sabih, Azhar M. Memon, Nezar M. Alyazidi, Mohammad S.Rahman, Azhar S. Hussain, and Gulam D. Khan for their unfailing help in pre-paring portions of the manuscript and performing effective numerous simulations.

In writing this volume, we took the approach of referring within the text topapers and/or books which we believe taught us some concepts, ideas, and meth-ods. We further complemented this by adding some remarks, observations, andnotes within and at the end of each chapter to shed some light on other relatedresults. We apologize in advance if we have committed injustice and assure allof the colleagues that any mistake was definitely unintentional. We also want toexpress our deep gratitude to all the researchers in the field who have made theirresults and publications easily available over the World Wide Web. Without this

xi

help, collecting the material discussed in the present book alone would have beentoo big a challenge to embark on.

Most of all, however, we would like to express our deepest gratitude to ourparents who taught us the value of the written word and to all the members of ourfamilies. Without their constant love, incredible patience, and (mostly) enthusiasticsupport this volume would not have been finished.

We would appreciate any comments, questions, criticisms, or corrections thatreaders may take the trouble of communicating tome at msmahmoud@kfupm.edu.sa,alsunni@kfupm.edu.sa, magdisadekmahmoud@gmail.com.

Dhahran, Saudi Arabia Magdi S. MahmoudMarch 2015 Fouad M. AL-Sunni

xii Acknowledgments

Contents

Part I Modeling and Analysis

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.1 Distributed Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1.1 Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.1.2 Value of Distributed Generation . . . . . . . . . . . . . . . 51.1.3 Applications and Issues . . . . . . . . . . . . . . . . . . . . . 51.1.4 Distributed Resources . . . . . . . . . . . . . . . . . . . . . . 61.1.5 Distributed Capacity . . . . . . . . . . . . . . . . . . . . . . . 71.1.6 Factors of DG Growth. . . . . . . . . . . . . . . . . . . . . . 71.1.7 Impacts on Transmission System Operation . . . . . . . 91.1.8 General Structure . . . . . . . . . . . . . . . . . . . . . . . . . 101.1.9 Integrating Distributed Energy Resources . . . . . . . . . 12

1.2 Supply–Demand in Electric Power Grid . . . . . . . . . . . . . . . . 121.2.1 Understanding the Grid . . . . . . . . . . . . . . . . . . . . . 121.2.2 Reliability Concepts . . . . . . . . . . . . . . . . . . . . . . . 131.2.3 Electric Power Dynamic Demand . . . . . . . . . . . . . . 141.2.4 The Need for Spinning Reserve . . . . . . . . . . . . . . . 141.2.5 Local Load Control . . . . . . . . . . . . . . . . . . . . . . . . 151.2.6 Ancillary Services . . . . . . . . . . . . . . . . . . . . . . . . . 151.2.7 Implementation Issues . . . . . . . . . . . . . . . . . . . . . . 15

1.3 Overview of Microgrids. . . . . . . . . . . . . . . . . . . . . . . . . . . 161.3.1 Control Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181.3.2 A Classification . . . . . . . . . . . . . . . . . . . . . . . . . . 191.3.3 Control Objectives and Methods . . . . . . . . . . . . . . . 211.3.4 Microsource Control . . . . . . . . . . . . . . . . . . . . . . . 231.3.5 Control and Protection Requirements. . . . . . . . . . . . 251.3.6 Reliable and Economical Operation . . . . . . . . . . . . . 26

1.4 Smart Grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261.4.1 Efficiency and Reliability. . . . . . . . . . . . . . . . . . . . 271.4.2 Environmental Benefits . . . . . . . . . . . . . . . . . . . . . 28

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1.4.3 Benefits to Consumers. . . . . . . . . . . . . . . . . . . . . . 281.4.4 Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

1.5 Technical Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291.5.1 Two-Way Communications . . . . . . . . . . . . . . . . . . 291.5.2 Control and Monitoring Techniques . . . . . . . . . . . . 301.5.3 Advanced Components . . . . . . . . . . . . . . . . . . . . . 301.5.4 Energy Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . 311.5.5 Robust Energy Management. . . . . . . . . . . . . . . . . . 33

1.6 DC Microgrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351.6.1 PV Sources Control. . . . . . . . . . . . . . . . . . . . . . . . 361.6.2 Storage Control . . . . . . . . . . . . . . . . . . . . . . . . . . 371.6.3 Grid Connection Control . . . . . . . . . . . . . . . . . . . . 381.6.4 DC Load Control . . . . . . . . . . . . . . . . . . . . . . . . . 381.6.5 Power Balancing Principle . . . . . . . . . . . . . . . . . . . 38

1.7 Outline of the Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391.7.1 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391.7.2 Chapter Organization. . . . . . . . . . . . . . . . . . . . . . . 40

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

2 Distributed Generation Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . 472.1 Combined Heat and Power Plants . . . . . . . . . . . . . . . . . . . . 47

2.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472.1.2 Microcogeneration Systems . . . . . . . . . . . . . . . . . . 482.1.3 Internal Combustion Engines . . . . . . . . . . . . . . . . . 492.1.4 Stirling Engines . . . . . . . . . . . . . . . . . . . . . . . . . . 492.1.5 Microturbines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512.1.6 Fuel Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

2.2 Renewable Energy Generation . . . . . . . . . . . . . . . . . . . . . . 552.2.1 Wind Power Plants . . . . . . . . . . . . . . . . . . . . . . . . 552.2.2 Small-Scale Hydrogeneration . . . . . . . . . . . . . . . . . 57

2.3 Solar Photovoltaic Generation. . . . . . . . . . . . . . . . . . . . . . . 582.3.1 Technology Basics . . . . . . . . . . . . . . . . . . . . . . . . 592.3.2 Grid-Connected Solar Systems . . . . . . . . . . . . . . . . 602.3.3 Future Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

2.4 Small Wind Turbine Systems . . . . . . . . . . . . . . . . . . . . . . . 622.4.1 Types of Wind Turbine Systems . . . . . . . . . . . . . . . 632.4.2 Wind Turbine Fundamentals. . . . . . . . . . . . . . . . . . 662.4.3 Control Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . 672.4.4 Generator Side Control . . . . . . . . . . . . . . . . . . . . . 682.4.5 Boost Converter Control . . . . . . . . . . . . . . . . . . . . 682.4.6 Rectifier Control . . . . . . . . . . . . . . . . . . . . . . . . . . 70

2.5 Storage Technologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702.5.1 Classification of Electrical Energy Storage . . . . . . . . 712.5.2 Mechanical Storage Systems. . . . . . . . . . . . . . . . . . 72

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2.5.3 Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 722.5.4 Flywheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 732.5.5 Superconducting Magnetic Energy Storage. . . . . . . . 732.5.6 Supercapacitors. . . . . . . . . . . . . . . . . . . . . . . . . . . 74

2.6 Inverter Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 742.6.1 Voltage Source Inverters . . . . . . . . . . . . . . . . . . . . 742.6.2 Inverter Realization for Microsources . . . . . . . . . . . 762.6.3 Inverter Realization . . . . . . . . . . . . . . . . . . . . . . . . 762.6.4 Unbalanced AC Voltages . . . . . . . . . . . . . . . . . . . . 77

2.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 782.8 Suggested Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

Part II Architectures and Integration

3 Control Methods for Microgrids . . . . . . . . . . . . . . . . . . . . . . . . . 893.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 893.2 Microgrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

3.2.1 Definition and Applications . . . . . . . . . . . . . . . . . . 903.2.2 Control Functions . . . . . . . . . . . . . . . . . . . . . . . . . 913.2.3 Components and Formation . . . . . . . . . . . . . . . . . . 923.2.4 Overview of Modeling. . . . . . . . . . . . . . . . . . . . . . 943.2.5 Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . 103

3.3 Control Approaches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1043.3.1 Control of Grid-Connected Mode . . . . . . . . . . . . . . 1043.3.2 Power Flow Control by Current Regulation . . . . . . . 1053.3.3 Power Flow Control by Voltage Regulation . . . . . . . 1053.3.4 Agent-Based Control . . . . . . . . . . . . . . . . . . . . . . . 1063.3.5 Distributed Control . . . . . . . . . . . . . . . . . . . . . . . . 1073.3.6 H1 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1093.3.7 Autonomous/Islanded Mode . . . . . . . . . . . . . . . . . . 1093.3.8 PQ and VSI Control . . . . . . . . . . . . . . . . . . . . . . . 1103.3.9 Autonomous Control . . . . . . . . . . . . . . . . . . . . . . . 1123.3.10 New Q– _V Droop Control . . . . . . . . . . . . . . . . . . . . 1123.3.11 Control Design Based on Transfer Function . . . . . . . 1133.3.12 Microgrid Control in both Modes . . . . . . . . . . . . . . 114

3.4 System of Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1163.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1163.4.2 SoS Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1163.4.3 Decentralized Control . . . . . . . . . . . . . . . . . . . . . . 1173.4.4 Multilevel Control. . . . . . . . . . . . . . . . . . . . . . . . . 1203.4.5 Networked Control Systems . . . . . . . . . . . . . . . . . . 1223.4.6 Comparative Analysis . . . . . . . . . . . . . . . . . . . . . . 125

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3.5 Modeling and Analysis of Inverter-Based Microgrids. . . . . . . 1263.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1283.5.2 Microgrid Model in Autonomous Mode. . . . . . . . . . 1293.5.3 State-Space Model of a Voltage Source Inverter . . . . 1323.5.4 Combined Model of All the Inverters . . . . . . . . . . . 1403.5.5 Network Model . . . . . . . . . . . . . . . . . . . . . . . . . . 1413.5.6 Load Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1433.5.7 Complete Microgrid Model . . . . . . . . . . . . . . . . . . 1443.5.8 Sensitivity Analysis . . . . . . . . . . . . . . . . . . . . . . . . 145

3.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1473.7 Suggested Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

4 Optimal Energy Management . . . . . . . . . . . . . . . . . . . . . . . . . . . 1594.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1594.2 A Microgrid Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1604.3 Microgrid and Load Forecasting . . . . . . . . . . . . . . . . . . . . . 162

4.3.1 Proposed NNE . . . . . . . . . . . . . . . . . . . . . . . . . . . 1624.3.2 Microgrid Environment Forecasting. . . . . . . . . . . . . 166

4.4 Multiobjective Energy Management. . . . . . . . . . . . . . . . . . . 1674.4.1 Battery Scheduling . . . . . . . . . . . . . . . . . . . . . . . . 1694.4.2 Fuzzy-Logic-Based Expert System . . . . . . . . . . . . . 170

4.5 Simulation Results I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1744.5.1 RE Power Generation and Load Forecasting. . . . . . . 1744.5.2 Multiobjective Intelligent Energy Management . . . . . 177

4.6 Optimal Energy Cost Management . . . . . . . . . . . . . . . . . . . 1814.7 Microgrid Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

4.7.1 PV Sources Control. . . . . . . . . . . . . . . . . . . . . . . . 1844.7.2 Storage Control . . . . . . . . . . . . . . . . . . . . . . . . . . 1854.7.3 Grid Connection Control . . . . . . . . . . . . . . . . . . . . 1864.7.4 DC Load Control . . . . . . . . . . . . . . . . . . . . . . . . . 1864.7.5 Power Balancing Principle . . . . . . . . . . . . . . . . . . . 187

4.8 Supervision Control Design . . . . . . . . . . . . . . . . . . . . . . . . 1884.8.1 Human–Machine Interface Layer. . . . . . . . . . . . . . . 1894.8.2 Prediction Layer . . . . . . . . . . . . . . . . . . . . . . . . . . 1894.8.3 Energy Management Layer. . . . . . . . . . . . . . . . . . . 1904.8.4 Operation Layer . . . . . . . . . . . . . . . . . . . . . . . . . . 192

4.9 Simulation Results II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1934.9.1 Optimization Results . . . . . . . . . . . . . . . . . . . . . . . 1944.9.2 Powers Flow Simulation I . . . . . . . . . . . . . . . . . . . 1964.9.3 Powers Flow Simulation II. . . . . . . . . . . . . . . . . . . 1994.9.4 Comparison and Discussion . . . . . . . . . . . . . . . . . . 200

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4.10 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2014.11 Suggested Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

5 A System of Systems Framework for Microgrids . . . . . . . . . . . . . 2095.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2095.2 Microgrid Subsystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

5.2.1 Microgrid Central Controller . . . . . . . . . . . . . . . . . 2115.2.2 Microsource and Load Controllers. . . . . . . . . . . . . . 2125.2.3 Microturbines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2135.2.4 Microsources and Fuel Cells. . . . . . . . . . . . . . . . . . 2135.2.5 Storage Devices . . . . . . . . . . . . . . . . . . . . . . . . . . 214

5.3 The Concept of SoS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2145.3.1 Microgrids as SoS. . . . . . . . . . . . . . . . . . . . . . . . . 2155.3.2 Grid-Connected Operation . . . . . . . . . . . . . . . . . . . 2165.3.3 Grid-Islanded Operation. . . . . . . . . . . . . . . . . . . . . 2165.3.4 Operation of the Microgrid Under

the SoS Framework. . . . . . . . . . . . . . . . . . . . . . . . 2195.4 Modeling of Microgrid . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

5.4.1 Microturbine Model . . . . . . . . . . . . . . . . . . . . . . . 2205.4.2 PV Solar Cell Model . . . . . . . . . . . . . . . . . . . . . . . 2225.4.3 Wind Turbine Model . . . . . . . . . . . . . . . . . . . . . . . 223

5.5 Microgrid Control Architecture . . . . . . . . . . . . . . . . . . . . . . 2255.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2265.5.2 Hierarchical Control . . . . . . . . . . . . . . . . . . . . . . . 2285.5.3 Consensus Control . . . . . . . . . . . . . . . . . . . . . . . . 2295.5.4 Centralized and Decentralized Control . . . . . . . . . . . 2305.5.5 More on Decentralized Control . . . . . . . . . . . . . . . . 234

5.6 Application to Islanded Microgrid . . . . . . . . . . . . . . . . . . . . 2355.6.1 Two-Level Control Strategy . . . . . . . . . . . . . . . . . . 2375.6.2 Local Subsystem Control . . . . . . . . . . . . . . . . . . . . 2375.6.3 Global Corrective Control . . . . . . . . . . . . . . . . . . . 2385.6.4 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . 239

5.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2415.8 Suggested Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

Part III Communication and Control

6 Networked Control of Microgrid System of Systems . . . . . . . . . . . 2516.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2516.2 Microgrid as SoS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2536.3 Microgrid Islanded System Modeling . . . . . . . . . . . . . . . . . 256

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6.4 Networked Control System. . . . . . . . . . . . . . . . . . . . . . . . . 2586.5 Closed-Loop Stability Results . . . . . . . . . . . . . . . . . . . . . . . 2616.6 Illustrative Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2656.7 Microalternator and Photovoltaic Systems . . . . . . . . . . . . . . 269

6.7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2696.7.2 Modeling of the Microalternator–PV System . . . . . . 2726.7.3 Microalternator . . . . . . . . . . . . . . . . . . . . . . . . . . . 2726.7.4 Photovoltaic System . . . . . . . . . . . . . . . . . . . . . . . 2756.7.5 Networked Control System Modeling . . . . . . . . . . . 2866.7.6 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . 298

6.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3016.9 Suggested Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307

7 Decentralized Voltage Control Methods . . . . . . . . . . . . . . . . . . . . 3097.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3097.2 Control Strategy I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310

7.2.1 Frequency Control . . . . . . . . . . . . . . . . . . . . . . . . 3117.2.2 Voltage Control . . . . . . . . . . . . . . . . . . . . . . . . . . 3127.2.3 Overcurrent Limiters . . . . . . . . . . . . . . . . . . . . . . . 3137.2.4 Islanding Detection Approach. . . . . . . . . . . . . . . . . 314

7.3 Small-Signal Dynamic Analysis . . . . . . . . . . . . . . . . . . . . . 3157.3.1 Dynamics of Grid-Connected Mode . . . . . . . . . . . . 3167.3.2 Dynamics of Autonomous Mode-Case 1 . . . . . . . . . 3187.3.3 Dynamics of Autonomous Mode-Case 2 . . . . . . . . . 320

7.4 Time-Domain Simulation Results . . . . . . . . . . . . . . . . . . . . 3217.4.1 Grid-Connected Mode . . . . . . . . . . . . . . . . . . . . . . 3217.4.2 Ride-Through Capability of DG Unit. . . . . . . . . . . . 3227.4.3 Transition Capability from Grid-Connected

to Islanded Mode . . . . . . . . . . . . . . . . . . . . . . . . . 3237.4.4 Autonomous Mode . . . . . . . . . . . . . . . . . . . . . . . . 327

7.5 Robust Control Strategy for Multi-Microgrids. . . . . . . . . . . . 3287.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3297.5.2 System Description . . . . . . . . . . . . . . . . . . . . . . . . 3307.5.3 Power Management. . . . . . . . . . . . . . . . . . . . . . . . 3307.5.4 Mathematical Model . . . . . . . . . . . . . . . . . . . . . . . 335

7.6 Control Strategy II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3377.6.1 Design Requirements. . . . . . . . . . . . . . . . . . . . . . . 3397.6.2 Existence Conditions . . . . . . . . . . . . . . . . . . . . . . . 3397.6.3 Real Stability Radius Constraints . . . . . . . . . . . . . . 3417.6.4 Controller Design Procedure. . . . . . . . . . . . . . . . . . 3417.6.5 A Decentralized Controller Scheme . . . . . . . . . . . . . 3437.6.6 Properties of the Closed-Loop System . . . . . . . . . . . 3437.6.7 Other Robustness Measures . . . . . . . . . . . . . . . . . . 347

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7.7 Decentralized Inverter Control . . . . . . . . . . . . . . . . . . . . . . 3487.7.1 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 3497.7.2 Power Sharing Control Strategy . . . . . . . . . . . . . . . 3527.7.3 Controller Design . . . . . . . . . . . . . . . . . . . . . . . . . 3537.7.4 Decentralized Information Acquisition . . . . . . . . . . . 3537.7.5 Stability Analysis Without Communication Delay . . . 3547.7.6 Model of Individual Inverter. . . . . . . . . . . . . . . . . . 3557.7.7 Combined Inverter Model . . . . . . . . . . . . . . . . . . . 3597.7.8 Network Model . . . . . . . . . . . . . . . . . . . . . . . . . . 3617.7.9 Microgrid Model. . . . . . . . . . . . . . . . . . . . . . . . . . 3637.7.10 System Stability Evaluation . . . . . . . . . . . . . . . . . . 3637.7.11 Stability Analysis with Communication Delay . . . . . 3637.7.12 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . 365

7.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3687.9 Suggested Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374

8 Advanced Control Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . 3798.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3798.2 Distributed Control Architecture . . . . . . . . . . . . . . . . . . . . . 379

8.2.1 Integrated Wind/Solar/RO System Modeling. . . . . . . 3818.2.2 Water Desalination System Description . . . . . . . . . . 3848.2.3 Short-Term Supervisory Predictive Control. . . . . . . . 3868.2.4 Supervisory Control System Design I . . . . . . . . . . . 3878.2.5 Simulation Results I . . . . . . . . . . . . . . . . . . . . . . . 3898.2.6 Integration for Long-Term Operation . . . . . . . . . . . . 3938.2.7 Supervisory Control System Design II . . . . . . . . . . . 3948.2.8 Simulation Results II . . . . . . . . . . . . . . . . . . . . . . . 3968.2.9 Distributed Energy Systems . . . . . . . . . . . . . . . . . . 4008.2.10 Distributed Frequency Control . . . . . . . . . . . . . . . . 4028.2.11 Simulation Results III . . . . . . . . . . . . . . . . . . . . . . 405

8.3 Multilevel Control of Droop-Controlled Microgrids . . . . . . . . 4088.3.1 A Generalized Multilevel Structure . . . . . . . . . . . . . 4098.3.2 Multilevel Control of AC Microgrids. . . . . . . . . . . . 4118.3.3 Inner Control Loops . . . . . . . . . . . . . . . . . . . . . . . 4128.3.4 Primary Control . . . . . . . . . . . . . . . . . . . . . . . . . . 4128.3.5 Secondary Control . . . . . . . . . . . . . . . . . . . . . . . . 4148.3.6 Tertiary Control . . . . . . . . . . . . . . . . . . . . . . . . . . 4158.3.7 Simulation Results IV . . . . . . . . . . . . . . . . . . . . . . 416

8.4 Multilevel Control of DC Microgrids. . . . . . . . . . . . . . . . . . 4218.4.1 Primary Control . . . . . . . . . . . . . . . . . . . . . . . . . . 4228.4.2 Secondary Control . . . . . . . . . . . . . . . . . . . . . . . . 4238.4.3 Tertiary Control . . . . . . . . . . . . . . . . . . . . . . . . . . 4248.4.4 Simulation Results V. . . . . . . . . . . . . . . . . . . . . . . 425

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8.5 Enhanced Compensation Technique. . . . . . . . . . . . . . . . . . . 4278.5.1 Microgrid Multilevel Control Scheme . . . . . . . . . . . 4288.5.2 DG Local Control . . . . . . . . . . . . . . . . . . . . . . . . . 4308.5.3 Fundamental Positive Sequence Powers

Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4318.5.4 Voltage and Current Controllers . . . . . . . . . . . . . . . 4318.5.5 Virtual Impedance Loop . . . . . . . . . . . . . . . . . . . . 4318.5.6 Compensation Effort Controller . . . . . . . . . . . . . . . 4348.5.7 Secondary Controller . . . . . . . . . . . . . . . . . . . . . . . 4358.5.8 Simulation Results VI . . . . . . . . . . . . . . . . . . . . . . 436

8.6 Distributed Cooperative Control . . . . . . . . . . . . . . . . . . . . . 4408.6.1 Microgrid Control Levels . . . . . . . . . . . . . . . . . . . . 4428.6.2 Large-Signal Inverter-Based Model . . . . . . . . . . . . . 4438.6.3 Cooperative Secondary Voltage Control . . . . . . . . . . 4478.6.4 Feedback Linearization and Tracking

Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . 4478.6.5 Required Sparse Communication Topology . . . . . . . 4518.6.6 Simulation Results VII . . . . . . . . . . . . . . . . . . . . . 452

8.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4558.8 Suggested Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462

9 Real-Time Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4679.1 Neural-Network-Based Secondary Control . . . . . . . . . . . . . . 467

9.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4679.1.2 An Autonomous Microgrid . . . . . . . . . . . . . . . . . . 4709.1.3 Primary Control . . . . . . . . . . . . . . . . . . . . . . . . . . 4719.1.4 Distributed Secondary Control . . . . . . . . . . . . . . . . 4749.1.5 Neural-Network-Based Distributed

Secondary Control . . . . . . . . . . . . . . . . . . . . . . . . 4759.1.6 Differential Evolution . . . . . . . . . . . . . . . . . . . . . . 4779.1.7 NN Training. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4789.1.8 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . 481

9.2 Optimal Control for Autonomous Microgrid . . . . . . . . . . . . . 4879.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4879.2.2 Autonomous Microgrid Controller. . . . . . . . . . . . . . 4889.2.3 Power Controller. . . . . . . . . . . . . . . . . . . . . . . . . . 4899.2.4 Voltage Controller. . . . . . . . . . . . . . . . . . . . . . . . . 4909.2.5 Current Controller . . . . . . . . . . . . . . . . . . . . . . . . . 4919.2.6 Coupling Inductance and Filter . . . . . . . . . . . . . . . . 4919.2.7 Lines Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4929.2.8 Load Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492

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9.3 Problem Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4929.3.1 Results and Discussions . . . . . . . . . . . . . . . . . . . . . 4939.3.2 Nonlinear Time Domain Simulation . . . . . . . . . . . . 4959.3.3 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . 499

9.4 Distributed Control for Autonomous Microgrid. . . . . . . . . . . 5049.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5049.4.2 Real-Time Digital Simulator . . . . . . . . . . . . . . . . . . 5059.4.3 Description of RTDS Hardware . . . . . . . . . . . . . . . 5069.4.4 Description of RTDS Software . . . . . . . . . . . . . . . . 5089.4.5 Distributed Control Scheme . . . . . . . . . . . . . . . . . . 5089.4.6 RTDS Implementation . . . . . . . . . . . . . . . . . . . . . . 5109.4.7 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . 5149.4.8 Comparison of RTDS and MATLAB Results . . . . . . 5159.4.9 Load Sharing During Faults . . . . . . . . . . . . . . . . . . 518

9.5 Experimental Verification of Inverter-Based Microgrid. . . . . . 5219.5.1 Modeling Results . . . . . . . . . . . . . . . . . . . . . . . . . 5239.5.2 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . 524

9.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528

10 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53110.1 Important Facts in Linear Algebra . . . . . . . . . . . . . . . . . . . . 531

10.1.1 Basic Notions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53110.1.2 Inner Product and Orthogonality . . . . . . . . . . . . . . . 53410.1.3 Kronecker Product and Stack of Matrices. . . . . . . . . 535

10.2 Linear Transformations and Matrix Groups . . . . . . . . . . . . . 53610.3 Elements of Graph Theory . . . . . . . . . . . . . . . . . . . . . . . . . 540

10.3.1 Basic Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54010.3.2 Laplacian Spectrum of Graphs . . . . . . . . . . . . . . . . 54110.3.3 Properties of Adjacency Matrix. . . . . . . . . . . . . . . . 541

10.4 Matrix Algebra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54310.4.1 Inverse of Block Matrices . . . . . . . . . . . . . . . . . . . 54410.4.2 Matrix Inversion Lemma . . . . . . . . . . . . . . . . . . . . 54510.4.3 Range, Kernel, Rank and Eigenvectors . . . . . . . . . . 54610.4.4 Symmetric and Skew-Symmetric Matrices . . . . . . . . 549

10.5 Singular Value Decomposition . . . . . . . . . . . . . . . . . . . . . . 55110.5.1 Geometric Interpretation. . . . . . . . . . . . . . . . . . . . . 55310.5.2 Example A.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55410.5.3 Some Properties of the SVD. . . . . . . . . . . . . . . . . . 55510.5.4 The QR Decomposition . . . . . . . . . . . . . . . . . . . . . 557

10.6 Useful Formulae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55810.6.1 Ackermann’s Formula for Eigenvalue

Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558

Contents xxi

10.6.2 Parseval Formula . . . . . . . . . . . . . . . . . . . . . . . . . 55910.6.3 Frobenius Formula . . . . . . . . . . . . . . . . . . . . . . . . 560

10.7 Inequalities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56010.7.1 Inequality 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56110.7.2 Inequality 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56110.7.3 Inequality 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56210.7.4 Inequality 4 (Schur Complements) . . . . . . . . . . . . . 56210.7.5 Inequality 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564

10.8 Lemmas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56510.9 Linear Matrix Inequalities . . . . . . . . . . . . . . . . . . . . . . . . . 568

10.9.1 Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56810.9.2 Some Standard Problems . . . . . . . . . . . . . . . . . . . . 56910.9.3 The S-procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 571

10.10 Lyapunov Map and Lyapunov Equation. . . . . . . . . . . . . . . . 57210.11 Persistence of Excitation and Sufficiently Rich Inputs . . . . . . 57310.12 Notes and References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 576References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 576

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577

xxii Contents

About the Authors

Magdi Sadek Mahmoud obtained B.Sc. (Honors) inCommunication Engineering, M.Sc. in ElectronicEngineering, and Ph.D. in Systems Engineering, allfrom Cairo University in 1968, 1972, and 1974,respectively. He has been a professor of engineeringsince 1984. He is now a Distinguished UniversityProfessor at KFUPM, Saudi Arabia. He was on thefaculty at different universities worldwide includingEgypt (CU, AUC), Kuwait (KU), UAE (UAEU), UK(UMIST), USA (Pitt, Case Western), Singapore(Nanyang Technological), and Australia (Adelaide).

He lectured in Venezuela (Caracas), Germany (Hanover), UK (Kent), USA (UoTexas at SA), Canada (Montreal, Alberta), and China (BIT, Yanshan). He is theprincipal author of 34 books, inclusive book-chapters, and the author/co-author ofmore than 500 peer-reviewed papers. He is the recipient of two national, oneregional, and four university prizes for outstanding research in engineering andapplied mathematics. He is a fellow of the IEE, a senior member of the IEEE, theCEI (UK), and a registered consultant engineer of information engineering andsystems (Egypt). He is currently actively engaged in teaching and research in thedevelopment of modern methodologies to distributed control and filtering, net-worked-control systems, triggering mechanisms in dynamical systems, fault-toler-ant systems, and information technology. He is a fellow of the IEE, a seniormember of the IEEE, the CEI (UK), and a registered consultant engineer ofinformation engineering and systems Egypt.

xxiii

Fouad M. AL-Sunni is professor of control andautomation in the Department of Systems Engineering.His areas of research include optimal control, robustcontrol, and Identification of dynamic systems. He haspublished in the areas of fuzzy logic, neural networks,optimal control, identification, time-delay systems,model predictive control, and control and engineeringeducation. He is a senior member of the IEEE, a seniormember of IIE, a member of INFORMS, and amember of ISA.

xxiv About the Authors

Notation and Symbols

Iþ The set of positive integers< The set of real numbers<þ The set of nonnegative real numbers<n The set of all n-dimensional real vectors<n�m The set of n� m-dimensional real matricesC� The open right-half complex planeCþ The closed right-half complex plane2 Belong to or element of� Subset ofS

UnionTIntersection

[[ Much greater than\\ Much less thanAt The transpose of matrix AA�1 The inverse of matrix AI An identity matrix of arbitrary orderIs The identity matrix of dimension s� sej The jth column of matrix Ixt or At The transpose of vector x or matrix AλðAÞ An eigenvalue of matrix AρðAÞ The spectral radius of matrix AλjðAÞ The jth eigenvalue of matrix AλmðAÞ The minimum eigenvalue of matrix A where λðAÞ are realλMðAÞ The maximum eigenvalue of matrix A where λðAÞ are real

Ay The Moore–Penrose-inverse of matrix A

P[ 0 Matrix P is real symmetric and positive-definiteP� 0 Matrix P is real symmetric and positive semi-definiteP\0 Matrix P is real symmetric and negative-definiteP� 0 Matrix P is real symmetric and negative semi-definiteAði; jÞ;Aij The ij-th element of matrix A

xxv

detðAÞ The determinant of matrix AtraceðAÞ The trace of matrix ArankðAÞ The rank of matrix AL2ð�1;1Þ Space of time domain square integrable functionsL2½0;1Þ Subspace of L2ð�1;1Þ with functions zero for t\0L2ð�1; 0� Subspace of L2ð�1;1Þ with functions zero for t[ 0L2ðj<Þ Square integrable functions on C0 including at 1H2 Subspace of L2ðj<Þ with functions analytic in ReðsÞ[ 0L1ðj<Þ Subspace of functions bounded on ReðsÞ ¼ 0 including at 1H1 The set of L1ðj<Þ functions analytic in ReðsÞ[ 0jaj The absolute value of scalar ajjxjj The Euclidean norm of vector xjjAjj The induced Euclidean norm of matrix Ajjxjjp The ‘p norm of vector xjjAjjp The induced ‘p norm of matrix AImðAÞ The image of operator/matrix AKerðAÞ The kernel of operator/matrix Amax D The maximum element of set Dmin D The minimum element of set Dsup D The smallest number that is larger than or equal to each

element of set Dinf D The largest number that is smaller than or equal to each

element of set Darg max D The index of maximum element of ordered set Sarg min D The index of minimum element of ordered set SBr The ball centered at the origin with radius rRr The sphere centered at the origin with radius rN The fixed index set f1; 2; . . .;Ng½a; bÞ The real number set ft 2 < : a� t\bg½a; b� The real number set ft 2 < : a� t� bgS The set of modes f1; 2; . . .; sgiff If and only if The Kronecker productOð:Þ Order of (.)diagð. . .ÞA Diagonal matrix with given diagonal elementsspecðAÞ The set of eigenvalues of matrix A (spectrum)min� polyðAÞðsÞ The minimal polynomial of matrix A

xxvi Notation and Symbols

Abbreviations

AC Alternating CurrentARE Algebraic Riccati EquationCAN Control Area NetworkCB Circuit BreakerCC Central ControllerCCGT Combined Cycle Gas TurbineCHP Combined Heat and PowerCO Carbon MonoxideDA Distribution AutomationDC Direct CurrentDCS Distributed Control SystemDEC Decentralized ControlDER Distributed Energy ResourceDFIG Doubly Fed Induction GeneratorDG Distributed GenerationDGS Distributed Generation SystemsDMS Distribution Management SystemsDNO Distribution Network OperatorDO Digital OutputDSM Demand Side ManagementGT Gas TurbineHC Hierarchical ControlIC Internal CombustionIED Intelligent Electronic DeviceI/O Input/OutputLMI Linear Matrix InequalityLQC Linear Quadratic ControlLV Low VoltageMC Microsource ControllerMT MicroturbineMV Medium Voltage

xxvii

PEI Power Electronic InterfacePF Power-FrequencyPI Proportional-IntegralPID Proportional-Integral-DerivativePMSG Permanent Magnet Synchronous GeneratorPQ Power QualityPV PhotovoltaicPX Power ExchangeRES Renewable Energy SourceSCADA Supervisory Control and Data AcquisitionSYGN Synchronous GeneratorSISO Single-Input Single-OutputSVD Singular Value DecompositionTDS Time-Delay SystemTES Thermal Energy Storage

xxviii Abbreviations