Modern Power System
Description
Comprehensive reference exploring fundamentals of power systems analysis and operation through a unique blend of traditional and modern concepts
Modern Power System explains the fundamentals of power systems analysis and operation, the latest developments with regard to transformation of energy sources from the conventional synchronous generators to the inverter-based sources, and the techniques and hardware used for this purpose. The book includes information on traditional power system concepts such as load flow, fault studies, protection, and stability as well as modern concepts including reactive power control, Flexible AC Transmission Systems (FACTS), HVDC transmission, renewable energy, and smart grids.
Readers will find insights on topics such as phasor measurement unit (PMUs), wide-area measurements and control, and SCADA systems as well as distribution side aspects such as smart meters, demand management, and energy trading. Readers will also learn about point-to-point HVDC transmission using line commutated converters and multiterminal HVDC transmission.
Additional topics discussed in include:
- Power system components such as transmission line parameters, transformer models, per-unit representation, and modeling of transmission lines
- Economic operation of power plants and systems, with information on unit commitment and automatic generation control
- Power system protection through instrument transformers, protective relays, and overcurrent relay coordination
- Reactive power compensation, covering voltage stability and ideal reactive compensation
- Water, solar, wind, hydrogen, and nuclear fusion as alternative energy sources
Modern Power System is an excellent textbook for undergraduate and graduate students in electrical engineering with a power engineering specialization, as well as practicing power system engineers seeking to keep up with the latest developments in the field.
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Arindam Ghosh, PhD, is a Research Academic Professor at Curtin University, Perth, Australia. He obtained his PhD from the University of Calgary, Canada. He was conferred the IEEE PES Nari Hingorani Custom Power Award in 2019. He has published over 450 peer reviewed journal and conference articles and has authored two books. He is a Fellow of the Indian National Academy of Engineering (INAE) and a Fellow of the Institute of Electrical and Electronics Engineers (IEEE).
Content
About the Author xv
Preface xvii
Acknowledgments xxiii
About the Companion Website xxv
1 Introduction 1
1.1 A Brief History of Electricity 1
1.1.1 The Dawn of Electricity 3
1.1.2 Development of Electrical Power Plant 4
1.2 Interconnection of Electricity Grids 9
1.3 Deregulation 10
1.4 Renewable Energy 13
1.5 Blackouts 15
1.5.1 Power System Oscillations 16
1.6 Smart Grid 18
1.7 Phasor Analysis 20
1.8 Concluding Remarks 21
References 21
2 Power System Components 23
2.1 Transmission Line Parameters 25
2.1.1 Line Resistance 25
2.1.2 Line Inductance 27
2.1.3 Line Charging Capacitance 31
2.2 Synchronous Machine Model 33
2.3 Transformer Model 35
2.4 Per Unit Representation 36
2.5 Modeling Transmission Lines 42
2.5.1 ABCD Parameters 43
2.5.2 Voltage Regulation 44
2.5.3 Short Line Approximation 45
2.5.4 Medium Line p Approximation 45
2.5.5 Medium Line T Approximation 46
2.5.6 Long Line Model 49
2.5.7 Equivalent-p Representation of a Long Line 53
2.5.8 Some Issues with Transmission Lines 55
2.6 Lossless Transmission Lines 56
2.6.1 Traveling Waves 58
2.6.2 Traveling Wave in Single-Phase, Two-Wire Line 60
2.7 Concluding Remarks 64
References 64
Problems 65
3 Power Flow Studies 69
3.1 Formation of Bus Admittance Matrix 70
3.1.1 Without Line Charging Capacitors 70
3.1.2 With Line Charging Capacitors 73
3.2 Load Flow Preliminaries 74
3.2.1 Classification of Buses 76
3.2.2 Data Preparation 77
3.3 Load Flow Methods 79
3.3.1 Gauss-Seidel Load Flow Method 80
3.3.2 Basics of Newton-Raphson Iterative Procedure 83
3.3.3 Newton-Raphson Load Flow Method 85
3.3.4 Fast Decoupled Load Flow 91
3.3.5 Line Flows 96
3.3.6 dc Load Flow 98
3.4 State Estimation 100
3.4.1 Principles of Estimation 100
3.4.2 Maximum-Likelihood Estimation 101
3.4.3 DC State Estimation 104
3.4.4 AC State Estimation 106
3.4.5 Bad Data Detection 110
3.5 SCADA and EMS 114
3.6 Concluding Remarks 115
References 116
Problems 117
4 Economic Operation of Power System 125
4.1 Economic Operation of a Power Plant 126
4.1.1 Economic Distribution of Loads Between Two Units of a Plant 126
4.1.2 Economic Distribution of Loads Between Multiple Units of a Plant 130
4.1.3 Consideration of Generator Limits 133
4.2 Economic Operation of a Power System 136
4.3 Unit Commitment 141
4.3.1 Spinning Reserve 145
4.3.2 Thermal Limit Constraints 145
4.3.3 Solution Methods for Unit Commitment Problem 146
4.4 Automatic Generation Control 148
4.4.1 Load Frequency Control (LFC) 153
4.4.2 Coordination Between LFC and Economic Operation 155
4.5 Concluding Remarks 156
References 157
Problems 157
5 Power System Fault Analysis 161
5.1 Transients in an RL Circuit 162
5.1.1 DC Source 162
5.1.2 AC Source 164
5.1.3 Fault in an AC Circuit 165
5.2 Short Circuit in an Unloaded Synchronous Generator 167
5.3 Symmetrical Fault in a Power System 170
5.3.1 Calculation of Fault Current Using Impedance Diagram 170
5.3.2 Calculation of Fault Current Using Bus Impedance Matrix 173
5.4 Symmetrical Components 175
5.4.1 Symmetrical Component Transformation 176
5.4.2 Real and Reactive Power 179
5.5 Sequence Circuits and Networks 180
5.5.1 Sequence Circuit for a Y-Connected Load 181
5.5.2 Sequence Circuit for a Delta-Connected Load 183
5.5.3 Sequence Circuit for a Synchronous Generator 186
5.5.4 Sequence Circuit for a Symmetrical Transmission Line 188
5.5.5 Sequence Circuits for Transformers 191
5.5.5.1 Y-Y-Connected Transformer 191
5.5.5.2 ¿-¿-Connected Transformer 193
5.5.5.3 Y-¿-Connected Transformer 195
5.5.6 Sequence Networks 196
5.6 Unsymmetrical Faults 198
5.6.1 Single-Line-to-Ground (1LG) Fault 199
5.6.2 Line-to-Line (LL) Fault 202
5.6.3 Double-Line-to-Ground (2LG) Fault 205
5.6.4 Fault Current Computation Using Sequence Networks 208
5.7 Concluding Remarks 216
Reference 216
Problems 216
6 Power System Protection 223
6.1 Protective Elements 224
6.1.1 Fuses 224
6.1.2 Circuit Breakers 226
6.2 Instrument Transformers 228
6.2.1 Current Transformer (CT) 229
6.2.2 Potential Transformer (PT) 230
6.3 Protective Relays 230
6.3.1 Overcurrent Relay 231
6.3.2 Directional Relay 232
6.3.3 Distance Protection 235
6.3.4 Differential Protection 236
6.3.5 Transformer Protection 237
6.3.6 Pilot Relays 239
6.4 Overcurrent Relay Coordination 241
6.5 Zones of Protection 245
6.6 Protection in the Presence of Distributed Renewable Generators 249
6.6.1 Protection Using Directional Overcurrent Relays 250
6.6.2 Inverse Time Admittance (ITA) Relay 252
6.7 IEC 61850 254
6.8 Concluding Remarks 256
References 257
Problems 258
7 Power System Stability and Control 263
7.1 Transient Stability 265
7.1.1 Power-Angle Curve 265
7.1.2 Swing Equation 268
7.1.3 Critical Clearing Angle 271
7.1.4 Critical Clearing Time 276
7.1.5 Simplified Calculation of Critical Clearing Angle 284
7.2 Multimachine System Stability 286
7.2.1 Classical Method 288
7.2.2 Pre-fault Bus Admittance Matrix 289
7.2.3 Reduction of Bus Admittance Matrix 292
7.2.4 Bus Admittance Matrices During Fault and Post-Fault 293
7.2.5 Multimachine Swing Equation 294
7.2.6 Oscillations in a Two-Area System 296
7.3 Excitation Control 298
7.3.1 Linearized Swing Equation 299
7.3.2 Excitation System 303
7.3.3 Automatic Voltage Regulator (AVR) 306
7.3.4 Power System Stabilizer (PSS) 309
7.4 Concluding Remarks 312
References 312
Problems 313
8 Reactive Power Compensation 319
8.1 Voltage Stability 320
8.2 Ideal Reactive Compensation 325
8.3 Ideal Shunt Compensation 326
8.3.1 Improving Voltage Profile 327
8.3.2 Improving Power-Angle Characteristics 332
8.3.3 Improving Stability Margin 334
8.3.4 Power Swing Damping 337
8.3.5 Shunt Compensator Representation 338
8.4 Ideal Series Compensation 340
8.4.1 Impact of Series Compensator on Voltage Profile 340
8.4.2 Improving Power-Angle Characteristics 343
8.4.3 Improving Stability Margin 346
8.4.4 Power Flow Control and Power Swing Damping 346
8.4.5 An Alternate Method of Series Compensation 349
8.5 Concluding Remarks 352
References 352
Problems 353
9 Flexible AC Transmission Systems (FACTS) 357
9.1 Static Var Compensator (SVC) 358
9.1.1 Thyristor-Switched Capacitor (TSC) 358
9.1.2 Thyristor-Controlled Reactor (TCR) 360
9.1.3 Composition of SVC 365
9.1.4 SVC Characteristics 366
9.2 Static Compensator (STATCOM) 368
9.3 High-Power Converters 369
9.3.1 Six-Step Converter 370
9.3.2 Twelve-Step Converter 372
9.3.3 6q-Step Converter 377
9.3.4 Multilevel Converters 377
9.4 Subsynchronous Oscillations 379
9.4.1 Subsynchronous and Supersynchronous Frequencies 380
9.4.2 Shaft Torsional Modes 381
9.4.3 Subsynchronous Frequency Analysis 384
9.4.4 Countermeasures to SSR 388
9.5 Thyristor-Controlled Series Compensator (TCSC) 389
9.5.1 When One of the Thyristors Is On 390
9.5.2 When Both Thyristors Are Off 392
9.5.3 Estimating the Fundamental Impedance of a TCSC 392
9.6 Static Synchronous Series Compensator (SSSC) 396
9.7 Other FACTS Devices 400
9.7.1 Unified Power Flow Controller (UPFC) 400
9.7.2 Thyristor-Controlled Braking Resistor (TCBR) 403
9.7.3 Thyristor-Controlled Voltage Regulator (TCVR) 404
9.7.4 Thyristor-Controlled Phase Angle Regulator (TCPAR) 406
9.8 Concluding Remarks 406
References 407
Problems 409
10 High-Voltage DC (HVDC) Transmission Systems 413
10.1 Attributes of DC Systems 414
10.1.1 Advantages and Disadvantages of HVDC Systems 414
10.1.2 Types of HVDC Systems 415
10.2 LCC-HVDC Systems 417
10.2.1 System Characteristics with Zero Ignition Angle 418
10.2.2 System Characteristics with Nonzero Ignition Angle 419
10.2.3 Overlap Angle 421
10.2.4 Inverter Operation 422
10.2.5 Active Power 423
10.2.6 Twelve-Pulse Converter 425
10.3 VSC-HVDC Systems 425
10.3.1 Control of a Voltage Source Converter (VSC) 426
10.3.2 VSC-HVDC Configuration 427
10.3.3 Direct Control of VSC-HVDC Systems 429
10.3.4 Vector Control of VSC-HVDC Systems 430
10.4 Multiterminal HVDC Systems 434
10.4.1 Multiterminal System Configurations 436
10.4.2 MTDC Control 437
10.5 dc Protection Systems 441
10.6 Concluding Remarks 442
References 443
Problems 444
11 Renewable Energy 447
11.1 Waterpower 448
11.1.1 Hydropower 448
11.1.2 Types of Hydropower Turbines 450
11.1.3 Pumped Hydro Storage (PHS) 450
11.1.4 Tidal Energy 452
11.1.5 Wave Energy 454
11.2 Solar Power 456
11.2.1 Solar Tracking 457
11.2.2 Solar Photovoltaic (PV) Systems 459
11.2.3 Maximum Power Point Tracking (MPPT) 462
11.2.4 Concentrated Solar Power (CSP) 466
11.3 Wind Power 467
11.3.1 Wind Turbine Types 468
11.3.2 Wind Power Calculations 470
11.3.3 Pitch Angle Control 472
11.3.4 Types of Wind Power Collectors 473
11.4 Hydrogen 478
11.4.1 Hydrogen Production 480
11.4.2 Hydrogen Storage and Transmission 482
11.4.3 Utilization of Hydrogen 483
11.5 Nuclear Fusion 484
11.6 Renewable Energy in Power Transmission Systems 486
11.6.1 Grid Forming Converter (GFC) 487
11.6.2 Virtual Synchronous Generator (VSG) 488
11.6.3 Fault Ride Through (FRT) 491
11.7 Renewable Energy in Power Distribution Systems 492
11.7.1 Voltage Rise and Line Loss 493
11.7.2 Reverse Power Flow and Voltage Unbalance 500
11.8 Concluding Remarks 504
References 506
Problems 508
12 Fundamentals of Smart Grid 511
12.1 Sensor Systems 513
12.1.1 Computation of Phasors from Instantaneous Measurements 513
12.1.2 Phasor Measurement Unit (PMU) 517
12.1.3 Smart Meter 519
12.2 Demand Response 520
12.2.1 Controlling Household Appliances 524
12.3 Cybersecurity 526
12.3.1 False Data Injection Attacks 527
12.4 Electric Vehicle (EV) 529
12.4.1 Types of Electric Vehicles 529
12.4.2 EV Charging 532
12.4.3 Wireless Charging 533
12.5 Smart Grid Communications 536
12.5.1 Smart Grid Communication Mediums 536
12.5.2 Communication Requirements 540
12.6 Smart Grid Standards 540
12.7 Smart Distribution Grids 542
12.7.1 Virtual Power Plant (VPP) 542
12.7.2 Microgrid (MG) 544
12.7.3 Microgrid Control 545
12.8 Concluding Remarks 548
References 548
Index 553
Preface
The electric power industry is a cornerstone of global infrastructure, vital for modern society and economic development. According to the International Energy Agency report on world energy employment in 2023, the power sector employed over 68 million people worldwide. Of these, over 36 million people were employed in the clean energy sector, while over 32 million people were employed in the fossil fuel-based power industry. According to the US Bureau of Labor Statistics report of 2023, 17,870 electrical engineers were employed in the power sector. Amongst all the technical societies of the Institute of Electrical and Electronic Engineers (IEEE), the Power and Energy Society (PES) is the second largest, having around 42,000 members worldwide.
Given its vast impact, the power industry requires a multidisciplinary approach for its secured operation and continues to evolve, a journey that I have followed with fascination. My early studies of foundational texts like W. D. Stevenson's book [1] have deeply influenced the structure and focus of this book, blending traditional principles with modern advancements. Most of the topics covered in Stevenson's book are still valuable to gain knowledge in the area. However, the power sector has seen a sea of changes since the time the fourth edition of the book appeared in 1982. These days, power electronic technology plays a crucial role in both power transmission and distribution systems. Thyristor-based high voltage DC (HVDC) transmission systems started appearing in the 1970s. Subsequently, voltage source converter (VSC)-based HVDC systems were adopted on a large scale at the turn of this century. Currently, VSC-HVDC systems are used for offshore windfarms. Moreover, point-to-point HVDC systems have given way to multiterminal HVDC systems for offshore wind collection systems.
Also, thyristor-based static var compensators (SVCs) also started appearing in large scales during the 1970s to enhance voltage stability in long transmission lines, as well as, for power oscillation damping. There were hundreds of SVCs installed throughout the world. Fixed series compensation of transmission lines to enhance power flow was initially hindered by incidents at Mojave power station, where resonance issues caused turbine damage in the early 1970s. These were caused due to the resonance between the series capacitors and line reactors at frequencies that are below the synchronous frequency. However, the initial hesitation was overcome using thyristor-controlled series compensators (TCSCs), which can effectively change the series reactance to avoid the subsynchronous oscillations reaching the rotor shafts. Moreover, other thyristor-based devices have become common like voltage regulator, phase angle regulator, etc.
With the advancement in power electronic technology, voltage source converter-based flexible AC transmission (FACTS) devices have found their applications in both voltage regulation and power flow control in long transmission systems. Shunt compensation was achieved using static compensators (STATCOMs), which started replacing the SVCs. On the other hand, static synchronous series compensators were placed in series with the lines to replace TCSCs. Both shunt and series compensations can be achieved simultaneously using a unified power flow compensator.
Due to the rising concerns of climate change and the resultant global temperature rise, more and more renewable energy generators are getting integrated into both power transmission and distribution systems. This has caused disruptions in the traditional operations of power systems. Most of the renewable energy generators are connected to power systems through power converters, which cannot provide inertia to maintain stability margins required in bulk power transmission systems. These systems require smarter converter controls and storage devices. In distribution systems, for instance, rooftop photovoltaics introduce challenges like voltage imbalances, voltage rises, and reverse power flow. Furthermore, there is a concern that renewable generators are intermittent and thus they cannot supply the required baseload.
To modernize the power system, the concept of the smart grid has been introduced, through which the power system is integrated with information and communication technology (ICT) to facilitate a smooth two-way power flow and to provide near instantaneous balance between generation and consumption. Power transmission systems can have modern energy management systems integrating phasor measurement units, which can be used in load control centers for more accurate state estimation and power dispatch. Distribution systems will be equipped with smart meters, through which the load demand can be managed. Parts of distribution systems can form virtual power plants or can have several microgrids. Substations can be modernized using tailored computer programs that can communicate between different protective relays without the complicated layout of cables. Since the smart grid relies heavily on ICT, measures must be taken to ensure that the communication and computation devices are cybersecure.
Against the backdrop of all the changes that have occurred in the power systems over the last three decades, this book aims to combine the traditional power systems with the newer technologies that are increasingly appearing in power systems. The materials covered in the book have been taught over several years over different courses at four different universities. The book can be used for a basic course on power systems on the undergraduate level, as well as, for a higher-level undergraduate course or a first-level graduate course on power engineering. For example, Chapters 2-7 (excluding Sections 3.4, 6.6, 7.2, and 7.3) can be used for a first-level course, and the rest of the book can be used for a second-level course.
The book is organized into 12 chapters. Chapter 1 introduces the book. Most of us take the use of electricity for granted - for comfort and household appliances, for entertainment, for knowledge, for medical treatment, or for transportation. However, the history of how we came to this stage is fascinating. In Section 1.1, a brief history of electricity is presented. In the subsequent sections, the development stages leading to the modern power systems are discussed, including interconnections of electric grids, deregulations, blackouts, and smart grid.
Chapter 2 discusses the main components of power systems. It begins with discussions on transmission system parameters. It is easy to comprehend that transmission lines will have resistance. However, how they are represented by line inductance and capacitance is derived using the laws of magnetics. Following these, simplified models of synchronous generators and transformers are presented. A power system may contain different power equipment with different voltage and power levels connected together through various step-up or step-down transformers. The presence of different voltage levels makes power system calculations extremely difficult. To simplify this, a power system is represented in its per unit form where all quantities are normalized to a common base. The final section of this chapter discusses different ways of modeling a power transmission system depending on its length and how they can be simplified for power system calculations.
Chapter 3 discusses load flow techniques. A power system is a network of transmission lines, loads and generators. Even though such a system can be visualized as an RLC circuit, the network is so complicated that the node voltage and loop current analyses are impossible to perform. For a set of given loads and generations, the complex bus voltages and power flow through different lines are determined using load flow (or power flow) studies. The first step in this process is to combine all the elements of the power system in a bus admittance matrix. Then, step-by-step iterative procedures are executed for the accurate determination of the bus voltages. Three different load flow procedures - Gauss-Siedel, Newton-Raphson, and fast decouples - are presented. Furthermore, the DC load flow is also presented, through which rough estimates of bus voltage magnitudes and angle can be computed using a simplified noniterative procedure. However, power flow calculations may not be accurate due to erroneous measurements. Power system state estimation, on the other hand, is a mixture of load flow and statistical estimation theory that can provide a much more accurate snapshot of the power system status. This is discussed in Section 3.4.
A power system may contain several generators. How these generators must be scheduled to cater to load demands economically is discussed in Chapter 4. Economic operations depend on the most economically efficient generators catering for a higher portion of load demand. Furthermore, the method of committing a particular number of units to serve the load demand is also discussed in the chapter. The basic concepts of automatic generation control and load frequency control are also discussed in the chapter.
Power system fault studies are presented in Chapter 5. Power system faults can be balanced or unbalanced. For balanced faults, it is assumed that all the three phases have been short-circuited to the earth at the same location. These faults can be analyzed using the single-line diagram assuming the balanced operation of the faulted circuit....
