Electric Power Principles – Sources, Conversion, Distribution and Use

Professor James Kirtley is currently teaching a course on electric power systems to both undergaraduate and graduate students at MIT (Massachusetts Institue of Technology). He has been a fellow of IEEE since 1990, was awarded the IEEE Third Millenium Medal in 2000 and the Nikola Tesla Award in 2002. Since 2007 Professor Kirtley has been associate editor of IEEE Power Engineering Society s Transactions on Energy Conversion. He lectures outside the university, writes exensively for journals and holds 23 patents. Amongst other areas, his research interests include electric ships, superconducting generator, intelligent monitoring of equipment and systems, and advanced motor/generator machines for kinetic energy storage systems.

Preface xi 1 Electric Power Systems 1 1.1 Electric Utility Systems 2 1.2 Energy and Power 3 1.2.1 Basics and Units 3 1.3 Sources of Electric Power 3 1.3.1 Heat Engines 4 1.3.2 Power Plants 5 1.3.3 Nuclear Power Plants 8 1.3.4 Hydroelectric Power 9 1.3.5 Wind Turbines 10 1.3.6 Solar Power Generation 12 1.4 Electric Power Plants and Generation 15 1.5 Problems 15 2 AC Voltage, Current and Power 17 2.1 Sources and Power 17 2.1.1 Voltage and Current Sources 17 2.1.2 Power 18 2.1.3 Sinusoidal Steady State 18 2.1.4 Phasor Notation 19 2.1.5 Real and Reactive Power 19 2.2 Resistors, Inductors and Capacitors 21 2.2.1 Reactive Power and Voltage 22 2.2.2 Reactive Power Voltage Support 23 2.3 Problems 26 3 Transmission Lines 31 3.1 Modeling: Telegrapher s Equations 32 3.1.1 Traveling Waves 33 3.1.2 Characteristic Impedance 33 3.1.3 Power 35 3.1.4 Line Terminations and Reflections 35 3.1.5 Sinusoidal Steady State 40 3.2 Problems 42 4 Polyphase Systems 45 4.0.1 Two-Phase Systems 45 4.1 Three-Phase Systems 47 4.2 Line Line Voltages 49 4.2.1 Example: Wye and Delta Connected Loads 50 4.2.2 Example: Use of Wye Delta for Unbalanced Loads 52 4.3 Problems 54 5 Electrical and Magnetic Circuits 57 5.1 Electric Circuits 57 5.1.1 Kirchoff s Current Law (KCL) 57 5.1.2 Kirchoff s Voltage Law (KVL) 58 5.1.3 Constitutive Relationship: Ohm s Law 58 5.2 Magnetic Circuit Analogies 60 5.2.1 Analogy to KCL 60 5.2.2 Analogy to KVL: Magnetomotive Force 61 5.2.3 Analogy to Ohm s Law: Reluctance 61 5.2.4 Simple Case 62 5.2.5 Flux Confinement 63 5.2.6 Example: C-Core 63 5.2.7 Example: Core with Different Gaps 64 5.3 Problems 66 6 Transformers 71 6.1 Single-phase Transformers 71 6.1.1 Ideal Transformer 72 6.1.2 Deviations from Ideal Transformer 73 6.2 Three-Phase Transformers 75 6.2.1 Example 77 6.3 Problems 80 7 Polyphase Lines and Single-Phase Equivalents 85 7.1 Polyphase Transmission and Distribution Lines 85 7.1.1 Example 87 7.2 Introduction To Per-Unit Systems 88 7.2.1 Normalization Of Voltage and Current 88 7.2.2 Three-Phase Systems 90 7.2.3 Networks with Transformers 90 7.2.4 Transforming from one base to another 91 7.2.5 Example: Fault Study 92 7.3 Appendix: Inductances of Transmission Lines 94 7.3.1 Single Wire 94 7.3.2 Mutual Inductance 96 7.3.3 Bundles of Conductors 96 7.3.4 Transposed Lines 97 7.4 Problems 98 8 Electromagnetic Forces and Loss Mechanisms 103 8.1 Energy Conversion Process 103 8.1.1 Principle of Virtual Work 104 8.1.2 Coenergy 108 8.2 Continuum Energy Flow 110 8.2.1 Material Motion 111 8.2.2 Additional Issues in Energy Methods 112 8.2.3 Electric Machine Description 116 8.2.4 Field Description of Electromagnetic Force: The Maxwell Stress Tensor 118 8.2.5 Tying the MST and Poynting Approaches together 120 8.3 Surface Impedance of Uniform Conductors 124 8.3.1 Linear Case 124 8.3.2 Iron 128 8.3.3 Magnetization 128 8.3.4 Saturation and Hysteresis 129 8.3.5 Conduction, Eddy Currents and Laminations 131 8.3.6 Eddy Currents in Saturating Iron 133 8.4 Semi-Empirical Method of Handling Iron Loss 136 8.5 Problems 139 9 Synchronous Machines 145 9.1 Round Rotor Machines: Basics 146 9.1.1 Operation with a Balanced Current Source 147 9.1.2 Operation with a Voltage Source 147 9.2 Reconciliation of Models 150 9.2.1 Torque Angles 150 9.3 Per-Unit Systems 151 9.4 Normal Operation 152 9.4.1 Capability Diagram 153 9.4.2 Vee Curve 153 9.5 Salient Pole Machines: Two-Reaction Theory 154 9.6 Synchronous Machine Dynamics 157 9.7 Synchronous Machine Dynamic Model 159 9.7.1 Electromagnetic Model 159 9.7.2 Park s Equations 160 9.7.3 Power and Torque 164 9.7.4 Per-Unit Normalization 164 9.7.5 Equivalent Circuits 167 9.7.6 Transient Reactances and Time Constants 168 9.8 Statement of Simulation Model 169 9.8.1 Example: Transient Stability 170 9.8.2 Equal Area Transient Stability Criterion 170 9.9 Appendix: Transient Stability Code 173 9.10 Appendix: Winding Inductance Calculation 176 9.10.1 Pitch Factor 180 9.10.2 Breadth Factor 180 9.11 Problems 182 10 System Analysis and Protection 185 10.1 The Symmetrical Component Transformation 185 10.2 Sequence Impedances 188 10.2.1 Balanced Transmission Lines 188 10.2.2 Balanced Load 189 10.2.3 Possibly Unbalanced Loads 190 10.2.4 Unbalanced Sources 191 10.2.5 Rotating Machines 193 10.2.6 Transformers 193 10.3 Fault Analysis 197 10.3.1 Single Line neutral Fault 198 10.3.2 Double Line neutral Fault 199 10.3.3 Line Line Fault 200 10.3.4 Example of Fault Calculations 201 10.4 System Protection 205 10.4.1 Fuses 206 10.5 Switches 207 10.6 Coordination 208 10.6.1 Ground Overcurrent 208 10.7 Impedance Relays 208 10.7.1 Directional Elements 209 10.8 Differential Relays 210 10.8.1 Ground Fault Protection for Personnel 211 10.9 Zones of System Protection 212 10.10 Problems 212 11 Load Flow 219 11.1 Two Ports and Lines 219 11.1.1 Power Circles 221 11.2 Load Flow in a Network 222 11.3 Gauss Seidel Iterative Technique 224 11.4 Bus Admittance 226 11.4.1 Bus Incidence 226 11.4.2 Alternative Assembly of Bus Admittance 227 11.5 Example: Simple Program 228 11.5.1 Example Network 228 11.6 MATLAB Script for the Load Flow Example 229 11.7 Problems 231 12 Power Electronics and Converters in Power Systems 235 12.1 Switching Devices 235 12.1.1 Diode 236 12.1.2 Thyristor 236 12.1.3 Bipolar Transistors 237 12.2 Rectifier Circuits 239 12.2.1 Full-Wave Rectifier 239 12.3 DC DC Converters 247 12.3.1 Pulse Width Modulation 249 12.3.2 Boost Converter 249 12.4 Canonical Cell 255 12.4.1 Bidirectional Converter 255 12.4.2 H-Bridge 257 12.5 Three-Phase Bridge Circuits 259 12.5.1 Rectifier Operation 259 12.5.2 Phase Control 261 12.5.3 Commutation Overlap 262 12.5.4 AC Side Current Harmonics 265 12.6 High-Voltage DC Transmission 270 12.7 Basic Operation of a Converter Bridge 271 12.7.1 Turn-On Switch 272 12.7.2 Inverter Terminal 272 12.8 Achieving High Voltage 273 12.9 Problems 274 13 Induction Machines 281 13.1 Introduction 281 13.2 Induction Machine Transformer Model 283 13.2.1 Operation: Energy Balance 289 13.2.2 Example of Operation 294 13.2.3 Motor Performance Requirements 294 13.3 Squirrel-Cage Machines 296 13.4 Single-Phase Induction Motors 297 13.4.1 Rotating Fields 297 13.4.2 Power Conversion in the Single-Phase Induction Machine 298 13.4.3 Starting of Single-Phase Induction Motors 300 13.4.4 Split Phase Operation 301 13.5 Induction Generators 303 13.6 Induction Motor Control 306 13.6.1 Volts/Hz Control 306 13.6.2 Field Oriented Control 307 13.6.3 Elementary Model 308 13.6.4 Simulation Model 309 13.6.5 Control Model 310 13.6.6 Field-Oriented Strategy 311 13.7 Doubly Fed Induction Machines 313 13.7.1 Steady State Operation 315 13.8 Appendix 1: Squirrel-Cage Machine Model 318 13.8.1 Rotor Currents and Induced Flux 319 13.8.2 Squirrel-Cage Currents 320 13.9 Appendix 2: Single-Phase Squirrel Cage Model 325 13.10 Appendix 3: Induction Machine Winding Schemes 326 13.10.1 Winding Factor for Concentric Windings 329 13.11 Problems 331 14 DC (Commutator) Machines 337 14.1 Geometry 337 14.2 Torque Production 338 14.3 Back Voltage 339 14.4 Operation 341 14.4.1 Shunt Operation 342 14.4.2 Separately Excited 343 14.4.3 Machine Capability 345 14.5 Series Connection 346 14.6 Universal Motors 348 14.7 Commutator 349 14.7.1 Commutation Interpoles 351 14.7.2 Compensation 351 14.8 Compound Wound DC Machines 352 14.9 Problems 354 15 Permanent Magnets in Electric Machines 357 15.1 Permanent Magnets 357 15.1.1 Permanent Magnets in Magnetic Circuits 359 15.1.2 Load Line Analysis 360 15.2 Commutator Machines 363 15.2.1 Voltage 365 15.2.2 Armature Resistance 366 15.3 Brushless PM Machines 367 15.4 Motor Morphologies 367 15.4.1 Surface Magnet Machines 367 15.4.2 Interior Magnet, Flux Concentrating Machines 368 15.4.3 Operation 369 15.4.4 A Little Two-Reaction Theory 371 15.4.5 Finding Torque Capability 374 15.5 Problems 380 Index 385