Power Systems

Preface xiii Nomenclature xv About the Companion Website xix 1 Introduction 1 1.1 What is a Power System? 1 1.2 What are the Attributes of a Good Power System? 1 1.3 Structure of a Power System 2 1.3.1 Physical Structure 2 1.3.2 Cyber Infrastructure 4 1.3.3 Organizational Structure 5 1.4 Historical Evolution 5 Problems 7 2 Electrical Loads and the Demand for Electricity 9 2.1 Overview 9 2.2 Residential Loads 9 2.3 Commercial and Industrial Loads 12 2.4 Load Aggregation over a Large Region 13 2.5 What Factors Shape the Aggregated Load Profile in the Short Run? 14 2.6 What Affects the Aggregated Electrical Load in the Long Run? 17 2.7 Metering and Billing 19 2.8 Flexibility 20 2.9 Outages 21 2.10 Complex Power, Reactive Power, and Power Factor 22 2.11 Parallel Loads 24 Reference 27 Further Reading 27 Problems 27 3 Primary Energy Conversion 31 3.1 Overview 31 3.2 Wind Generation 31 3.2.1 How Much Power is There in the Wind? 31 3.2.2 How Does a Turbine Blade Extract Wind Power? 32 3.2.3 Controlling a Wind Turbine 33 3.2.4 Locating Wind Farms 34 3.2.5 Advantages and Disadvantages of Wind Generation 36 3.3 Thermal Generation 37 3.3.1 Concept of Heat Engine 37 3.3.2 Fossil-Fueled Steam Plants 38 3.3.3 Other Types of Steam Plants 39 3.3.3.1 Nuclear Power Plants 39 3.3.3.2 Concentrated Solar Power Plants 40 3.3.3.3 Geothermal Plants 40 3.3.3.4 Combined Heat and Power Plants – Cogeneration 40 3.3.4 Gas-Fired Generation 41 3.3.4.1 Open Cycle Gas Turbines (OCGT) 41 3.3.4.2 Combined Cycle Gas Turbines (CCGT) 41 3.3.5 Internal Combustion Engines 42 3.4 Hydroelectric Generation 42 3.4.1 Impoundment Hydro Plants 42 3.4.2 Diversion Hydro Plants 44 3.5 Photovoltaic Generation 44 3.6 Storage Systems 47 3.6.1 Pumped Hydro Plants 48 3.6.2 Electrochemical Batteries 48 3.6.3 Other Energy Storage Technologies 49 3.6.4 Applications of Energy Storage Systems 50 3.7 Choosing a Generation Technology 50 Further Reading 52 Problems 52 4 Electromechanical Power Conversion 57 4.1 Overview 57 4.2 Structure of a Generator 57 4.3 Three-Phase Systems 60 4.3.1 Advantages of Three-Phase Systems 60 4.3.2 Three-Phase Sources 60 4.3.3 Three-Phase Loads 63 4.3.3.1 Y-Connected Loads 64 4.3.3.2 Δ-Connected Loads 66 4.3.3.3 Δ-Y Equivalence 67 4.3.4 Powers in Three-Phase Systems 69 4.3.5 Single-Phase Representation and One-Line Diagrams 69 4.4 Per Unit System 70 4.4.1 Choosing Base Quantities in Single-Phase Systems 71 4.4.2 Choosing Base Quantities in Three-Phase Systems 71 4.4.3 Converting Per Unit Impedances 74 4.5 Synchronous Generator Model 75 4.6 Controlling an Isolated Synchronous Generator 76 4.7 Connecting a Generator to the Grid 77 4.8 Operating a Synchronized Generator 78 4.9 Synchronous Condenser 82 4.10 Generator Limits 82 Further Reading 84 Problems 85 5 Electronic Power Conversion 89 5.1 Overview 89 5.2 Switches 89 5.3 Voltage Source Converters 90 5.3.1 Single-Phase Voltage Source Converter 90 5.3.2 Converter Operation 92 5.3.3 Three-Phase Converter 94 5.4 Applications of Power Electronics in Power Systems 95 5.4.1 Battery Energy Storage 95 5.4.2 PV Generation 96 5.4.3 Type 4 Connection of a Wind Turbine 97 5.4.4 Type 3 Connection of a Wind Turbine 98 5.4.5 High-Voltage dc Links (HVDC) 100 Further Reading 101 6 Balancing Load and Generation 103 6.1 Overview 103 6.2 Power Balance 103 6.3 Single Generator 104 6.4 Multiple Generators 106 6.5 Electronically Connected Generation and Battery Energy Storage 108 6.6 Secondary Frequency Control 109 6.7 System Response to Large Disturbances 110 6.8 Economic Dispatch 110 6.8.1 Heat Rate Curve and Cost Curve 111 6.8.2 Mathematical Formulation 112 6.8.3 Piecewise-Linear Cost Curves 116 6.8.4 Load Flexibility and Storage 118 6.9 Unit Commitment 120 6.9.1 How Many Generating Units do we Need? 120 6.9.2 Formulating the Unit Commitment Problem 121 6.9.3 Solving the Unit Commitment Problem 124 6.10 Handling of Uncertainty 126 Reference 129 Further Reading 129 Problems 129 7 Network Components 135 7.1 Overview 135 7.2 ac Lines 135 7.3 dc Lines 140 7.4 Transformers 140 7.4.1 Single-Phase Transformer 140 7.4.2 Three-Phase Transformer 145 7.4.3 Transformer Ratings 146 7.4.4 Three-Phase Transformers in the Per Unit System 147 7.4.5 Tap-Changing Transformer 148 7.4.6 Phase-Shifting Transformer 152 7.5 Switchgear 154 7.6 Reactive Compensation Devices 154 7.7 Substations 155 Further Reading 156 Problems 156 8 Power Flow 163 8.1 Overview 163 8.2 Qualitative Relation Between Flows and Voltages 163 8.3 Nodal Analysis 165 8.3.1 An Example of Nodal Analysis 165 8.4 Formulation of the Power Flow Problem 169 8.5 Solving the Power Flow Equations 172 8.5.1 Newton–Raphson Method 172 8.5.2 Applying the Newton–Raphson Method to the Power Flow Problem 175 8.6 Calculating the Line Flows 180 8.7 Power Flow Applications 181 8.8 Optimal Power Flow 188 Further Reading 189 Problems 189 9 Analysis of Balanced Faults 197 9.1 Overview 197 9.2 Two Simple Examples 198 9.3 Balanced Fault Calculations in Large Systems 201 9.4 Modeling Generators for Fault Calculations 205 9.5 Inverter-Based Generation 210 Reference 210 Further Reading 210 Problems 211 10 Analysis of Unbalanced Faults 215 10.1 Overview 215 10.2 Symmetrical Components 215 10.2.1 Notation 215 10.2.2 Concept of Symmetrical Components 216 10.2.3 Calculating the Sequence Components 216 10.2.4 Relation Between the Neutral and Zero-sequence Currents 219 10.3 Sequence Networks 220 10.3.1 Sequence Networks Representation of Impedance Loads 220 10.3.2 Sequence Networks Representation of Generators 225 10.3.3 Sequence Networks Representation of Three-phase Lines and Cables 226 10.3.4 Sequence Networks Representation of Three-phase Transformers 226 10.3.5 Sequence Networks Representation of Power Systems 228 10.4 Unbalanced Faults 230 10.4.1 Balanced Three-phase Fault 231 10.4.2 Single Line-to-ground Fault 232 10.4.3 Line-to-line Fault 234 10.4.4 Double Line-to-ground Fault 235 10.5 Unbalanced Fault Calculations in Large Systems 237 References 240 Further Reading 240 Problems 240 11 Introduction to Power System Stability 245 11.1 Overview 245 11.2 P–V Curves 245 11.3 Effect of Outages 248 11.4 Cascading Overloads 249 11.5 Electromechanical or Transient Stability 252 11.5.1 Modeling the Mechanical Dynamics of Synchronous Generators: the Swing Equation 253 11.5.2 Modeling the Electrical Dynamics of Synchronous Generators 256 11.5.3 A Simple Model of the Rest of the System 257 11.5.4 Stable and Unstable Operating Points 257 11.5.5 Large Disturbances 259 11.5.6 Equal Area Criterion 261 11.5.7 Factors Influencing Stability 266 11.5.8 Transient Stability Analysis Using Time Domain Simulation 267 11.5.9 Simulating the Dynamics of Multi-generator Systems 270 11.5.10 Damping 277 11.6 Detailed Dynamic Models 279 11.7 Power System Oscillations 279 11.8 Preventing Instabilities 279 Further Reading 280 Problems 281 12 Introduction to Competitive Electricity Markets 287 12.1 Overview: Why Competition? 287 12.2 Fundamentals of Markets 287 12.3 Wholesale Electricity Markets 291 12.4 Bidding in a Centralized Market 294 12.5 Variation of Market Price with Time 294 12.6 Effect of Transmission Capacity Limits 297 12.7 Two-Settlement Markets 299 12.8 Ancillary Services 300 12.9 Retail Markets 301 12.10 Unbundled Industry Structure 301 Further Reading 303 Problems 303 Index 307