Operation and Control in Power Systems, Second Edition

In power system engineering, practically all results of modern control theory can be applied. Such an application will result in a more economical, more convenient and higher service quality operation and in less inconvenience in the case of abnormal conditions. For its analytical treatment, control system design generally requires the determination of a mathematical model from which the control strategy can be derived. While much of the control theory postulates that a model of the system is available, it is also necessary to have a suitable technique to determine the models for the process to be controlled. It is therefore essential to model and identify power system components using both physical relationships and experimental or normal operating data. The objective of system identification is the determination of a mathematical model that characterizes the operation of a system in some form. The available information is either system output or a function of the system output. The input may be a known function applied for the purpose of identification, or an unknown function which could possibly be monitored, or a combination of both. The planning of the operation and control of isolated or interconnected power systems present a large variety of challenging problems. Solving these requires the application of several mathematical techniques from various sources at the appropriate process step. Moreover, the knowledge of optimization techniques and optimal control methods is essential to understand the multi-level approach that is used. Operation and Control in Power Systems is an introductory course text for undergraduate students in electrical and mechanical engineering. In fifteen chapters, it deals with the operation and control of power systems, ranging from load flow analysis to economic operation, optimal load flow, unit commitment, load frequency, interconnected systems, voltage and reactive power control and advanced topics. Various models that are needed in analysis and control are discussed and presented through out the book. This second edition has been extended with mathematical support material and with methods to prevent voltage collapse. It also includes more advanced topics in power system control, such as the effect of shunt compensators, controllable VAR generation and switching converter type VAR generators.

Introduction1.1 Structure of a Power System1.2 Models for Analysis and Control1.3 Scheduling Studies1.4 Modes of Operation1.5 Synchronizing Coefficient 2 Load Flow Analysis2.1 Bus Classification2.2 Modelling for Load Flow Studies2.3 Gauss-Seidel Iterative Method2.4 Newton-Raphson Method2.4.1 Rectangular Coordinates Method2.4.2 The Polar Coordinates Method2.5 Sparsity of Network Admittance Matrices2.6 Triangular Decompostion2.7 Optimal Ordering2.8 Decoupled Methods2.9 Fast Decoupled Methods2.10 Load Flow Solution Using Z Bus2.10.1 Bus Impedance Formation2.10.2 Addition of a Line to the Reference Bus2.10.3 Addition of a Radial Line and New Bus 2.10.4 Addition of a Loop Closing Two Existing Buses in the System 2.10.5 Gauss-Seidel Method Using Z-bus for Load Flow Solution 2.11 Load Flow Solution with Static Load Model 2.12 Comparision of Various Methods for Power Flow Solution QuestionsProblems 3 Economic Operation of Power Systems3.1 Characteristics of Steam Plants3.2 Input Output Curves 923.3 The Incremental Heat Rate Characteristic 3.4 The Incremental Fuel Cost Characteristic 3.5 Heat Rate Characteristic 3.6 Incremental Production Cost Characteristics 3.7 Characteristics of Hydro Plants 3.8 Incremental Water Rate Characteristics 3.9 Incremental Production Cost Characteristic 3.10 Generating Costs at Thermal Plants 3.11 Analytical Form for Input-Output Characteristics of Thermal Units 3.12 Constraints in Operation 3.13 Plant Scheduling Methods 3.14 Merit Order Method 3.15 Equal Incremental Cost Method : Transmission Losses Neglected 3.16 Transmission Loss Formula – B. Coefficients 3.17 Active Power Scheduling 3.18 Penalty Factor 3.19 Evaluation of for Computation 3.20 Hydro Electric Plant Models 3.21 Pumped Storage Plant 3.22 Hydro Thermal Scheduling 3.23 Energy Scheduling Method 3.24 Short Term Hydro Thermal Scheduling 3.24.1 Method of Lagrange Multipliers (losses neglected) 3.24.2 Lagrange Multipliers Method Transmission Losses Considered 3.24.3 Short Term Hydro Thermal Scheduling using B-Coefficients for Transmission losses Questions Problems 4 Optimal Load Flow4.1 Reactive Power Control for Loss Minimization 4.2 Gradient Method for Optimal Load Flow 4.3 Non-Linear Programming 4.4 Lagrange Function for Optimal Load Flow 4.5 Computational Procedures 4.6 Conditions for Optimal Load Flow 4.7 Implementation of optimal conditions Questions Problems 5 Unit Commitment5.1 Cost Function Formulation 5.2 Constraints for Plant Commitment Schedules 5.3 Priority-List Method 5.4 Dynamic Programming 5.5 Unit Commitment by Dynamic Programming Questions Problems6 Load Frequency Control6.1 Speed Governing Mechanism 6.2 Speed Governor 6.3 Steady State Speed Regulation 6.4 Adjustment of Governor Characteristics 6.5 Transfer Function of Speed Control Mechanism 6.6 Transfer Function of a Power System 6.7 Transfer Function of the Speed Governor 6.8 Governing of Hydro Units 6.9 Penstock Turbine Model 6.10 Modal for a Steam Vessel 6.11 Steam Turbine Model 6.12 Reheat Type Steam Turbine Model 6.13 Single Control Area 6.14 The Basics of Load Frequency Control 6.15 Flat Frequency Control 6.16 Real Power Balance for Load Changes 6.17 Transfer Function of a Single Area System 6.18 Analysis of Single Area System 6.19 Dynamic Response of Load Frequency Control Loop: Uncontrolled Case 6.20 Control Strategy 6.21 PID Controllers 6.22 The optimal Control Problem 6.23 The Linear Regulator Problem 6.24 Matrix Riccati Equation 6.25 Application of Modern Control Theory 6.26 Optimal Load Frequency Control – Single Area System 6.27 Optimal Control for Tandem Compound Single Reheat Turbine – Generator System 6.28 Optimal Control of Hydro Speed Governing System 6.29 A Review of Optimal Control 6.30 Load Frequency Control with Restrictions on the Rate of Power Generation6.31 Load Frequenc1y Control using Output Feedback 6.32 Load frequency Control and Economic Dispatch Questions Problems 7 Control of Interconnected Systems7.1 Interconnected Operation 7.2 Flat Frequency Control of Interconnected Stations 7.3 Flat Tie-Line and Flat Frequency Control 7.4 Tie-Line Bias Control 7.5 Complete Tie-Line Bias Control 7.6 Two Area System – Tie-Line Power Model 7.7 Block Diagram for Two Area System 7.8 Analysis of Two Area System 7.9 Dynamic Response 7.10 Tie-Line Bias Control – Implementation 7.11 The Effect of Bias Factor on System Regulation 7.12 Scope for Supplementary Control 7.13 State Variable Model for a Three Area System 7.14 State Variable Model for a Two Area System 7.15 State Variable Model for a Single Area System 7.16 Model Reduction and Decentralised Control Questions Problems 8 Voltage and Reactive Power Control8.1 Impedance and Reactive Power 8.2 System Voltage and Reactive Power 8.3 Reactive Power Generation by Synchronous Machines 8.4 Effect of Excitation Control 8.5 Voltage Regulation and Power Transfer 8.6 Exciter and Voltage Regulator 8.7 Block Schematic of Excitation Control 8.8 Static Excitation System 8.9 Brushless Excitation Scheme 8.10 Automatic Voltage Regulators for Alternators 8.11 Analysis of Generator Voltage Control 8.12 Steady State Performance Evaluation 8.13 Dynamic Response of Voltage Regulation Control 8.14 Stability Compensation for Voltage Control 8.15 Stabilizing Transformer 8.16 Voltage Regulators 8.17 IEEE Type 1 Excitation System 8.18 Power System Stabilizer 8.19 Reactive Power Generation by Turbo Generator 8.20 Synchronous Compensators 8.21 Reactors 8.22 Capacitors 8.23 Tap–Changing Transformers 8.24 Tap–Staggering Method 8.25 Voltage Regulation and Short Circuit Capacity 8.26 Loading Capability of a Line 8.27 Compensation in Power Systems 8.28 Load Compensation 8.29 Static Compensators 8.30 Steady State Performance of Static var compensators 8.31 Overvoltages on Sudden Loss of Load 8.32 Voltage Dips 8.33 Subsynchronous Resonance Questions Problems9 Introduction to Advanced Topics9.1 Facts Controllers 9.1.1 Series Controllers 9.1.2 Shunt Controller 9.1.3 Series – Series Controllers 9.1.4 Series – Shunt Controllers 9.1.5 Power Flow Control 9.1.6 Static Var Compensator(SVC) 9.1.7 Unified Power Flow Controller 9.1.8 Advantages due to FACTS devices 9.2 Effect of Shunt 9.3 Controllable Var Generation 9.4 Switching Convestor Type VAR Generators 9.5 Voltage Stability 9.6 Methods for prevention of voltage collapse 9.7 Shunt and Series Connected Compensators 9.8 Power Quality 9.8.1 Power Quality Index 9.8.2 Voltage Sags 9.8.3 Rectifier Loads 9.8.4 Flicker 9.8.5 Power Acceptability or Voltage Tolerance 9.8.6 Solutions to Power Quality problem 9.9 Data Base for Control 9.10 State Estimation 9.11 Power System Security 9.12 Steady State Security Assessment 9.13 Application to Outage Studies 9.14 Pattern Recognition Methods 9.15 Power System Control Centres 9.16 Level Decomposition in Power Systems 9.17 Network Automation 9.18 Load Prediction 9.19 Load Prediction using Metereological Data 9.20 Spectral Expansion Method 9.21 Prediction by Scaling a Standard Load 9.22 Short – Term Load Forecasting Using Exponential Smoothing 9.23 Peak Power Demand Prediction 9.24 State Estimation in Load Forecasting 9.25 Generating Capacity Reliability and Outage Probabilities Questions Objective Questions Answers to Objective Questions Index

Dr. P.S.R. Murty obtained his PhD degree in Electrical Engineering from the Technical University in Berlin. He has worked for over four decades in the university education of electrical engineering students at several institutes. He is currently the Director of the School of Electrical Engineering at Shreenidhi Institute of Science and Technology in Hyderabad, India.