Design and Application of Modern Synchronous Generator Excitation Systems

Jicheng Li Tsinghua University China

V V I I > I—I I I f c t t I l \ l - J J LQj CHINA ELECTRIC POWER PRESS

Contents

About the Author xxi Foreword xxiii Preface xxvii Introduction Acknowledgement xxxi

1 Evolution and Development of Excitation Control 1 1.1 Overview 1 1.2 Evolution of Excitation Control 1 1.2.1 Single Variable Control Based on Classical Control Theory 1 1.2.1.1 Proportional Control 2 1.2.1.2 PID Control 4 1.2.2 Linear Multivariate Control Based on Modern Control Theory 1.2.2.1 Linear Optimal Control Principle 7 1.2.2.2 Quadratic Performance Index 8 1.2.2.3 Linear Optimal Controller 10 1.3 Linear Multivariable Total Controller 11 1.3.1 Overview of TAGEC 11 1.3.2 TAGEC Control 12 1.3.2.1 TAGEC-I 12 1.3.2.2 TAGEC-II 12 1.3.2.3 TAGEC-III 13 1.3.3 Mathematical Model of TAGEC Control System 14 1.3.4 Composition of TAGEC System 15 1.3.4.1 Sampling Operation 15 1.3.4.2 Matrix Operation 17 1.3.4.3 Stability Margin Monitoring Control 17 1.3.4.4 TAGEC Input and Output 18 1.3.5 Digital Simulation Test of Power Transmission System 18 1.3.5.1 Composition of Power System 18 1.3.5.2 Generators 18 1.3.5.3 Excitation and Speed Governing System 19 1.3.5.4 Power System Stability Test 19 1.3.5.5 Power System Stability Test Result 19 1.4 Nonlinear Multivariable Excitation Controller 20 1.5 Power System Voltage Regulator (PSVR) 25 1.5.1 Overview 25 1.5.2 Effect of SVR on Improvement of System Voltage Characteristics

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1.5.3 Composition of PSVR 29 1.5.3.1 Basic Control of PSVR 29 1.5.3.2 Basic Equation of PSVR Control 29 1.5.4 Comparison between PSVR and AVR in Control Characteristics 31 1.5.5 Basic Functions of PSVR 31 1.5.5.1 Basic Control 31 1.5.5.2 Program Voltage Setting 31 1.5.5.3 Output Limit 31 1.5.5.4 Anomaly Self-Detection 31 1.5.5.5 Control Stability 31 1.5.6 PSVR Simulation Test 33

2 Characteristics of Synchronous Generator 35 2.1 Electromotive Force Phasor Diagram of Synchronous Generator 35 2.1.1 Non-salient Pole Generator 35 2.1.1.1 Electromotive Force Phasor Diagram of Non-salient Pole Generator 35 2.1.1.2 Emf Equation of Non-salient Pole Generator 35 2.1.2 Salient Pole Generator 36 2.1.2.1 Emf Phasor Diagram of Salient Pole Generator 36 2.1.2.2 Emf Equation of Salient Pole Generator 37 2.2 Electromagnetic Power and Power Angle Characteristic of Synchronous Generator 38 2.2.1 Power and Torque Balance Equations 38 2.2.2 Electromagnetic Power and Power Angle Characteristic Expressions 38 2.2.2.1 Power Angle Characteristic Curve of Non-salient Pole Generator 40 2.2.2.2 Power Angle Characteristic Curve of Salient Pole Generator 40 2.2.2.3 Power Angle Expression of Reactive Power 40 2.3 Operating Capacity Characteristic Curve of Synchronous Generator 41 2.3.1 Operating Capacity Diagram of Non-salient Pole Generator 41 2.3.1.1 Power Diagram of Non-salient Pole Generator 41 2.3.1.2 Operating Capacity Curve of Non-salient Pole Generator 42 2.3.2 Operating Capacity Curve of Salient Pole Generator 44 2.4 Influence of External Reactance on Operating Capacity Characteristic Curve 45 2.5 Operating Characteristic Curves of Generator 50 2.5.1 Operating Characteristic Curve of Hydro Generator 51 2.5.1.1 No-Load Saturation Characteristic Curve 57 2.5.1.2 Short Circuit Characteristic Curve 51 2.5.1.3 Air Gap Line 52 2.5.1.4 Load Characteristic Curve {coscp = 0.9) 52 2.5.1.5 Load Characteristic Curve (cos<p = 0) 52 2.5.2 Capacity Characteristics Curve of Hydro Generator 52 2.5.3 V-Shaped Curve of Hydro Generator 52 2.5.3.1 Normal Operating Area 53 2.5.3.2 Unstable Operating Area 53 2.5.3.3 Phase-Modulated Operation Capacity 53 2.6 Transient Characteristics of Synchronous Generator 54 2.6.1 Transient Reactance X' 54 2.6.2 Transient Emf E'q 57 2.6.3 Transient Equation of Rotor Excitation Circuit 59 2.6 A Change in Transient Emf in the Case of Three-Phase Short Circuit 60 2.6.5 Influence of Change of Excitation Voltage on Transient Emf 62

Contents vii

3 Effect of Excitation Regulation on Power System Stability 67 3.1 Definition and Classification of Power System Stability 67 3.1.1 Steady-State Stability 67 3.1.2 Dynamic Stability 67 3.1.3 Transient Stability 67 3.2 Criterion of Stability Level 68 3.3 Effects of Excitation Regulation on Power System Stability 68 3.3.1 Effect of Excitation Regulation on Steady-State Stability 68 3.3.2 Influence of Excitation Regulation on Transient Stability 70 3.3.2.1 Enhancement of the Steady-State Stability of Power System 72 3.3.2.2 Improving Transient Stability 74 3.3.2.3 Improving Dynamic Stability 74

4 Static and Transient State Characteristics of Excitation Systems 77 4.1 Static Characteristics of Excitation System 77 4.1.1 Block Diagram of Static Characteristics 77 4.1.2 Natural Ratio of Generator Voltage to Reactive Current of Generator 77 4.1.2.1 Formula Relating Generator Voltage and Reactive Current 77 4.1.2.2 Determination of Natural Ratio of Generator Voltage to Reactive Current of Generator 78 4.1.3 Static Voltage Droop Ratio of Generator 80 4.1.3.1 A Setting Voltage Static Error 80 4.1.3.2 Static Error Caused by the Load Disturbance/Q 81 4.2 Ratio and Coefficient of Generator Voltage to Reactive Current of Generator 81 4.2.1 Ratio of Generator Voltage to Reactive Current of Generator 81 4.2.2 Determination of Ratio and Coefficient of Generator Voltage to Reactive Current of Generator at

Different Operation Connection Modes 81 4.2.3 Natural Ratio and Additional Coefficient of Generator Voltage to Reactive Current of

Generator 83 4.2.3.1 Natural Regulation Ratio of Generator Voltage to Reactive Current of Generator 83 4.2.3.2 Additional Regulation Coefficient of Ratio of Generator Voltage to Reactive Current of

Generator 83 4.2.4 Formation of Additional Coefficient of Reactive Current Compensation 85 4.2.4.1 Analog AVR 85 4.2.4.2 Digital AVR 86 4.2.5 Conclusions 86 4.3 Transient State Characteristics of Excitation System 87 4.3.1 Transient Response of Large Disturbance Signal 87 4.3.1.1 Ceiling Voltage Factor of Excitation System 87 4.3.1.2 Voltage Response Ratio of Excitation System 88 4.3.2 Transient Response of Small Deviation Signal 90 4.3.3 Unit Step Response 91 4.3.4 Frequency Response 92 4.4 Stability Analysis of Excitation System 94

5 Control Law and Mathematical Model of Excitation System 97 5.1 Basic Control Law of Excitation System 97 5.1.1 Basic Terms of Excitation Control System 97 5.1.2 Transfer Function of Control System 98 5.1.3 Basic Control Law of Excitation Controller 98 5.1.3.1 Proportional Control Law (P) 99

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5.1.3.2 Integral Control Law (I) 99 5.1.3.3 Proportional-Integral Control Law (PI) 100 5.1.3.4 Differential Control Law (D) 101 5.1.3.5 Proportional-Differential Control Law (PD) 101 5.1.3.6 Proportional-Integral-Differential Control Law (PID) 103 5.1.4 Numerical Description of the PID Control Law 105 5.1.4.1 Position Algorithm 105 5.1.4.2 Increment Algorithm 106 5.1.4.3 Practical Algorithm 106 5.1.5 Parallel Feedback Correction of Excitation Control System 107 5.1.5.1 Parallel Correction - Proportional Feedback 107 5.1.5.2 Parallel Correction - Dynamic Feedback 108 5.2 Mathematical Model of the Excitation System 108 5.2.1 Static Self-Excitation System 109 5.2.1.1 Series Compensation Self-Excitation System 109 5.2.1.2 Feedback Compensation Self-Excitation System 109 5.2.1.3 Proportional-Integral (PI) Self-Excitation System 109 5.2.2 AC Exciter System 110 5.2.2.1 AC Shunt-Exciter-Type Self-Excitation System 110 5.2.2.2 AC Separate-Exciter-Type Excitation System 113 5.2.2.3 Feedback Compensation Brushless Excitation System 113 5.2.2.4 PI Type Brushless Excitation System 114 5.2.3 Rectifier 115 5.3 Mathematical Model of Excitation Control Unit 118 5.3.1 Load Current Compensator (LCC) 118 5.3.2 Automatic Reactive Power Regulator (AQR) 118 5.3.3 Automatic Power Factor Regulator (APFR) 119 5.3.4 Under-Excitation Limiter (UEL) 120 5.3.5 Over-Excitation Limiter (OEL) 121 5.3.6 Power System Stabilizer (PSS) 123 5.3.6.1 AP Type PSS 123 5.3.6.2 Aw Type PSS 123 5.3.6.3 A/ Type PSS 123 5.4 Parameter Setting of Excitation System 124 5.4.1 Setting of Proportional AVR Parameters 124 5.4.1.1 AVR Steady-State Open-Loop Gain KA 124 5.4.1.2 Setting of AVR Phase Compensation and Damping Loop Parameters 124 5.4.2 Frequency Response and Step Response Calculation 125 5.4.3 PI AVR Parameter Setting 126 5.4.3.1 AVR Gain KA 128 5.4.3.2 Integral Time Constant 129 5.4.4 PSS Parameter Setting 131 5.4.4.1 Setting of Time Constant Tg and Gain Kpss for the Washout Filter 131 5.4.4.2 Phase Compensation 131 5.4.4.3 Gain and Output Limit 133 5.4.4.4 Setting of PSS Gain and Phase Compensation 133

6 Basic Characteristics ofThree-Phase Bridge Rectifier Circuit 137 6.1 Overview 137 6.2 Operating Principle of Three-Phase Bridge Rectifier 137

6.3 Type I Commutation State 139 6.4 Commutation Angle 144 6.5 Average Rectified Voltage 144 6.5.1 Zero Rectifier Control Angle a and Commutation Angle y 144 6.5.2 a > 0, y = 0, for Zero Rectifier Load 145 6.5.3 a > 0, y — 0, in Controllable and Loaded State 145 6.6 Instantaneous Rectified Voltage Value 147 6.7 Effective Element Current Value 147 6.8 Fundamental Wave and Harmonic Value for Alternating Current 152 6.8.1 Fundamental Wave for Alternating Current 152 6.8.2 AC Harmonic Value 153 6.9 Power Factor of Rectifying Device 156 6.10 Type III Commutation State 161 6.11 Type II Commutation State 167 6.12 External Characteristic Curve for Rectifier 168 6.13 Operating Principle of Three-Phase Bridge Inverter Circuit 170

7 Excitation System for Separately Excited Static Diode Rectifier 775 7.1 Harmonic Analysis for Alternating Current 175 7.2 Non-distortion Sinusoidal Potential and Equivalent Commutating Reactance 177 7.2.1 Non-distortion Sinusoidal Potential and Equivalent Commutating Reactance 177 7.2.2 Non-distortion Sinusoidal Potential Determined by Simplification 178 7.2.3 Calculation of Equivalent Commutating Reactance 179 7.3 Expression for Commutation Angle y, Load Resistance r*, and Commutating Reactance Xy 182 7.4 Rectified Voltage Ratio ßu and Rectified Current Ratio ß{ 184 7.4.1 Rectified Voltage Ratio ßu 184 7.4.2 Rectified Current Ratio /?, 185 7.5 Steady-State Calculations for AC Exciter with Rectifier Load 186 7.6 General External Characteristics of Exciter 189 7.7 Transient State Process of AC Exciter with Rectifier Load 191 7.8 Simplified Transient Mathematical Model of AC Exciter with Rectifier Load 193 7.8.1 Simplified Computation Method of External Characteristics of Rectifier 193 7.8.2 Simplified Computation Method of External Characteristics of Exciter 194 7.9 Transient State Process of Excitation System in Case of Small Deviation Change in Generator

Excitation Current 196 7.10 Influence of Diode Rectifier on Time Constant of Generator Excitation Loop 200 7.11 Excitation Voltage Response for AC Exciter with Rectifier Load 201 7.11.1 Excitation Voltage Responses of AC Exciter without Load 201 7.11.2 Excitation Voltage Response of AC Exciter with Load 201 7.11.3 Field Voltage Response When Three-Phase Short-Circuit Occurs in the Generator 204 7.12 Short-Circuit Current Calculations for AC Exciter 205 7.12.1 Abrupt Short Circuit on DC Side of Rectifier 205 7.12.2 Determination of Transient Rotor Current-Free Component in Case of Abrupt Generator

Terminal Three-Phase Short Circuit 209 7.13 Calculations for AC Rated Parameters and Forced Excitation Parameters 211 7.13.1 Determination of Distortion Sinusoidal Potential Ex and Rated Power PN 211 7.13.2 Determination of Rated Parameters for AC Pilot Exciter 212

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8 Brushless Excitation System 215 8.1 Evolution of Brushless Excitation System 215 8.1.1 Diode Brushless Excitation System 215 8.1.2 SCR Brushless Excitation System 218 8.2 Technical Specifications for Brushless Excitation System 219 8.2.1 Ratings 219 8.2.2 AC Exciter 220 8.2.3 AC Pilot Exciter 221 8.2.4 Rotating Rectifier 221 8.3 Composition of Brushless Excitation System 221 8.3.1 Wiring 221 8.3.2 Composition of AC Excitation Unit 222 8.3.2.1 AC Main Exciter 222 8.3.2.2 Rotating Rectifier 224 8.4 Voltage Response Characteristics of AC Exciter 224 8.4.1 Excitation Voltage Response when Generator Is Subject to Three-Phase Short Circuit 226 8.5 Control Characteristics of Brushless Excitation System 227 8.5.1 Time Constant Compensation in Case of Small Deviation Signals 227 8.5.2 Time Constant Compensation in Case of Large Disturbance Signal 230 8.5.2.1 Connect Additional Resistors in Series 230 8.5.2.2 Increasing the Excitation Voltage Multiple of the Exciter 230 8.5.2.3 Comparison of the Above Two Methods 231 8.6 Mathematical Models for Brushless Excitation System 232 8.6.1 Determination of Saturation Coefficient 233 8.6.2 I-Type Model 234 8.6.2.1 Block Diagram of I-Type Model 234 8.6.2.2 Derivation of I-Type Model 235 8.6.2.3 Linearization of Small Deviation Signal AC Exciter Model 237 8.6.3 AC-I Model 238 8.6.3.1 The Block Diagram 238 8.6.3.2 Saturation Coefficient SE 238 8.6.3.3 Armature Reaction Coefficient KD 238 8.7 AC2 Model 243 8.8 Generator Excitation Parameter Detection and Fault Alarm 246 8.8.1 Determination of Excitation Voltage and Current of Rotor Excitation Winding 246 8.8.2 Protection, Fault Monitoring, and Alarm of Brushless Exciter 248 8.8.2.1 Fault Types 248 8.8.2.2 Fault Monitoring 249 8.8.2.3 Telemetry Detection Technology 254

9 Separately Excited SCR Excitation System 255 9.1 Overview 255 9.2 Characteristics of Separately Excited SCR Excitation System 255 9.2.1 Characteristics of Hydro-generator SCR Excitation System 255 9.2.2 Characteristics of SCR Excitation System for Steam Turbine Generator 258 9.3 Influence of Harmonic Current Load on Electromagnetic Characteristics of Auxiliary

Generator 260 9.3.1 Harmonic Current mmf 260 9.3.1.1 Harmonic Current Value 260 9.3.1.2 mmf Generated by Harmonic Current 261

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9.3.2 Influence of Harmonie mmf on Voltage Waveform of Generator without Damping Winding 263 9.3.3 Influence of Harmonic mmf on Voltage Waveform of Generator with Damping Winding 264 9.3.4 Damping Winding Loss and Allowable Value 265 9.3.5 Stator Winding and Core Loss 266 9.3.5.1 Stator Winding Loss 266 9.3.5.2 Stator Core Loss 267 9.3.6 Armature Reaction and Power Factor 267 9.4 Parameterization of Separately Excited SCR Excitation System 268 9.4.1 Auxiliary Generator 268 9.4.1.1 Preselected Commutation Reactance Value X 269 9.4.1.2 Calculated emf and Actual AC Stator Current of Auxiliary Generator 270 9.4.1.3 Rated Phase Current of Auxiliary Generator 270 9.4.1.4 Rated Phase Voltage of Auxiliary Generator 270 9.4.1.5 Capacity of Auxiliary Generator 270 9.4.2 Calculation of SCR Control Angle in Different Operating States 270 9.4.2.1 No-Load Operating Status 270 9.4.2.2 Rated Operating Status 277 9.4.2.3 Forced Excitation Status 271 9.4.3 Current-Sharing Reactor 271 9.5 Separately Excited SCR Excitation System with High-/Low-Voltage Bridge Rectifier 272 9.6 Parameterization of High-/Low-Voltage Bridge Rectifier 276 9.7 Transient Process of Separately Excited SCR Excitation System 281

10 Static Self-Excitation System 285 10.1 Overview 285 10.2 Characteristics of Static Self-Excitation System 288 10.2.1 Main Circuit Connection 288 10.2.2 Field Flashing Circuit 289 10.2.3 Stable Operating Point of Static Self-Excitation System 290 10.2.4 Short-Circuit Current of Self-Excited Generator 291 10.2.4.1 Relevant Expressions in Case of Three-Phase Short Circuit 292 10.2.4.2 Transient Characteristics of Three-Phase Short Circuit 294 10.2.5 Critical External Reactance 296 10.2.6 Influence of Short-Circuit Mode on Short-Circuit Current 297 10.2.7 Terminal Voltage Recovery of Self-Excited Generator after Short-Circuit Fault is Cleared 299 10.2.8 Inversion De-excitation of Self Thyristor Excitation System 300 10.2.9 Excitation Transformer Protection Scheme 302 10.3 Shaft Voltage of Static Self-Excitation System 307 10.3.1 Overview 307 10.3.2 Source and Protection of Shaft Voltage 307 10.3.3 Shaft Grounding System for Large Steam Turbine Generator 309 10.3.4 New Shaft Grounding Device 309 10.4 Coordination between Low Excitation Restriction and Loss-of-Excitation Protection 311 10.4.1 Generator Operating Limit Diagram 312 10.4.2 Admittance Measurement Principle and Derivation 316 10.4.3 Comparison of Impedance and Admittance Measurement 319 10.5 Electric Braking of Steam Turbine 321 10.5.1 Selection of Braking System 321 10.5.1.1 Mechanical Braking 321 10.5.1.2 Electric Braking 321

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10.5.2 Basic Expression for Electric Braking 323 10.5.3 Selection of Braking Transformer 324 10.5.4 Key Points of Design of Electric Braking Circuit 325 10.6 Electric Braking Application Example at Pumped-Storage Power Station 326 10.6.1 Composition of Electric Braking System 326 10.6.2 Control of Electric Braking System 326 10.6.2.1 Setting of Control Logic of Monitoring System 326 10.6.2.2 Excitation System Electric Braking Execution Procedure 327 10.6.2.3 Short-Circuit Switch Hard Wiring Latching 328 10.6.2.4 Protection Latching at Time of Electric Braking Put-In 328

11 Automatic Excitation Regulator 329 11.1 Overview 329 11.2 Theoretical Basis of Digital Control 330 11.2.1 Digital Discrete Technology 330 11.2.2 Z-Transform 331 11.2.3 Discretization of Continuous System 332 11.2.4 Transfer Function of Holder 333 11.2.5 Discrete Similarity Model and Bilinear Transformation 336 11.3 Digital Sampling and Signal Conversion 337 11.3.1 AC Sampling 337 11.3.2 Fourier Algorithm for AC Sampling 338 11.3.3 Three-Phase One-Point Algorithm 339 11.3.4 Speed Measurement Algorithm 340 11.4 Control Operation 340 11.5 Per-Unit Value Setting 345 11.6 Digital Phase Shift Trigger 346 11.6.1 Digital Phase Shift Trigger 346 11.6.2 Characteristics of Digital Phase Shift 347 11.7 External Characteristics of Three-Phase Fully Controlled Bridge Rectifier Circuit 348 11.7.1 Three-Phase Fully Controlled Bridge Rectifier Circuit 348 11.7.2 Linear Phase Shift Element 348 11.7.3 Cosine Phase Shift Element 350 11.7.4 Mathematical Model of Three-Phase Fully Controlled Rectifier 350 11.8 Characteristics of Digital Excitation Systems 351 11.8.1 Overview 351 11.8.2 Characteristics of Typical Digital Excitation System 353 11.8.3 Operation Modes of Digital Excitation System 354 11.8.4 Functions of Digital Excitation System 355

12 Excitation Transformer 365 12.1 Overview 365 12.2 Structural Characteristics of Resin Cast Dry-Type Excitation Transformer 367 12.2.1 Core 368 12.2.2 Winding Insulation Structure 368 12.2.3 Winding Material 368 12.2.4 Heat Dissipation and Cooling 368 12.3 Application Characteristics of Resin Cast Dry-Type Excitation Transformer 369 12.4 Specification for Resin Cast Dry-Type Excitation Transformer 369 12.4.1 Rated Capacity of Excitation Transformer 369

12.4.2 Connection Set 370 12.4.3 Insulation Class and Temperature Rise 370 12.4.4 Impedance Voltage 371 12.4.5 Short-Time Current Overload Capacity 372 12.4.6 Resistance to Sudden Short-Circuit Current 375 12.4.6.1 Calculation of Sudden Short-Circuit Current 375 12.4.6.2 Thermal Stability 375 12.4.6.3 Dynamic Stability under Action of Sudden Short-Circuit Current 376 12.4.7 Overcurrent Protection 376 12.4.8 Overvoltage Suppression 376 12.4.8.1 Closing Surge Overvoltage 376 12.4.8.2 Opening Overvoltage 377 12.4.8.3 Atmospheric Overvoltage 377 12.4.9 AC R-C Protection 377 12.4.9.1 Role of R-C Protection 377 12.4.9.2 Energy Conversion Caused by Commutation Voltage Effect 377 12.4.9.3 Energy Conversion Caused by Reverse Current Recovery Effect 378 12.4.9.4 Calculation of Magnetic Energy Stored 379 12.4.10 Test Voltage 381 12.4.11 Noise 382 12.4.11.1 Overview 382 12.4.11.2 Sound Wave, Sound Pressure, Sound Intensity, and Sound Intensity Level 382 12.4.11.3 Noise of Epoxy Dry-Type Excitation Transformer 382 12.4.11.4 Noise Reduction Measures 382 12.4.11.5 Structure Carrier Noise Reduction Design 385 12.4.12 Electrostatic Shield 387 12.4.13 Operational Environmental Impact 388 12.4.13.1 Environmental Class 388 12.4.13.2 Climate Class 388 12.4.13.3 Fire Class 388 12.4.13.4 Operating Environment 388 12.5 Harmonic Current Analysis 389 12.5.1 Overview 389 12.5.1.1 Harmonic Current Analysis 389 12.5.1.2 Influence of Harmonic Current 391 12.5.1.3 Harmonic Loss Calculation 392 12.5.2 Excitation Transformer Capacity Calculation Checking Example: 740 MVA ABB

Hydro-Turbine of Three Gorges Hydro Power Station 393 12.5.2.1 Specification for Technical Parameters of Excitation Transformer 394

13 Power Rectifier 395 13.1 Specification and Essential Parameters for Thyristor Rectifier Elements 395 13.1.1 Overview 395 13.1.2 Specification for Thyristor Rectifier Elements 395 13.1.3 Operating Characteristics of Thyristor 395 13.1.3.1 Nominal Voltage 398 13.1.3.2 Rated Current 398 13.2 Parameterization of Power Rectifier 400 13.2.1 Thyristor Element Parameters 400 13.2.2 Calculation of Reverse Repetitive Peak Voltage (URRM) 400

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13.2.3 Calculation of Thyristor Element Loss 401 13.2.4 Selection of Radiator 401 13.2.5 Selection of Fan Model 403 13.2.5.1 Calculation of Ventilation Quantity 403 13.2.5.2 Selection of Fans 404 13.2.6 Selection of Quick Fuse Parameters 404 13.2.7 Calculation of Rectifier Loss 406 13.3 Cooling of Large-Capacity Power Rectifier 407 13.3.1 AN Radiator 407 13.3.2 AF Radiator 407 13.3.3 Heat Pipe Radiator 408 13.3.3.1 Working Principle of Heat Pipe 408 13.3.3.2 Loop Heat Pipe (LHP) Radiator 409 13.3.3.3 Selection of Power Radiator 410 13.3.3.4 Design of High-Power Heat Pipe Rectifier 411 13 A Current Sharing of Power Rectifier 413 13.4.1 Background 413 13.4.2 Factors Influencing Effect of Current Sharing 414 13.4.2.1 AC-Side Inlet Line 474 13.4.2.2 DC-Side Outlet Line 414 13.4.2.3 Commutation Process 414 13.4.2.4 Thyristor Parameters 415 13.4.3 Digital Current Sharing 415 13.4.4 Comparison Between Digital and Conventional Current Sharing 415 13.4.5 Conclusions 416 13.5 Protection of Power Rectifier 416 13.5.1 Power Rectifier Anode Overvoltage Suppressor 417 13.5.2 R-C Protection of Power Rectifier Thyristor Elements 421 13.5.2.1 Working Principle of R-C Protection 421 13.5.2.2 Principle for Parameter Selection for Commutation Snubber 422 13.5.2.3 Energy Conversion of Commutation Process 426 13.5.2.4 Commutation Snubber Parameter Calculation Program 426 13.5.2.5 R-C Snubber Parameter Verification 427 13.6 Thyristor Damage and Failure 429 13.6.1 Factors Affecting Thyristor Operation Safety in Lectotype Design 429 13.6.2 Thyristor Damage and Failure Analysis and Identification 430 13.6.2.1 Thyristor Overvoltage Breakdown 430 13.6.2.2 Thyristor Overcurrent 431 13.6.2.3 Too Large On-State Current Critical Rise Rate (di/dt) 431 13.7 Capacity of Power Rectifiers Operating in Parallel 433 13.7.1 Verification and Calculation of Thyristor Power Cabinet Capacity 433 13.7.1.1 Calculation of Power Rectifier Load 433 13.7.1.2 Calculation of Power Rectifier Thyristor Element Loss 434 13.7.1.3 Calculation of Thyristor Junction Temperature and Radiator Temperature Rise 434 13.7.2 Influence of Altitude on Output Capacity of Power Rectifier 437 13.8 Uncertainty of Parallel Operation of Double-Bridge Power Rectifiers 437 13.8.1 Background 437 13.8.2 Analysis of Uncertainty of Protection Action of Fast Fuses in Double-Bridge Parallel Scheme 437 13.9 Five-Pole Disconnector of Power Rectifier 439

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14 De-excitation and Rotor Overvoltage Protection of Synchronous Generator 441 14.1 Overview 441 14.2 Evaluation of Performance of De-excitation System 443 14.2.1 Equivalent Generator Time Constant Method 443 14.2.2 Valid De-excitation Time Method 446 14.2.3 Generator Voltage-Based De-excitation Time Determination Method 446 14.3 De-excitation System Classification 447 14.3.1 Linear Resistor De-excitation System 447 14.3.1.1 Expression for Linear De-excitation Time 447 14.3.1.2 Linear Resistor De-excitation Commutation Conditions 448 14.3.1.3 Stepped Linear Resistor De-excitation System 450 14.3.2 Nonlinear Resistor De-excitation System 452 14.3.2.1 Expression for Nonlinear De-excitation Time 453 14.3.2.2 Nonlinear Resistor De-excitation Commutation Conditions 454 14.3.3 Crowbar De-excitation System 455 14.3.3.1 Overview 455 14.3.3.2 Functions of Crowbar 456 14.3.4 AC Voltage De-excitation System 459 14 A Influence of Saturation on De-excitation 463 14.5 Influence of Damping Winding Circuit on De-excitation 465 14.6 Field Circuit Breaker 467 14.6.1 DC Field Circuit Breaker 468 14.6.1.1 CEX Series of Modular DC Contactors from France's Lenoir Elec 468 14.6.1.2 HPB Series of Fast DC Circuit Breakers from Switzerland's Secheron 469 14.6.1.3 UR Series of DC Circuit Breakers from Switzerland's Secheron 469 14.6.1.4 Gerapid Series of Fast DC Circuit Breakers 471 14.6.2 AC Field Circuit Breaker 475 14.6.2.1 AC Air Circuit Breaker 475 14.6.2.2 AC Disconnector 475 14.6.2.3 DC Disconnector 475 14.7 Performance Characteristics of Nonlinear De-excitation Resistor 477 14.7.1 U-I Characteristic Expression for Single Valve 478 14.7.2 U-I Characteristic Expression for Elements 479 14.7.3 Temperature Coefficient of SiC Nonlinear Resistor 480 14.7 A Calculation of Temperature Rise 480 14.7.5 De-excitation Time 481 14.7.6 Parameter Selection for SiC Nonlinear Resistor 481 14.7.7 Timeliness of SiC Nonlinear Resistor 482 14.7.8 Damage and Failure Forms for SiC Nonlinear Resistor 482 14.7.9 Specifications 484

15 Excitation System Performance Characteristics of Hydropower Generator Set 485 15.1 Overview 485 15.2 Static Self-Excitation System of Xiangjiaba Hydro Power Station 485 15.2.1 Overview 485 15.2.2 Generator Parameters and Excitation System Configuration 487 15.2.3 Function and Component of Excitation System 489 15.2.4 Composition of Excitation System 489 15.2.4.1 Automatic Voltage Regulator 489 15.2.4.2 Thyristor Rectifier 497

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15.2.4.3 De-excitation and Overvoltage Protection Device 501 15.2.4.4 Excitation Transformer 507 15.2.4.5 Electric Braking 508 15.2.5 System Control Logic 510 15.2.5.1 Control Logic Mode 510 15.2.5.2 Excitation System Start and Stop Condition 512 15.2.5.3 Special Running Modes 512 15.2.5.4 Limiters 514 15.2.5.5 PSS 519

16 Functional Characteristics of Excitation Control and Starting System of Reversible Pumped Storage Unit 521

16.1 Overview 521 16.2 Operation Mode and Excitation Control of Pumped Storage Unit 521 16.2.1 Operation Modes of Pumped Storage Unit 521 16.2.2 Excitation Control Characteristics of Pumped Storage Unit 522 16.2.3 Selection of Main Circuit of Excitation System of Pumped Storage Unit 523 16.3 Application Example of Excitation System of Pumped Storage Unit 525 16.3.1 Excitation System of Units of Tianhuangping Pumped Storage Power Station 525 16.3.2 Composition of Excitation System 527 16.3.2.1 Excitation Transformers 527 16.3.2.2 Power Rectifiers 527 16.3.2.3 Initial Field Flashing Circuit and De-excitation System 527 16.3.2.4 Overvoltage Protection Devices 527 16.3.2.5 Excitation Regulator 528 16.3.3 Excitation Regulator Software 529 16.3.4 Excitation Regulator Software Flow Diagram 530 16.3.4.1 Overview 530 16.3.4.2 Switching Between Automatic Mode and Manual Mode 531 16.3.4.3 Reactive Power/Power Factor Regulator 531 16.3.4.4 Reactive Power Capacity Characteristic Curves and Limiters of Generator 532 16.3.4.5 Limiters 532 16.3.4.6 Stator Current Limiter 535 16.3.4.7 Rotor Power Angle Limiter 536 16.3.4.8 Voltage/Frequency Limiter Generating Additional Frequency Signals 537 16.3.4.9 PSS 538 16.3.5 Additional Functions of Excitation Regulator 540 16.3.5.1 Limitation Protection 540 16.3.5.2 Operation and Switching of Excitation Regulator 540 16.3.5.3 Debugging and Self-Test of Excitation Regulator 540 16.3.6 Excitation Regulation in Different Operation Modes 540 16.3.6.1 Working Conditions Including GO, GCO, PMO, and PCO Provided for Pumped Storage Units of

Tianhuangping Pumped Storage Power Station 540 16.3.6.2 Simultaneous Start under PMO Conditions 541 16.3.6.3 Pump Operation Mode 541 16.3.6.4 Electric Braking 541 16.3.6.5 SFC or Back-To-Back Operation 541 16.3.6.6 Test Operation Mode 541 16.4 Working Principle of SFC 542 16.4.1 Connection of SFC of Pumped Storage Unit 542

Contents xvii

16.4.2 Composition of SFC 542 16.4.2.1 Power Unit 543 16.4.2.2 Control and Protection Units 544 16.4.2.3 SFC Control Mode 545 16.4.3 SFC Start Procedure 548 16.4.3.1 SFC Auxiliaries Start Process 548 16.4.3.2 SFC Preparation Process 548 16.4.3.3 SFC Start Process 548 16.4.3.4 SFC Standby Process 549 16.4.3.5 SFC Auxiliaries Stop Process 549 16.4.4 Establishment of SFC Electrical Axis 549 16.4.5 Starting System of SFC of Units of Tiantang Pumped Storage Power Station 55i 16.4.5.1 Composition of SFC System 551 16.4.5.2 Back-To-Back Start 553 16.4.6 Electromagnetic Induction Method for Identification of Initial Position of Rotor 554 16.4.7 Capacity Calculation of SFC 557 16.4.8 SFC Power Supply Connection 559 16.5 SFC Current and Speed Dual Closed-Loop Control System 560 16.5.1 Speed Control of Pump Motor Unit during SFC Start 560 16.5.2 Unit Voltage Control during SFC Start of Pump Motor Unit 561 16.5.3 Synchronization Control of Pump Motor Unit 561 16.6 Influence of SFC Start Current Harmonic Components on Power Station and Power System 562 16.6.1 Harmfulness and Characteristics of Harmonics 562 16.6.2 Simplified Calculation of Harmonic Components 563 16.6.3 Improvement of Harmonic Operation State of SFC 565 16.7 Local Control Unit (LCU) Control Procedure for Pumped Storage Unit 566 16.7.1 LCU Configuration 566 16.7.2 LCU Control Program 566 16.7.3 GO Control Process 567 16.7A PMO Control Flow 567 16.8 Pumped Storage Unit Operating as Synchronous Condenser 568 16.8.1 GCO Mode 568 16.8.2 PCO Mode 568 16.8.3 PCO Start Mode and Coordination 569 16.9 De-excitation System of Pumped Storage Unit 569 16.9.1 Composition of AC De-excitation System 569 16.9.2 Functional Characteristics of AC De-excitation System 570 16.9.2.1 AC Field Circuit Breaker Application Characteristics 570 16.9.2.2 Coordination of Thyristor Rectifier Bridge Trigger Pulse AC Field Circuit Breaker 570 16.9.2.3 De-excitation System Composed of AC Switch and Linear Resistor Crowbar 570 16.9.2.4 Characteristics of AC De-excitation System 571 16.9.3 Operation Time Sequence of AC De-excitation System 57i 16.9.3.1 De-excitation for Stop in Normal Case 571 16.9.3.2 De-excitation for Stop in Case of Fault 572 16.10 Electric Braking of Pumped Storage Unit 572 16.11 Shaft Current Protection of Pumped Storage Unit 574 16.11.1 Configuration of Shaft Current Protection 574 16.11.2 Problems and Handling 576 16.11.2.1 Shaft Current Protection Action Caused by Metal Lap Joint Between Upper Bushing Back and Oil

Cooler Upper Cover Plate 576

Contents

16.11.2.2 Decrease in Upper Insulation of Thrust Bearing Caused by Impurities in Lubricating Oil 576 16.11.2.3 Equipment Grounding in Insulation Measurement Area 577 16.12 Application Characteristics of PSS of Pumped Storage Unit 577

17 Performance Characteristics of Excitation System of 1000 MW Turbine Generator Unit 579

17.1 Introduction of Excitation System of Turbine Generator of Malaysian Manjung 4 Thermal Power Station 579

17.2 Key Parameters of Turbine Generator Unit and Excitation System 581 17.2.1 Key Parameters of Generator Unit 581 17.2.2 Key Parameters of Excitation System 581 17.2.2.1 Data of Generator Unit 581 17.2.2.2 Data of Excitation System 584 17.3 Parameter Calculation of Main Components of Excitation System 585 17.3.1 Excitation Transformer 585 17.3.1.1 Excitation Transformer Output Current 585 17.3.1.2 Transformer Output Voltage 585 17.3.1.3 Excitation Transformer Capacity 586 17.3.1.4 Design Values of Excitation Transformer 586 17.3.2 DC Field Circuit Breaker 586 17.3.2.1 Rated Operating Voltage of Field Circuit Breaker 586 17.3.2.2 Rated Current of Main Contact of Field Circuit Breaker 587 17.3.2.3 Design Values of Field Circuit Breaker 587 17.3.3 Field Discharge Resistor 587 17.3.4 Crowbar 588 17.3.5 Field Flashing 588 17.3.5.1 Excitation Data 588 17.3.5.2 AC Flashing - Design of the Transformer 588 17.3.6 Current Transformer 589 17.3.6.1 Current Transformer on Primary Side of Excitation Transformer 589 17.3.6.2 Current Transformer on Secondary Side of Excitation Transformer 589 17.3.7 Parameters and Configuration of Excitation System 589 17 A Block Diagram of Automatically Regulated Excitation System 592 17.4.1 AVR Reference Voltage 592 17.4.2 AVR Reference Voltage Limitation 592 17.4.3 Main Voltage Control Loop for Static Excitation System - VREG 593 17.4.4 Under-Excitation Limit - UEL 593 17.4.5 Overexcitation Limitation for Static Excitation System - OEL 593 17.4.6 Dual-Input PSS 595 17.4.7 Stator Current Limitation - STCL 595 17.4.8 Reactive Power or Power Factor Regulators - RPPF 596 17.4.9 Droop 596 17.4.10 Potential - Source Excitation System ST7B 596

18 Performance Characteristics of 1000 MW Nuclear Power Steam Turbine Excitation System 601

18.1 Performance Characteristics of Steam Turbine Generator Brushless Excitation System of Fuqin Nuclear Power Station 601

18.1.1 Basic Parameters 601 18.1.1.1 Generator Parameters 601

Contents xix

18.1.1.2 Exciter Parameters 601 18.1.1.3 Excitation Transformer Parameters 601 18.1.2 Description of Excitation System 601 18.1.2.1 Automatic Regulation Excitation System 602 18.1.2.2 External Communication Network 603 18.1.2.3 Excitation System Monitoring and Protection 603 18.2 Structural Characteristics of Brushless Excitation System 608 18.2.1 Basic Parameters 608 18.2.2 Structural Characteristics 608 18.2.3 Rotary Diode Rectifier 610 18.3 Analysis of Working State of Multi-Phase Brushless Exciter 612 18.3.1 Overview 612 18.3.2 Working State Analysis of Odd-Numbered Diodes' Rectifier Circuit 612 18.3.3 Double-Layer Fractional Slot Variable Pitch Wave Winding Connection 614 18.3.4 Phase Angle of 39-Phase Outgoing Lines Emf 615 18.3.5 Phase Angle of Emf in Single Winding 615 18.3.6 Phase Analysis of Single Winding Emf 616 18.3.7 Phase of Phase Emf 616 18.3.8 Armature Winding Phase Emf Phase Diagram 677 18.3.9 Phasor Diagram of Total Emf Composed of 39-Phase Windings 617 18.4 Calculation of Excitation System Parameters of Fuqing Nuclear Power Station 618 18.4.1 Ceiling Parameters 618 18.4.2 Excitation Transformer 618 18.4.3 Thyristor Bridge 619 18.4.4 Other Thyristor Protections 622 18.4.5 Flashing Circuit 622 18.4.6 De-excitation Circuit 623 18.4.7 Field Circuit Breaker 623 18.5 Static Excitation System of Sanmen Nuclear Power Station 624 18.5.1 Introduction 624 18.5.2 Basic Parameters 624 18.5.2.1 Available Synchronous Machine Data 624 18.5.2.2 Excitation System Rated Output Value 626 18.5.2.3 Excitation Transformer Parameters 626 18.5.2.4 Thyristor Rectifier Parameters 626 18.5.2.5 DC Short Circuit 627 18.5.2.6 Nonlinear Field Suppression 627 18.5.3 Functional Description of Static Excitation System 627 18.5.3.1 Overview 627 18.5.3.2 Control Electronics 628

References 639

Index 643