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TB 144 1999 SC 14 WG 14.19 Static synchronous compensator (STATCOM)

Rapid developments of solid state power electronic devices in the last three decades have led to the development and widespread application of static var compensators (SVCs). These shunt connected reactive compensation equipment provided an important means for enhancing electric power transmission system performance. Continued rapid developments in power electronic devices and control techniques let to utilisation of gate turn-off thyristor (GTO) devices to form new power electronic shunt compensation equipment which offered more robust output.

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TABLE OF CONTENTS

1 APPLICATION TO ELECTRIC POWER SYSTEMS

      1.1 Introduction        

      1.2 Statcom Applications      

            1.2.1 Voltage Regulation and Control       

            1.2.2 Improvement of Steady-State  Power  Transfer Capacity    

            1.2.3 Improvement of Transient Stability Margin             

            1.2.4 Damping  of Power  System  Oscillations                       

            1.2.5 Damping of Sub synchronous Power System Oscillations    

            1.2.6 Balanced Loading of individual Phases.                        

            1.2.7 Reactive Compensation of AC-DC Converters and HVDC Links          

            1.2.8 Power Quality improvement             

            1.2.9 Flicker Control          

            1.2.10 Applications involving Energy Storage                    

      1.3 Summary

      1.4 References

2 DESCRIPTION AND FUNDAMENTAL CONCEPTS

      2.1 Introduction

      2.2 Fundamental Concepts

            2.2.1 Reactive Power Genera/ion by Switching Power Converters

                  2.2.1.1 Voltage-Sourced d.c. to a.c. Converters

                  2.2.1.2 Current-Sourced d.c. to a.c. Converter

                  2.2.1.3 A.c. to ac. Frequency Changer

                  2.2.1.4 Power-Doubling Scheme

            2.2.2 Comparison of Approaches.

                  2.2.2.1 Voltage-Sourced Converter

                  2.2.2.2 Current-Sourced Converter

                  2.2.2.3 A.c. to a.c. Frequency Changer

                  2.2.2.4 Power Doubling Scheme

      2.3 Practical Statcom Power Circuit Structures

            2.3.1 Two, Three and Multi-level Converter Configurations

            2.3.2 Harmonic Reduction Techniques

                  2.3.2.1 Harmonic Reduction Using Pulse Width Modulation

                  2.3.2.2 Harmonic Neutralization Using Magnetic Coupling

                  2.3.2.3 Harmonic Reduction Using Multi-level Converter Configurations

      2.4 Basic Control Concepts

      2.5 Statcom Losses Versus Reactive Output

      2.6 Statcom-Based Static VAR Systems (SVS)

      2.7 References

3 OPERATIONAL AND PERFORMANCE CHARACTERISTICS

      3.1 Introduction

      3.2 V-L and V-Q Characteristics

      3.3 Voltage Regulation Stability Versus System Impedance

      3.4 Impact on Voltage Stability Margin

      3.5 Impact on Steady-State Power Transfer Margin

      3.6 Impact on Transient Stability Margin

      3.7 Load Compensation

      3.8 Capability to Exchange Real Power.

      3.9 Unbalanced Operation

      3.10 Comparison with a Rotating Synchronous Compensator.

      3.11 Physical Size and Installation     

      3.12 Environmental Impact of Statcom

      3.13 Summary

      3.14 References.

4. CONTROL

      4.1 Introduction

      4.2 Space-Vector Control Concepts

      4.3 Converter Control

            4.3.1 Voltage Space Vector Control

                  4.3.1.1 Modulation Depth and Phase Angle Control

                  4.3.1.2 Phase Angle Control.

            4.3.2 Control of System Side DC-current (Transformer Saturation Control)

            4.3.3 Voltage Balancing Control   

            4.3.4 DC-Capacitor Voltage Limit Control 

            4.3.5 Converter Current Limit Control      

            4.3.6 Control of STATCOM with Energy Storage   

      4.4 Power System Control   

            4.4.1 Power System Voltage Control        

            4.4.2 Power Oscillation Damping Control..             

            4.4.3 Reactive Power Reserve Control.

            4.4.4 Power Factor Control.

            4.4.5 Power Phase Sequence Control

            4.4.6 Start-up/Shut-down Control

      4.5 References

5 PROTECTIONS

      5.1 Introduction

      5.2 General Requirements

      5.3 Conventional Plant Component Protection

            5.3.1 General

            5.3.2 Transformer Protection.

            5.3.3 Busbar Protection

                  5.3.3.1 Phase Fault Protection

                  5.3.3.2 Earth (Ground) Fault Protection

                  5.3.3.3 Overvoltage Protection.

                  5.3.4 Filler Protection

      5.4 Converter Protection

            5.4.1 General

            5.4.2 GTO Thyristor Valve Protection 

                  5.4.2.1 Overcurrent Protection

                  5.4.2.2 Overvoltage Protection

            5.4.3 Capacitor Protection.

      5.5 Impact of Power System Disturbances On The Statcom

            5.5.1 Transient Overvoltages

            5.5.2 Harmonic Interaction

            5.5.3 Power System Faults

            5.5.4 Impact of Geomagnetically Induced Currents (GICs)

      5.6 References

6. HARMONICS

      6.1 Introduction

      6.2 Harmonic Distortion.

      6.3 Harmonics Generated By Statcom and Power System Effects

      6.4 Statcom Harmonic Reduction Techniques for Utility Applications

      6.5 Harmonic Characteristics of Utility Systems

      6.6 References

7. APPLICATION STUIJY CONSIDERATIONS

      7.1 Introduction

            7.1.1 Early Planning Stage

            7.1.2 Detailed Planning

            7.1.3 Operational Stage

      7.2 Load Flow Studies.

            7.2.1 STATCOM Models for Load Flow Studies

      7.3 Large Disturbance (Transient Stability) Studies

            7.3.1 STATCOM Models for Transient Stability Studies

            7.3.2 Description of the Basic Model

                  7.3.2.1 Controlled Voltage Source Model

                  7.3.2.2 Controlled Current Source Model

                  7.3.2.3 Simplified Controlled Current Source Model

      7.4 Small Disturbance (Steady-State Stability) Studies

      7.5 Long-Term Voltage Stability Studies.

      7.6 Electromagnetic Transient Studies

      7.7 Harmonic Performance Studies.

      7.8 Phase Unbalance Studies

      7.9 Fault Level Studies

      7.10 References

8. FUNCTIONAL SPECIFICATION CONSIDERATIONS

      8.1 Introduction

      8.2 Utility and Manufacturer Information Requirements

            8.2.1 General Requirements.

            8.2.2 Power System Characteristics.

            8.2.3 Steady-state Performance

            8.2.4 Dynamic Performance, Control and Monitoring Facilities

            8.2.5 Maintenance, Test and Spares

            8.2.6 Site & Environmental

            8.2.7 Other Considerations

      8.3 Equipment Design Standards

9. GUIDE-LINES FOR TESTING

      9.1 Introduction

      9.2 Factory and off Site Tests

      9.3 Site Tests.

            9.3.1 Pre-commissioning tests                                    

            9.3.2 Sub-system tests                      

            9.3.3 System tests             

                  9.3.3.1 Operational tests      

                  9.3.3.2 Harmonic Performance              

                  9.3.3.3 System Dynamic Performance tests    

                  9.3.3.4 Staged Fault tests         

                  9.3.3.5 Continuous operation test       

                  9.3.3.6 Trial Operation.

      9.4 Documentation

      9.5 Example of Statcom Commissioning and Performance Tests

            9.5.1 Voltage Regulation Response.

            9.5.2 Response to Switching Adjacent Capacitor

            9.5.3 Response to Opening the 500kV Inter-tie at Sullivan

      9.6 References

10. OVERVIEW OF EXISTING ANO PROPOSED INSTALLATIONS

      10.1 Introduction

      10.2 Shin-Shinano

      10.3 Inuyama.

      10.4 Teine

      10.5 Sullivan

      10.6 Inez

      10.7 East Claydon

      10.8 Reisby Hede Windfarm

      10.9 References

11 DEVELOPMENTS AND APPLICATIONS

      11.1 Introduction.

      11.2 Developments in Power Electronic Switching Devices and Conventional Converter Components

            11.2.1 Advances in Gate Turn-off (GTO) Thyristors

            11.2.2 Advances in Other Types of Power Electronic Switching Devices

            11.2.3 Advances in Snubber Circuit Ratings

      11.3 Developments in Switching Converter Technology

            11.3.1 Application of Multi-level Converter Configurations

            11.3.2 Application of Soft Switching and Resonant Converters 

            11.3.3 Application of Pulse Width Modulation (PWM) Techniques

            11.3.4 Future Trend in Application of Converter Technology Developments.

      11.4 Future Applications of Converter Based Technologies to Power Systems

            11.4.1 Active Power Applications of STATCOM

            11.4.2 Energy Storage Applications

            11.4.3 Applications to Series Compensation of Transmission Lines

            11.4.4 High Voltage Direct Current Transmission Applications

            11.4.5 Applications for Power Quality Improvement

      11.5 Cost Trends

      11.6 Cigre Activity

      11.7 References