THE IMPACT OF STATIC VAR COMPENSATOR (SVC) ON POWER SYSTEM STABILITY A Project Presented to the faculty of the Department of Electrical & Electronic Engineering California State University, Sacramento Submitted in partial satisfaction of the requirements for the degree of MASTER OF SCIENCE in Electrical and Electronic Engineering by Shuchuang Tang FALL 2015 © 2015 Shuchuang Tang ALL RIGHTS RESERVED ii THE IMPACT OF STATIC VAR COMPENSATOR (SVC) ON POWER SYSTEM STABILITY A Project by Shuchuang Tang Approved by: __________________________________, Committee Chair Dr. Fethi Belkhouche __________________________________, Second Reader Dr.Preetham Kumar ____________________________ Date iii Student: Shuchuang Tang I certify that this student has met the requirements for format contained in the University format manual, and that this project is suitable for shelving in the Library and credit is to be awarded for the project. __________________________, Graduate Coordinator ___________________ Dr. Preetham Kumar Date Department of Electrical and Electronic Engineering iv Abstract of THE IMPACT OF STATIC VAR COMPENSATOR (SVC) ON POWER SYSTEM STABILITY by Shuchuang Tang This project investigates the application of static VAR compensator (SVC) to improve power system stability. A static VAR compensator is a set of electrical devices that can be used to provide fast acting reactive power on high-voltage electricity transmission networks. SVCs can be used to regulate voltage, power factor, harmonics, and stabilize the system. Unlike a synchronous condenser which is a rotating electrical machine, a static VAR compensator has no significant moving parts (other than the internal switch gear). There are two types of SVCs: Thyristor Controlled Reactor (TCR) and Thyristor Switched Capacitor (TSC). Both types are discussed in this report, where the application of SVC in single and multi-machine system is carried out and discussed in details. Simulink is used to study the characteristics of SVC and its impact on power system stability. Results show the effectiveness of SVCs in maintaining power system stability. _______________________, Committee Chair Dr. Fethi Belkhouche _______________________ v Date ACKNOWLEDGEMENTS First, I would like to take this opportunity to convey my sincere regards to Dr. Fethi Belkhouche, my adviser for helping with my project and being very helpful throughout this project. It was his helped me to get through the problem in project and made the project come out. Then, I would also like to acknowledge and thank Dr. Preetham Kumar, faculty member, EEE department and Graduate Advisor for being part of the review committee and extending his guidance for better formulation for our project. I also thank him for his review and comments on the project report. Last, I would like to thank all my family and friends who help me overcome the hard time during the project work. vi TABLE OF CONTENTS Page List of Tables ............................................................................................................... ix List of Figures ............................................................................................................... x Chapter 1. BACKGROUND INFORMATION OF THE PROJECT …………………….. 1 Introduction ....................................................................................................... 1 Research Status on SVC .................................................................................. 2 2. THE CHARACTERISTIC OF TWO DIFFERENT COMPENSATORS .............. 4 Thyristor Controlled Reactor (TCR) ................................................................. 4 Thyristor Switched Capacitors (TSC) ............................................................... 6 3. ANALYSIS OF SINGLE-LOAD SYSTEM WITH SVC .................................... 10 Characteristic of SVC ..................................................................................... 10 Model of Single-Load System ........................................................................ 11 Results Analysis .............................................................................................. 12 4. ANALYSIS OF SINGLE-MACHINE SYSTEM WITH SVC ............................ 14 The Control Theory of SVC ........................................................................... 14 Model Building ............................................................................................... 15 Results Analysis .............................................................................................. 18 vii 5. ANALYSIS OF MULTI-MACHINE SYSTEM WITH SVC .............................. 20 Model Building ............................................................................................... 20 State Equations for Multi-Machine System .................................................... 22 Results Analysis .............................................................................................. 24 6. CONCLUSIONS................................................................................................... 30 Appendix A. ............................................................................................................ 32 Appendix B. ............................................................................................................. 33 References ................................................................................................................... 38 viii LIST OF TABLES Tables Page 1. The Data of TCR Model…………………….…………………………………...33 2. The Data of TCS Model…………………………………………………………34 3. The Data of Single-Load System Model………….…………...……….………. 35 4. The Data of Single-Machine System Model……………………………………. 36 5. The Data of Multi-Machine System Model………………………………….…. 37 ix LIST OF FIGURES Figures Page 1. TCR Circuit Diagram………………………………….…………………………. 4 2. System with TCR Model.………………………..………………………………. 5 3. System without TCR Model……………………………………………………... 5 4. Comparison of Primary Current with and without TCR…………………………. 6 5. Voltage of Thyristor………………………………….………………………….. 6 6. TSC Circuit Diagram………………………………….…………………………. 7 7. System with TSC Model………………………………….………………...……. 8 8. Comparison of Capacitor Voltage in the Two States……………………….……. 8 9. Comparison of Primary Current in the Two States………………………………. 9 10. V-I Characteristic of SVC in Voltage Regulation Model……..…………………10 11. The Power System with SVC……………………………………………………12 12. The Load Voltage with SVC and without SVC………….………………………13 13. The Control Diagram of Single-Machine System. ……………………………. 14 14. Single-machine System………………………………….………………….…. 15 15. TCR Block……………………………………………………………………….16 16. TSC Block……………………………………………………………………….16 17. Voltage Measurement Block…………………………………………….………17 18. Voltage Regulator Block………………………………….………...……………17 19. Simulink Results…………………………………………………………………18 x 20. The Model of Two-Machines System………………………………….……..…20 21. The Control Block for the Hydraulic Generator…………………………………21 22. Subsystem of the Control Block…………………………………………………21 23. The Electromagnetic Torque and Electrical Power of the Two Machines without SVC…………………………………………………………………………...….25 24. The Rotor Speed and Stator Voltage of the Two machines without SVC ………26 25. The Voltage and Line Power of Bus 1 and Bus 4 without SVC…………………26 26. The Electromagnetic Torque and Electrical Power of Two Machines with SVC .......................................................................................................................27 27. The Rotor Speed and Stator Voltage of the Two machines with SVC…………. 28 28. The Voltage and Line Power of Bus 1 and Bus 4 with SVC…………………….28 xi 1 1. BACKGROUND INFORMATION OF THE PROJECT Introduction The stability of an interconnected power system is related to its ability to return to normal or stable operation after being subjected to some form of disturbance. Conversely, a condition denoting loss of synchronism means instability. Power system stability has been recognized as an essential part of power system planning for a long time. With interconnected systems continually growing in size and extending over vast geographical regions, it is becoming increasingly more difficult to maintain synchronism between the various parts of a large power system. Small disturbances are continually occurring in power systems. In a dynamically unstable system, the oscillation amplitude is large and persists for a long time. This constitutes a serious threat to system security and creates undesirable operating conditions. Following a sudden disturbance on the power system, the rotor speed, rotor angular differences and the power transfer undergo fast changes in which the magnitudes depend on the severity of the disturbance. For a large disturbance, changes in angular differences may be large enough to make the machines out of step. Static VAR Compensator (SVC) is currently widely used in power systems. By adjusting the firing angle, it can smoothly and rapidly provide reactive power control and therefore provide effective control to the bus voltage [1]. In addition, SVC can enhance the transient stability [2] and provide additional damping to the power system as well [3]. In transmission applications, SVCs are used to regulate the grid voltage. If the power system's reactive load is capacitive (leading), the SVC will use TCR to consume 2 reactive power from the system, lowering the system voltage. Under inductive (lagging) conditions, the capacitor banks are automatically connected, thus providing a higher system voltage.