Voltage And Power Stability On HVAC Systems And Transmission

ABSTRACT

Voltage stability problems usually occur in heavily loaded systems. While the disturbance leading to voltage collapse may be initiated by different kinds of contingencies, the underlining problem is an inherent weakness in the power system. This project will illustrate the basic issues related to voltage instability by considering the characteristics of transmission system and afterwards examining how we can improve voltage stability by using reactive power compensation devices. Main consideration in this project will be focused on delivering the reactive power directly to buses in a distributing system, by installing sources of reactive power. The reason is that transmission lines can be operated with varying load and nearly constant voltage at both ends if adequate sources of reactive power are available at both ends. Before these considerations, there will be the description of the voltage stability phenomena and ways of improving it, because only with the description and researches this project will be understandable and complete.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

• OBJECTIVE OF THE PROJECT
• AIM OF THE PROJECT
• SCOPE OF THE PROJECT
• FACTORS CAUSING VOLTAGE INSTABILITY
• OUTCOMES OF VOLTAGE INSTABILITY
• ADVANTAGES OF THE PROJECT
• DISADVANTAGES OF THE PROJECT

CHAPTER TWO

• LITERATURE REVIEW
• OVERVIEW OF STATIC VAR COMPENSATOR
• REACTIVE POWER AND VOLTAGE CONTROL
• SYNCHRONOUS GENERATORS
• SHUNT CAPACITORS

CHAPTER THREE

METHODOLOGY

• BASIC CONCEPTS AND DEFINITIONS
• STATIC VAR COMPENSATOR (SVC)
• MODEL OF SVC WITH PSCAD REPRESENTATION OF ITS CONTROL
• SVC CONTROL SCHEME
• STUDIED SYSTEM

CHAPTER FOUR

4.1       SIMULATION AND RESULTS

CHAPTER FIVE

• CONCLUSION

CHAPTER ONE

1.1                                               INTRODUCTION

Today’s changing electric power systems create a growing need for flexibility, reliability, fast response and accuracy in the fields of electric power generation, transmission, distribution and consumption. Flexible Alternating Current Transmission Systems (FACTS) are new devices emanating from recent innovative technologies that are capable of altering

voltage, phase angle and/or impedance at particular points in power systems. Their fast response offers a high potential for power system stability enhancement apart from steady- state flow control. Among the FACTS controllers, Static Var Compensator (SVC) provides fast acting dynamic reactive compensation for voltage support during contingency events which would otherwise depress the voltage for a significant length of time. SVC also dampens power swings and reduces system losses by optimized reactive power control. Power System Computer Aided Design/Electromagnetic Transients Direct Current (PSCAD/EMTDC) has been used in this paper to conduct simulations on voltage regulation at the point of connection of SVC to the system.

However, the aim of this paper is to enhance voltage stability using Static Var Compensator at the event of occurrence of fault in the system.

1.2                               BACKGROUND OF THE PROJECT

Voltage stability problems usually occur in heavily loaded systems. While the disturbance leading to voltage collapse may be initiated by a different kinds of contingencies, the underlining problem is an inherent weakness in the power system. Loss of power system stability may cause a total blackout of the system. It is the interconnection of power systems, for reasons of economy and of improved availability of supply across the broader areas that makes widespread disruptions possible. Current civilization is susceptible to case of power system blackout, the consequences of systems failure are social and economic as well. Even short disturbance can be harmful for industrial companies, because restarting of process might take several hours. In recent years, voltage instability has been responsible for several major network collapses. This project will illustrate the basic issues related to voltage instability by considering the characteristics of transmission system and afterwards examining how we can improve voltage stability by using reactive power compensation devices[8,9].

1.3                                 OBJECTIVES OF THE PROJECT

Explaining basic principles of equipment used for improving voltage and power stability. Main consideration in this project will be focused on delivering the reactive power directly to bus (in this project we will consider one bus) in a distributing system, by installing sources of reactive power. The reason is that transmission lines can be operated with varying load and nearly constant voltage at both ends if adequate sources of reactive power are available at both ends. Before these considerations, there will be the description of the voltage stability phenomena and ways of improving it.

1.4                                         AIM OF THE PROJECT

The main aim of this work is to enhance voltage and power stability using Static Var Compensator at the event of occurrence of fault in the system.

1.5                                                        SCOPE OF THE PROJECT

Power systems are complex systems consisting of large number of generating units and interconnected network of transmission lines. The voltage stability is an issue of prime importance in this complex power system network since the demand for electric power is increasing drastically. The control of reactive power in the transmission lines will enhance the voltage stability of the power system network. This paper presents the design and implementation of the Static VAR Compensator (SVC) in the transmission network for reactive power flow control to improve the voltage stability. The proposed method detects automatically the optimal number of SVCs required for the control of reactive power[10].

1.6                                     FACTORS CAUSING VOLTAGE INSTABILITY

The main factors causing voltage instability are:

1. High reactive power consumption at heavy loads
2. Generating stations are too far from load centres.
3. Source voltages are too low.
4. Poor coordination between various control and protective systems
5. The inability of the power system to meet demands for reactive power in the heavily stressed system to keep voltage in the desired range.

1.7                                   OUTCOMES OF VOLTAGE INSTABILITY

• Loss of load in area
• Tripping of transmission lines
• Voltage collapse in the system.

1.8                                                ADVANTAGES OF THE PROJECT

The main advantage of SVCs over simple capacitor bank compensation schemes is their near-instantaneous response to changes in the system voltage.

1. Dynamic compensation can be achieved by SVC [12].

1.9                                            DISADVANTAGES OF THE PROJECT

However, static VAR compensators are more expensive than Capacitor banks

CHAPTER FIVE

5.1                                                                    CONCLUSION

In this paper, the basic structure of an SVC operating under typical bus voltage control and its model are described. The model is based on representing the controller as variable impedance that changes with the firing angle of the Thyristor Controlled Reactor (TCR), which is used to control voltage in the system. Simulations carried out confirmed that Static Var Compensator could provide the fast acting voltage support necessary to prevent the possibility of voltage reduction and voltage collapse at the bus to which it is connected.