Enhancement Of Power System Stability Using Interline Power Flow Controllers (IPFC) And Unified Power Flow Controllers (UPFC)

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.

Power system stability is governed by bus voltage magnitudes, phase angle, real and reactive power support provided at the  load  bus. This mainly depends on the amount of transmitted real power, which is effectively restricted by the line impedance and thermal limits of the transmission lines. This leads to over loading and/or under utilization of various transmission lines in case of an interconnected system. A IPFC and UPEC are hence proposed to facilitate exchange of real and reactive power between the transmission lines. Due to improved power flow, better stability limits can be realized.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1      BACKGROUND OF THE STUDY

• BACKGROUND OF THE STUDY
• OBJECTIVE OF THE STUDY
• AIM OF THE STUDY
• SCOPE OF THE PROJECT
• FACTORS CAUSING VOLTAGE INSTABILITY
• OUTCOMES OF VOLTAGE INSTABILITY

CHAPTER TWO

• LITERATURE REVIEW
• REVIEW OF THE STUDY
• OVERVIEW OF POWER SYSTEM STRUCTURE
• POWER SYSTEM COMPONENTS
• BASIC CONCEPTS AND DEFINITIONS OF POWER SYSTEM STABILITY

CHAPTER THREE

METHODOLOGY

• INTRODUCTION
• THE INTERLINE POWER FLOW CONTROLLER
• UNIFIED POWER FLOW CONTROLLER

CHAPTER FOUR

4.1     SIMULATION AND RESULTS

CHAPTER FIVE

• CONCLUSION
• REFERENCES

CHAPTER ONE

1.0                                               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.

Rapid development of power electronics has facilitated implementation of highly advanced FACTS based controllers. The main  objective of these FACTS based controllers is to achieve flexible control over one or more transmission line parameters namely voltage, line impedance and power angle in order to enhance  power flow and stability limits [Wirth, E, 2000]. A Unified Power Flow Controller (UPFC) provides selective or simultaneous control over the basic transmission line parameters for one transmission line at a time [Gyugyi, L.; Schauder, 1995].

Interline Power Flow Controllers (IPFC) And Unified Power Flow Controller (UPFC), can be efficiently used to control the transmission line parameters in case of interconnected systems [Gyugyi, 1999]. Enhanced power flow and hence better stability is ensured by real power exchange between under utilized and over loaded transmission lines and by providing the necessary reactive power support.

In this paper, attempt is  made  to  enhance the stability of a given power system by using a generalized IPFC and UPFC. The entire power system network is simulated using power system blockset present in MATLAB/Simulink.

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.

1.3                                   PROBLEM STATEMENT

The enhancement of transient stability of the power system is one of the most challenging research areas in power engineer. This study presents the method to enhance transient stability of power system by Interline Power Flow Controllers (IPFC) And Unified Power Flow Controller (UPFC). The mathematical model of power system equipped with a UPFC and IPFC are systematically derived. The parameters of UPFC and IPFC were modeled into power flow equation and thus it is used to determine control strategy. The swing curves of the three phase faulted power system without and with a UPFC and IPFC were tested and compared in various cases. From the simulation results, the UPFC and IPFC can enhance transient stability of power system.

1.4                                 OBJECTIVES OF THE PROJECT

The main objective of this work is to achieve flexible control over one or more transmission line parameters namely voltage, line impedance and power angle in order to enhance  power flow and stability limits.

1.5                                         AIM OF THE PROJECT

The main aim of this work is to enhance voltage stability using Interline Power Flow Controllers (IPFC) And Unified Power Flow Controller (UPFC).

1.6                                                        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 work presents implementation of Interline Power Flow Controllers (IPFC) And Unified Power Flow Controller (UPFC). in the transmission network for reactive power flow control to improve the voltage stability.

1.7                                     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.

1.8                                   OUTCOMES OF VOLTAGE INSTABILITY

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