A Seminar On:-

FLEXIBLE AC TRANSMISSION SYSTEM

CONTENTS

Introduction

Types of FACTS Controllers

FACTS Controllers

Benefits of FACTS Controllers

Control of power system

Conclusion

Reference

INTRODUCTION

The term FACTS describes a wide range of controllers ,many of which incorporate large power electronic converters.

In general ,FACTS devices possess the following technological attributes:

i) Provide dynamic reactive power support and ii) Voltage control

iii) Improve system stability

iv) Control real and reactive power flow

FACTS is a new integrated concept based on electronic based converter to enhance system utilization and reliability,stability,and power quality of ac transmission system

HISTORY

Dr. Narain Hingorani is a father of FACTS technology.

The first FACTS installation was at C . J. Slattsubstation near Arlington, Oregon.

This is a 500 kv 3 Ph 60 Hz substation and was developed by EPRI, the Bonneille Power Administration and general electric component

OBJECTIVES OF FACTS CONTROLLERS

The main objectives of FACTS controllers are the following:

1. Regulation of power flows in prescribed transmission routes.

2. Secure loading of transmission lines nearer to their thermal limits.

3. Prevention of cascading outages by contributing to emergency control.

TYPES OF FACTS CONTROLLERS

Series controllers:

The series controller could be a variable impedance, such as capacitor, reactor, or a power electronics based variable source of main frequency, and harmonic frequencies to serve the desired load.

In principle, all series controllers inject voltage in series with the line. As long as the voltage is in phase quadrature with the line current, the series controller only supplies or consumes variable reactive power.

Series controllers include SSSC, IPFC, TCSC, TSSC, TCSR, and TSSR.

Shunt Controllers.

As in the case of series controllers, the shunt controllers may be variable impedance, variable source, or a combination of these.

In principle, all shunt controllers inject current into the system at the point of connection.

Even a variable shunt impedance connected to the line voltage causes a variable current flow and hence represents injection of current into the line.

Any other phase relationship will involve handling of real power as well. Shunt controllers include STATCOM, TCR, TSR, TSC, and TCBR

FACTS CONTROLLERS

A static synchronous compensator (STATCOM) also known as synchronous condenser.

STATCOM is a regulating device used on alternating current electricity transmission networks .

It is based on a power electronics voltage source converter

STATCOM :

Uses:

It is installed to support electricity networks that have a poor power factor and often poor voltage regulation

Mostly used for voltage stability

It is also provide better reactive power support at low AC voltage

The current can nbe maintained at rated value even down to low AC voltages

Static VAR compensator is a set of electrical devices for providing fast acting reactive power on high voltage electricity transmission system .

Elements which may be used to make an SVC typically include:

i) TCR where reactor may be air or iron cored

ii) TSC

iii) Harmonic filter

SVC :

Advantages :

Gives instantaneous response to changes in the system voltage.

They are in general cheaper, higher capacity, faster and more reliable than dynamic compensaror scheme.

Enhance controllability and increase power transfer capability

Benefits of facts controllers Cost

Convenience

Environmental impact

Contribute to optimal system operation by reducing power losses and improving voltage profile.

Increase the loading capability of the lines to their thermal capabilities, including short term and seasonal.

Provide greater flexibility in sitting new generation

CONTROL OF POWER SYSTEM

In any power system, the creation, transmission, and utilization of electrical power can be separated into three areas, which traditionally determined the way in which electric utility companies had been organized. These are illustrated in Figure 1 and are:

• Generation

• Transmission

• Distribution

Although power electronic based equipment is prevalent in each of these three areas, such as with static excitation systems for generators and Custom Power equipment in distribution systems

The focus of this paper and accompanying presentation is on transmission, i.e. moving the power from where it is generated to where it is utilized.

CONTROLLABILITY

To illustrate that the power system only has certain variables that can be impacted by control, we have considered here the power-angle curve, shown in Figure 2.

Although this is a steady-state curve and the implementation of FACTS is primarily for dynamic issues, this illustration demonstrates the point that there are primarily three main variables that can be directly controlled in the power system to impact its performance. These are:

• Voltage

• Angle

• Impedance

DISADVANTAGES:

High initial costs

Joints required for contraction and expansion

Generally rough riding quality

High repair cost

CONCLUSION

This paper has presented various FACTS controllers and analyzed their control attributes and benefits.

The flexible ac transmission system (FACTS), a new technology based on power electronics, offers an opportunity to enhance controllability, stability, and power transfer capability of ac transmission systems.

The application of FACTS controllers throws up new challenges for power engineers, not only in hardware implementation, but also in design of robust control systems, planning and analysis.

REFERENCES

[1] Y. N. Yu, Electric Power System Dynamics. Academic Press, 1983.

[2] P. W. Sauer and M. A. Pai, Power System Dynamics and Stability. Prentice Hall, 1998.

[3] J. R. Smith, G. Andersson, and C. W. Taylor, “Annotated Bibliography on Power System Stability Controls: 1986- 1994”, IEEE Trans. on PWRS, 11(2)(1996), pp. 794–800.

[4] N. G. Hingorani and L. Gyugyi, Understanding FACTS: Concepts and Technology of Flexible AC Transmission Systems. New York: IEEE Press, 2000.

[5] N. G. Hingorani, “FACTS-Flexible AC Transmission System”, Proceedings of 5th International Conference on AC and DC Power Transmission-IEE Conference Publication 345, 1991, pp. 1

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