The electricity supply industry is undergoing a profound transformation worldwide. Market forces, scarcer natural resources, and an ever-increasing demand for electricity are some of the drivers responsible for such unprecedented change. Against this background of rapid evolution, the expansion programs of many utilities are being thwarted by a variety of well-founded, environment, land-use, and regulatory pressures that prevent the licensing and building of new transmission lines and electricity generating plants.
Types of FACTS Controllers
Benefits of FACTS Controllers
Control of power system
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
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
Dr. Narain Hingorani is a father of FACTS technology.
The first FACTS installation was at C . J. Slatt
substation 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
1. Regulation of power flows in prescribed
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
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
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
Series controllers include SSSC, IPFC, TCSC, TSSC, TCSR, and
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
A static synchronous compensator (STATCOM)
also known as synchronous condenser.
STATCOM is a regulating device used on
alternating current electricity transmission
It is based on a power electronics voltage source
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
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
i) TCR where reactor may be air or iron
iii) Harmonic filter
Gives instantaneous response to changes in the
They are in general cheaper, higher capacity,
faster and more reliable than dynamic
Enhance controllability and increase power
Benefits of facts controllers
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
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:
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
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.
High initial costs
Joints required for contraction and expansion
Generally rough riding quality
High repair cost
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.
 Y. N. Yu, Electric Power System Dynamics. Academic Press, 1983.
 P. W. Sauer and M. A. Pai, Power System Dynamics and Stability. Prentice
 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),
 N. G. Hingorani and L. Gyugyi, Understanding FACTS: Concepts and
Technology of Flexible AC Transmission Systems. New York: IEEE Press, 2000.
 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