Flexible AC Transmission System FACTS refers to a family of power electronics-based devices designed to increase power transfer capability of power transmission system. The main objective of FACTS is to obtain AC systems with a high level of flexibility just as in high-voltage DC systems. FACTS uses power electronics for controlling power flow in a transmission system. This paper provides a brief introduction to FACTS devices or controllers. Matthew N. O. Sadiku | Adedamola A. Omotoso | Sarhan M. Musa | Adebowale E. Shadare "Flexible Alternating Current Transmission Systems" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-1 , December 2018, URL: http://www.ijtsrd.com/papers/ijtsrd19063.pdf

1. International Journal of Trend in
International Open Access Journal
ISSN No: 2456 - 6470
@ IJTSRD | Available Online @ www.ijtsrd.com
Flexible Alternating Current
Matthew N. O. Sadiku, Adedamola A. Omotoso, Sarhan M. Musa, Adebowale E. Shadare
Roy G. Perry College of Engineering
ABSTRACT
Flexible AC Transmission System (FACTS) refers to
a family of power electronics-based devices designed
to increase power transfer capability of power
transmission system. The main objective of FACTS is
to obtain AC systems with a high level of flexibility
just as in high-voltage DC systems.
power electronics for controlling power flow in a
transmission system. This paper provides a brief
introduction to FACTS devices or controllers.
KEY WORDS: flexible AC transmission system,
power electronics, voltage source converters
INTRODUCTION
In conventional AC transmission system,
of power that can be sent over a transmission line is
limited by many factors such as the length
overheating, and system stability, transient stability
limit, voltage limit, and short circuit current limit.
ideal transmission the active power should be equal to
the apparent power so that the power factor can be
unity. This is where the role of flexible AC
transmission system (FACTS) comes in
FACS devices can potentially overcome the
limitations by using advanced solutions based on
modern power electronics.
A flexible alternating current transmission system
(FACTS) consists of static equipment used
overcome certain limitations in the static an
transmission of electrical energy. IEEE defines
FACTS as "a power electronic based system and other
static equipment that provide control of one or more
AC transmission system parameters to enhance
controllability and increase power transfer capability”
[1]. In a power system, FACTS devices enable control
of active and reactive power flow. Using the devices
opens up the potential of reducing power losses of a
transmission line.
International Journal of Trend in Scientific Research and Development (IJTSRD)
International Open Access Journal | www.ijtsrd.com
6470 | Volume - 3 | Issue – 1 | Nov – Dec 2018
www.ijtsrd.com | Volume – 3 | Issue – 1 | Nov-Dec 2018
Flexible Alternating Current Transmission Systems
Matthew N. O. Sadiku, Adedamola A. Omotoso, Sarhan M. Musa, Adebowale E. Shadare
Engineering, Prairie View A&M University, Prairie View
Flexible AC Transmission System (FACTS) refers to
based devices designed
to increase power transfer capability of power
transmission system. The main objective of FACTS is
o obtain AC systems with a high level of flexibility
FACTS uses
power electronics for controlling power flow in a
provides a brief
introduction to FACTS devices or controllers.
C transmission system,
power electronics, voltage source converters
In conventional AC transmission system, the amount
of power that can be sent over a transmission line is
limited by many factors such as the length of the line,
transient stability
it, voltage limit, and short circuit current limit. For
ideal transmission the active power should be equal to
the apparent power so that the power factor can be
unity. This is where the role of flexible AC
in. The use of
FACS devices can potentially overcome the
by using advanced solutions based on
flexible alternating current transmission system
consists of static equipment used to
s in the static and dynamic
IEEE defines
FACTS as "a power electronic based system and other
static equipment that provide control of one or more
AC transmission system parameters to enhance
ower transfer capability”
In a power system, FACTS devices enable control
of active and reactive power flow. Using the devices
opens up the potential of reducing power losses of a
The concept of FACTS was introduced by Hingorani
in 1988 [2]. Since then, FACTS applications have
increased significantly. The number of FACTS
devices installed in practical power systems has
steadily increased. It is expected that
play a significant role in the next generation of
electric power grids.
FEATURE OF FACTS
The objectives of FACTS include
the transmission capabilities while maintaining the
stability of power systems, (ii) to control power so
that if flows on the desired routes, (iii) to increase
loading capacity of transmission lines,
blackouts.
The design of FACTS devices is based on the
combination of traditional power system components
(such as inductors, capacitors, transformers, and,
switches) and power electronics elements (such a
transistors and thyristors). FACTS
power systems are illustrated in Figure 1 and
explained as follows [4]:
STATCOM: The static sy
(STATCOM) is a shunt-connected FACT device
which is used in controlling the bus
varying impedance. It is also used for
power compensation of the transmission line.
SVC: The static VAR compensator (SVC) is the
first generation of FACTS controllers.
used to stabilize the load voltage in the power
system and to improve the power factor of the
load.
SSSC: The static synchronous series compensator
(SSSC) is a VSC-based serial FACTS device
can provide capacitive or inductive compensatio
It has the same power electronic topology as
STATCOM except that it is incorporated through
Research and Development (IJTSRD)
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Dec 2018
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Transmission Systems
Matthew N. O. Sadiku, Adedamola A. Omotoso, Sarhan M. Musa, Adebowale E. Shadare
Prairie View, Texas
The concept of FACTS was introduced by Hingorani
Since then, FACTS applications have
The number of FACTS
devices installed in practical power systems has
. It is expected that FACTS will
play a significant role in the next generation of
The objectives of FACTS include [3]: (i) to increase
the transmission capabilities while maintaining the
stability of power systems, (ii) to control power so
that if flows on the desired routes, (iii) to increase
capacity of transmission lines, (iv) to prevent
The design of FACTS devices is based on the
combination of traditional power system components
(such as inductors, capacitors, transformers, and,
switches) and power electronics elements (such as
FACTS controllers used in
are illustrated in Figure 1 and
The static synchronous compensator
connected FACT device
which is used in controlling the bus voltage by
It is also used for reactive
power compensation of the transmission line.
VAR compensator (SVC) is the
first generation of FACTS controllers. It is often
used to stabilize the load voltage in the power
system and to improve the power factor of the
The static synchronous series compensator
based serial FACTS device that
can provide capacitive or inductive compensation.
It has the same power electronic topology as
STATCOM except that it is incorporated through

2. International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456
@ IJTSRD | Available Online @ www.ijtsrd.com
a series coupling transformer instead of the shunt
transformer as in the STATCOM.
UPFC: The unified power flow controller (UPFC)
is a versatile FACTS device which can provide
simultaneous control of all basic parameters of the
power system. It can provide both power flow and
voltage control. It can control both the real and the
reactive power flow. Although UPFC can be
installed in different location in the po
it is more effective when it is located at some
optimal location.
Other FACTS devices include thyristor contr
series capacitor (TCSC), thyristor control
shifting transformers (TCPST), dynamic flow
controller (DFC), and the super conducting magnetic
energy storage (SMES) unit. These FACTS
controllers are capable of changing the parameters of
the transmission lines in a fast and effective manner.
They can be connected to the power system in series,
shunt or hybrid.
APPLICATIONS
FACTS devices have been used for controlling the
voltage, impedance, and phase angle of high voltage
AC lines. They can be used to increase transient
stability of the transmission systems and
three phase arc furnace loads. Modern FACTS
devices are based on using voltage source converter
(VSC) to inject a controllable AC waveform into the
power system. The VSC is a basic element of the
modern FACTS.
Other applications include power flow control,
reactive power compensation, power quality
improvement, and interconnection of renewable and
distributed power generation.
BENEFITS
Using FACTS devices in power systems
number of benefits. These include [5]:
It enhances the reliability of AC grids
It increases power transmission capability and
improves transient stability
It provides dynamic reactive power support and
voltage control
It improves power quality and transmission
efficiency
It reduces operation and transmission investment
cost
It reduces power delivery costs
International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456
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a series coupling transformer instead of the shunt
The unified power flow controller (UPFC)
ich can provide
simultaneous control of all basic parameters of the
It can provide both power flow and
It can control both the real and the
Although UPFC can be
installed in different location in the power system,
it is more effective when it is located at some
Other FACTS devices include thyristor controllable
thyristor controllable phase-
dynamic flow
and the super conducting magnetic
These FACTS
the parameters of
in a fast and effective manner.
They can be connected to the power system in series,
FACTS devices have been used for controlling the
and phase angle of high voltage
They can be used to increase transient
systems and for balancing
Modern FACTS
devices are based on using voltage source converter
(VSC) to inject a controllable AC waveform into the
The VSC is a basic element of the
Other applications include power flow control,
power quality
improvement, and interconnection of renewable and
in power systems provides a
the reliability of AC grids
transmission capability and
It provides dynamic reactive power support and
It improves power quality and transmission
It reduces operation and transmission investment
It facilitates the connection of the renewable
generation to the grid
Other benefits of FACTs include cost (which
outweighs other consideration), convenien
environmental impact [6].
CHALLENGES
Although FACTS devices can solve several power
system problems, they have their own challenges and
limitations. They are not widely used in the power
industry. Their cost and complexity of the devices
have prevented their deployment
the electric transmission system
of FACTS devices has raised concern on stability
since FACTS increases the stress level of the system.
Power flows in a power network are not easily
controlled due to the fact that the line parameters are
not easily changed. As more FAC
deployed, the coordination problem comp
increases [8]. Proper placement of
controllers is crucial in order to obtain good
performance.
CONCLUSION
FACTS is a technology that is based on power
electronics. Advances in power
now offer fast FACTS devices. The devices are
to enhance transient stability, controllability and
power transfer capability of transmission systems. It is
expected that FACTS devices will be used in smart
grids for various control purposes.
information about FACTS, one should consult [9,10
REFERENCES
1. “Flexible AC transmission system,”
the free encyclopedia
https://en.wikipedia.org/wiki/Flexible_AC_transm
ission_system
2. N. G. Hingorani, “Power electronics in electric
utilities: Role of power electronics in future power
systems,” Proceedings of IEEE Special Issue on
Power Electronics, April 1988.
3. “ELG4125: Flexible AC transmission systems
(FACTS),”http://www.site.uottawa.ca/~rhabas
LG4125FACTS.pdf
4. A. Abu-Siada, “Review of flexible AC
transmission systems; enabling technologies for
future smart grids,” Proceedings of International
Conference on High Voltage Engineering and
International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470
Dec 2018 Page: 810
It facilitates the connection of the renewable
Other benefits of FACTs include cost (which
outweighs other consideration), convenience, and
Although FACTS devices can solve several power
system problems, they have their own challenges and
They are not widely used in the power
cost and complexity of the devices
their deployment and integration into
the electric transmission system [7]. The introduction
FACTS devices has raised concern on stability
since FACTS increases the stress level of the system.
ower flows in a power network are not easily
controlled due to the fact that the line parameters are
As more FACTS technologies are
on problem complexity
Proper placement of the FACTS
controllers is crucial in order to obtain good
FACTS is a technology that is based on power
Advances in power electronics technology
now offer fast FACTS devices. The devices are used
to enhance transient stability, controllability and
power transfer capability of transmission systems. It is
expected that FACTS devices will be used in smart
ol purposes. For more
FACTS, one should consult [9,10].
Flexible AC transmission system,” Wikipedia,
the free encyclopedia
https://en.wikipedia.org/wiki/Flexible_AC_transm
, “Power electronics in electric
utilities: Role of power electronics in future power
Proceedings of IEEE Special Issue on
, April 1988.
“ELG4125: Flexible AC transmission systems
http://www.site.uottawa.ca/~rhabash/E
Siada, “Review of flexible AC
transmission systems; enabling technologies for
Proceedings of International
Conference on High Voltage Engineering and

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@ IJTSRD | Available Online @ www.ijtsrd.com
Power System, Bali, Indonesia, October 2017, pp.
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Smart Cities: Fostering Public
Alliances, December. 2013
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Transmission Systems,” Power Engineering
Journal, December 1995, pp. 282-286.
7. M. Bocovich et al., “Overview of series connected
flexible AC transmission systems (FACTS),
American Power Symposium, September 2013.
Figure 1
International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456
www.ijtsrd.com | Volume – 3 | Issue – 1 | Nov-Dec 2018
, Bali, Indonesia, October 2017, pp.
R. G. Zaher, “Flexible AC
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8. S. L. Nilsson, “Security aspects of flexible AC
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Electrical Power & Energy
3, 1995, pp. 173-179.
9. X. P. Zhang, C. Rehtanz, a
Transmission Systems: Modeling and Control.
Berlin, Germany: Springer
10. N. G. Hingorani and L. Gyugyi,
FACTS: Concepts and Tec
Transmission Systems. Wiley
Figure 1 Major FACTS devices [4].
International Journal of Trend in Scientific Research and Development (IJTSRD) ISSN: 2456-6470
Dec 2018 Page: 811
S. L. Nilsson, “Security aspects of flexible AC
transmission systems Controller applications,”
Electrical Power & Energy Systems, vol. 17, no.
X. P. Zhang, C. Rehtanz, and B. Pal., Flexible AC
Transmission Systems: Modeling and Control.
Berlin, Germany: Springer-Verlag, 2006
N. G. Hingorani and L. Gyugyi, Understanding
FACTS: Concepts and Technology of Flexible AC
Wiley-IEEE Press, 1999.