International Journal of Advanced Engineering Technology
E-ISSN 0976-3945
Research Article
IMPORTANCE OF FACTS CONTROLLERS IN POWER
SYSTEMS
Surekha Manoja *, Dr. Puttaswamy P. S.b
Address for Correspondence
*a
Assistant Professor, Department of Electrical and Electronics, Vidya Vikas Institute of Engineering and
Technology, Mysore, Karnataka, India,
b
Professor in Department of Electrical and Electronics, PES College of Engineering, Mandya, Karnataka, India
ABSTRACT
Economic growth of the country is directly depicted with the development of electric power sector. As electricity demand
continues to rise, there is an immediate need to increase the quality and reliability of today's highly complex power systems.
Traditional power flows from power stations to the nearest big city are giving way to more complex patterns. Growth in the
use of renewable sources also becomes a problem, as these generations are often located in remote regions where the power
grid is traditionally weak. Construction of new transmission systems is not always the best option due to environmental
crisis, land use, permit granting and cost considerations. In these aspects Flexible AC Transmission Systems (FACTS)
technology with relatively low investment, compared to new transmission or generation facilities allows the industries to
enhance power system performance, improve quality of supply and also provide an optimal utilization of the existing
resources. This paper discusses various FACTS controllers which can be employed in power systems and their implications
in developing countries.
KEY WORDS: FACTS, Power System, SVC, STATCOM, UPFC, SSSC, TCSC
1. INTRODUCTION
To meet the increasing load demand and satisfy the
stability and reliability criteria, either existing
transmission or generation facilities must be
utilized more efficiently, or new facilities should be
added to the power system. Given the constraints,
such as lack of investment and difficulties in
getting new transmission line right-of ways, the
later is often difficult but the former can be
achieved by using FACTS controllers. FACTS
controllers are products of FACTS technology; a
group of power electronics controllers expected to
revolutionize the power transmission and
distribution system in many ways.
FACTS
technology can boost power transfer capability by
20-30% by increasing the flexibility of the systems.
FACTS controllers can also increase the load
ability or “distance” to voltage collapse of power
system, so that additional loads can be added in the
system without expansion of new transmission and
generating facilities(1). Many of today’s wind
turbines are induction type generators that absorb
large amounts of VARs (Volt-Amperes Reactive)
from the grid. For such machines, VAR flow
fluctuates with the power output of the turbines.
Uncompensated, these variations in VAR flow can
cause severe voltage fluctuations, affecting overall
power quality and the reliability of the local
transmission
grid.
Traditionally,
switched
capacitors have been used to compensate for
fluctuating VAR requirements. A typical wind farm
can experience 50-100 capacitor switching events
on a given day. Such frequent switching can cause
stresses, effectively reducing life-cycle times of the
capacitor switches and transients into the Grid.
IJAET/Vol.II/ Issue III/July-September, 2011/207-212
To overcome this one need to think about the role
of FACTS controllers, where the switching
operation is faster and smooth, voltage is being
regulated; power factor correction has been
corrected continuously(2,3).
There are number of FACTS controllers/devices
that have been developed depending upon the
targeted goals to be achieved. Static Var
Compensator
(SVC),
Static
Synchronous
Compensator (STATCOM), Thyristor-Controlled
Series Capacitor (TCSC), Static Synchronous
Series Compensator (SSSC) and Unified Power
Flow Controller (UPFC) are popular FACTS
Controllers. They can be connected to power
system at any appropriate location either in series
or in shunt or in a combination of series and shunt.
The SVC and STATCOM are connected in shunt,
whereas TCSC and SSSC are connected in series.
UPFC is connected in a combination of both shunt
and series(4,5). This paper high lightens the
importance of various FACTS controllers in power
systems and their implications in developing
countries along with their benefits and limitations.
Several authors have demonstrated the importance
of FACTS controllers for steady state and transient
stability studies (1-8).
2. HISTORY OF DEVELOPMENT
FACTS has come a long way since the early 1970s,
when the concept was developed for generating
controllable reactive power through switching
power converters. The first FACTS device was the
Static Var Compensator (SVC), which was
brought to the market by, the Electric Power
Research Institute (EPRI) two decades ago. This
compensator consists of a fast thyristor switch
International Journal of Advanced Engineering Technology
E-ISSN 0976-3945
controlling a shunt capacitor bank and/or a reactor,
rectifiers to manage a capacitor bank connected in
to provide dynamic shunt compensation.
series with a line, enabling the utility to transfer
Dynamic shunt compensation automatically and
more power on a particular transmission line.
instantaneously adjusts the reactive power output
Testing of the first single phase TCSC began in
smoothly thus maintaining the voltage at required
1991 by American Electric Power Co., based in
level. Conventional Thyristor and siliconColumbus, Ohio. In 1992, the Western Area Power
controlled rectifiers formed the technological
Administrator, based in Golden, Colorado, installed
foundation for this device. More than 800 SVCs are
world’s first three phase TCSC that raises the
being installed worldwide both for utility and
capacity of a transmission line by almost 30%.
industrial (especially in electric arc furnace and
Since then, there has been significant breakthrough
rolling mills) purposes. Even the utilities in
in the research and development of TCSC.
developing countries took the benefit of SVCs
In 1998, ABB commissions the world’s first full
since its invention. ABB remains the pioneer in the
scale TCSC for Sub-synchronous Resonance (SSR)
deployment of SVC and has supplied 55% of the
mitigation in 400 kV grid in Sweden. Again in
total installation and more than half of which were
1999, ABB commissions the full scale TCSC for
being installed during 1980s. Approximately 13%
damping of power oscillations in a 500 kV power
of SVCs supplied by ABB were being installed in
system interconnection in Brazil. Though series
Asian countries. Table 1.1 shows list of SVCs
compensation has long been used in transmission
installed in Asian countries. The Static Var
system in Asian countries, the use of controllable
series compensation like TCSC has just beginning
Compensator plays vital role in Flicker reduction,
to emerge. At the end of year 2004, there were
Voltage
stabilization,
Reactive
power
three TCSC in operation; two in China and one in
compensation;
improved
power
factor,
India, bringing Asia into the forefront of the
increased voltage on the load bus, Reduction of
advanced FACTS technology. Table 1.2 shows all
harmonics. The next generation of FACTS
the major TCSC installations in the world.
devices, the Thyristor Controlled Series
Capacitor (TCSC), uses silicon controlled
TABLE 1.1 LIST OF UTILITY SCALE SVCS IN ASIA
Sl. No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Year
1981
1981
1986
1987
1987
1987
1987
1987
1987
1987
1988
1988
1988
1988
1988
1988
1989
1989
1991
1991
1992
1992
1992
1995
1995
1999
1999
1999
Capacity
(MVAR)
120
120
80
290
270
300
200
200
20
80
100
50
45
45
45
20
190
190
200
200
280
280
300
-25 to 50
-50 to 300
200
150
150
-20 to +80
-40 MVA
Voltage level
kV)
500
500
115
500
500
420
380
380
132
132
230
230
132
132
132
132
500
500
275
275
400
400
420
150
230
345
380
380
500
IJAET/Vol.II/ Issue III/July-September, 2011/207-212
Country
China
China
Thailand
China
China
Iran
Saudi Arabia
Saudi Arabia
Srilanka
Yemen
Singapore
Singapore
India
India
India
Srilanka
Thailand
Thailand
Malaysia
Malaysia
India
India
Iran
Indonesia
Thailand
South Korea
Saudi Arabia
Saudi Arabia
Japan
Japan
Place
CNTIC - Wu Han I
CNTIC - Wu Han I
EGAT - Chumphon
Guangdong Gen. Pow. Co.- Jiang Men
CNTIC - Dalian
Tavanir - Omdieh
SCECO E - Shedgum
SCECO E - Faras
Galle CEB
YGEC Alsthom - Sanaa
Kallang Basin Substation
Labrador substation
TNEB – Madurai
TNEB - Trichur
TNEB - Singaropet
CEB - Chunnakam
EGAT - Tha Tako1
EGAT - Tha Tako2
NEB - K1 North2
NEB - K1 North1
NTPC - Kanpur 2
NTPC - Kanpur 1
TAVINIR – Omedieh
Jember substation (Bali)
EGAT - Bang Saphan
KEPCO - Seo-Daegu
SCECO C - Riyadh I
SCECO C - Riyadh II
Tokyo
Osaka
International Journal of Advanced Engineering Technology
E-ISSN 0976-3945
TABLE 1.2 LIST OF TCSC INSTALLATIONS
SL.
NO.
YEAR
1
1992
USA
2x165
230
2
1993
USA
208
500
3
1998
Sweden
400
4
1999
Brazil
COUNTRY
CAPACITY
MVAR
5
2002
China
55 controlled
350 fixed
6
2004
India
118
controlled
788 fixed
7
2004
China
VOLTAGE
KV
PURPOSE
PLACE
To increase power transfer
capability
Controlling line
Power flow
SSR mitigation
Kayenta substation,
Arizona
C.J.Slatt substation
in Northern Oregon
Stöde
500
To damp low frequency
oscillations
TCSC at Imperatriz
TCSC at Sarra de
500
Stability
improvement, low frequency
oscillation
mitigation
Pinguo substation,
State power
south company,
Guangzhou
400
Compensation, Damping of
inter regional power oscillation
Raipur substation
220
Increase Stability
margin, suppress low frequency
oscillation
North-West China
Power System
The second generation of FACTS, which is based
high response speed and no harmonic pollution
on voltage source converters (VSC), known as
etc.
The technology of STATCOM in improving
STATCOM
(STAtic
synchronous
COMpensator), has a very promising future
transmission system capability has been
application. A STATCOM works by rebuilding the
successfully applied in power systems in developed
incoming voltage waveform by switching back and
countries, such as Japan, USA , UK and China. It is
forth from reactive to capacitive load. If it is
also quite interesting to note that the Bharat Heavy
reactive, it will supply reactive AC power. If it is
Electric Limited (BHEL), India, was successful in
capacitive, it will absorb reactive AC power. This
developing distribution scale STATCOM also
known as D-STATCOM, which has been
is how it acts as a source/sink. Usually a
successfully installed in industry. The worlds first
STATCOM is installed to support electricity
commercial STATCOM (±80 MVA, 154 kV) was
networks that have a poor power factor and often
developed by Mitsubishi Electric Power Products,
poor voltage regulation. There are a number of
Inc. and installed at Inuyama substation in Japan in
other uses for STATCOM devices including, wind
1991. STATCOM also finds its application in
energy voltage stabilisation and harmonic filtering.
industries for flicker reduction. There are about 20
However, they are widely used for voltage stability.
STATCOMs operating successfully around the
It is recognized to be one of the key advanced
world. Table 1.3 presents some of the major utility
technologies of future power system. STATCOM
scale STATCOM which is in operation.
has several advantages of being small/compact,
TABLE 1.3 UTILITY SCALE STATCOM IN DIFFERENT COUNTRIES
SL.
NO.
1
YEAR
COUNTRY
Japan
CAPACITY
MVAR
± 80 MVA
VOLTAGE
KV
154
1991
2
1992
Japan
50 MVA
500
3
1995
USA
161
4
1996
China
± 100
MVA
± 20 MVA
5
2001
UK
0 to +225
400
6
2001
USA
- 41 to
+133
115
7
2003
USA
± 100
138
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PURPOSE
PLACE
Power system and
voltage stabilization
Inumaya
substation
Shin Shinano
Substation
Sullivan
substation
China
To regulate bus
voltage
Reactive
compensation,
improve system
stability
Dynamic reactive
compensation
Dynamic reactive
compensation
dynamic var
control ditions
East Claydon
VELCO Essex
substation
SDG&E Talega
substation
International Journal of Advanced Engineering Technology
E-ISSN 0976-3945
TABLE 1.4 LIST OF UNIFIED POWER FLOW CONTROLLER INSTALLED
SL.
NO.
1
YEAR
COUNTRY
USA
CAPACITY
MVAR
± 320 MVA
VOLTAGE
KV
138
1998
2
2003
South Korea
80
154
A complementary second-generation FACTS
controller is the Static Synchronous Series
Compensator (SSSC), which is simply a series
version of STATCOM. This series connected
device could perform the functions of a thyristorconnected series capacitor to increase or decrease
the power flow along a specific line. Combining
the static compensator and the synchronous series
capacitor into a single device with a common
control system represents the third generation of
FACTS. The device is known as “Unified Power
Flow Controller (UPFC)”. It has the unique
ability to simultaneously control all three
parameters of power flow (voltage, line impedance
and phase angle). In this configuration, the seriescapacitor component, connected in series with a
line, injects an AC voltage with controllable
magnitude and phase angle. The static compensator
component, connected as a shunt, supplies or
absorbs the real power demanded by the series
capacitor through a common DC link, and provides
var control. The first utility demonstration of a
Unified Power Flow Controller is constructed at
the Inez substation of American Electric Power in
1998 and 80 MVA UPFC have been constructed at
Gangjin substation in South Korea(4).
Table 1.4 shows the list of UPFC installed in
different countries. The most recent development in
the field of FACTS controller is the “Convertible
Static Compensators (CSC)”. The CSC offers the
full flexibility by allowing its converters to be
connected in shunt (STATCOM), in series (SSSC),
in shunt/series (UPFC) or in series/series (IPFC)
with two lines. The world’s first CSC was installed
at New York Power Authority’s Marcy 345 kV
substation, which is capable of operating in eleven
different control modes.
The full scale CSC came into operation in early
2004.
NEED, BENEFITS AND LIMITATIONS
Some of the benefits of installing FACTS
Controllers are Dynamic reactive power
compensation ,Steady-state and transient stability
enhancement ,Voltage regulation, Power transfer
capacity increase, Three-phase voltage balancing,
Reduced transmission losses, Flicker mitigation,
IJAET/Vol.II/ Issue III/July-September, 2011/207-212
PURPOSE
PLACE
Dynamic voltage
support
AEP Inez
substation
Gangjin
substation
Oscillation damping . Benefits mentioned leads to
the implementation of FACTS controllers for the
need and essential of Power System and resulting
in lower cost when compared with implementation
of new generation or new transmission line (6).
With these overall benefits, the transmission
system needs FACTS Controllers for
• Steady state voltage regulation and control
• Steady state control of power flow on a
transmission line.
• Transient stability enhancement
• Damping
at
transmission
system
oscillation frequencies (0.2-2 Hz)
Benefits for the power system from Steady State
Voltage regulation and control are
• Reduction in transformer tap change
operations and shunt capacitor switching
• Better voltage profiles for customers
• System more prepared to withstand
contingencies.
Benefits of Steady state control of power flow on a
transmission line are
• Reduce unscheduled line flow and allow
increased contract flow
• Control over loads to allow higher system
flow
• Force current flow in cold weather
conditions to prevent ice formation
• Force current flow to help control over
voltage
Benefits of Transient stability enhancement
• Allow increased steady state loading
• Reduce need for load shedding or other
special protection measures
• Reduce susceptibility for system collapse
from multiple contingency events.
Benefits of Enhanced Dynamic Stability
• Allow system operation over larger range
of loading profiles without power and
voltage oscillations
• Reduced need for special protection
systems
Just like everything has got its own advantage and
disadvantage even FACTS has issues that have
limited its application.
International Journal of Advanced Engineering Technology
E-ISSN 0976-3945
A Comparative study with the present control
Costs higher than alternatives for many
techniques with FACTS controllers is shown
applications
in tables 1.5, 1.6, and 1.7. Tables depicts the
• Size of power semi conductors needs to
replacement of present techniques by FACTS
increase
controllers, being power system engineer one
• Semi conductor costs have not decreased
need to think about the optimal operation of
as predicted
power system and should go on working
• Transient over load capability not as much
smoothly
under any situation. Though it’s
as generators or other transmission
possible
to
achieve the same with present
equipment
techniques,
FACTS
plays a vital role in
• Long term reliability and equipment life
mitigating
the
problems
in faster means.
not well established.
• Technology is changing and still under
research.
TABLE 1.5 COMPARATIVE STUDY WITH THE PRESENT CONTROL TECHNIQUES AND FACTS
CONTROLLERS TO CONTROL VOLTAGE
•
NON FACTS CONTROL METHODS
Electric Generators
Synchronous condenser
Transform tap Changer
Shunt capacitors/ Reactor
•
•
•
•
FACTS CONTROLLERS
SVC
STATCOM
SMES
BESS
TABLE 1.6 COMPARATIVE STUDY WITH THE PRESENT CONTROL TECHNIQUES AND FACTS
CONTROLLERS TO CONTROL POWER FLOW
•
•
•
•
•
NON FACTS CONTROL METHODS
Generator schedules
FACTS CONTROLLERS
TCSC
Transmission line switching
TCPST
Conventional Phase angle regulator
UPFC
HVDC transmission
Inter-phase Power Controller
SSSC
IPFC
TABLE 1.7 COMPARATIVE STUDY WITH THE PRESENT CONTROL TECHNIQUES AND FACTS
CONTROLLERS TO IMPROVE TRANSIENT STABILITY
•
•
•
•
NON FACTS CONTROL METHODS
Braking Resistor
Excitation
Special Protection System
Independent Pole Tripping
FACTS CONTROLLERS
TCBR
TCPST
SVC, STATCOM, TCSC, UPFC
IPFC
TABLE 1.8 TECHNICAL BENEFITS OF MAIN FACTS CONTROLLERS
Load Flow Control
Voltage Control
SVC
STATCOM
TCSC
UPFC
IJAET/Vol.II/ Issue III/July-September, 2011/207-212
Transient Stability
Dynamic Stability
International Journal of Advanced Engineering Technology
6. CONCLUSION
FACTS controllers have been developed to
improve the voltage performance of long distance
AC transmission, and later their use has been
extended to load flow control in meshed and
interconnected systems. For most applications in
AC transmission systems and for network
interconnections, SVC, FSC, TCSC SSSC are fully
sufficient to match the essential requirements of the
grid. STATCOM and UPFC are tailored solutions
for special needs.
FACTS devices consist of power electronic
components and conventional equipment which can
be combined in different configurations. It is
therefore relatively easy to develop new devices to
meet extended system requirements. Such recent
developments are the TPSC (Thyristor protected
Series Compensation) and the Short Circuit Current
Limiter (SCCL).
The market of FACTS equipment for load flow
control is expected to develop faster in the future as
a result of the liberalization and deregulation in the
power industry.
The table 1, 2, 3, 4 in the paper gives us
information about the initial installation of various
FACTS controllers. Presently FACTS have been
installed in several other countries knowing their
importance and their need for the power system.
This paper discuses various FACTS controllers in
power systems and their implications in developing
countries along with their benefits and limitations.
The power industry term FACTS covers a number
of technologies that enhance the security, capacity
and flexibility of power transmission systems.
FACTS solutions enable power grid owners to
increase existing transmission network capacity
while maintaining or improving the operating
margins necessary for grid stability. As a result
more power can reach consumers with a minimum
impact on the environment, after substantially
shorter project implementation times, and at lower
investment costs- all compared to the alternative of
building new transmission lines or power
generation facilities.
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