FACTS COntroller

1. SEMINAR REPORT
On
FACTS CONTROLLERS
Submitted by
Name: DEBAYON SAHA
Roll: 10300512028 (12/EI/28)
Reg.: 121030110360
Department of Applied Electronics & Instrumentation Engineering
Haldia Institute of Technology
ICARE COMPLEX, HIT CAMPUS, P.O- HIT, HALDIA, PURBA MEDINIPUR,
PIN-721657
May, 2015

2. ACKNOWLEDGEMENT
Apart from the efforts of myself, the success of any project depends largely on the encouragement
and guidelines of many others. I take this opportunity to express my gratitude to the people who
have been helpful in the successful completion of this report. I want to express my gratitude to all
the people who have given their heart whelming support to finish this report. First of all I would
like to express my thanks and deep regards to my mentor prof. Ashim Halder for his exemplary
guidance and encouragement throughout the course of this report. I would express my thanks to
prof. Soumya Roy & prof. Monodipon Sahoo. I would like to thanks whole Applied Electronics &
Instrumentation Department for their support. I would like to express my thanks to my parents for
their financial as well as moral support. The guidance and support received from all the members
who contributed in this report, was vital for the successful completion of this report. I am grateful
for their constant support and help. My thanks and appreciations also go to my colleague in
developing the report and people who have willingly helped me out with their abilities.
------------------------------------
Name: DEBAYON SAHA
Roll No.: 10300512028 (12/EI/28)
Reg. No.: 121030110360
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3. ABSTRACT
Modern power systems are highly complex and are expected to fulfill the growing demands of
power wherever required, with acceptable quality and costs. The economic and environmental
factors necessitate the location of generation at places away from load centres. The restructuring of
power utilities has increased the uncertainties in system operation. The regulatory constraints on
the expansion of the transmission network has resulted in reduction of stability margins and
increased the risks of cascading outages and blackouts. This problem can be effectively tackled by
the introduction of high power electronic controllers for the regulation of power flows and
voltages in AC transmission networks. This allows 'flexible' operation of AC transmission systems
whereby the changes can be accommodated easily without stressing the system. Power electronic
based systems and other static equipment that provide controllability of power flow and voltage
are termed as FACTS Controllers.
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4. TABLE OF CONTENTS
SL NO TOPIC PAGE NO
1. ACKNOWLEDGEMENT 1.
2. ABSTRACT 2.
3. TABLE OF CONTENTS 3.
4. INTRODUCTION 4.
5. WHAT IS FACTS 5.
6. FACTS CONTROLLERS 5.
7. WHY FACTS CONTROLLERS 5.
8. TYPES OF FACTS CONTROLLERS 5.
9. STATIC VARIABLE COMPENSATOR (SVC) 6.
10. VOLTAGE SOURCE CONVERTER (VSC) 8.
11. STATIC SYNCHRONOUS COMPENSATOR (STATCOM) 9.
12. THYRISTOR CONTROLLED SERIES COMPENSATOR (TCSC) 10.
13. STATIC SYNCHRONOUS SERIES COMPENSATOR (SSSC) 11.
14. UNIFIED POWER FLOW CONTROLLER (UPFC) 12.
15. OTHERS FACTS DEVICES 13.
16. BENEFITS OF FACTS CONTROLLERS 13.
17. CONCLUSION 14.
18. REFERENCES 15.
19. BIBLIOGRAPHY 16.
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5. INTRODUCTION
Modern power systems are designed to operate efficiently to supply power on demand to various
load centres with high reliability. The generating stations are often located at distant locations for
economic, environmental and safety reasons. For example, it may be cheaper to locate a thermal
power station at pithead instead of transporting coal to load centres. Hydropower is generally
available in remote areas. A nuclear plant may be located at a place away from urban areas. Thus,
a grid of transmission lines operating at high or extra high voltages is required to transmit power
from the generating stations to the load centres. In addition to transmission lines that carry power
from the sources to loads, modern power systems are also highly interconnected for economic
reasons. The interconnected systems benefit by (a) exploiting load diversity, (b) sharing of
generation reserves and (c) economy gained from the use of large efficient units without
sacrificing reliability. However, there is also a downside to ac system interconnection- the security
can be adversely affected as the disturbances initiated in a particular area can spread and
propagate over the entire system resulting in major blackouts caused by cascading outages.
FACTS devices incorporating power electronics based devices can control the parameters of an AC
transmission system to control reactive power and enhance the load capability. FACTS devices are
also very reliable than other devices. Now let’s see about the FACTS devices.
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6. WHAT IS FACTS
A flexible alternating current transmission system (FACTS) is a system composed of static
equipment used for the AC transmission of electrical energy. It is meant to enhance controllability
and increase power transfer capability of the network. It is generally a power electronics-based
system.
FACTS is defined by the IEEE 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."
According to Siemens "FACTS Increase the reliability of AC grids and reduce power delivery
costs. They improve transmission quality and efficiency of power transmission by supplying
inductive or reactive power to the grid.
FACTS contains the design of the different schemes and configurations of FACTS devices is based
on the combination of traditional power system components (such as transformers, reactors,
switches, and capacitors) with power electronics elements (such as various types of transistors and
thyristors).
FACTS CONTROLLERS
FACTS Controllers are the power electronics based circuits or devices which are used to control
the power flow of Flexible AC Transmission Systems.
The FACTS controller is defined as a power electronic based system and other static equipment
that provide control of one or more AC transmission system parameters.
WHY FACTS CONTROLLERS
Earlier days Mechanical Circuit Breakers like Relay, Contactors etc are used to control the power
flow of the transmission systems and for the security of AC transmission system.
Mechanical Circuit Breakers was not very reliable and they can not compensate the power loss due
to Reactive Power of the transmission systems which can be performed by FACTS Controllers.
FACTS Controllers are also very reliable.
TYPES OF FACTS CONTROLLERS
Depending on the power electronic devices used in the control, the FACTS controllers can be
classified as:
1. Variable impedance type
2. Voltage Source Converter (VSC) based.
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7. Variable Impedance Type:
 Static Variable Compensator (SVC)
 Thyrister Controlled Series Compensator (TCSC)
Voltage Source Converter (VSC) Type:
 Static Synchronous Compensator (STATCOM)
 Static Synchronous Series Compensator (SSSC)
 Unified Power Flow Controller (UPFC)
Facts Controllers can also be classified as follows depending on the connection of the controller:
1. Shunt Connected Controllers
2. Series Connected Controllers
3. Hybrid/Combined Controllers
Shunt Connected Controllers:
 Static Variable Compensator (SVC)
 Static Synchronous Compensator (STATCOM)
Series Connected Controllers:
 Thyrister Controlled Series Compensator (TCSC)
 Static Synchronous Series Compensator (SSSC)
Hybrid/Combined Controllers:
 Dynamic Power Flow Controller (DPFC)
 Unified Power Flow Controller (UPFC)
STATIC VARIABLE COMPENSATOR (SVC)
Static Variable Compensator is the first generation FACTS controllers. Basically, SVC is a variable
impedance device where the current through a reactor is controlled using back to back connected
thyristor valves.
A static VAR compensator is a set of electrical devices for providing fast-acting reactive power on
high-voltage electricity transmission networks. SVCs are part of the Flexible AC transmission
system device family, regulating voltage, power factor, harmonics and stabilizing the system.
Unlike a synchronous condenser which is a rotating electrical machine, a static VAR compensator
has no significant moving parts (other than internal switchgear). Prior to the invention of the SVC,
power factor compensation was the preserve of large rotating machines such as synchronous
condensers or switched capacitor banks.
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8. The SVC is an automated impedance matching device, designed to bring the system closer to unity
power factor. SVCs are used in two main situations:
 Connected to the power system, to regulate the transmission voltage ("Transmission
SVC")
 Connected near large industrial loads, to improve power quality ("Industrial SVC")
In transmission applications, the SVC is used to regulate the grid voltage. If the power system's
reactive load is capacitive (leading), the SVC will use thyristor controlled reactors to consume
VARs from the system, lowering the system voltage. Under inductive (lagging) conditions, the
capacitor banks are automatically switched in, thus providing a higher system voltage. By
connecting the thyristor-controlled reactor, which is continuously variable, along with a capacitor
bank step, the net result is continuously variable leading or lagging power.
In industrial applications, SVCs are typically placed near high and rapidly varying loads, such as
arc furnaces, where they can smooth flicker voltage.
Principle: Typically, an SVC comprises one or more banks of fixed or switched shunt capacitors or
reactors, of which at least one bank is switched by thyristors. Elements which may be used to
make an SVC typically include:
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9.  Thyristor controlled reactor (TCR), where the reactor may be air- or iron-cored
 Thyristor switched capacitor (TSC)
 Harmonic filter(s)
 Mechanically switched capacitors or reactors (switched by a circuit breaker)
By means of phase angle modulation switched by the thyristors, the reactor may be variably
switched into the circuit and so provide a continuously variable MVAR injection (or absorption) to
the electrical network. In this configuration, coarse voltage control is provided by the capacitors;
the thyristor-controlled reactor is to provide smooth control. Smoother control and more flexibility
can be provided with thyristor-controlled capacitor switching. The thyristors are electronically
controlled. Thyristors, like all semiconductors, generate heat and deionized water is commonly
used to cool them. Chopping reactive load into the circuit in this manner injects undesirable odd-
order harmonics and so banks of high-power filters are usually provided to smooth the waveform.
Since the filters themselves are capacitive, they also export MVARs to the power system.
More complex arrangements are practical where precise voltage regulation is required. Voltage
regulation is provided by means of a closed-loop controller. Remote supervisory control and
manual adjustment of the voltage set-point are also common.
Generally, static VAR compensation is not done at line voltage; a bank of transformers steps the
transmission voltage (for example, 230 kV) down to a much lower level (for example, 9.5 kV). This
reduces the size and number of components needed in the SVC, although the conductors must be
very large to handle the high currents associated with the lower voltage. In some static VAR
compensators for industrial applications such as electric arc furnaces, where there may be an
existing medium-voltage busbar present (for example at 33kV or 34.5kV),the static VAR
compensator may be directly connected in order to save the cost of the transformer.
Another common connection point for SVC is on the delta tertiary winding of Y-connected auto-
transformers used to connect one transmission voltage to another voltage.
The dynamic nature of the SVC lies in the use of thyristors connected in series and inverse-
parallel, forming "thyristor valves"). The disc-shaped semiconductors, usually several inches in
diameter, are usually located indoors in a "valve house".
VOLTAGE SOURCE CONVERTER (VSC)
VSCs’ are the power electronics based devices made of thyristor which can control the reactive
power of the transmission system.
Basically VSC ideal bi-directional switches. It converts voltage and currents from DC to AC while
the exchange of power can be in both directions
 From AC to DC (rectifier mode)
 From DC to AC (inverter mode)
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10. A typical Voltage Source Converter (VSC)
STATIC SYNCHRONOUS COMPENSATOR (STATCOM)
A static synchronous compensator (STATCOM), also known as a "static synchronous condenser"
("STATCON"), is a regulating device used on alternating current electricity transmission networks.
It is based on a power electronics voltage-source converter and can act as either a source or sink of
reactive AC power to an electricity network. If connected to a source of power it can also provide
active AC power. It is a member of the FACTS family of devices. It is inherently modular and
electable.
Usually a STATCOM is installed to support electricity networks that have a poor power factor and
often poor voltage regulation. There are however, other uses, the most common use is for voltage
stability. A STATCOM is a voltage source converter (VSC)-based device, with the voltage source
behind a reactor. The voltage source is created from a DC capacitor and therefore a STATCOM has
very little active power capability. However, its active power capability can be increased if a
suitable energy storage device is connected across the DC capacitor. The reactive power at the
terminals of the STATCOM depends on the amplitude of the voltage source. For example, if the
terminal voltage of the VSC is higher than the AC voltage at the point of connection, the
STATCOM generates reactive current; on the other hand, when the amplitude of the voltage
source is lower than the AC voltage, it absorbs reactive power. The response time of a STATCOM
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11. is shorter than that of an SVC, mainly due to the fast switching times provided by the IGBTs of the
voltage source converter. The STATCOM also provides better reactive power support at low AC
voltages than an SVC, since the reactive power from a STATCOM decreases linearly with the AC
voltage (as the current can be maintained at the rated value even down to low AC voltage).
The strategy of STATCOM controller is to keep the DC capacitor voltage constant while
controlling the modulation index to keep the voltage constant during the disturbance interval.
THYRISTOR CONTROLLED SERIES COMPENSATORE (TCSC)
TCSC comprised of a series capacitor bank, shunted by a Thyristor Controlled Reactor (TCR), to
provide a smoothly variable series capacitive reactance. It is a one-port circuit in series with
transmission line. It uses natural commutation. Its switching frequency is low; it contains
insignificant energy storage and has no DC-port. Insertion of a capacitive reactance in series with
the line’s inherent inductive reactance lowers the total effective impedance of the line and thus
virtually reduces its length. As a result, both angular and voltage stability gets improved.
Furthermore, in contrast to capacitors switched by circuit breakers, TCSC will be more effective
because thyristors can offer flexible adjustment, and more advanced control theories can be easily
applied.
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12. STATIC SYNCHRONOUS SERIES COMPENSATOR (SSSC)
Static Synchronous Series Compensator (SSSC) is a series compensator of FACTS family. It injects
an almost sinusoidal voltage with variable amplitude. It is equivalent to an inductive or a
capacitive reactance in series with the transmission line. The heart of SSSC is a VSI (voltage source
inverter) that is supplied by a DC storage capacitor. With no external DC link, the injected voltage
has two parts: the main part is in quadrature with the line current and emulates an inductive or
capacitive reactance in series with the transmission line, and a small part of the injected voltage is
in phase with the line current to cover the losses of the inverter. When the injected voltage is
leading the line current, it will emulate a capacitive reactance in series with the line, causing the
line current as well as power flow through the line to increase. When the injected voltage is
lagging the line current, it will emulate an inductive reactance in series with the line, causing the
line current as well as power flow through the line to decrease.
SSSC is superior to other FACTS equipment and the benefits of using SSSC are:
Elimination of bulky passive components -capacitors and reactors,
Symmetric capability in both inductive and capacitive operating modes,
Possibility of connecting an energy source on the DC side to exchange real power with the AC
network.
An SSSC comprises a voltage source inverter and a coupling transformer that is used to insert the
ac output voltage of the inverter in series with the transmission line. The magnitude and phase of
this inserted ac compensating voltage can be rapidly adjusted by the SSSC controls. The SSSC
injects the compensating voltage in series with the line irrespective of the line current. The
transmitted power Pq, therefore becomes a parametric function of the injected voltage. The SSSC,
therefore can increase the transmittable power, and also decrease it, simply by reversing the
polarity of the injected ac voltage.
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13. UNIFIED POWER FLOW CONTROLLER (UPFC)
The UPFC can provide simultaneous control of all basic power system parameters (transmission
voltage, impedance and phase angle). The controller can fulfill functions of reactive shunt
compensation, series compensation and phase shifting meeting multiple control objectives. From a
functional perspective, the objectives are met by applying a boosting transformer injected voltage
and an exciting transformer reactive current. The injected voltage is inserted by a series
transformer. Besides transformers, the general structure of UPFC contains also a "back to back" AC
to DC voltage source converters operated from a common DC link capacitor.
UPFC is the combination of Static Synchronous Compensator (STATCOM) and Static Synchronous
Series Compensator (SSSC). It is a VSC type device. It impacts both active and reactive power flow
in transmission line.
The shunt converter (STATCOM) is primarily used to provide active power demand of the series
converter (SSSC) through a common DC link. STATCOM can also generate or absorb reactive
power and thereby provide independent shunt reactive compensation for the line.
SSSC provides the main function of the UPFC by injecting a voltage with controllable magnitude
and phase angle in series with the line via a voltage source.
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14. OTHERS FACTS DEVICES
Others FACTS devices are as follows:
 Thyristor Controlled Phase Shifting Transformer (TCPST)
 Interline Power Flow Controller (IPFC)
 Thyristor Controlled Braking Resistor (TCBR)
 Thyristor Controlled Voltage Limiter (TCVL)
 Thyristor Controlled Voltage Regulator (TCVR)
 Interphase Power Controller (IPC)
 Distributed Power Flow Controller (DPFC)
 NGH-SSR damping
BENEFITS OF FACTS CONTROLLERS
Benefits of FACTS controllers are as follows:
 To increase the power transfer capability of transmission networks.
 To provide direct control of power flow over designated transmission routes.
 Increase the loading capability of lines to their thermal capabilities.
 Control of power flow as ordered so that it follows on the prescribed transmission
corridors.
 To increase the reliability of transmission network.
 To compensate the power loss due to reactive power of transmission system.
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15. CONCLUSION
Use of FACTS controllers in the field of transmission system is a new topic. In this article
we have discussed about some of the FACTS Controllers, their types, their circuits, working
principal, advantages and disadvantages. Continuous research is going on worldwide on
this topic. We can tune or use different control algorithms to tune this FACTS systems like
PSO, Genetic algorithm, Fuzzy Logic etc.
The installation of FACTS devices is very important in the context of INDIA & CHINA.
Because the population of these two countries are increasing day by day; as a result the
demand of electricity and power also increasing. For this reason we have set a stable and
powerful power transmission system which have very low transmission loss. FACTS
devices can take this responsibility well & they are very reliable as well as perform well.
Using FACTS we can enhance the controllability and power transfer capability of a
transmission system. More research work is needed in this area for the improvement of
human needs.
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16. REFERENCES
1. www.wikipedia.org
2. www.google.com
3. www.webopedia.org
4. www.ieeeexplore.org
5. www.projectmatter.com
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17. BIBLIOGRAPHY
1. Book Power Generation Engineering. Author R.P AJWALIA (Atul Parakashan)
2. A. L’Abbate, G. Migliavacca, U. Häger x, C. Rehtanz x ERSE (ENEA - Ricerca sul Sistema
Elettrico) [former CESI RICERCA] Spa, Milan, Italy Technical University of Dortmund,
Dortmund, Germany
3. European Transmission System
4. V. Kakkar, Head of Deptt (EEE), and N. K. Agarwal, Assist. Prof. (EEE) VITS Ghaziabad.
5. L. Gyugyi, N.G. Hingorani, “Understanding FACTS,” IEEE Press, 1st Edition, December
1999.
6. M.H. Rashid, “Power Electronics,” Prentice Hall, 3rd Edition, 2004.
7. K.R. Padiyar, “FACTS Controllers in Power Transmission & Distribution”, New Age
International Publishers, 1st Edition, 2005
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