International Journal of Scientific Research Engineering & Technology (IJSRET)
Volume 1 Issue 5 pp 022-027 August 2012
www.ijsret.org
ISSN 2278 – 0882
Introduction to Fact Devices and Introducing New
Generation of Statcom
Vertika Jain
Electrical Deptt. MIT, Meerut
Email:dvertikaj28@hotmail.com
ABSTRACT
In recent years, increased demands on transmission,
absence long- term planning and the need to provide open
access to generating companies and customers, all
together have created tendencies towards less security and
reduced quality of supply. The FACTS technology is
essential to alleviate some but not all of these difficulties
by enabling utilities to get the most service from their
transmission facilities and enhance grid reliability.
Flexible alternating – current transmission systems
(FACTS) are defined by the IEEE as “ ac transmission
systems incorporating power electronics- based and other
static controllers to enhance controllability and increase
power transfer capability”. There currently exists no
formal classification scheme for flexible alternatingcurrent transmission systems (FACTS) controllers and the
paper aim to remedy this.
The FACTS based controller’s gives instantaneous
control of transmission voltage and increase capacity
providing larger flexibility in bulk power transmission. It
is also in damping out major grid oscillations. Static VAR
controllers (SVC) control only one of the three
parameters
(voltage,
impedance, phase
angle)
determining the power flow in the AC power system viz
the amplitude of voltage at selected terminals of
transmission line. It has long been realized that an all
solid state or advanced, static VAR compensator, which
is true equivalent of ideal synchronous condenser, is
technically feasible with the use of Gate Turn-off (GTO)
thyristor. The UPFC is recently introduced FACTS
controller which has the capability to control all the four
transmission parameters.
Keywords: FACTS Devices, classification, STATCOM.
Basically the FACTS controllers are of four types:1. Series Controllers
2. Shunt Controllers
3. Combined Series-Series Controllers
4. Combined Series -Shunt controllers
II.
I.
INTRODUCTION
Flexible AC transmission system (FACTS) gives solution
to the problems and limitations which are introduced in
power system with the introduction of power electronics
based control for reactive power. Flexible AC
transmission system (FACTS) is defined as “Alternating
current transmission systems incorporating power
electronics based and other static controllers to enhance
controllability and increase power transfer capability”.
The FACTS technology making use of power electronics
promotes the control of transmission line. It also increases
load on the line upto the thermal limits without having
compromise with the reliability. The line capacity is thus
increased which improves the reliability of the system.
Due to this, there is a maximum utilisation of available
equipments and additional bulk transfers are possible.
This also avoids the construction of the new transmission
line which is time consuming process.
BASIC TYPES OF FACTS CONTROLLERS
1. Series controller
The series controller could be variable impedance, such
as capacitor, reactor etc or a power electronics based
variable source of main frequency, subsynchronous and
harmonic frequencies (or a combination) to serve the
desire need. All series controllers inject voltage in series
with the line. Even variable impedance multiplied by the
current flow through it represents an injected series
voltage in 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. Any phase
relationship will involve handling of real power as well.
IJSRET @ 2012
International Journal of Scientific Research Engineering & Technology (IJSRET)
Volume 1 Issue 5 pp 022-027 August 2012
www.ijsret.org
Fig. 1 Series Controller
2. Shunt Controllers
As in the case of series controllers, shunt controllers may
be variable impedance, variable source or a combination
of these. In principle all shunt controller inject current
into the system. Even variable shunt impedance causes a
variable current injection in to the line. As long as
injected current is in phase quadrature with the line
voltage it supplies or consumes variable reactive power.
Any other phase relationship will involve real power
exchange also.
Fig. 2 Shunt Controller
3. Combined series-series controller
This could be a combination of separate series controllers,
which are controlled in a coordinated manner, or it could
be a unified controller. The series controllers could
provide independent series reactive compensation but
also could transfer real power among the lines via the
power link (D.C link). The real power transfer capability
of the unified series-series controller, referred to as
interline power flow controller, makes it possible to
balance both the real and reactive power flow in the lines.
And thereby maximize the utilization of the transmission
system. Note that the term “unified” here means that the
D.C terminals of all controller converters are all
connected together for real power transfer.
ISSN 2278 – 0882
4. Combined series-shunt controller
This is a combination of series and shunt controllers
which are controlled in a coordinated manner or a unified
power flow controller with series and shunt elements. In
principle combined shunt and series controller inject
current in to the system with the shunt part of the
controller and voltage in series in the line with the series
part of the controller. However when the shunt and series
controllers
are unified,
there
can be
a real
power exchange between the series and shunt controllers
via the power link. Inferring from one and two of above,
the shunt converter of the UPFC injects current into the
line while the series converter injects voltage in series
with the line. The power link enables real power
exchange between the two. The system as against only
influencing From the above discussion it can be inferred
that the word unified emphasizes or refers to the existence
of a power link via which the combination of controllers
i.e. series – series and series - shunt exchange real power,
also the power link if provided with a storage system such
as d.c. capacitors, batteries etc, is much more effective for
controlling the system dynamics. This has to do with
dynamic pumping of real power in and out of transferring
of real power within the systems as in the case of power
links lacking storage. After all the above discussion
FACTS can be defined as:-Alternating current
transmission systems incorporating power electronic
based and other controllers to enhance controllability and
increase power transfer capability. FACTS controller can
be defined as:-A power electronic based system and other
static equipment that provide control of one or more AC
transmission system parameters below a list of FACTS
controllers that fall into the four categories discussed has
been given. The working of each has not been discussed
as their general principal of working has already been
discussed.
Shunt Controllers
1. Static Synchronous Compensator (STATCOM)
2. Static Synchronous Generator (SSG)
3. Battery Energy Storage System (BESS)
4. Super Conducting Magnetic Energy Storage (SMES)
5 . Static VAR compensator (SVC)
6. Thyristor Controlled Reactor (TCR)
7. Thyristor Switched Reactor (TSR)
8. Thyristor Switched Capacitor (TSC)
9. Static VAR Generator or Absorber.
IJSRET @ 2012
International Journal of Scientific Research Engineering & Technology (IJSRET)
Volume 1 Issue 5 pp 022-027 August 2012
www.ijsret.org
ISSN 2278 – 0882
Series controller
1. Static Synchronous Series Comparator (SSSC)
2. Inter line Power Flow Controller (IPFC)
3. Thyristor Controlled Series Capacitor (TCSC)
4. Thyristor Switched Series Capacitor (TSSC)
5. Thyristor Controlled Series Reactor (TCSR)
6. Thyristor Switch Series Reactor (TSSR)
5.The loading capacity of the line is greatly increased
upto their thermal capacities. Thus upgrading of lines is
possible.
Combined shunt and series connected controllers:1. Unified Power Flow Controller (UPFC)
2. Thyristor Controlled Phase Shifting Transformer
(TCPST).
7.There is increase in utilisation of cost generation due to
cost effective enhancement of transmission line capacity.
6.It limits the impacts of faults and equipment failures.
The reactive power flow in the lines can be decreased and
the lines are made to carry more active power.
STATCOM (Static synchronous compensator):- A static
synchronous generator operated as a shunt connected
static VAR compensator whose capacitive or inductive
output current can be controlled independent of the AC
system voltage. STATCOM is one of the key FACTS
controllers. It can be based on a voltage sourced or
current sourced converter seems to be preferred and will
the basis for presentation of most converter based FACTS
controllers. For the voltage sourced converter, its AC
output voltage is controlled such that it is just right for
required reactive current flow for any ac bus voltage DC
capacitor voltage is automatically adjusted as required to
serve as a voltage source for the converter. STATCOM
can be designed to also act as an active filter to observe
system harmonics.
III. ADVANTAGES OF FACTS
The following are the benefits that are principally derived
by using the FACTS controllers.
1. It controls line impedance angle and voltage which
helps in controlling the power in transmission lines.
The power flow in the transmission lines can be made
optimum.
2.It helps in damping out the oscillations and avoids
damage of various equipments.
IV.
INTRODUCING
A
NEW
GENERATION OF STATCOM
Modular Multilevel Converter design makes all the
difference SVC PLUS uses Voltage-Sourced Converter
(VSC) technology based on Modular Multilevel
Converter (MMC) design.
1. The MMC provides a nearly ideal sinusoidal-shaped
waveform on the AC side. Therefore, there is only little–
if any – need for high-frequency filtering and no need for
low order harmonic filtering.
2. MMC allows for low switching frequencies, which
reduces system losses.
3. The MMC technology provides a high degree of
flexibility in converter design and station layout.
4. SVC PLUS uses robust, proven standard components,
such as typical AC power transformers, reactors,
capacitors, and industrial class IGBTs (Insulated Gate
Bipolar Transistors) that are widely used for traction and
industrial drives.
Convincing advantages in all respects
SVC PLUS reduces the time and resources required for
project development. The relatively low number of
components simplifies design, planning, and engineering
tasks.
3.It supports the power system security by increasing the
transient stability limit. It also limits overloads and short
circuit currents.
4.The reserve requirements for generators are
considerably reduced as these controllers provide secure
and controllable tie line connections to neighbouring
electric utilities.
IJSRET @ 2012
International Journal of Scientific Research Engineering & Technology (IJSRET)
Volume 1 Issue 5 pp 022-027 August 2012
www.ijsret.org
ISSN 2278 – 0882
Converter Arrangement
Compact and adaptable, thanks to MMC technology
The design of SVC PLUS is fully flexible. Both
containerized and conventional building solutions are
available. A low space requirements due to the reduced
size and few passive components. A small physical
footprint reduces the high costs. SVC PLUS is the ideal
solution when space is limited and costly. Examples are
the extension of existing substations or new substations in
congested areas such as megacities.
Modular system design
The MMC technology offers a high degree of flexibility.
Standardized configurations are available: +/-25, +/-35,
and +/-50 MVAr as containerized solutions. Up to
four of these units can be configured as a fully parallel
operating system.
Easily expendable and relocatable.
Open rack modular system configuration enables
Transformer less grid connection up to 36 kV and
+/-100MVAr. Hybrid solutions with mechanically
switched capacitors (MSC) or reactors (MSR) are
available.
Space requirement: SVC “Classic” versus SVC PLUS
Power module with capacitor
Harmonic performance
Due to the MMC technology, the degree of harmonic
generation emission is quite small. High frequency
noise is absorbed by small standardized high-frequency
blocking filters, resulting in an SVC design which is
practically independent from individual network
impedances.
Operational advantages
A very high level of system availability, thanks to the
redundancy of power modules. Minimized maintenance
and service requirements. Standard WinCC and
SIMATIC TDC control and protection hardware and
software are fully proven in practice in a wide range of
applications worldwide (e.g. SVC “Classic”, HVDC).
IJSRET @ 2012
International Journal of Scientific Research Engineering & Technology (IJSRET)
Volume 1 Issue 5 pp 022-027 August 2012
www.ijsret.org
Network stabilization
High dynamic performance: very fast response time
Excellent under voltage performance: highly efficient
voltage support. Economical benefits. MMC with low
switching frequencies means reduced losses. Fewer
components translate into less time and cost demands for
planning, engineering, construction, and commissioning.
Lower space requirements help reduce property costs.
Tested and proven performance.
Siemens has always been a leader in the reactive power
compensation business, both in conventional and
innovative technologies. Reactive power compensation
based on thyristor-controlled technology started in the
mid 1970s and has achieved a high degree of maturity in
many applications, worldwide. Based on Siemens’ vast
experience in shunt and series compensation, active
filtering, and HVDC PLUS, SVC PLUS® was developed.
It helps substantially improve the quality of power supply
– within little time and at comparatively little expense.
The performance and operational capabilities of standard
control hardware and software have already been proven
in SVC “Classic” projects. The use of well proven
standard design key components such as reactors,
capacitors, converter cooling, and auxiliary equipment,
safe guard the reliability of SVC PLUS and guarantee
operator convenience right from the start. Examples of
applications and projects.
Utility application:
Kikiwa SVC PLUS, New Zealand: Installed to meet the
reactive power demand of the connected load during and
after system faults. Mocuba SVC PLUS, Mozambique:
Provides the most flexible solution regarding system
parameters and equipment design.
Haywards SVC PLUS, New Zealand: Represents an
integrated part of the reactive power and voltage control
of Cockstrait HVDC. Rio Branco SVC PLUS, Brazil:
Due to compact design there is the option to relocate the
unit. Blackwater SVC PLUS, Australia: Designed to
compensate for phase unbalances due to railway
operations. Goliath SVC PLUS, Norway: Scored with
small Footprint for indoor installation.
Grid access:
Thanet offshore wind (UK): Thanet wind farm has a
capacity of 300 MW and is located 11 km off the Kent
coast of England. Two SVC PLUS systems ensure Grid
Code Compliance. The performance of the system has
been proved since 2010.
ISSN 2278 – 0882
Greater Gabbard wind farm (UK): The 500 MW wind
farm is located 23 km off the Suffolk coast of England.
The three SVC PLUS systems improve the voltage
stability and the necessary power factor correction. Since
2010 the SVCs have been in commercial operation.
London Array wind farm (UK): London Array is the
world’s largest wind farm with a capacity of 630 MW.
Four SVC PLUS systems will be installed for reactive
power compensation and Grid Code Compliance.
In 2010 Siemens was awarded two additional offshore
wind grid access projects in the UK: Lincs wind farm
and Gwynt y Môr wind farm. The compact, modular,
SVC PLUS design allows the onshore connection
substation to fit into limited space.
Mobility applications:
SVC PLUS technology can be used for Static Frequency
Converter purposes in traction supplies.
Industry applications:
SVC PLUS can also be used to improve flicker
performance in industrial applications.
V.
CONCLUSIONS
In this paper SVC PLUS uses Voltage- Sourced converter
(VSC) technology based on Modular Multilevel
Converter (MMC) design & it allows low switching
losses and reduces system losses.
Due to MMC technology, the degree of harmonic
generation emission is quite small standardized high
frequency blocking filters, resulting in a SVC design.
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International Journal of Scientific Research Engineering & Technology (IJSRET)
Volume 1 Issue 5 pp 022-027 August 2012
www.ijsret.org
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IJSRET @ 2012
ISSN 2278 – 0882