Middle-East Journal of Scientific Research 20 (1): 134-138, 2014
ISSN 1990-9233
© IDOSI Publications, 2014
DOI: 10.5829/idosi.mejsr.2014.20.01.11278
Design of Thyristor Controlled Series Capacitor for
High Voltage Controllability and Flexibility
Ravi Kant Kumar, Sanjeet Kumar, Santan Kumar and K.S.S. Prasad
Department of EEE,
Bharath University, Chennai, India
Abstract: In this paper a series controller from the Flexible AC Transmission System (FACTS) family called as
‘Thyristor Controlled Series Capacitor’ (TCSC) is designed using PIC microcontroller. Thyristor controlled
series compensator (TCSC), is the first generation of FACTS controller, can govern line impedance through
introduction of a thyristor controlled capacitor in series with the transmission line. A grid of transmission lines
operating at high voltages is required to transmit power from generating stations to load. Inaddition to
transmission lines that carry power from source to load, modern power systems are highly interconnected for
economic reasons. The large interconnected transmission networks occur to faults due to the lightning
discharges and reduce insulation strength. Changing loads and atmospheric conditions are unpredictable
factors. This may cause overloading of lines due to which voltage collapse takes place. All the above said
things are undesirable for secure and economic operation of a line. These problems can be erased by providing
sufficient margin of working parameters and power transfer, but it is not possible due to expansion of
transmission network. Still the required margin is reduced by introduction of fast dynamic control over reactive
and active power by high power electronic controllers. The TCSC is used as series compensator in transmission
system, it can be designed to control the power flow in order to increase the power transfer limits or to improve
the transient stability. The paper also presents experimental results of a TCSC connected to a single-phase or
three phase system. The TCSC controller can provide a very fast action to increase the synchronization power
through quick changing of the equivalent capacitive reactance to the full compensation in first few cycles after
a fault, hence subsequent oscillations are damped. The various problems existing on long distribution lines that
can be occurs by the connection of variable series compensation, as a TCSC provides, are discussed.
Key words: TCSC
FACT
TCR
Series Compensator
INTRODUCTION
Harmonics
Transmission line
The proposed FACTS devices, possibly the TCSC
(Thyristor Controlled Series Capacitor) have given the
best results in terms of performance and flexibility. The
TCSC has been used in many applications: for controlling
the power flow, for damping system oscillations, for
suppressing sub-synchronous resonance, for limiting
fault currents, etc. Therefore, the modeling of the device
has become of great interest [3].
The main purpose of this paper is to furnish a
concise study of TCSC in simple way. Thyristor
controlled series capacitors (TCSCs) have been used in
transmission networks to control then equivalent
impedance of transmissions lines and therefore the power
flow in the network. They have renewed the interest in
transmission line series compensation because of their
To meet rising demand of power, FACTS devices are
introduced in the transmission line to enhance its power
transfer capability; either in series or in shunt. The series
compensation is an economic method of improving power
transmission capability of the lines. Series compensation
will: Increase power transmission capability [1]. Improve
system stability. Reduce system losses. Improve voltage
profile of the lines. Optimize power flow between parallel
lines. Thyristor-controlled series capacitors (TCSC) is also
a type of series compensator, can provide many benefits
for a power system including controlling power flow in the
line, damping power oscillations and mitigating sub
synchronous resonance [2].
Corresponding Author: Ravi Kant Kumar, Department of EEE, Bharath University, Chennai, India.
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Middle-East J. Sci. Res., 20 (1): 134-138, 2014
control system flexibility [4]. Although mechanical
switching could, in principle, be applied to achieve some
flexibility, the fast electronic control and proven reliability
of the thyristors lead to maximum controllability of the
transmission system. The TCSC concept is that it uses an
extremely simple main circuit. The capacitor is inserted
directly in series with the transmission line and the
thyristor-controlled inductor is mounted directly in
parallel with the capacitor. Thus no interfacing equipment
like e.g. high voltage transformers is required. This makes
TCSC much more economic than some other competing
FACTS technologies. Series compensation will: Increase
power transmission capability [5]. Improve system
stability. Reduce system losses. Improve voltage profile
of the lines. Optimize power flow between parallel lines
[6].
Fig. 1: TSCS
TCSC (Thyristor Controlled Series Capacitor): Thyristor
Controlled Series Capacitor (TCSC) is one of the important
members of FACTS family that is increasingly applied
with long transmission lines by the utilities in modern
power systems. It can have various roles in the operation
and control of power systems, such as scheduling power
flow; decreasing unsymmetrical components; reducing
net loss; providing voltage support; limiting short-circuit
currents; mitigating sub synchronous resonance (SSR);
damping the power oscillation; and enhancing transient
stability.
TCSC is a capacitive reactance compensator [9],
which consists of a series capacitor bank shunted by a
thyristor-controlled reactor in order to provide a smoothly
variable series capacitive reactance.
The introduction of thyristor technology brings the
concept of series compensation still a large step further.
Important added benefits are:
Facts (Flexible AC Transmission System): The term
FACTS describes a wide range of controllers, many of
which incorporate large power electronic converters that
can increase the flexibility of power systems making them
more controllable. Recent development of power
electronics introduces the use of flexible ac transmission
system (FACTS) controllers in power systems [7]. FACTS
controllers are capable of controlling the network
condition in a very fast manner and this feature of FACTS
can be exploited to improve the voltage stability and
steady state and transient stabilities of a complex power
system. This allows increased utilization of existing
network closer to its thermal loading capacity and thus
avoiding the need to construct new transmission lines.
The main objectives of FACTS controllers are the
following:
Post-fault dynamic stability improvement
Damping of active power oscillations
Mitigation of sub-synchronous resonance (SSR)
risks.
Regulation of power flows in prescribed transmission
routes.
Secure loading of transmission lines nearer to their
thermal limits.
Prevention of cascading outages by contributing to
emergency control.
Damping of oscillations that can threaten security or
limit the usable line capacity.
TCSC is one of the most important and best known
FACTS devices, which has been in use for many years to
increase the power transfer as well as to enhance system
stability. The main circuit of a TCSC is shown in Fig. 2
[10]. The TCSC consists of three main components:
capacitor bank C, bypass inductor L and bidirectional
thyristors SCR1 and SCR2. The firing angles of the
thyristors are controlled to adjust the TCSC reactance in
accordance with a system control algorithm, normally in
response to some system parameter variations. According
to the variation of the thyristor firing angle or conduction
angle, this process can be modeled as a fast switch
between corresponding reactance’s offered to the power
system.
FACTS controller is defined as power electronic
based system and other static equipment that provide
control of one or more AC transmission system
parameters. Out of numbers of FACTS devices the one
which is very efficient is the TCSC [8].
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Middle-East J. Sci. Res., 20 (1): 134-138, 2014
Fig. 2: Configuration of a TCSC
Circuit Diagram Explantion of TCSC
Fig. 4: Block Diagram
help of driver is used to control the fluctuations of the
voltage at the output where the load is operated with high
efficiently.
Equipments Required:
Hardware Requirements:
TRIAC
Driver IC
Capacitor
Controller
Regulator
Diodes
TCSC Steady-State Operation: The basic circuit of TCSC
is illustrated in Figure 1. It consists of a capacitor in
parallel with a thyristor-controlled inductor. The control
variable is the firing angle
of the thyristors, with
reference to the capacitor voltage zero crossings. The
thyristors are fired when the capacitor voltage and current
are opposite in polarity [11]. This is equivalent to thyristor
firing angles between 90° and 180°.
The TCSC can operate in three different modes. In
the bypassed mode, the thyristor path is conducting
continuously, the capacitor is bypassed and the apparent
impedance becomes inductive. In the blocked mode, the
thyristor path is blocked continuously, which is
equivalent to the fixed capacitor reactance. Finally in the
Vernier mode, the thyristor path is partially conducting
resulting in a flow current circulating in the TCSC loop.
Depending on the conduction time of the thyristors, this
current may have the same or opposite direction with the
internal capacitor current. In this way the TCSC appears
as an apparent reactance that may be capacitive or
inductive
:
:
:
:
:
:
BTA06
OC3021
0.01µF (500V); 1000µF
PIC16F877A
LM7805
IN4007
Existing System: To meet the ever growing demand for
bulk power transmission over long distance, one solution
is to build HVDC transmission lines. On the other hand
increasing the capacity of existing transmission lines can
achieve the same objective. There are many more AC lines
than DC lines in today’s power networks. Technical
renovation could greatly enhance the utilization of
existing AC lines, which can be more cost effective than
building new lines. One of the main approaches to meet
the transmission requirements is to improve the usage and
capacity of existing lines
Proposing System: The presented TCSC device
comprises of a series capacitor bank, shunted by a
Thyristor Controlled Reactor (TCR), to provide a
smoothly variable series capacitive reactance. It is a oneport 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.
Block Diagram of System
Description: The AC voltage of 230 is sent to power line
through the capacitor and inductor where that impedance
is used to control the reactive power and microcontroller
is used to generate the 5V pulse and also TRIAC with the
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Middle-East J. Sci. Res., 20 (1): 134-138, 2014
Fig. 5: Complete Ciruit Diagram
Fig. 6: Simulation Diagram of a TCSC System
Circuit Diagram Explantion of Complete Circuit: A 220v,
50Hz step-down transformer whose primary voltage is
220v and secondary voltage is 12v.
Which is connected with bridge rectifier and with the
help of this rectifier we convert the 12v ac voltage to 12v
dc voltage, here a capacitor (100mF, 25v) is used to reduce
the unwanted noise.12v dc voltage is passes through the
regulator (LM7805) and resultant output voltage is 5v dc.
Output terminal of the regulator is divide in to two
terminals, one is goes to optocoupler circuit input and
another is goes to the 12th pin (+VCC) of the
microcontroller. The 5V pulse width modulation generated
by the microcontroller is send to the MOC3021 driver
(optocoupler), it is nothing but the gallium arsenide
infrared emitting diodes, optically coupled to a silicon
bilateral switch where the driver is used to the boost the
pulse. And the resulted pulse is sent to the gate terminal
of the TRIAC and it is triggered to ON position and make
a close loop to flow the power inside the circuit. The AC
voltage of 220V, 50Hz is send to the power line where the
inductance and capacitance is used to control the reactive
power. And take fast response when the any fault occurs
during the power flow in Transmission line.
Fig. 7: Output wave form of TCSC system
Fig. 8: Simulation diagram of non TCSC system
RESULT
Fig. 9: Output wave form of non TCSC syestem
CONCLUSION
Simulation result is performed in MATLAB Simulink
software. Simulation diagram of purposed TCSC system
and its output waveform is shown in Fig. 6 and Fig. 7
respectively.
Simulation diagrams of existing system without TCSC
schematic simulation diagram and its waveform is shown
in Fig. 8 and Fig. 9 respectively.
Thyristor ControlSeries Capacitors (TCSC) is
maintain the system stability that means if any error
occurs during the transmission of electric power, this
device is solve the e rror and work continuously
[12-16].
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Middle-East J. Sci. Res., 20 (1): 134-138, 2014
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