SHORT PAPER
International Journal of Recent Trends in Engineering, Vol 2, No. 7, November 2009
Voltage Profile Improvement Using Static Var
Compensators (SVC) And Thyristor Controlled
Voltage Regulator (TCVR)
M.Arun Bhaskar1 C.Subramani2 M.Jagdeesh Kumar3 Dr.S.S.Dash4
Dr.P.Chidambaram5
1
Senior Lecturer , Department of EEE, Velammal Engineering College, Chennai, India
Email: m.arunbhaskar@gmail.com
Senior Lecturer2, Assistant Professor3, Professor5, Department of EEE, Velammal Engg. College, India
Email: csmsrm@gmail.com, mpjagdeesh@yahoo.com, drpchida@hotmail.com
Professor4, Department of EEE, SRM University, Chennai, India
Email: munu_dash_2k@yahoo.com
Abstract - The voltage level of the system changes when
SVC and the power system. The power system is
there is change in load and the drop in the load voltage leads
modeled as an equivalent voltage source Vs, behind
to an increased demand for the reactive power that, if not
equivalent system impedance Xs, as viewed from the
met by the power system leads to a further decline in the
SVC terminals. The system impedance Xs indeed
bus voltage. This decline eventually leads to a progressive
corresponds to the short circuit MVA at the SVC bus and
rapid decline of voltage at that location, which may have a
is obtained as [12, 13]
cascading effect on neighboring regions that causes voltage
collapse.
2
In this paper, FACTS controllers such as Static
VAr Compensators (SVC) and Thyristor Controlled
Voltage Regulators (TCVR) are used to maintain the
voltage with in the limits. SVC will either supply the
reactive power or extract the reactive power and the TCVR
will inject series voltage at the load end so as to avoid
voltage collapse. Smooth variation of reactive power is
possible by controlling the firing angle of the thyristors.
SVC and TCVR models are developed and tested in IEEE
test system, and the outputs are given.
xs =
sc
(1)
Where Sc = the 3 phase short circuit MVA at the SVC
bus
Vb = the base line to line voltage
MVAb = the base MVA of the system
If the SVC draws a reactive current Isvc then in the
absence of the SVC voltage regulator the SVC bus
voltage is given by
Vs=Vsvc + Isvc Xs
(2)
The SVC current thus results in a voltage drop
of IsvcXs in phase with the system voltage Vs. the SVC
bus voltage decreases with the inductive SVC current and
increases with the capacitive current. [3]Equation
represents the power system characteristic or the system
load line. This equation implies that the SVC is more
effective in controlling the voltage in the weak bus
system and less effective in strong ac systems (low Xs)
The voltage control action in the linear range is
described as
Vsvc = Vref + XSLISVC
(3)
Where Isvc is positive if inductive, negative if
capacitive
Index Terms - FACTS, Voltage Stability, TCVR, SVC
I. INTRODUCTION
In recent years, greater demands have been
placed on the transmission network, and these demands
will continue to increase because of the increasing
number of non utility generators and heightened
competition among utilities themselves. Added to this is
the problem that it is very difficult to acquire new rights
of way. Increased demands on transmission, absence of
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. It
must be stressed, however, that for many of the capacity
expansion needs, building of new lines or upgrading
current and voltage capability
III. VOLTAGE REGULATION BY THYRISTOR
CONTROLLED VOLTAGE REGULATOR
The basic concept of voltage regulation is the addition
of an
appropriate in-phase component to the
prevailing terminal (bus) voltage in order to change
(increase or decrease) its magnitude to the value
specified (or desired). Thus voltage regulation could
theoretically be achieved by a synchronous in-phase
voltage source with controllable amplitude, ± ∆ V, in
series with the ac system and the regulated terminal.
II. VOLTAGE CONTROL BY THE SVC
The voltage control action of the SVC can be
explained through a simplified block representation of the
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SHORT PAPER
International Journal of Recent Trends in Engineering, Vol 2, No. 7, November 2009
after 5 cycles TCVR is connected in the load bus and the
voltage amplitude is increased from 4.4kV to 4.9kV.
igure. 5 Simulation Model of SVC
Figure. 12 Voltage profile improvement in 7th bus of IEEE 14 Bus
system using TCVR
IV. SIMULATION RESULTS
B. MODELLING OF TCVR
TCVR is considered as the common voltage
regulator. It is able to smoothly vary voltage magnitude
with a tap changing in the control range of –αmin < αl <α
max A static model of TCVR with a tap ratio is connected
in a series impedance of the distribution line
The TCVR operates by inserting an in-phase
voltage to the main bus voltage so as to change its
magnitude. It is modeled by an ideal tap changer
transformer in series with the branch. Its value depends
on the main bus voltage magnitude Vb of the line in
which the device is located. The additional voltage is in
the range -0.15 Vb ≤ VTCVR ≤ 0.15 Vb p.u
C. SVC CONNECTED IN AN IEEE 14 BUS SYSTEM
SVC with PI controller is used in the closed loop
system and depending on the load the firing angle is
adjusted automatically and the voltage is maintained with
in the limit.
The initial load connected is 5+j50*10-3.After 10
cycles another load of 2.5+j25*10-3 is included and there
will be dip in the voltage level from 5kV to 4.4kV
and after 5 cycles SVC is connected in the 7th bus and the
voltage amplitude is increased from 4.4kV to 5kV.
Figure. 9 Voltage profile improvement in 7th Bus of IEEE 14 Bus system
using SVC
D. TCVR CONNECTED IN IEEE 14 BUS SYSTEM
TCVR with PI controller is used in the closed loop
system and depending on the load the firing angle is
adjusted automatically and the voltage is maintained with
in the limit.
The initial load connected is 5+j50*10-3.After 10
cycles another load of 2.5+j25*10-3 is included and there
will be dip in the voltage level from 5kV to 4.4kV and
Figure. 6 Simulation model of TCVR
E. SVC CONNECTED IN AN IEEE 30 BUS SYSTEM
SVC with PI controller is used in the closed loop
system and depending on the load the firing angle is
adjusted automatically and the voltage is maintained with
in the limit.
The initial load connected is 5+j50*10-3.After 10
cycles another load of 2.5+j25*10-3 is included and there
will be dip in the voltage level from 5.2 kV to 4kV and
after 5 cycles SVC is connected in the load bus and the
voltage amplitude is increased from 4kV to 5.2kV.
Figure. 15 Voltage profile improvement in 7th bus of IEEE 30 Bus system
using SVC
F. TCVR CONNECTED IN AN IEEE 30 BUS SYSTEM
TCVR with PI controller is used in the closed loop
system and depending on the load the firing angle is
adjusted automatically and the voltage is maintained with
in the limit.
The initial load connected is 5+j50*10-3.After 10
cycles another load of 2.5+j25*10-3 is included and there
will be dip in the voltage level from 5kV to 3.5kV and
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© 2009 ACADEMY PUBLISHER
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International Journal of Recent Trends in Engineering, Vol 2, No. 7, November 2009
[4] IEEE Special Stability Controls Working Group,” Static
Var compensator Models for Power Flow and Dynamic
Performance Simulation”, IEEE Trans.on Power Systems,
Vol.9, pp229-240, Feb 1994
[5] G.M.Huang and P.Yan,” The impacts of TCSC and SVC on
power system and load curtailments”, Power Engineering
Society Summer Meeting, Vol 1, pp.33-37, July,2001
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Electrical Systems, Cornwall: MPG Books Ltd, 2002
[7] Paul M.Anderson and A.A.Fouad, Power System Control
and Stability, New York: IEEE Press, pp.37-39, 1994
[8]Hingorani, N.G.”Flexible AC Transmission”, IEEE
Spectrum, Vol.30, pp.40-45, April 1993
[9] L.Gyugyi,” Power electronics in electric utilities: static
VAR compensators “, Proceedings of the IEEE, vol.76,
pp.483-494, April 1988
[10] M.R.Iravani and Maratukulam.D,”Review of
semiconductor controlled phase shifters for power system
applications”, IEEE Transaction on power systems, vol.9,
pp.1833-1839, Nov 1994
[11] Dr.P.S.Bimbhra,”Power Electronics”, pg 680- 684,
Khanna Publishers, 2006
[12] Narain G. Hingorani, Laszlo Gyugyi., “Understanding
FACTS: Concepts and Technology of Flexible AC
Transmission Systems”, IEEE Press,1999
[13] R. Mohan Mathur, Rajiv K. Varma, “Thyristor-Based
FACTS Controllers for Electrical Transmission
Systems”,Wiley, 2002
after 5 cycles TCVR is connected in the load bus and the
voltage amplitude is increased from 3.5kV to 4.5kV.
Figure.17 Voltage profile improvement in 7th bus of IEEE 30 Bus system
using TCVR
G. COMBINED OPERATION
In Combined operation, for 10% fall in
voltage TCVR will inject the reactive power and improve
the voltage profile and if the voltage sag is more than
10%, then for the first 10% TCVR will act and there after
SVC will supply the reactive power so as to maintain the
voltage value with in the limit.
Figure.19 Voltage profile improvement in combined operation of SVC &
TCVR
V. CONCLUSION
In this paper SVC and TCVR are simulated using
MATLAB simulink technique. These two devices
improve the voltage profile; both are used at the load end
to maintain the voltage with in the prescribed limit. SVC
is connected in parallel with the load and TCVR gives
series injection. For small variation in the voltage TCVR
acts and for large variation SVC works so as to increase
the voltage to the desired value. In coordinated control
for the first 10% variation in the voltage TCVR injects
the voltage in-phase with the prevailing bus voltage and
if the variation is more than 10%, for the first 10% TCVR
works and thereafter SVC injects the reactive power so as
to maintain the voltage. These have been tested in IEEE
14 and IEEE 30 bus system and the results obtained
found to be satisfactory.
VI. REFERENCES
[1] Garng .M.Huang, Senior Member, IEEE, and Yishan Li,
Student Member IEEE,” Composite power system
reliability evaluation for systems with SVC and TCPAR”
IEEE transaction on energy systems,2003,pg 771-776
[2] Manuel Castilla Dept. of Electrical Engineering, Spain,
Jaime Gutierrez, Dept .Applied Physics III, Juan Carlos
Montafio, Spanish Research Council .” Power –Quality
Improvement in Reactive Power Control Using FC-TCR
“IEEE transaction on energy systems, 2002, pg 880-885
[3] J.Arrillaga, R.M.Duke, New Zealand Electricity New
Zealand. “A static alternative to the transformer On Load
Tap Changer”, IEEE Transaction on power Apparatus and
Systems, 2000, vol.2 pp 5-99.
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