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International Journal Of Engineering And Computer Science ISSN:2319-7242
Volume 3, Issue 7 July, 2014 Page No. 7262-7266

STUDY OF REACTIVE POWER

COMPENSATION USING STATIC VAR
COMPENSTOR
Prof. Ameenudin Ahmad1, Mukesh Kumar Tanwer2

Faculty,Electrical & Electronics Engineering Dept. AFSET,

Faridabad, Haryana
amen.49@gmail.com

Student, Electrical & Electronics Engineering Dept. AFSET,

Faridabad, Haryana
mukesh672000@gmail.com

Abstract: This paper presents an application of a Static Var Compensator (SVC). A SVC is based on Power Electronics and other static
devices known as FACTS (Flexible AC Transmission Systems) Controllers which it could be used to increase the capacity and the flexibility
of a broadcast network. The effect of wind generators on power quality is an important issue; non uniform power invention causes
differences in system voltage and frequency. Therefore wind farm requires high reactive power compensation; the advances in high power
semiconducting devices have led to the development of FACTS. The FACTS device such as SVC inject reactive power into the system which
helps in maintaining a better voltage profile.
current[1]. The system under study is an interconnected
Keywords: FACTS, SVC, voltage stability, power limits, Voltage network located in the southeast area of Venezuela, where it is
collapse; Reactive power injection; FACTS devices. found a very important loads related to oil industry. This real
and complex system, allows the study of strategies and feasible
1. Introduction solutions for the application of the SVC. The following figure
shows the systems under study:
The purposes of generators are to supply the active power, to
provide the primary voltage control of the power system and to The objectives of this study were to increase the transmitted
bring about, or at least contribute to the desired reactive power power, under the thermal capacity, through an overhead
balance in the areas adjacent to the generating stations. A transmission lines using a voltage stability criterion. The used
generator absorbs reactive power when under excited and it approach has been the voltages stability, with the purpose of
produces reactive power when overexcited. The reactive power keeping the voltage magnitude on the main buses within the
output is continuously controllable through varying the range of 0.8-1.2 p.u. during the transients state and after a fault
excitation current. The allowable reactive power absorption or located anywhere in the systems.
production is dependent on the active power output. For short-
term operation the thermal limits are usually allowed to be
2. Static VAR Compensator (SVC)
overridden. The step-response time in voltage control is from
several tenths of a second and upwards. The rated power factor
The FACTS are controllers based on solid states technologies,
of generators usually lies within the range 0.80 to 0.95.
whose two main objectives are: the increase of the
Generators installed remotely from load centers usually have a
transmission capacity and the control of the power flow over
high rated power factor; this is often the case with large hydro-
designated transmission routes. On this way, the Controllers
turbine generators. A SVC is one of controllers based on
FACTS can be classified into four categories: Series
Power Electronics known as FACTS (Flexible AC
Controllers, Shunt Controllers, Combined series-series
Transmission Systems) Controllers, which can control one or
Controllers, Combined series-shunt Controllers. The SVC fall
more variables in a power system. The compensator studied in
into Shunt Controllers category and it function as a fast
the present work is made up of a fixed reactance connected in
generators or as an fast absorber of reactive power, with the
series to a Thyristor Controlled Reactor (TCR) – based on bi-
purpose so as to maintain or control specific parameters of the
directional valves- and a fixed bank of capacitors in parallel
electric power systems (typically bus voltage).
with the combination reactance-TCR. The thyristors are turned
on by a suitable control that regulates the magnitude of the

Prof. Ameenudin Ahmad1 IJECS Volume3 Issue 7 July, 2014 Page No. 7262-7266 Page 7262
 Fig.1 Model of the electric system under study for TCR and TSC(SVC)

The SVC consists of a Thyristor Controlled Reactor (TCR) and of current is concerned, the thyristor–controlled reactor (TCR)
a Fixed Capacitors(FC) banks. The TCR is a thyristor controlled is a controllable susceptance, and can therefore be applied as a
inductor whose effectives reactance varied in a continuous static compensator[1].
manner by partial conduction control of thyristor valve. [1], [2].
The basic elements of a TCR are a reactor in series with a Also, the conduction angle σ can be define as a function of the
bidirectional thyristor switch as show in figure Nº 2. firing angle α by:

σ = 2(π−α) (1)

The instantaneous current in the TCR is given by:

2V
(cosα−cosωt), α<ωt<α+σ
i= XL (2)
0, α+σ<ωt<α+π

Fig. 2. Thyristor Controlled Reactor (TCR)

where V is the voltage r.m.s applied the TCR and XL=ωL is
fundamental-frequency reactance of the reactor. The
The thyristors conduct alternates half-cycles of supply
fundamental component is found by Fourier analysis and is
frequency depending of the firing angle α, which is measured
given by:
from a zero crossing of voltage. Full conduction is obtained
with a firing angle of 90°. The current is essentially reactive and
sinusoidal. Partial conduction is obtained with firing angles V σ−sen σ
I1 = [A] r.m.s (3)
between 90º and 180º. Firing angle between 0° and 90º are not X
allowed as they produced asymmetrical current with a dc L π
component. The effect of increasing the firing angle is to reduce We can write equation (3) as:
the fundamental harmonic component of the current. This is
equivalent to an increase in the inductance of the reactor, I1= BL (σ) V (4)
reducing its reactive power as well as its current. So far as the
fundamental component where BL(s) is an adjustable fundamental-frequency
susceptancia controlled by the conduction angle according to
the following control law,

Prof. Ameenudin Ahmad1 IJECS Volume3 Issue 7 July, 2014 Page No. 7262-7266 Page 7263
 σ−sen σ The fixed capacitors bank (FC) alone supplies a part of the
BL (σ ) = (5) capacitive var required by the system, while the other part by
πX L the passive filters. The filters are placed in parallel with the
as a function of the firing angle, α fixed capacitors bank and they are tuned to the most relevant
harmonic frequency. The third harmonic can be attenuated by
2(π− α) +sen2 α the delta connection of the TCR. The fixed capacitors (FC),
BL (α) = (6)
and the thyristor controlled reactor may be considered
πX L
essentially to consist of a variable reactor (controlled by delay
The maximum value of the variable susceptancia is 1/XL, angle α) and a fixed capacitors, with an overall var demand
obtained with σ =180º ( α=90º) and the current on the reactor is versus var output characteristic as shown in figure No 4.
maximum. The minimum value is zero, obtained with σ = 0º
(α=180º). This control principle is called phase control[1].

A. Characteristic of SVC for phase 1

Speed of response: The TRC has a control in its firing angle α
that varies between 90º and 180º. Its speed of response is
sufficiently quickly in applications caused by rapidly fluctuating
loads. On the other hand, in power system is important that the
control of the TCR is stable and exact.

Independent Phase Control: The Three-Phase TCR used in the

Fig 2.9 SVC current verses voltage Characteristic.
SVC, can be independently controlled the three-phase of a
power system, so that it can balance any unsymmetrical three-
phase load when it are presented [3].Under unbalance
conditions, a TCR can generate more harmonics than under Fig. 4.Vars demand versus vars output characteristic
balanced conditions. For this reason, it is necessary, usually, to
placed passive filter LC, using for that the same compensation As seen, the constant capacitive var generation ―QC‖ of the
capacitors. In this case, the injection of the reactive power of the fixed capacitor is opposed by the variable var absorption
SVC is due to the filters and the fixed capacitors. ―QL‖ of the thyristor-controlled reactor, to yield the total var
output ―Q‖ required. At the maximum capacitive var output,
Response to Overvoltage and Undervoltage: This is one of the the thyristor-controlled reactor is off (α=180°). To decrease
most important characteristics of the SVC, because it the capacitive output, the current in the reactor is increase by
compensates the voltage when conditions of very high or very decreasing firing angle α. At zero var output, the capacitive
low voltage are presented in the bus where the compensator is and inductive current become equal and thus the capacitive
placed. In that case, it injects the reactive power necessary to and inductive vars cancel out. In the studied case the
restore the normal voltage magnitude. capacitive vars equal the maximum inductive vars that output
the TCR.
B. Thyristor Controlled Reactor with Unswitched (Fixed)
Capacitor (TCR-FC) Principles of operation:

Two types of Thyristor-controlled elements are used in SVCs:

The SVC under study, consist of a thyristor controlled reactor
(TCR) and a fixed capacitors bank (FC) as it is shown in figure 1. TSC — Thyristor-switched capacitor
No 3 showing voltage drop of series impedence. 2. TCR — Thyristor- controlled reactor
From a power-frequency point of view they can both be
Fig. 3 Basic FC-TFIGCR type static var compensator considered as a variable reactance, capacitive or inductive,
respectively

3. Voltage Regulation Stability

The static var compensator (SVC) is frequently used to
regulate the voltage at dynamic loads. But also, it is used to
provide a voltage support inside of a power system when it
takes place small gradual system changes such as natural
increase in system load, or large sudden disturbance such as
loss of a generating unit or a heavily loaded line[6]. These
events can alter the pattern of the voltage waveform in such a
manner that it can damage or lead to mal function of the
protection devices. Generally, there are sufficient reserves and
the systems settles to stable voltage level. However, it is
possible, (because a combination of events and systems
conditions), that the additional reactive power demands may
lead to voltage collapse, causing a major breakdown of part or
all system.

Prof. Ameenudin Ahmad1 IJECS Volume3 Issue 7 July, 2014 Page No. 7262-7266 Page 7264
The SVC can improve and increase significantly the maximum B. Results
power through the lines. This is achieved, if the SVC is
operated an instant after of a disturbance providing the In figure No 5 and in Table I are shown the results of the
necessary flow of power. Therefore, if the approach of simulation without the dynamic compensator (SVC) and a
maximum transmitted power, is of voltages, it is possible to three-phase fault located at ―Guri‖ bus, where it can be seen
increase the power flow. In the studied case, it is seen that the that the maximum power flow through ―Malena‖ –―San
transmitted power rise enough according to the used approach, Gerónimo‖ overhead lines reach 2175.6 Mva per phase,
keeping the voltage magnitude within the range of 0.8-1.2 p.u.. keeping the level voltage within the specified range of 1.2-0.8
p.u.
4. Power Systems in RP
The power system considerate in this study, is modeled by
means of the ATP/EMTP program [4], [5]. It is a part of the
interconnected power system of Venezuela, located in the
southeast region of the country. It consists of four (4) generator
bus, twelve (12) load bus, nine (9) power transformers, three (3)
reactors and twenty three (23) transmission lines. All the
elements were modeled using the ATP/EMTP models like : the
sources type 59 for the generators, the saturable transformer for
the three-phase transformers, pi-equivalent circuit for the
transmission lines and uncoupled, lumped, series R-L-C branch Fig. 5 Voltage levels at the system buses for three-phase fault
for the loads. To turn on or to turn off the thyristors[1],[2],[6] a without SVC
transient analysis control system(TACS) is used.

A. Simulation Results

The results are obtained for four cases of the network state:

a. Network without the wind generators and the SVC

devices with standard load.
b. Network without the wind generators and the SVC
devices with increased load.
c. Network with integration of the wind generators.

The simulations were carried out for the following

contingencies: Fig. 6 Voltage levels at TCR (deg) for three-phase fault with
SVC
a. Load increase in order to rise the power flow through the Table I.-Power increased for three-phase fault
main transmission system.
Transmitted Maximum Power Power
b. Three-phase fault in the "Guri" bus after the load increase. Power Transmitter Increment Increment
(pu) (MVA) (MVA) (%)
In the contingency ―a‖ the load at ―San Gerónimo‖ bus is System
increased, and the voltage profile will be different. Therefore, without 0.42 75.6 - -
each time the load is increased it will be necessary to run a SVC
power flow analysis program to get the new voltage profile System
which it will be the new initial conditions for the fault with SVC 0.62 211.4 111.0 67.8 %
calculations. (800)
In the contingency ―b‖, the three-phase short-circuit have a System
clearance time of three cycles. After this time interval the with SVC 0.59 1056.2 580.6 41.35 %
transmission line is out of operation, therefore the configuration (400)
of the system changes and the control system will be able to
Thermal Capacity = Sb = 5480 MVA (three lines)
change the operation point of the SVC.

At the second step a SVC was connected to ―Malena‖ bus. A

dynamic compensator of 400 Mvar capacitive supplies by the 5. Conclusions
filters and the fixed capacitor allow to rise the maximum power
through the lines between ―Malena‖ and ―San Gerónimo‖ buses
for the three phase fault about 48 % while the voltage level was This disconnection can deteriorate a production inequity and
kept within the range of 1.2-0.8 p.u. The inductive rating of the therefore accelerate the advent of a major incident in the
compensator to fully compensate for the reactive power network. The impacts of the addition of generators in an
requirement at the ―Malena‖ bus is 400Mvar. Hence a electrical supply network on the voltage stability are
compensator of –400, +400Mvar will meet the voltage presented. The performance of FSIG with SVC or no SVC is
requirement. compared in the simulation. It can be seen that SVC can

Prof. Ameenudin Ahmad1 IJECS Volume3 Issue 7 July, 2014 Page No. 7262-7266 Page 7265
improve static and dynamic stability of power system. And the 6. References
performance comparison of only FSIG connected to power grid
and coordinated control of FSIG and DFIG are researched too. [1]. Miller T.J.E., ―Reactive Power Control in Electric
Additionally to the increment of the maximum transmitted Systems‖, Wiley&Sons, New York, (1982).
power through the main power lines, the SVC offers other
operative advantages that should be considered in the analysis [2]. HingoraniNarain y Gyugyi, Lazlo. ‖Understanding
of costs, since it contributes to improve substantially: the FACTS: concepts and technology of flexible AC
transient system stability, the quality standards of the electric transmission systems‖, IEEE Press, New York (2000).
service at low voltage level, the unbalances of the system and
the voltage profiles in the steady and transient state. [3]. Gyugyi, L, Otto, R. y Putman, T.H. ―Principles and
For last, it is important to stand up the practical and simple Applications of Static Thyristor-Controlled Shunt
handling of the models of the ATP/EMTP to implement a very Compensator‖, Trans IEEE Power ApparSyst 97, pp
complex study. 1935-1945, September/October, 1978.

[4]. Van Dommelen Daniel,‖ Alternative Transients

Programs Rule Book‖, Leuven EMTP Center (LEC),
Belgium, 1987.

[5]. Dommel Hermann, ―Electromagnetic Transients

Program reference manual (EMTP Theory Book)‖,
Bonneville Power Administration, Portland, 1986.

[6]. Kundur P., Power Systems Stability and Control,

McGraw-Hill, New York (1994).

[7]. Heier S, ―Grid integration of wind energy conversion

system,‖[M]. Chichester: TohnWiley&Sons Ltd, 1999

[8]. Sun T, Chen Z,Blaabjerg F, ―Voltage recovery of grid-

connected wind turbines with DFIG after a short-circuit
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Author Profile

Mukesh kr. Tanwer was born in Faridabad (Haryana), India,

in 1990. He received the Bachelor in Electrical and
Electronics degree from Lingayas institute of management
and technology(affiliated to MDU), Faridabad, in 2012 and,
the Master in Power System degree from AFSET, Faridabad
(Haryana), in 2014 in Electrical engineering. His research
interest is in power electronics.

Prof. Ameenudin Ahmad1 IJECS Volume3 Issue 7 July, 2014 Page No. 7262-7266 Page 7266