International Journal of Reviews in Computing

15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

40


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
APPLICATIONS OF FACTS CONTROLLERS IN POWER
SYSTEMS FOR ENHANCE THE POWER SYSTEM
STABILITY: A STATE-OF-THE-ART

BINDESHWAR SINGH

Research Scholar,
Kamla Nehru Institute of Technology, Sultanpur-228118, U.P., India,

E-mail: bindeshwar.singh2025@gmail.com



ABSTRACT

This paper presents a comprehensive review on enhancement of power system stability such as rotor angle
stability, frequency stability, and voltage stability by using different FACTS controllers such as TCSC,
SVC, SSSC, STATCOM, UPFC, IPFC in an integrated power system networks. Also this paper presents
the current status of the research and developments in the field of the power system stability such as rotor
angle stability, frequency stability, and voltage stability enhancement by using different FACTS controllers
in an integrated power system networks. Authors strongly believe that this survey article will be very much
useful to the researchers for finding out the relevant references in the field of enhancement of power system
stability by using different FACTS controllers in an integrated power system network.


Index Terms-Flexible AC Transmission Systems (FACTS), FACTS Controllers, SVC, TCSC, SSSC,
STATCOM, UPFC, IPFC, Power Systems, Power System Stability, Frequency Stability,
Lyapunov Stability, Oscillatory Stability, Small-Signal Stability, Terms and Definitions,
Transient Stability, Voltage Stability.

1. INTRODUCTION

In recent years, power demand has increased
substantially while the expansion of power
generation and transmission has been severely
limited due to limited resources and environmental
restrictions. As a consequence, some transmission
lines are heavily loaded and the power system
stability becomes a power transfer-limiting factor.
Flexible AC transmission systems (FACTS)
controllers have been mainly used for solving
various power system steady state control
problems. However, recent studies reveal that
FACTS controllers could be employed to enhance
power system stability in addition to their main
function of power flow control. This literature
shows an increasing interest in this subject for the
last two decades, where the enhancement of power
system stability using FACTS controllers in an
integrated power system network has been
extensively investigated.
Power system stability has been recognized as an
important problem for its secure operation since
1920s [1, 2]. Result of the first laboratory tests on
miniature systems were reported in 1924 [3]; the
first field tests on the stability on a practical power
system were conducted in 1925 [4,
5].Traditionally, the problem of stability has been
one of maintaining the synchronous operation of
generators operating in parallel, known as rotor
angle stability. The problem of rotor angle stability
is well understood and presented in literatures [6]-
[10]. With continuous increase in power demand,
and due to limited expansion of transmission
systems, modern power system networks are being
operated under highly stressed conditions. This has
been imposed the threat of maintaining the required
bus voltage, and thus the systems have been facing
voltage instability problem [11]-[13].
Due to increase in power demand, modern power
system networks are being operated under highly
stressed conditions. This has resulted into the
difficulty in meeting reactive power requirement,
especially under contingencies, and hence
maintaining the bus voltage within acceptable
limits. Voltage instability in the system, generally,
occurs in the form of a progressive decay in
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

41


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
voltage magnitude at some of the buses. A possible
outcome of voltage instability is loss of load in an
area, or tripping of transmission lines and other
elements by their protective systems leading to
cascaded outages and voltage collapse in the
system [13, 14]. Voltage collapse is the process by
which the sequence of events, accompanying
voltage instability, leads to a blackout or
abnormally low voltages in a significant part of a
power system [10, 15, 16].
In this work, the current status of power system
stability enhancement by using FACTS controllers
was discussed and reviewed. This paper is
organized as follows: Section II discusses the
definitions and dynamic phenomena regarding with
power system stability. Section III introduces the
shortcoming of a literature survey. Section IV
introduces the review on improvement of power
system stability by placement and coordination of
FACTS controllers in an integrated power system
networks. Section V presents the results and
discussion of the paper. Section VI presents the
conclusions of the paper.

2. MATHEMATICAL MODELING OF AN
INTGRATED POWER SYSTEM
NETWORKS FOR ENHANCEMENT OF
POWER SYSTEM STABILITY
VIEWPOINT

Safe operation of electric power system is largely
related to its stability which depends of the ability
in making all generators supplying the network
rotate synchronously despite faults and other
contingencies. Stability of general dynamical
systems and more specific definitions for power
systems are introduced in the chapter. Dynamical
phenomena in power systems along with main
causes of in-stability and their underlying
phenomena are briefly described.

Electric power systems are constituted by the
interconnection of a huge number of different
components. They can therefore be considered
among the most complex systems to be planned
and safely operated. This complexity arises as a
consequence of the large amount of devices
contemporaneously in operation, each one with its
own internal dynamics, that however interact with
each other, giving rise to a complex collective
behavior. The wide geographic extension of
electric power systems that can span entire
countries and even continents, adds even greater
complexity to issues connected to their analysis
and control.
During their operation power systems undergo a
large number of disturbances, some of them
occurring continually, such as modifications in
load demands, while others are less common but
nonetheless can potentially be very dangerous,
such as faults and structural changes like tripping
of circuit breaker. From a practical viewpoint such
disturbances are usually classified as either small
or large, respectively, depending on the effects they
have on system behavior. Just like any other
dynamical system, the most basic requirement
related to power system secure operation is
therefore its stability.
Although several mathematical definitions have
been proposed for generic dynamical systems, and
most of them can be usefully applied to power
systems too, the need for more practical definitions
have led joint IEEE/CIGRE Task Forces to propose
commonly agreed definitions [10,16]. Quoting
from [10]:

"Power system stability is the ability of an electric
power system, for a given initial operating
condition, to regain a state of operating
equilibrium after being subjected to a physical
disturbance, with most system variables bounded
so that practically the entire system remains
intact."

Under very general assumptions the dynamics of
power systems can be described by a switched set
of coupled algebraic and ordinary differential
equations of the form [6]:
( , , )
i
x f x y t

=
(1)
{ }
1
0 ( , , ), ,......,
i k
g x y t i e e =
(2)
The index i spans over a discrete set of possible
events that make the system change its intrinsic
dynamics, at specified time instants. State variables
x are not allowed to change instantaneously
following an event, while algebraic variables y,
which are defined by equation (2) as implicit
function of the state variables x, can undergo
discontinuities. Systems of this kind fall into the
wide category of hybrid systems, i.e. systems in
which continuous dynamics co-exists with discrete
events. A more detailed description of such hybrid
systems along with a more formal mathematical
framework suitable for their application to the
description of power systems is presented in [17].
Examples of discrete events that can trigger a
structural change in system's dynamics are faults,
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

42


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
tripping or reclosure of a transmission line, load
shedding and under load tap changer action.
Due to the explicit dependence on time of right-
hand sides of equations (1-2) the system is said to
be non-autonomous.
In the foregoing discussion it is assumed that the
hypotheses of the implicit function theorem are
satisfied. In particular the Jacobian of g with
respect to y is supposed to verify:
( , )
det 0
g x y
y

(3)
which guarantees that there exist a function h(x)
such that the algebraic variables can be expressed
as y = h(x), therefore the differential-algebraic
equations (DAE) (1)-(2) can be replaced by:
( , ( )) x f x h x

=
(4)
A typical power system stability study considers
the system to be in a pre-disturbance steady state,
mathematically described by [18]:
prefault
x x

=
(5)
0 ( , , )
prefault
f x y t =
(6)
0 ( , , ),
prefault fault
g x y t t t =
(7)
where
prefault
x

is the pre-fault equilibrium point,

and
fault
t is the time instant when fault happens.
During the fault, most often a short circuit at some
network location, system's dynamics are described
by:
0 ( , , )
fault
f x y t =
(8)
0 ( , , ),
fault fault fault cl
g x y t t t t t = +
(9)
where
cl
t is the fault clearing time. Studying
system's stability is thus the question of whether
post-fault state variables reach a new acceptable
equilibrium point or not. The post-fault equilibrium
point
postfault
x

can either be the same as pre-fault

equilibrium or differ from it. Analogously, post-
fault dynamics can either be the same as pre-fault
dynamics, in which case
( ) ( )
postfault prefault
f x f x = or differ from it, i.e.

( ) ( )
postfault prefault
f x f x , depending on the
event of structural changes following the
intervention of protective equipment, like line
tripping or load shedding. The aforementioned
definition from does not explicitly mention
equilibrium points in order to allow for the
possibility that satisfactory operation can also be
attained while some state variables remain on a
limit cycle, thus never reaching a true equilibrium
point, but still remaining limited within an
acceptable region. This possibility is however not
commonly encountered in actual power system
operation, since small parameter variations can
either transform stable limit cycles into unstable
ones or into stable equilibrium points.

3. ANALYSIS OF POWER SYSTEM
STABILITY IN AN INTEGRATED
POWER SYSTEM NETWORKS BY
USING LYAPUNOVS STABILITY
THEORY

A. Mathematical Definitions:

For a given dynamical system described by the set
of first order ordinary differential equations
( ) x f x

= , the following definition holds:

Equilibrium point: If:
( ) ( ) ,
o o
x t x x t x t t

= =
(10)
than the state x

is said to be an equilibrium point.

Which means that the system is in an equilibrium
state if once x(t) is equal to x

it remains
( ) x t x

= for all subsequent time. From this

condition it follows that:
x

is an equilibrium point ( ) 0 f x

=
(11)
The definitions of stability for an equilibrium point
of the generic system ( ) x f x

= can be formalised
using the classical definition by Lyapunovs [18,
19, 20]:

Stability: The equilibrium point x = 0 is said to be
stable if:
0, , ( , ) :
o o
t t t
( , ) ( ) ,
o o o
x t x t t t (12)

Also figures 1 explain the definitions of stability.

International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

43


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC



Fig. 1. Illustration of the definition of stability.

Roughly stated, the definition implies that
trajectories initiating sufficiently close to the
equilibrium point will eventually remain in its
neighborhood. If ( , )
o
t can be chose
independent of
o
t uniform stability holds
according to the following definition:

Uniform stability: The equilibrium point x = 0 is
said to be uniformly stable if:
0, 0, ( ) :
o
t
( ) ( ) ,
o o
x x t t t
(13)
Also figure 2 explain the definitions of uniform
asymptotic stability.



Fig. 2. Illustration of the definition of uniform
asymptotic stability.

Instability: The equilibrium point x = 0 is said to
be unstable if it is not stable:
The following definition of asymptotic stability
entails the convergence of system's trajectories
towards the equilibrium point:

Asymptotic Stability: The equilibrium point x = 0
is said to be asymptotically stable if, in addition to
being stable:
0, ( ) :
o o
t t
( ) lim ( ) 0
o o
t
x t x t

=
(14)

Also figure 3 and 4 explain the definitions of
asymptotic stability and exponential stability
respectively.



Fig. 3. Illustration of the definition of asymptotic
stability.




Fig. 5. Illustration of the definition of exponential
stability.

Therefore in the case of asymptotic stability,
systems trajectories initiating sufficiently close to
the equilibrium point will eventually converge to it.
All definitions have been given with respect to the
equilibrium point x = 0.Equilibria others than the
origin can be analogously analysed after a suitable
coordinate transformation which translates the
origin into the equilibrium point of interest [18].

B. Stability Criteria:

Stability analysis of nonlinear systems is largely
based on the use of the two stability criteria firstly
introduced by A. M. Lyapunov in the late 19th
century [21].The first of them relates the local
stability of the equilibrium point of a nonlinear
system to the much more easily tractable stability
of its linear approximation. The second method of
Lyapunov, also known as the Lyapunov's direct
method, is based on the use of an energy function.
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

44


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
Since it will be used in subsequent analysis is
presented in the various open literatures.

1) Lyapunov's Linearization Method:

It is well known that for the linear system:
,
n n
x Ax A

=
(15)
(0)
o
x x =
The time evolution of state variables, in case A has
distinct eigen values is given by:
1
( )
i
n
t
i i o
i
x t x e

=
=

(16)
where:

i
is the (possibly complex) i-th eigenvalue of
the state matrix A.

i
is the right eigenvector of the state matrix A
corresponding to the i-th eigenvalue
i
.

i
is the left eigenvector of the state matrix A
corresponding to the i-th eigenvalue
i
.

From equation (16) it is easily derived that the
origin is:

Stable: if none of the eigen-values has positive real
parts;
Asymptotically stable: if all eigen-values have
negative real parts;
Unstable: if at least one eigenvalue has positive
real part;

The Lyapunov's first method is a straightforward
extension of this criterion to general nonlinear
systems, based on the fact that, assuming f (x)
continuously differentiable:

. .
( ),
h o t
x x
f
x x f x x x x
x

=

= + =

(17)
where
. . h o t
f denotes higher order terms. The
system:
,
x x
f
x J x J
x

=

= =

(18)
is called the linearization of the original nonlinear
system. The relationship between the actual
nonlinear system and its linearization is
summarised in the following:

Theorem Lyapunov's linearization method:

If all eigen-values of J have negative real
parts than the equilibrium point x

of the
actual nonlinear system is asymptotically
stable.
If at least one eigenvalue of J has positive real
part than the equilibrium point x

of the
actual nonlinear system is unstable.
If there exists at least one eigenvalue of J with
zero real part, than, from first order analysis,
nothing can be said on stability of the
equilibrium point x

of the actual nonlinear

system.

Differently from the linear case, nonlinear systems
with eigen-values on the imaginary jw axis can
either be stable, even asymptotically, or unstable.
In this case analysis of higher order terms, which
affect the so called center manifold, is necessary to
draw conclusions about the stability of the
equilibrium point [19, 20].

4. DEFINITIONS, CLASSIFICATIONS,
AND DYNAMIC PHENOMENA
REGARDING WITH POWER SYSTEM
STABILITY


In this section, we provide a formal definition of
power system stability. The intent is to provide a
physically based definition which, while
conforming to definitions from system theory, is
easily understood and readily applied by power
system engineering practitioners.

A. Proposed Definition of Power System Stability
in Power Systems:

The proposed definitions of power system stability
given in open literatures as follows:

Power system stability is the ability of an electric
power system, for a given initial operating
condition, to regain a state of operating
equilibrium after being subjected to a physical
disturbance, with most system variables bounded
so that practically the entire system remains
intact.

International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

45


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
B. Classification of Power System Stability in
Power System Networks:

Power system stability is essentially a single
problem; however, the various forms of
instabilities that a power system may undergo
cannot be properly understood and effectively dealt
with by treating it as such. Because of high
dimensionality and complexity of stability
problems, it helps to make simplifying assumptions
to analyze specific types of problems using an
appropriate degree of detail of system
representation and appropriate analytical
techniques. Analysis of stability, including
identifying key factors that contribute to instability
and devising methods of improving stable
operation, is greatly facilitated by classification of
stability into appropriate categories [10].
Classification, therefore, is essential for meaningful
practical analysis and resolution of power system
stability problems.

The classification of power system stability
proposed here is
based on the following considerations [10]:

The physical nature of the resulting mode of
instability as indicated by the main system
variable in which instability can be observed.
The size of the disturbance considered which
influences the method of calculation and
prediction of stability.
The devices, processes, and the time span that
must be taken into consideration in order to
assess stability.
The appropriate method of calculation and
prediction of stability.

Fig. 1 gives the overall picture of the power system
stability problem, identifying its categories and
subcategories. The following are descriptions of
the corresponding forms of stability phenomena.



Fig. 1. Classification of power system stability in
power system environments.

1. Rotor Angle Stability of Power Systems:

Rotor angle stability refers to the ability of
synchronous machines of an interconnected power
system to remain in synchronism after being
subjected to a disturbance. It depends on the ability
to maintain/restore equilibrium between
electromagnetic torque and mechanical torque of
each synchronous machine in the system.
Instability that may result occurs in the form of
increasing angular swings of some generators
leading to their loss of synchronism with other
generators.
The rotor angle stability problem involves the
study of the electromechanical oscillations inherent
in power systems. A fundamental factor in this
problem is the manner in which the power outputs
of synchronous machines vary as their rotor angles
change. Under steady-state conditions, there is
equilibrium between the input mechanical torque
and the output electromagnetic torque of each
generator, and the speed remains constant. If the
system is perturbed, this equilibrium is upset,
resulting in acceleration or deceleration of the
rotors of the machines according to the laws of
motion of a rotating body. If one generator
temporarily runs faster than another, the angular
position of its rotor relative to that of the slower
machine will advance. The resulting angular
difference transfers part of the load from the slow
machine to the fast machine, depending on the
power-angle relationship. This tends to reduce the
speed difference and hence the angular separation.
The power-angle relationship is highly nonlinear.
Beyond a certain limit, an increase in angular
separation is accompanied by a decrease in power
transfer such that the angular separation is
increased further. Instability results if the system
cannot absorb the kinetic energy corresponding to
these rotor speed differences. For any given
situation, the stability of the system depends on
whether or not the deviations in angular positions
of the rotors result in sufficient restoring torques
[10]. Loss of synchronism can occur between one
machine and the rest of the system, or between
groups of machines, with synchronism maintained
within each group after separating from each other.

The change in electromagnetic torque of a
synchronous machine following a perturbation can
be resolved into two components:

International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

46


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
Damping torque component, in phase with the
speed deviation.

Synchronizing torque component, in phase
with rotor angle deviation.
Damping torque component, in phase with the
speed deviation.

System stability depends on the existence of both
components
of torque for each of the synchronous machines.
Lack of sufficient synchronizing torque results in a
periodic or non-oscillatory instability, whereas
lack of damping torque results in oscillatory
instability.

For convenience in analysis and for gaining useful
insight into
the nature of stability problems, it is useful to
characterize rotor angle stability in terms of the
following two subcategories:

Small-disturbance (or small-signal) rotor
angle stability: is concerned with the ability of
the power system to maintain synchronism
under small disturbances. The disturbances are
considered to be sufficiently small that
linearization of system equations is
permissible for purposes of analysis [10].

Small-disturbance stability depends on the
initial operating state of the system. Instability
that may result can be of two forms: i) increase
in rotor angle through a non oscillatory or a
periodic mode due to lack of synchronizing
torque, or ii) rotor oscillations of increasing
amplitude due to lack of sufficient damping
torque.
In todays power systems, small-disturbance
rotor angle stability problem is usually
associated with in sufficient damping of
oscillations. The periodic instability problem
has been largely eliminated by use of
continuously acting generator voltage
regulators; however, this problem can still
occur when generators operate with constant
excitation when subjected to the actions of
excitation limiters (field current limiters).
Small-disturbance rotor angle stability
problems maybe either local or global in
nature. Local problems involve a small part of
the power system, and are usually associated
with rotor angle oscillations of a single power
plant against the rest of the power system.
Such oscillations are called local plant mode
oscillations. stability (damping) of these
oscillations depends on the strength of the
transmission system as seen by the power
plant, generator excitation control systems and
plant output [10].
Global problems are caused by interactions
among large groups of generators and have
widespread effects. They involve oscillations
of a group of generators in one area swinging
against a group of generators in another area.
Such oscillations are called inter-area mode
oscillations. Their characteristics are very
complex and significantly differ from those of
local plant mode oscillations. Load
characteristics, in particular, have a major
effect on the stability of inter-area modes [10].
The time frame of interest in small-disturbance
stability studies is on the order of 10 to 20
seconds following a disturbance.

Large-disturbance rotor angle stability or
transient stability: as it is commonly referred
to, is concerned with the ability of the power
system to maintain synchronism when
subjected to a severe disturbance, such as a
short circulation a transmission line. The
resulting system response involves large
excursions of generator rotor angles and is
influenced by the nonlinear power-angle
relationship.
Transient stability depends on both the initial
operating state of the system and the severity
of the disturbance. Instability is usually in the
form of a periodic angular separation due to
insufficient synchronizing torque, manifesting
as first swing instability. However, in large
power systems, transient instability may not
always occur as first swing instability
associated with a single mode; it could be a
result of superposition of a slow inter-area
swing mode and a local-plant swing mode
causing a large excursion of rotor angle
beyond the first swing [10]. It could also be a
result of nonlinear effects affecting a single
mode causing instability beyond the first
swing.
The time frame of interest in transient stability
studies is usually 3 to 5 seconds following the
disturbance. It may extend to 1020 seconds
for very large systems with dominant inter-
area swings.

As identified in Fig. 1, small-disturbance rotor
angle stability as well as transient stability are
categorized as short term phenomena.
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

47


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC

The term dynamic stability also appears in the
literature as a class of rotor angle stability.
However, it has been used to denote different
phenomena by different authors. In the North
American literature, it has been used mostly to
denote small-disturbance stability in the presence
of automatic controls (particularly, the generation
excitation controls) as distinct from the classical
steady-state stability with no generator controls
[10].
Dynamic phenomena related to rotor angle
stability, which is the main subject of the present
thesis, are typically confined in a time frame
ranging from tenth of to few tens of seconds.
Torsional transients in generators turbine shafts,
which are associated with time constants in the sub
synchronous range, i.e. tens of millisecond, could
also give rise to instability phenomena which
should be taken into account in several practical
situations.

A properly working power system is operated in
such a way as to constantly maintain a balance
between the powers produced in generators and
that absorbed by the loads. In current power
systems electric power is being produced, almost
totally, in conventional power plants where either a
thermal or an hydraulic source of energy is
transformed into electric energy by means of
synchronous generators. Although this situation
might change in future due to the constant increase
in the amount of distributed generation which is
based on the use of alternative energy sources, i.e.
wind, sun, fuel cells and so on, which are coupled
to the transmission network through power
electronics based converters, the synchronous
generator will remain the main tool for energy
conversion for a longtime to come.

The ability of all synchronous machines,
interconnected through the transmission network,
to maintain a synchronous operation is referred to
as rotor angle stability. Steady state operation is
therefore characterised, for each synchronous
generator, by a state of equilibrium between the
mechanical torque applied by the prime mover
through the turbine shaft and the electric torque
due to the loading of the generator. If an unbalance
arises as a consequence of a disturbance, the state
of equilibrium is perturbed and some generators
rotors may accelerate while others may decelerate.
The behavior of the system after the perturbation
largely depends upon the amplitude of the
disturbance. Actual systems must operate in an
equilibrium in which they should be able to
withstand at least small disturbances. This is
possible due to the nature of power-angle
relationship for a synchronous generator, which
states that the electric power and hence electric
torque increases sinusoidally as the angle with
respect to the rest of the system increases. Due to
the nonlinear nature of the power-angle
relationship, a large perturbation and hence a large
displacement of a machine angle against the rest of
the system, will eventually result in a decrease in
the electrical power injected into the network
which will lead to a further unbalance between
mechanical torque and electrical torque and thus
produce an increase in angular separation. A
classical classification of rotor angle related
stability analysis is roughly based on the magnitude
of the disturbance.

2. Voltage Stability of power Systems:

Voltage stability refers to the ability of a power
system to maintain steady voltages at all buses in
the system after being subjected to a disturbance
from a given initial operating condition. It depends
on the ability to maintain/restore equilibrium
between load demand and load supply from the
power system. Instability that may result occurs in
the form of a progressive fall or rise of voltages of
some buses. A possible outcome of voltage
instability is loss of load in an area, or tripping of
transmission lines and other elements by their
protective systems leading to cascading outages.
Loss of synchronism of some generators may result
from these outages or from operating conditions
that violate field current limit [22]-[23].
Progressive drop in bus voltages can also be
associated with rotor angle instability. For
example, the loss of synchronism of machines as
rotor angles between two groups of machines
approach 180 causes rapid drop in voltages at
intermediate points in the network close to the
electrical center [10]. Normally, protective systems
operate to separate the two groups of machines and
the voltages recover to levels depending on the
post-separation conditions. If, however, the system
is not so separated, the voltages near the electrical
center rapidly oscillate between high and low
values as a result of repeated pole slips between
the two groups of machines. In contrast, the type of
sustained fall of voltage that is related to voltage
instability involves loads and may occur where
rotor angle stability is not an issue.

International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

48


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
The term voltage collapse is also often used. It is
the process by which the sequence of events
accompanying voltage instability leads to a
blackout or abnormally low voltages in a
significant part of the power system [10], [16].
Stable (steady) operation at low voltage may
continue after transformer tap changers reach their
boost limit, with intentional and/or unintentional
tripping of some load. Remaining load tends to be
voltage sensitive, and the connected demand at
normal voltage is not met.
The driving force for voltage instability is usually
the loads; in response to a disturbance, power
consumed by the loads tends
to be restored by the action of motor slip
adjustment, distribution voltage regulators, tap-
changing transformers, and thermostats. Restored
loads increase the stress on the high voltage
network by increasing the reactive power
consumption and causing further voltage reduction.
A run-down situation causing voltage instability
occurs when load dynamics attempt to restore
power consumption beyond the capability of the
transmission network and the connected generation
[10], [23][24].
A major factor contributing to voltage instability is
the voltage drop that occurs when active and
reactive power flow through inductive reactances
of the transmission network; this limits the
capability of the transmission network for power
transfer and voltage support. The power transfer
and voltage support are further limited when some
of the generators hit their field or armature current
time-overload capability limits. Voltage stability is
threatened when a disturbance increases the
reactive power demand beyond the sustainable
capacity of the available reactive power resources.

While the most common form of voltage instability
is the progressive drop of bus voltages, the risk of
overvoltage instability also exists and has been
experienced at least on one system [25]. It is
caused by a capacitive behavior of the network
(EHV transmission lines operating below surge
impedance loading) as well as by under excitation
limiters preventing generators and/or synchronous
compensators from absorbing the excess reactive
power. In this case, the instability is associated
with the inability of the combined generation and
transmission system to operate below some load
level. In their attempt to restore this load power,
transformer tap changers cause long-term voltage
instability.

Voltage stability problems may also be
experienced at the terminals of HVDC links used
for either long distance or back-to-back
applications [26], [27]. They are usually associated
with HVDC links connected to weak ac systems
and may occur at rectifier or inverter stations, and
are associated with the unfavorable reactive power
load characteristics of the converters. The HVDC
link control strategies have a very significant
influence on such problems, since the active and
reactive power at the ac/dc junction are determined
by the controls. If the resulting loading on the ac
transmission stresses it beyond its capability,
voltage instability occurs. Such a phenomenon is
relatively fast with the time frame of interest being
in the order of one second or less. Voltage
instability may also be associated with converter
transformer tap-changer controls, which is a
considerably slower phenomenon [27].Recent
developments in HVDC technology (voltage
source converters and capacitor commutated
converters) have significantly increased the limits
for stable operation of HVDC links in weak
systems as compared with the limits for line
commutated converters.

One form of voltage stability problem that results
in uncontrolled over voltages is the self-excitation
of synchronous machines. This can arise if the
capacitive load of a synchronous machine is too
large. Examples of excessive capacitive loads that
can initiate self-excitation are open ended high
voltage lines and shunt capacitors and filter banks
from HVDC stations [28].The over voltages that
result when generator load changes to capacitive
are characterized by an instantaneous rise at the
instant of change followed by a more gradual rise.
This latter rise depends on the relation between the
capacitive load component and machine reactances
together with the excitation system of the
synchronous machine. Negative field current
capability of the exciter is a feature that has a
positive influence on the limits for self-excitation.

As in the case of rotor angle stability, it is useful to
classify voltage stability into the following
subcategories:
Voltage instability in the power system occurs due
to incapability of power system to supply loads
under disturbances. Disturbances may be either
large or small in nature. Accordingly, voltage
stability can be classified in following two
subcategories:

International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

49


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
Large-disturbance voltage stability: refers to
the systems ability to maintain steady
voltages following large disturbances such as
system faults, loss of generation, or circuit
contingencies. This ability is determined by
the system and load characteristics, and the
interactions of both continuous and discrete
controls and protections. Determination of
large-disturbance voltage stability requires
the examination of the nonlinear response of
the power system over a period of time
sufficient to capture the performance and
interactions of such devices as motors, under
load transformer tap changers, and generator
field-current limiters. The study period of
interest may extend from a few seconds to
tens of minutes.

Small- disturbance voltage stability: refers to
the systems ability to maintain steady
voltages when subjected to small
perturbations such as incremental changes in
system load. This form of stability is
influenced by the characteristics of loads,
continuous controls, and discrete controls at a
given instant of time. This concept is useful
in determining, at any instant, how the system
voltages will respond to small system
changes. With appropriate assumptions,
system equations can be linearized for
analysis thereby allowing computation of
valuable sensitivity information useful in
identifying factors influencing stability. This
linearization, however, cannot account for
nonlinear effects such as tap changer controls
(dead bands, discrete tap steps, and time
delays). Therefore, a combination of linear
and nonlinear analyzes is used in a
complementary manner [29].

As noted above, the time frame of interest for
voltage stability problems may vary from a few
seconds to tens of minutes. Therefore, voltage
stability may be either a short-term or a long-term
phenomenon as identified in Figure 1.

Short-term voltage stability: involves
dynamics of fast acting load components such
as induction motors, electronically controlled
loads, and HVDC converters. The study
period of interest is in the order of several
seconds, and analysis requires solution of
appropriate system differential equations; this
is similar to analysis of rotor angle stability.
Dynamic modeling of loads is often essential.
In contrast to angle stability, short circuits
near loads are important. It is recommended
that the term transient voltage stability not be
used.

Long-term voltage stability: involves slower
acting equipment such as tap-changing
transformers, thermostatically controlled
loads, and generator current limiters. The
study period of interest may extend to several
or many minutes, and long-term simulations
are required for analysis of system dynamic
performance [30], [31]. Stability is usually
determined by the resulting outage of
equipment, rather than the severity of the
initial disturbance. Instability is due to the
loss of long-term equilibrium (e.g., when
loads try to restore their power beyond the
capability of the transmission network and
connected generation), post-disturbance
steady-state operating point being small-
disturbance unstable, or a lack of attraction
toward the stable post-disturbance
equilibrium (e.g., when a remedial action is
applied too late) [23]. The disturbance could
also be a sustained load buildup (e.g.,
morning load increase). In many cases, static
analysis [30] can be used to estimate stability
margins, identify factors influencing stability,
and screen a wide range of system conditions
and a large number of scenarios. Where
timing of control actions is important, this
should be complemented by quasi-steady-
state time-domain simulations [23].

3. Frequency Stability of Power Systems:

Frequency stability refers to the ability of a power
system to maintain steady frequency following a
severe system upset resulting in a significant
imbalance between generation and load. It depends
on the ability to maintain/restore equilibrium
between system generation and load, with
minimum unintentional loss of load. Instability that
may result occurs in the form of sustained
frequency swings leading to tripping of generating
units and/or loads.

Severe system upsets generally result in large
excursions of frequency, power flows, voltage, and
other system variables, thereby invoking the
actions of processes, controls, and protections that
are not modeled in conventional transient stability
or voltage stability studies. These processes may be
very slow, such as boiler dynamics, or only
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

50


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
triggered for extreme system conditions, such as
volts/Hertz protection tripping generators. In large
interconnected power systems, this type of
situation is most commonly associated with
conditions following splitting of systems into
islands. Stability in this case is a question of
whether or not each island will reach a state of
operating equilibrium with minimal unintentional
loss of load. It is determined by the overall
response of the island as evidenced by its mean
frequency, rather than relative motion of machines.
Generally, frequency stability problems are
associated with inadequacies in equipment
responses, poor coordination of control and
protection equipment, or insufficient generation
reserve. Examples of such problems are reported in
references [32]. In isolated island systems,
frequency stability could be of concern for any
disturbance causing a relatively significant loss of
load or generation [33].

During frequency excursions, the characteristic
times of the processes and devices that are
activated will range from fraction of seconds,
corresponding to the response of devices such a
sunder frequency load shedding and generator
controls and protections, to several minutes,
corresponding to the response of devices such as
prime mover energy supply systems and load
voltage regulators. Therefore, as identified in Fig.
1, frequency stability may be a short-term
phenomenon or a long-term phenomenon. An
example of short-term frequency instability is the
formation of an under generated island with
insufficient under frequency load shedding such
that frequency decays rapidly causing blackout of
the island within a few seconds . On the other
hand, more complex situations in which frequency
instability is caused by steam turbine over speed
controls or boiler/reactor protection and controls
are longer-term phenomena with the time frame of
interest ranging from tens of seconds to several
minutes [32].

During frequency excursions, voltage magnitudes
may change significantly, especially for islanding
conditions with under frequency load shedding that
unloads the system. Voltage magnitude changes,
which may be higher in percentage than frequency
changes, affect the load-generation imbalance.
High voltage may cause undesirable generator
tripping by poorly designed or coordinated loss of
excitation relays or volts/Hertz relays. In an
overloaded system, low voltage may cause
undesirable operation of impedance relays.

We have classified power system stability for
convenience in
Identifying causes of instability, applying suitable
analysis tools, and developing corrective measures.
In any given situation, however, any one form of
instability may not occur in its pure form. This is
particularly true in highly stressed systems and for
cascading events; as systems fail one form of
instability may ultimately lead to another form.
However, distinguishing between different forms is
important for understanding the underlying causes
of the problem in order to develop appropriate
design and operating procedures.
While classification of power system stability is an
effective and convenient means to deal with the
complexities of the problem, the overall stability of
the system should always be kept in mind.
Solutions to stability problems of one category
should not be at the expense of another. It is
essential to look at all aspects of the stability
phenomenon and at each aspect from more than
one viewpoint.

4. Transient Stability of Power Systems:

Among the large disturbances which could affect
the transient stability of the system, short circuits
and possibly subsequent tripping of the faulted
transmission line are the most common. Instability
which may a rises from these severe disturbances is
often characterized by a constantly increasing
angular separation without any periodicity. This
kind of behavior is often referred to as first swing
instability.
As it is the case in small signal stability non
oscillatory unstable behavior was largely
eliminated by the widespread use of fast acting
regulators. Most common instability behavior is
therefore in the form of large oscillations with
increasing amplitude among generators of different
areas.
In actual power system the classification based on
the nature of the disturbance could result quite
artificial. Some real occurrences of system
instability, although caused by large disturbances,
i.e. generator tripping, manifested as small signal
stability problem, i.e. oscillations of growing
amplitude.

5. Dynamic Stability of Power Systems:

One of the most important parts of power system
stability is dynamic stability. Controlling devices to
improve dynamic stability of power systems are
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

51


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
called power systems tabilizers (PSS) and FACTS
controllers. The problem is to determine the proper
place of stabilizers next to generators which needs
those stabilizers. Changes and expansions of the
network may cause movement of stabilizers. One
solution of this problem is collecting the stabilizers
in one place of network and connecting them to
network through a channel. In the open literatures,
we use internet as a vast and easy-accessible
network instead of connecting channel which we
try to settle the limitations by using two new
methods.

6. Damping of Power System Oscillation:

As described in previous sections, an oscillation of
synchronous generator rotor with respect to
network reference is usually in the range of 0:2-
2Hz. This is, however, a result of the simplifying
assumptions used in generator's rotor
representation, which is considered to be
constituted by a single rigid mass. The rotor of an
actual generating unit is a very complex
mechanical system obtained by the interconnection
of several shaft sections. This structure has
therefore several torsional modes of vibration, with
each section oscillating against the others [10].
Such oscillations can appear at both sub-
synchronous. And super synchronous frequencies,
ranging from few tens to few hundreds of Hz.
Potentially dangerous undamped sub-synchronous
oscillations appear as a result of the interaction of
torsional modes with synchronous generators'
controllers or series capacitor compensated
transmission lines. In the latter case, adverse
interactions result in the so-called sub-synchronous
resonance (SSR) phenomena [34]-[35].

6. Dynamical phenomena in power systems:

Due to the large amount of different devices
contemporaneously acting in electric power
systems, they are affected by several complex
dynamical phenomena. In order to better
understand the causes of each phenomenon and
make the system working properly, it is of great
importance to analyze the range of dynamics which
have a role in system's behavior. A classification of
dynamical phenomena could therefore result very
useful for analysis purposes. The need for
classification arises from the necessity to divide
such a complex problem as system stability into
sub-problems, utilizing simplifying assumptions
with the aim of rendering each sub-problem more
amenable to mathematical and/or numerical
analysis. Simplifications, on the other hand, should
be carefully made in order to maintain a sufficient
degree of approximation in system's response.
Figure 3 show that a schematic drawing which
illustrates a commonly used time-scale
decomposition of dynamical phenomena in power
systems [36]-[37].



Figure 3: A schematic drawing illustrating time-
scale of dynamical phenomena in power systems

A first rough classification can be made separating
slow from fast phenomena, since very fast
transients such as those due to lightning or
switching of circuit breakers die out very quickly,
i.e.in the order of
4
10

s compared to slow
phenomena such as load restoration or
secondary/tertiary regulation involved in voltage or
frequency stability evaluation which require study
periods spanning several minutes or even hours.
A word of caution is necessary, because although
classifications may result very useful, many
phenomena are so intertwined that in some
situations it is difficult to attribute the cause of a
particular failure to a single phenomenon.





5. CONCEPTS AND RELATIONSHIP
BETWEEN RELIABILITY, SECURITY,
AND POWER SYSTEM STABILITY IN
POWER SYSTEM NETWORKS

In this section, we discuss the relationship between
the concepts of power system reliability, security,
and stability. We will also briefly describe how
these terms have been defined and used in practice.

A. Conceptual Relationship [38], [39]

International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

52


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
Reliability of a power system: refers to the
probability of its satisfactory operation over
the long run. It denotes the ability to supply
adequate electric service on a nearly
continuous basis, with few interruptions over
an extended time period.
Security of a power system: refers to the
degree of risk in its ability to survive imminent
disturbances (contingencies) without
interruption of customer service. It relates to
robustness of the system to imminent
disturbances and, hence, depends on the
system operating condition as well as the
contingent probability of disturbances.
Stability of a power system: as discussed in
Section II, refers to the continuance of intact
operation following a disturbance. It depends
on the operating condition and the nature of
the physical disturbance.

The following are the essential differences among
the three aspects of power system performance:
Reliability is the overall objective in power
system design and operation. To be reliable,
the power system must be secure most of the
time. To be secure, the system must be stable
but must also be secure against other
contingencies that would not be classified as
stability problems e.g., damage to equipment
such as an explosive failure of a cable, fall of
transmission towers due to ice loading or
sabotage. As well, a system may be stable
following a contingency, yet insecure due to
post-fault system conditions resulting in
equipment overloads or voltage violations.
System security may be further distinguished
from stability in terms of the resulting
consequences. For example, two systems may
both be stable with equal stability margins,
but one may be relatively more secure
because the consequences of instability are
less severe.
Security and stability are time-varying
attributes which can be judged by studying
the performance of the power system under a
particular set of conditions. Reliability, on the
other hand, is a function of the time-average
performance of the power system; it can only
be judged by consideration of the systems
behavior over an appreciable period of time.

C. NERC Definition of Reliability [40]

NERC (North American Electric Reliability
Council) defines
power system reliability as follows.

Reliability, in a bulk power electric system, is the
degree to which the performance of the elements of
that system results in power being delivered to
consumers within accepted standards and in the
amount desired. The degree of reliability may be
measured by the frequency, duration, and
magnitude of adverse effects on consumer service.

Reliability can be addressed by considering two
basic functional aspects of the power systems:

Adequacy-he ability of the power system to supply
the aggregate electric power and energy
requirements of the customer at all times, taking
into account scheduled and unscheduled outages of
system components.

Security-the ability of the power system to
withstand sudden disturbances such as electric
short circuits or non anticipated loss of system
components.

The above definitions also appear in several IEEE
and CIGRE Working Group/Task Force documents
[41], [42].

Other alternative forms of definition of power
system security
have been proposed in the literature. For example,
in reference
[43], security is defined in terms of satisfying a set
of inequality constraints over a subset of the
possible disturbances called the next contingency
set.

6. SHORTCOMING OF LITERATUTERE
SURVEY

One of the major causes of voltage instability is the
reactive power limits of the power systems. The
many literatures have proposed solutions for this
problem, by using suitable location of Flexible AC
Transmission Systems (FACTS) and proper
coordination between FACTS controllers to
improve voltage stability of the power systems.
Hence, improving the systems reactive power
handling capacity via Flexible AC transmission
System (FACTS) device is a remedy for prevention
of voltage instability and hence voltage collapse.
The several literatures are proposed the different
methods/techniques for enhancement of power
system stability by placement of FACTS
controllers, and coordination of FACTS
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

53


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
controllers, one of the shortcomings of such
methods is that they only consider the normal state
of system. However, voltage collapses are mostly
initiated by a disturbance (e.g. the outage of a line,
or fault on system or generation unit, or increased
in load demand). So to locate FACTS devices,
consideration of contingency conditions is more
important than consideration of normal state of
system and some approaches are proposed to locate
of FACTS devices with consideration of
contingencies, too presented in the many
literatures.

7. IMPROVEMENT OF POWER SYSTEM
STABILITY BY PLACEMENT AND
COORDINATION OF FACTS
CONTROLLERS IN AN INTEGRATED
POWER SYSTEM NETWORKS

A. By Placement of FACTS Controllers in an
integrated power system networks

1. Small Signal Voltage Stability of an
integrated power system networks:

While small signal and transient instability
phenomena are mostly related to synchronous
generators and their control, voltage stability is
mostly related to network and loads. Voltage
stability can be defined as the ability of a power
system to maintain voltage magnitude at all buses
within acceptable limits after the system has
experienced a disturbance. The loss of equilibrium
between load demand and load supply is the main
cause of voltage instability, which results in
unacceptable low voltages across the network [44].
Voltage instability phenomena often appear as a
sudden decrease of voltage therefore called voltage
collapse. Many loads supplied by a power system
are controlled in such a way as to have some sort of
restorative behavior. Large industrial motors
drives, thermostatically controlled heating loads,
tap-changing transformers are examples of loads
that respond to disturbances trying to restore their
power consumption. This restorative action has the
effect to further increase the stress on an already
stressed system. In particular reactive power
demand could increase beyond the available
capability, leading to the intervention of limiting
protections such as over excitation limiters in
synchronous generators.

A new method called the Extended Voltage
Phasors Approach (EVPA) has been suggested for
placement of FACTS controllers in power systems
for identifying the most critical segments/bus in
power system from the voltage stability view point
in [45]. A residues based approach has been
proposed for allocation of FACTS controllers in
power system to enhance the system stability [46]-
[47]. A sensitivity based approach has been
proposed for placement of FACTS controllers in
open power markets to reduce the flows in heavily
loaded lines, resulting in an increased loadability,
low system loss, improved voltage stability of the
network, reduced cost of production and fulfilled
contractual requirement by controlling the power
flows in the network in [48]-[49]. A sensitivity
based approach called Bus Static Participation
Factor (BSPF) has been proposed for determine the
optimal location of static VAR compensator (SVC)
for voltage security enhancement in [50]. In [51], a
sensitivity analysis method has been proposed for
determine the optimal placement of static VAR
compensator (SVC) for voltage security
enhancement in Algerian Distribution System.
Reference [52], presents a sensitivity based
approach has been proposed for optimal placement
of UPFC to enhance voltage stability margin under
contingencies. In [53], a sensitivity based
technique used for determine the minimum amount
of shunt reactive power (VAr) support which
indirectly maximizes the real power transfer before
voltage collapse is encountered. Sensitivity
information that identifies weak buses is also
available for locating effective VAr injection sites.
A new approach based on sensitivity indices has
been used for the optimal placement of various
types of FACTS controllers such as TCSC,
TCPAR and SVC in order to minimize total system
reactive power loss and hence maximizing the
static voltage stability in [54]. A mixed integer
optimization programming algorithm has been
proposed for allocation of FACTS controllers in
power system for security enhancement against
voltage collapse and corrective controls, where the
control effects by the devices to be installed are
evaluated together with the other controls such as
load shedding in contingencies to compute an
optimal VAR planning [55]. In [56], a mixed
integer non-linear optimization programming
algorithm is used for determine the type, optimal
number, optimal location of the TCSC for
loadability and voltage stability enhancement in
deregulated electricity markets. Chang and Huang
et al. showed that a hybrid optimization
programming algorithm for optimal placement of
SVC for voltage stability reinforcement [57].
Orfanogianni and Bacher et al. suggested an
optimization-based methodology is used for
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

54


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
identify key locations of TCSC and UPFC include
the nonlinear constraints of voltage limitation, zero
megawatt active power exchange, voltage control,
and reactive power exchange in the ac networks
[58]. A stochastic searching algorithm called as
genetic algorithm has been proposed for optimal
placement of static VAR compensator for
enhancing voltage stability in [59]. Reference [60],
genetic algorithm (GA) and particle swarm
optimization (PSO) has been proposed for optimal
location and parameter setting of UPFC for
enhancing power system security under single
contingencies. References [61], [62], a novel
optimization based methodology such as a
simulated annealing has been proposed for optimal
location of FACTS devices such as TCSC and
SVC in order to relieve congestion in the
transmission line while increasing static security
margin and voltage profile of power system
networks. In [63], the Goal Attainment (GA)
method based on the SA approach is applied to
solving general multi-objective VAR planning
problems by assuming that the Decision Maker
(DM) has goals for each of the objective functions.
The VAR planning problem involves the
determination of location and sizes of new
compensators considering contingencies and
voltage collapse problems in a power system.
Rashed et al. suggested a Genetic Algorithm (GA)
and PSO techniques for optimal location and
parameter setting of TCSC to improve the power
transfer capability, reduce active power losses,
improve stabilities of the power network, and
decrease the cost of power production and to fulfill
the other control requirements by controlling the
power flow in multi-machine power system
network [64].
A Graph Search Algorithm has been addressed for
optimal placement of fixed and switched capacitors
on radial distribution systems to reduce power and
energy losses, increases the available capacity of
the feeders, and improves the feeder voltage profile
[65]. In [66], the theory of the normal forms of
diffeomorphism algorithm has been addressed for
the SVC allocation in multi-machine power system
for power system voltage stability enhancement. In
[67], a knowledge and algorithm based approach is
used to VAR planning in a transmission system.
The VAR planning problem involves the
determination of location and sizes of new
compensators considering contingencies and
voltage collapse problems in a power system. Fang
and Ngan et al. [68] sugested an augmented
Lagrange Multipliers approach for optimal location
of UPFC in power systems to enhances the steady
state performance and significantly increase the
loadability of the system.

Reference [69] discusses the effect of TCSC on the
small signal voltage stability for a simple power
system with an infinitive bus and a dynamic load.
The small signal voltage stability region is derived
for this simple system. The paper has one serious
drawback that infinitive bus is not a good model
for a generator for voltage stability studies since
only the voltage instability caused by insufficient
transfer capability can be examined. It is well
known that the generator field current limiting
action limits the output of the reactive power,
which is essential in the voltage stability analysis.
Canizares and Faur studied the effects of SVC and
TCSC on voltage collapse [70]. In [71], voltage
stability assessment of the system with shunt
compensation devices including shunt capacitors,
SVC and STATCOM is studied and compared in
the IEEE 14-bus test system. In [72], Effects of
STATCOM, SSSC and UPFC on Voltage Stability
is studied. Study of STATCOM and UPFC
Controllers for Voltage Stability Evaluated by
Saddle-Node Bifurcation Analysis is carry out in
[73]. Also In [74], Static Voltage Stability Margin
Enhancement Using STATCOM, TCSC and SSSC
is compared. So far no work has been reported in
open literature for the effects of SVC, STATCOM,
TCSC and UPFC on voltage stability. Reference
[75], considers four FACTS controllers in order to
increase the loadability margin of a power system.
The appropriate representation including the
equations in the DC parts of these FACTS devices
is incorporated in the continuation power flow
(CPF) process in static voltage stability study.
Based on the above observation, an effort made in
this paper is to compare the merits and demerits of
some FACTS devices, namely, SVC, STATCOM,
TCSC and UPFC, in terms of Maximum Loading
Point (MLP) in static voltage stability study. This
leads to a more practical solution in terms of MLP
or voltage stability margin, which may be useful
for utilities to select the most beneficial FACTS
devices among SVC, STATCOM, TCSC and
UPFC.
Kumkratug and Haque [76] demonstrated the
capability of the SSSC to control the line flow and
to improve the power system stability. A control
strategy of an SSSC to enlarge the stability region
has been derive dusing the direct method. The
effectiveness of the SSSC to extend the critical
clearing time has been confirmed though
simulation results on a single machine infinite bus
system. The effectiveness of the STATCOM to
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

55


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
control the power system voltage was presented in
[77]. However, the effectiveness of the STATCOM
to enhance the angle stability has not been
addressed. Hammad [78] presented a fundamental
analysis of theapplication of SVC for enhancing
the power systems stability. Messina and Barocio
[79] studied the nonlinear modal interaction in
stressed power systems with multiple SVC voltage
support. It was observed that SVC controls can
significantly influence nonlinear system behavior
especially under high-stress operating conditions
and increased SVC gains. Rosso et al. [80]
presented a detailed analysis of TCSC control
performance for improving power system stability
with different input signals. Namely, the line active
power and the line current magnitude were
considered. The simulation results demonstrated
that the TCSC damping capability is more effective
with line current input signal.
Interline Power Flow Controller (IPFC) is an
extension of the UPFC, which can be efficiently
used to control the transmission line parameters in
case of interconnected systems
[81]. Enhanced power flow and hence better
stability is ensured by real power exchange
between under utilized and over loaded
transmission lines and by providing the necessary
reactive power support.
In [82], paper presented an application of Single-
input Fuzzy Logic Controller (SFLC) to determine
the control signal of a Static Compensator
(STATCOM) synchronous for improvement of
power system stability. This compensation scheme
is relevant to Flexible AC Transmission systems
(FACTSs) technology which is used worldwide to
improve system dynamic performance. STATCOM
improves the damping of electromechanical
oscillations when used in transmission systems.
The SFLC uses only one input variable which is
called assigned distance. The SFLC has the
advantages of reduced number of rules. Thus,
generation, estimation and tuning of control rules
are much easier while comparing with the existing
conventional Fuzzy Logic Controllers (FLCs). The
proposed control method is applied to control the
AC and DC bus voltage of a STATCOM connected
at a load bus in a Single Machine Infinite Bus
(SMIB) System and also to improve the power
system stability.

2. Transient Stability of an integrated power
system networks:

A structure preserving energy margin sensitivity
based analysis has been addressed for determine
the effectiveness of FACTS devices to improve
transient stability of a power system in [83].
Reference [84], suggested a Trajectory Sensitivity
Analysis (TSA) technique for the evaluation of the
effect of TCSC placement on transient stability.

3. Rotor Angle Stability of an integrated power
system networks:

Reference [85], presented a simple method of
evaluating the first swing stability of a large power
system in the presence of various flexible ac
transmission system (FACTS) devices. First a
unified power flow controller (UPFC) and the
associated transmission line are considered and
represented by an equivalent piecircuit model.
The above model is then carefully interfaced to the
power network to obtain the system reduced
admittance matrix which is needed to generate the
machine swing curves. The above pie circuit model
can also be used to represent other FACTS devices
(SSSC and STATCOM) by selecting appropriate
values of control parameters of the UPFC. The
complex voltage at two end buses of the pie-circuit
model is also evaluated during simulation to
implement various existing control strategies of
FACTS devices and to update the reduced
admittance matrix. The effectiveness of the
proposed method of generating dynamic response
and hence evaluating first swing stability of a
power system in the presence of various FACTS
devices is tested on the ten-machine New England
system and the 20-machine IEEE test system in
this literature.
Chaudhuri et al. [86],[87], demonstrated that the
use of global stabilizing signals for effective
damping of multiple swing modes through single
FACTS device is one of the potential options worth
exploring.
Farsangi et al. [88] presented the minimum
singular value, the right half plane zeros, the
relative gain array, and the Hankel singular values
as indicators to find the stabilizing signals of
FACTS devices for damping inter-area oscillations.
Kulkarni and Padiyar [89] proposed a location
index based on circuit analogy for the series
FACTS controllers. The feedback signals used
were synthesized using local measurements. The
method is validated on two different multi machine
power systems and very important comments have
been highlighted in this work.
Power system stability enhancement [90] via
excitation and FACTS-based stabilizers is
thoroughly investigated in this paper. This study
presents a singular value decomposition-based
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

56


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
approach to assess and measure the controllability
of the poorly damped electromechanical modes by
different control inputs. The design problem of a
power system stabilizer and different FACTS-
based stabilizers is formulated as an optimization
problem. An eigenvalue-based objective function
to increase the system damping and improve the
system response is developed. Then, a real-coded
genetic algorithm is employed to search for optimal
controller parameters. In addition, the damping
characteristics of the proposed schemes are also
evaluated in terms of the damping torque
coefficient with different loading conditions for
better understanding of the coordination problem
requirements. The proposed stabilizers are tested
on a weakly connected power system with different
loading conditions. The damping torque coefficient
analysis, nonlinear simulation results, and
eigenvalue analysis show the effectiveness and
robustness of the proposed control schemes over a
wide range of loading conditions.
In [91], paper presented a new approach to the
implementation of the effect of FACTS devices on
damping local modes and inter-area modes of
oscillations based on a simple fuzzy logic
proportional plus conventional integral controller
in a multi-machine power system. The proposed
controller uses a combination of a FLC and a PI
controller. In comparison with the existing fuzzy
controllers, the proposed fuzzy controller combines
the advantages of a FLC and a conventional PI
controller. By applying this controller to the
FACTS devices such as UPFC, TCSC and SVC the
damping of local modes and inter-area modes of
oscillations in a multi-machine power system will
be handled properly. In addition, the paper
considers the conventional PI controller and
compares its performance with respect to the
proposed fuzzy controller. Also the effects of the
auxiliary signals in damping multimodal oscillation
have been shown. Finally, several fault and load
disturbance simulation results are presented to
highlight the effectiveness of the proposed FACTS
controller in a multi-machine power system.
M. Noroozian [92]-[94], examined the
enhancement of multi machine power system
stability by use TCSCs and SVCs. SVC was found
to be more effective for controlling power swings
at higher levels of power transfer; when it design to
damp the inter-area modes, it might excite the local
modes, and its damping effect dependent on load
characteristics. While TCSC is not sensitive to the
load characteristic and when it is designed to damp
the inter-area modes, it does not excite the local
modes.

4. Dynamic Stability of an integrated power
system networks:

The emergence of FACTS devices and in particular
GTO thyristor-based STATCOM has enabled such
technology to be proposed as serious competitive
alternatives to conventional SVC [95]. From the
power system dynamic stability viewpoint, the
STATCOM provides better damping
characteristics than the SVC as it is able to
transiently exchange active power with the system.
Reference [96], presented the modeling of Voltage
Sourced Inverter (VSI) type Flexible AC
Transmission System (FACTS) controllers and
control methods for power system dynamic
stability studies. The considered FACTS
controllers are the Static Compensator
(STATCOM), the Static Synchronous Series
Compensator (SSSC), and the Unified Power Flow
Controller (UPFC). In this paper, these FACTS
controllers are derived in the current injection
model, and it is applied to the linear and nonlinear
analysis algorithm for power system dynamics
studies. The parameters of the FACTS controllers
are set to damp the inter-area oscillations, and the
supplementary damping controllers and its control
schemes are proposed to increase damping abilities
of the FACTS controllers. For these works, the
linear analysis for each FACTS controller with or
without damping controller is executed, and the
dynamic characteristics of each FACTS controller
are analyzed.

B. By Coordination of FACTS Controllers in
an integrated power System networks

1. Small Signal Voltage Stability of an
integrated power system networks:

A new methodology has been addressed for the
solution of voltage stability when a contingency
has occurred, using coordinated control of FACTS
devices located in different areas of a power
system. An analysis of the initial conditions to
determine the voltage stability margins and a
contingency analysis to determine the critical
nodes and the voltage variations are conducted.
The response is carried out by the coordination of
multiple type FACTS controllers, which
compensate the reactive power, improving the
voltage stability margin of the critical modes [97].
Canizares and Faur et al. presented the steady-state
models with controls of two FACTS controllers,
namely SVC and TCSC, to study their effect on
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

57


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
voltage collapse phenomena in power system to
increase system loadability [98]. A new method
has been suggested for the potential application of
coordinated secondary voltage control by multiple
FACTS voltage controllers in eliminating voltage
violations in power system contingencies in order
to achieve more efficient voltage regulation in a
power system. The coordinated secondary voltage
control is assigned to the SVCs and Static
Compensators (STATCOM) in order to eliminate
voltage violations in power system contingencies
[99]. A new methodology has been proposed for
decentralized optimal power flow control for
overlapping area in power systems for the
enhancement of the system security [100].
In [101], a new method based on the optimization
method is called non-linear optimization
programming technique has been addressed for
tuning the parameters of the PSS for enhancing
small-signal stability. Feng et al. suggested a
comprehensive approach for determination of
preventive and corrective control strategies to
contain voltage collapse in stressed power systems
[102]. An immune-based algorithm has been
addressed for optimal coordination of local
physically based controllers in order to presence or
retain mid and long term voltage stability [103].In
[104], a new methodology has been proposed for
coordinated control of FACTS devices in power
system for security enhancement.
In [105], a genetic algorithm based on the method
of inequalities has been addressed for the
coordinated synthesis PSS parameters in a multi-
machine power system in order to enhance overall
system small signal stability. Etingov et al.
suggested an emergency control system based on
the ANN technique for finding a coordinated
control system action (load shedding, generation
tripping) to prevent the violation of power system
stability [106]. A fuzzy logic based method is used
for decentralized coordination of FACTS devices
for power system stability enhancement in [107].
Hiyama et al. [108] presented a coordinated fuzzy
logic-based scheme for PSS and switched series
capacitor modules to enhance overall power system
voltage stability. Ramirez et al. [109] presented a
technique to design and coordinate PSSs and
STATCOM-based stabilizers to enhance the
system stability and avoid the adverse interaction
among stabilizers. Ramirez et al. [110] extended
the work to coordinate among three different types
of stabilizers, namely, PSSs, TCSC, and UPFC.
The results exhibit a meritorious performance of
the coordinated stabilizers. A systematic approach
to establish the dynamic model of a multi-machine
power system installed with multiple SVCs,
TCSCs, TCPSs, STATCOMs, and UPFCs was
presented [111]. The adverse interactions among
these stabilizers, which may lead to the loss of the
system stability, has been examined.

2. Transient Stability of an integrated power
system networks:

Tan and Wang et al. showed that an adaptive non-
linear coordinated design technique for coordinated
design of series and shunt FACTS controllers such
as a Static Phase Shifter (SPS) and a Static VAR
Compensators (SVC) controller in power systems
environments for enhance the transient stability of
the power system [112]. A non-linear technique
has been proposed for robust non-linear
coordinated excitation and SVC control for power
systems for enhance the transient stability of the
power systems [113]. In [114], an optimization
based approach has been suggested for power
system optimization and coordination of FACTS
controllers to significant transient stability
improvement and effective power oscillation
damping. Reference [115], a Particle Swarm
Optimization (PSO) Algorithm has been suggested
for coordinated design of a TCSC controller and
PSS in power systems for enhancing the power
system stability.

3. Rotor Angle Stability of an integrated power
system networks:

Wang et al. [116] have discussed the issue of
selection of typical operating conditions for robust
design of multiple stabilizers in coordinated
manner to damp multimode oscillations in multi
machine power systems.
In [117], a co-ordinated control scheme for
STATCOM and generator excitation to achieve
transient stability, damping and voltage regulation
enhancement of power systems is presented. First,
the nonlinear model of STATCOM installed in a
power system is derived. Then, using the feedback
linearisation technique, the nonlinearities of the
generator and the STATCOM model are alleviated.
With the help of robust control theory, the variation
of system structure, the parameter uncertainties and
the interconnection between the generator and
STATCOM are taken into consideration in the
controller design. Only local measurements are
required. The performance of the proposed control
scheme is evaluated through a real time test by
means of the real time digital simulator (RTDS).
The results present comparisons of the system
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

58


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
performance with different controllers, over a wide
range of operating conditions. It is shown that the
proposed co-ordinated control can provide better
stability, voltage control and damping than other
schemes.
In [118], an eigen value analysis approach has been
addressed for the problem of the most effective
selection of generating units to be equipped with
excitation system stabilizers in multi-machine
power systems which exhibit dynamic instability
and poor damping of several inter machine modes
of oscillations. An eigen value sensitivity based
analysis approach has been addressed for design
and coordinate multiple stabilizers in order to
enhance the electro-mechanical transient behaviour
of power systems [119]. In [120], a modal analysis
technique has been addressed for coordinated
control of inter-area oscillation in the china
southern power grid for parameter setting of
selected power system stabilizers (PSS) and HVDC
damping controllers. In [121], a Decentralized
Modal Control (DMC) algorithm has been
addressed for simultaneously selecting the power
system stabilizers (PSS) parameters in multi-
machine power system in order to enhance
damping of the power system oscillations.
Torsional oscillations are excited as a result of
interactions between the shaft systems of steam
turbine-generator (T-G) sets and: (1) series
capacitor compensated networks, and (2) power
system controllers, e.g., excitation systems,
governors and HVDC converter controllers.
Torsional oscillations impose torsional torques on
the shaft sections of T-G sets and as a result of the
fatigue phenomenon reduce the life-time of the
shaft sections. This problem solved in [122], an
eigen value sensitivity based analysis approach has
been addressed for coordinated control of SVC and
PSSs in power system in order to enhance damping
power system oscillations. In [123], a modal
analysis based technique has been presented for
design of robust controllers for damping inter-area
oscillations application to the European power
system. Gasca and Chow et al. has suggested a
modal analysis based technique for the design of
damping controllers in multi-machine power
system or inter-area oscillations [124]. Ammari et
al. [125] has addressed sensitivity and residues
based techniques for robust solution for the
interaction phenomena between dynamic loads and
FACTS controllers for enhance damping of power
system oscillations. In [126], a sensitivity based
techniques such as a linear matrix inequalities
techniques has been proposed for the design of
robust PSS which places the system poles in
acceptable region in the complex plane for a given
set of operating and system conditions to enhance
the damping of power system oscillations over the
entire set of operating conditions. A frequency
response technique has been used for coordinated
design of under-excitation limiters and power
system stabilizers (PSS) in power system for
enhance the electro-mechanical damping of power
system oscillations [127]. A root locus technique
has been proposed for design of power system
stabilizers (PSS) for damping out tie-line power
oscillations in power system to enhance the
damping of power system oscillations for different
combinations of power system stabilizers
parameters [128]. In [129], a projective control
method has been addressed for coordinated control
of two FACTS devices such as TCSC and
Thyristor Controlled Phase Angle Regulator
(TCPAR) for damping inter-area oscillations to
enhance the power transfers and damping of power
system oscillations. A problem of interest in the
power industry is the mitigation of power system
oscillations. These oscillations are related to the
dynamics of system power transfer and often
exhibit poor damping, with utilities increasing
power exchange over a fixed network, the use of
new and existing equipment in the transmission
system for damping these oscillations is being
considered in several literatures. The above
problems are solved in lieratuters [130], [131], a
projective control method has been addressed for
coordinated control of TCSC and SVC for
enhancing the dynamic performance of a power
system. In [132], a new method has been proposed
for the design of power system controllers aimed at
damping out electro-mechanical oscillations used
for applied to the design of both PSS for
synchronous generators and supplementary signals
associated to other damping sources. Milanovic
and Hiskens et al. suggested a new method for
tuning of SVC controllers in the presence of load
parameters uncertainty to enhance the damping of
electro-mechanical oscillations in power systems
[133]. Lie et al. presented a linear optimal
controller for the designed to implement multiple
variable series compensators in transmission
networks of inter-connected power system is
utilized to damp inter-area oscillations and enhance
power system damping [134]. An application of a
normalized

H loop shaping techniques has been
proposed for design and simplification of damping
FACTS controllers in the linear matrix inequalities
(LMI) framework in power system for enhance
damping inter-area oscillation of power system
[135]. In [136], a linear optimal controller has been
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

59


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
addressed for the designed to implement multiple
variable series compensators (VSCs) in
transmission network of interconnected power
system is utilized to damp inter-area oscillations
and enhance power system damping during large
disturbances. In [137], an eigen-value analysis
technique is used for coordinated control of PSS
and FACTS controllers to enhance damping of
power system oscillations in multi-machine power
system. Zhao and Jiang et al. suggested a H-
infinity optimization technique for simultaneous
tuning of SVC controllers design to improve the
damping power system [138]. Chaudhuri and Pal et
al. suggested a H-infinity damping control design
optimization technique based on the mixed
sensitivity formulation in a linear matrix inequality
(LMI) framework for robust damping control
design for multiple swing modes damping in a
typical power system model using global
stabilizing signals [139]. A systematic procedure
for the synthesis of a Supplementary Damping
Controller (SDC) for Static Var Compensator
(SVC) for a wide range of operating conditions is
used for testing in multi-machine power systems to
enhance the damping of the inter-area oscillations,
providing robust stability and good performance
characteristics both in frequency domain and time
domain [140]. In [141], a bifurcation subsystem
based methodology has been proposed for -
synthesis power system stabilizers design in a two-
area power system. The secure operation of power
systems requires the application of robust
controllers, such as Power System Stabilizers
(PSS), to provide sufficient damping at all credible
operating conditions. Recently, many researchers
have investigated the use of robust control
techniques including H-infinity optimization and
-synthesis techniques for developing advanced
and automated procedures for power system
damping controller design. A several control
design techniques [142] such as the classical phase
compensation approach, the -synthesis, and a
linear matrix inequality technique has been used
for coordinate two PSS to stabilize a 5-machine
equivalent of the South/ Southeast Brazilian power
system. In [143], a Prony methods based on Prony
signal analysis and incorporates both local and
inter-area electro-mechanical oscillatory modes
along with root locus and sequential decentralized
control techniques has been used for PSSs design
in multi-machine power systems. . In [144], a
projective control principle based on eigen-value
analysis has been presented for coordinated control
design of supplementary damping controller of
HVDC and SVC in power system to enhance the
damping of power system oscillations. A non-
linear optimization programming techniques has
been addressed for simultaneous coordinated
tuning of PSS and FACTS controllers for damping
power system oscillations in multi-machine power
systems [145]. Electro-mechanical oscillations in
power systems are a problem that has been
challenging engineers for decades. These
oscillations may be very poorly damped in some
cases, resulting in mechanical fatigue at the
machines and unacceptable power variations across
important transmission lines. For this reason, the
use of controllers to provide better damping for
these oscillations is of utmost importance. A non-
linear programming based algorithm has been
proposed for the design of power system damping
controllers for damp electro-mechanical
oscillations in power systems [146]. A non-linear
programming based algorithm has been proposed
for the design of simultaneous coordinated tuning
of PSS and FACTS controllers for damping power
system oscillations in multi-machine power
systems [147]. Simoes et al. presented a non-linear
optimization technique is used to coordinated
control of Power Oscillation Damping (POD)
controllers implemented in the two TCSC of the
Brazilian North-South (NS) inter-connection, in the
year 1999, were solely intended to damp the low-
frequency NS oscillation mode [148]. In [149], an
optimization technique is used to tuning of power
system stabilizers in power systems. Small
disturbance stability, particularly in the context of
positive damping of electro-mechanical modes or
oscillations among the interconnected synchronous
generator in power systems, constitutes one of the
essential criteria for secure system operation.
Power system stabilizers (PSSs) together with their
coordination have been developed for enhancing
system stability. However, the use of PSSs only
may not be, in some cases, effective in providing
sufficient damping for inter-area oscillations,
particularly with increasing transmission line
loading over long distances. Drawing on the
availability of FACTS devices at present, which
have been developed primarily for active- and/or
reactive power flow and voltage control functions
in the transmission system, more effective
measures have been proposed for improving
system damping. Nguyen, and Gianto et al. [150]-
[151] has been proposed a optimization based
technique for control coordination of PSSs and
FACTS controllers for Optimal oscillations
damping in multi-machine power system. Damping
of power system oscillations between
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

60


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
interconnected areas is very important for the
system secure operation. Power system stabilizers
(PSS) and FACTS devices are used to enhance
system stability. In large power systems, using only
conventional PSS may not provide sufficient
damping for inter-area oscillations. In these cases,
FACTS power oscillation damping controllers are
effective solutions. But uncoordinated local control
of FACTS devices and PSSs may cause
destabilizing interactions. In [152], an optimization
based approach has been suggested for power
system optimization and coordination of FACTS
controllers to significant transient stability
improvement and effective power oscillation
damping. In [153], a simulated annealing based
algorithm has been addressed for PSS and FACTS
based stabilizers tuning in power systems. The
design problem of PSS and FACTS based
stabilizes is formulated as an optimization problem.
An eigen value based objective function is used to
increase the system damping. Then SA algorithm is
employed to search for optimal stabilizer
parameters. Different control schemes have been
proposed in and tested on a weakly connected
power system with different disturbances loading
conditions and parameter variations. The problem
of poorly damped, low frequency oscillations,
associated with the generator rotor swings has been
a matter of concern to power engineers for along
time. Damping of electro-mechanical oscillations
between interconnected synchronous generators is
necessary for secure system operation. These
problem is improved, in [154], a fuzzy set theory
based algorithms has been suggested for coordinate
stabilizers so as to increase the operational
dynamic stability margin of power system for
TCSC and UPFC in power system environments. A
hybrid fuzzy logic algorithm has been proposed for
the coordination of FACTS controllers in power
system. The coordination method is well suitable to
series connected FACTS devices like TCSC, SSSC
in damping multi-modal oscillations in multi-
machine power systems [155].

4. Dynamic Stability of an integrated power
system networks:

In [156], a projective control method has been
addressed for coordinated control of TCSC and
SVC for enhancing the dynamic performance of a
power system. In [157], a new real and reactive
power coordination method has been proposed for
UPFC to improve the performance of the UPFC
control. Lei et al. suggested a sequential quadratic
programming algorithm for optimization and
coordination of FACTS device stabilizers (FDS)
and power system stabilizers (PSS) in a multi-
machine power system to improve system dynamic
performance [158]. Najafi and Kazemi et al. [159]
suggested an optimization based technique for
coordination of PSSs and FACTS damping
controllers in large power systems for dynamic
stability improvement. Sebaa and Boudour et al.
[160] has been suggested a genetic algorithm for
coordinated design of PSSs and SVC-based
controllers in power system to enhance power
system dynamic stability. In [161], a fuzzy set
theory based algorithms has been suggested for
coordinate stabilizers so as to increase the
operational dynamic stability margin of power
system for TCSC and UPFC in power system
environments. A fuzzy logic based method has
been used for coordinated control of TCSC and
UPFC in power systems to increase the operational
dynamic stability margin of power system [162].
Reference [163], a load flow control technique has
been proposed for coordinated control of FACTS
controllers in power system for enhancing steady
dynamic performance of power systems during
normal and abnormal operation conditions.

8. RESULTS AND DISCUSSIONS

The following tables give summary of the paper as:

5.1 By Placement of FACTS controllers in large-
scale emerging power system networks

From figure 1 it is concluded that the 39 of total
literatures are reviews based on voltage stability,
02 of total literatures are reviews based on transient
stability, 10 of total literatures are reviews based on
rotor angle stability, and 02 of total literatures are
reviews based on dynamic stability by placement
of FACTS controllers in an integrated power
system networks.

ISSN:


P

Figure
large-s
5.2 By
large-
From
literatu
04 of t
stabili
rotor a
review
of FA
system


Figur
in larg

5.3 By
contro
system

2076-3328
Publication
e 1 By placem
scale emerging
y Coordinatio
-scale emergin
figure 2 it is
ures are review
total literatures
ty, 39 of total l
angle stability,
ws based on dy
ACTS control
m networks.
e 2 By coordi
ge-scale emerg
y Placement a
ollers in la
m networks
0
5
10
15
20
25
30
35
40
0
10
20
30
40
Internatio


n of Little
ment of FACT
g power system
on of FACTS
ng power syste
concluded tha
ws based on v
s are reviews b
literatures are r
, and 08 of tot
ynamic stability
llers in an in
ination of FAC
ging power sy
and Coordina
arge-scale em
onal Journa
15
th
J
2009 - 2011 IJ
www
Lion Sci
TS controllers
m networks
S controllers
em networks
at the 15 of to
voltage stabili
based on transie
reviews based
tal literatures a
y by coordinati
ntegrated pow
CTS controlle
ystem network
ation of FACT
merging pow
TotalNo.of
Literatures
Surveybased
onPlacemen
ofFACTS
controllers
TotalNo.
Literatures
surveybase
on
coordinatio
ofFACTS
controllers
al of Revie
July 2011. Vol. 6
JRIC & LLS. All r
w.ijric.org
61
entific R&

in
in
otal
ity,
ent
on
are
ion
wer

ers
ks
TS
wer
From f
literatu
06 of to
stability
rotor an
reviews
and co
integrat



Figure
FACTS
power
From f
maximu
Stabilit
coordin
power s

9. C
This re
definiti
a fund
practica
signific
system
provide
systema
and th
stability
reliabil
establis
a rigoro
stability
materia
and to e
d
nt
ed
n
1
1
2
2
3
3
4
ews in Com
rights reserved
.

&D, Islam
figure 3 it is c
ures are review
otal literatures
y, 49 of total li
ngle stability,
s based on dy
oordination of
ted power syst
e 3 By place
S controllers
system netwo
figure 3 finally
um research
ty and rotor an
nation of FACT
system networ
ONCLUSION
eport has add
ion and classifi
damental viewp
al ramification
cant detail. A
stability that
ed. A salient
atic classificat
he identificatio
y behavior. Lin
lity, security,
shed and discu
ous treatment
y from mathem
al is provided
establish theor
0
5
10
15
20
25
30
35
40
mputing
E
mabad PAK
concluded that
ws based on v
are reviews ba
iteratures are re
and 10 of tota
ynamic stability
f FACTS con
tem networks.
ement and c
s in large-sc
orks
y it is also con
work carryou
ngle stability by
TS controllers
rks.
NS

dressed the iss
fication in pow
point and has
ns of stability
precise defin
is inclusive
feature of t
tion of power s
on of differen
nkages betwee
, and stabi
ussed. The repo
of definitions
matics and cont
d as backgrou
etical connecti
E-ISSN: 2076-333
KISTAN
IJRIC
t the 54 of tot
voltage stability
ased on transien
eviews based o
al literatures ar
y by placemen
ntrollers in a
oordination o
cale emergin
ncluded that th
ut from voltag
y placement an
in an integrate
sue of stabilit
er systems from
s examined th
y phenomena i
nition of pow
of all forms
the report is
system stability
nt categories o
en power system
ility are als
ort also include
and concepts o
trol theory. Th
und informatio
ions.
TotalNo.
Literatures
Surveybased
onPlacemen
ofFACTS
controllers

36

C
tal
y,
nt
on
re
nt
an

of
ng
he
ge
nd
ed
ty
m
he
in
er
is
a
y,
of
m
so
es
of
his
on
d
nt
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

62


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
This paper has also addressed a survey on
enhancement of power system stability such as
rotor angle stability, frequency stability, and
voltage stability by using different FACTS
controllers such as TCSC, SVC, SSSC,
STATCOM, UPFC, and IPFC in an integrated
power system networks. Also this paper discussed
the current status of the research and developments
in the field of the power system stability such as
rotor angle stability, frequency stability, and
voltage stability enhancement by using different
FACTS controllers in an integrated power system
networks. Authors strongly believe that this survey
article will be very much useful to the researchers
for finding out the relevant references in the field
of enhancement of power system stability by using
different FACTS controllers in an integrated power
system network.

ACKNOWLEDGMENT

The authors would like to thanks Dr. S. C.
Srivastava, and Dr. S. N. Singh, Indian Institute of
Technology, Kanpur, U.P., India, and Dr. K.S.
Verma, and Dr. Deependra Singh, Kamla Nehru
Institute of Technology, Sultanpur, U.P., India, for
their valuables suggestions regarding placement
and coordination techniques for FACTS controllers
form voltage stability, and voltage security point of
view in multi-machine power systems
environments.


REFERENCES

[1] C.P.Steinmetz, Power Control and Stability of
electric generation stations, AIEE Trans., Vol.
XXXIX, Part II, pp. 1215-1287, July 1920.
[2] AIEE Subcommittee on Interconnections and
Stability Factors, First report of power system
stability, AIEE Trans., pp.51-80, 1926.
[3] R.D. Evens and R.C. Bergvall, Experimental
Analysis of Stability and Power Limitations,
AIEE Trans., pp. 39-58, 1924.
[4] R. Wilkins, Practical Aspects of System
Stability, AIEE Trans., pp. 41-50, 1926.
[5] R.D. Evans and C.F. Wagner, Further Studies
of Transmission System Stability, AIEE Trans.,
pp. 51-80, 1926.
[6] P.M. Anderson and A. A. Foaud, Power System
Control and Stability, The lowa University
Press, 1977.
[7] M.A, Pai, Power System Stability Analysis by
the Direct Method, North Holland, New York,
1981.
[8] Y.N. Yu, Electric Power System dynamics,
Academic Press, New York 1983.
[9] A.A. Fouad and V. Vittal, Power System
transient stability analysis, the Prentice Hall,
New Jersey, 1992.
[10] P.Kundur, Power System Stability and
Control,Mc. Graw Hill, New York,1994.
[11] Survey of the voltage collapse phenomenon,
North American Electric Reliability Council
Report,1991.
[12] N.W.Miller, R. D. Aquila, K.M. Jimma, M. T.
Sheehan, and G. L. Comegys, Voltage Stability
of Puget Sound System Under Abnormally Cold
Wheather Conditions, IEEE Trans. on Power
Systems, Vol. 8, No. 3, pp.1133-1142, August
1993.
[13] IEEE/CIGRE Joint Task Force on Stability
Terms and Definitions, Definition and
Classification of Power System Stability, IEEE
Trans. on Power Systems, Vol. 19, No.3, pp.
1387-1401, August 2004.
[14] T. Van Cutsen and C. Vournas, Voltage
Stability of Electric Power Systems, Norwewll,
M. A. Kuwer, 1998.
[15] IEEE System Dynamic Performance
Subcommittee, Voltage stability power
system:Concepts, Analytical tools and Industrial
experience, IEE document 90 Th0358-2-PWR-
1990.
[16] C.W.Taylor, Power System Voltage Stability,
Mc Graw Hill, New York, 1994.
[17] I. A. Hiskens and M. A. Pai, Hybrid systems
view of power system modelling, in
Proceedings of the IEEE International
Symposium on Circuits and Systems, no. 2,
Geneva, Switzerland, May 2000, pp. 228-231.
[18] H. Khalil, Nonlinear Systems, 3rd edition. Prentice
Hall, 2001.
[19] J. J. Slotine, Applied Nonlinear Control. New
York: Prentice Hall, 1990.
[20] S. Sastry, Nonlinear Systems. New York: Springer
Verlag, 2004.
[21] A. M. Lyapunov, The general problem of motion
stability. in Russian 1892: Reprinted in Ann.
Math. Study n. 17, 1949, Princeton University
Press.
[22] Y. Zou, M. H. Yin, and H. D. Chiang,
Theoretical foundation of the controlling UEP
method for direct transient-stability analysis of
network-preserving power system models,
IEEE Trans. Circuits Syst., vol. 50,no. 10, pp.
1324-1336, Oct. 2003
[23] T. Van Cutsem and C. Vournas, Voltage Stability
of Electric Power Systems. Norwell, MA:
Kluwer, 1998.
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

63


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
[24] D. J. Hill, Nonlinear dynamic load models with
recovery for voltage stability studies, IEEE
Trans. Power Systems, vol. 8, pp. 166176,
Feb.1993.
[25] T. Van Cutsem and R. Mailhot, Validation of a
fast voltage stability analysis method on the
Hydro-Quebec System, IEEE Trans. Power
Systems, vol. 12, pp. 282292, Feb. 1997.
[26] J. D. Ainsworth, A. Gavrilovic, and H. L.
Thanawala, Static and synchrounous
compensators for HVDC transmission convertors
connected to weak AC systems, 28th Session
CIGRE, 1980, Paper 3101.
[27] CIGRE Working Group 14.05 Report, Guide for
Planning DC Links Terminating at AC Systems
Locations Having Low Short-Circuit Capacities
Part I: AC/DC Interaction Phenomena, CIGRE
Guide No. 95, 1992.
[28] CIGRE Working Group 14.05 Report,
Interaction between HVDC convertors and
nearby synchronous machines, CIGRE Brochure
119, Oct.1997.
[29] T. Van Cutsem, and R. Maihot, Validation of a
fast voltage stability analysis methods, Proc.
IEEE, Vol. 88, pp.208-227, 2000.
[30] G. K. Morison, B Gao, and P. Kundur, Voltage
Stability Analysis Using Static And Dynamic
Approaches, IEEE Trans. Power Systems, Vol,
8, No. 3, pp. 1159-1171, August 1993.
[31] D. J. Hill p. a. Lof, and G. Anderson, Analysis
of long-term Voltage Stability, Proc. 10
th
power
system computational Conference, pp. 1252-
1259, august 1990.
[32] P. Kundur, A survey of utility experiences with
power plant response during partial load
rejections and system disturbances, IEEE
Trans. Power Apparatus and Systems, vol. PAS-
100, pp. 24712475, May 1981.
[33] N. Hatziargyriou, E. Karapidakis, and D.
Hatzifotis, Frequency stability of power system
in large islands with high wind power
penetration, Bulk Power Syst. Dynamics
Control Symp.IV Restructuring, vol. PAS-102,
Aug. 2428, 1998, Santorini, Greece.
[34] IEEE Sub-synchronous Resonance Working
Group, \Second benchmark model for computer
simulation of sub-synchronous resonance," IEEE
Trans. Power App. Syst., vol. 104, pp. 1057-
1066, 1985.
[35] J. V. Milanovic and T. M. David, Stability of
distribution networks with embedded generators
and induction motors," in IEEE PES Winter
Meeting, vol. 2, 2002, pp. 1023-1028.
[36] G. Anderson, Dynamics and Control of Electric
Power Systems. Zurich, Switzerland: EEH -
Power Systems Laboratory ETH, 2004.
[37] V. Knazkins, Stability of power systems with
large amounts of distributed generation," Ph.D.
dissertation, KTH Institution for Elektrotekniska
System, Stockholm, Sweden, Oct. 2004.
[38] L. H. Fink and K. Carlsen, Operating under
stress and strain, IEEE Spectrum, vol. 15, pp.
4853, Mar. 1978.
[39] R. Billinton, Power System Reliability
Evaluation. New York: Gordon and Breach,
1970.
[40] NERC Planning Standards (1997, Sept.).
[Online]. Available:
http://www.nerc.com/~filez/pss-psg.html.
[41] IEEE Working Group Report, Reliability
indices for use in bulk power system supply
adequacy evaluation, IEEE Trans. Power
Apparatus and Systems, vol. PAS-97, pp. 1097
1103, July/Aug. 1978.
[42] CIGRE TF 38.03.12 Report, Power system
security assessment: A position paper,
ELECTRA, no. 175, Dec. 1997.
[43] T. E. Dy Liacco, Control of Power Systems Via
the Multi-Level Concept, Case Western
Reserve Univ., Syst. Res. Center, Rep. SRC-68-
19, June 1968.
[44] T. Van Cutsem,Voltage instability: phenomena,
countermeasures, and analysis methods," Proc.
IEEE, vol. 88, no. 2, pp. 208-227, Feb. 2000.
[45] N. K. Sharma, A. Ghosh, and R. K. Verma, A
Novel Placement Strategy for FACTS
Controllers, IEEE Trans. on Power Delivery,
Vol. 18, No.3, July 2003.
[46] O. O. Obadina and G. J. Berg, Identifying
Electrically Week and Strong Segments of a
Power Systems from a Voltage Stability
Viewpoint, IEE Proc. Pt.C, Vol-137, No.3, pp.
205-212, May 1990.
[47] L. A. S. Pilotto, W. W. Ping , A. R. Carvalho, W.
F. Long, F. L. Alvarado, C. L. Demarco, and A.
Edris, Coordinated Design of FACTS
Controllers to Enhance Power System Dynamic
Performance , International Colloquium on
HVDC and FACTS , Johannesburg, Sept. 1997.
[48] S. N. Singh and A. K. David, Placement of
FACTS Devices in Open Power Market,
Proceeding of the 5
th
International Conference on
Advance in Power System Control, Operation
and Management, APSCOM 2000, Hong Kong,
pp. 173-177, October 2000.
[49] S. N. Singh and A. K. David, A new approach
for placement of FACTS Devices in Open Power
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

64


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
Market, IEEE Power Engg. Rev., 2001, 21(9),
pp. 58-60.
[50] M. K. Verma, and S. C. Srivastava, Optimal
Placement of SVC for Static and Dynamic
Voltage Security Enhancement, International
Journal of Emerging Electric Power Systems,
Vol.2, issue-2, 2005.
[51] Fadela Benzergua, Abdelkader Chaker, Mounir
Khiat, and Naima Khalfallah, Optimal
Placement of Static VAR Compensator in
Algerian Network, Information Technology
Journal, Vol.6, No.7, pp.1095-1099, 2007.
[52] Srekanth Reddy Donapati, and M. K. Verma,
An Approach for Optimal Placement of UPFC
to enhance Voltage Stability Margin under
Contingencies, Fifteenth National Power
Systems Conference (NPSC), IIT Bombay,
December 2008 pp.441-446.
[53] V.Ajjarapu, Ping Lin Lau, and S. Battula, An
Optimal Reactive Power Planning Strategy
Against Voltage Collapse, IEEE Trans on
Power Systems, Vol.9, No.2, May 1994.
[54] C. P. Gupta, Voltage Stability Margin
Enhancement using FACTS controllers, Ph. D.
Thesis, IIT Kanpur, October, 2000.
[55] Naoto Yorino, E. E. El-Araby, Hiroshi Sasaki,
and Shigemi Harada, A new Formulation for
FACTS Allocation for Security Enhancement
against Voltage Collapse, IEEE Trans. on
Power Systems, Vol. 18, No.1, February 2003.
[56] Ashwani kumar Sharma,Optimal Number and
Location of TCSC and Loadability Enhancement
in Deregulated Electricity Markets Using
MINLP, International Journal of Emerging
Electric Power Systems, Vol.5, Issue 1, 2006.
[57] C. S. Chang, and J. S. Huang, Optimal SVC
Placement for Voltage Stability
Reinforcements, Electric Power System
Research, Vol.42, pp.165-172, 1997.
[58] Tina Orfanogianni, and Rainer Bacher, Steady-
State Optimization in Power Systems with Series
FACTS Devices, IEEE Trans on Power
Systems, Vol.18, No.1, February 2003.
[59] Mohd WAzir Mustafa, and Wong Yan Chiew,
Optimal Placement of Static VAR Compensator
Using Genetic Algorithms, Elektrika, Vol. 10,
No.1, pp.26-31, 2008.
[60] H.I. Shaheen, G. I. Rashed, and S.J. Cheng,
Optimal Location and Parameters Setting of
UPFC based on GA and PSO for Enhancing
Power System Security Under Single
Contingencies, Power and Energy Society
General Meeting-Convesion and delivery of
Electrical Energy in The 21
st
Century,
2008,IEEE, 20-24 July, 2008, pp.1-8.
[61] M. Gitizadeh, and M. Kalanta, A New
Approach for Congestion Management via
Optimal Location of FACTS Devices in
Deregulated Power Systems, DRPT 2008, 6-9
April 2008, Nanjing China.
[62] S. Gerbex, R. Cherkaui, and A. J. Germond,
Optimal Location of FACTS Devices to Enhance
Power Systems Security, In Proc., 2003, IEEE
Bologria Power Tech. Conf., pp.23-26.
[63] Yuan-Lin Chen, Weak Bus-Oriented Optimal
Multi-Objective VAR Planning, IEEE Trans on
Power Systems, Vol. 11, No.4, November 1996.
[64] G. I Rashed, H. I. Shaheen, and S. T. Cheng,
Optimal Location and Parameter Setting of
TCSC by Both Genetic Algorithm and Particle
Swarm Optimization, 2007, IEEE Second conf.
on Industrial Electronics and Applications,
China.
[65] J. C.Carlisle, and A. a. El Keib, A Graph Search
Algorithm for Optimal Placement of Fixed and
Switched Capacitors on Radial Distribution
System, IEEE Trans. on Power Delivery, Vol.
15, No. 1, January 2000.
[66] Jing Zhang, J. Y. Wen, S. J. Cheng, and Jia Ma,
A Novel SVC Allocation Method for Power
System Voltage Stability Enhancement by
Normal Forms of Diffeomorphism, IEEE Trans.
on Power Systems, Vol. 22, No. 4, November
2007.
[67] Ying-Yi Hong, and Chen-Ching Liu, A
heuristic and Algorithmic Approach to VAR
Planning, IEEE Trans on Power Systems, Vol.
7, No.2, May 1992.
[68] W.L.Fang, and H. W. Ngan, Optimizing
location of UPFC using the Methods of
Augmented Lagrange Multipliers, IEE
Proc.,Gener., Transm.,Distrib.,Vol 146, No.5,
Sep. 1999.
[69] X. Li, L. Bao and et al, Effects of FACTS
controllers on small-signal voltage stability, in
Proceedings of Power Engineering Society
Winter Meeting, 2000, Singapore, 23-27 Jan.
2000, vol. 4, pp2793 -2799.
[70] C. A. Canlzares, Z. T. Faur, "Analysis SVC and
TCSC Controllers in Voltage Collapse," IEEE
Trans. Power Systems, Vol. 14, No. 1,February
1999, pp. 158-165.
[71] A. Sode-Yome and N. Mithulananthan,
Comparison of shunt capacitor, SVC and
STATCOM in static voltage stability margin
enhancement, International Journal of Electrical
Engineering Education, UMIST, Vol. 41, No. 3,
July 2004.
[72] R. Natesan and G. Radman,Effects of
STATCOM, SSSC and UPFC on Voltage
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

65


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
Stability, Proceedings of the system theory
thirty- Sixth southeastern symposium, pp. 546-
550, 2004.
[73] A. Kazemi, V. Vahidinasab and A.
Mosallanejad, Study of STATCOM and UPFC
Controllers for Voltage Stability Evaluated by
Saddle-Node Bifurcation Analysis, First
International Power and Energy Conference
PECon/IEEE, Putrajaya, Malaysia, November
28-29, 2006.
[74] Arthit Sode-Yome, Nadarajah Mithulananthan
and Kwang Y. Lee, Static Voltage Stability
Margin Enhancement Using STATCOM,TCSC
and SSSC, IEEE/PES Transmission and
Distribution Conference & Exhibition, Asia and
pacific, Dalian , Chine, 2005.
[75] M ehrdad Ahmadi Kamarposhti, Mostafa
Alinezhad, Hamid Lesani, and Nemat Talebi,
Comparison of SVC, STATCOM, TCSC, and
UPFC Controllers for Static Voltage Stability
Evaluated by Continuation Power Flow
Method, 2008 IEEE Electrical Power & Energy
Conference, 2008.
[76] P. Kumkratug and M. H. Haque, Improvement
of Stability Region and damping of a Power
System by Using SSSC, Proceedings of IEEE
Power Engineering Society General Meeting,
1317 July 2003, vol. 3,pp. 14171421.
[77] H. F. Wang, H. Li, and H. Chen, Application of
Cell Immune Response Modelling to Power
System Voltage Control by STATCOM, IEE
Proc.-Gener. Transmi. Distib., 149(1)(2002), pp.
102107.
[78] A. E. Hammad, Analysis of Power System
Stability Enhancement by Static VAR
Compensators, IEEE Trans. PWRS, 1(4)(1986),
pp. 222227.
[79] A. R. Messina and E. Barocio, Nonlinear
Analysis of Interarea Oscillations: Effect of SVC
Voltage Support, Electric Power Systems
Research, 64(1)(2003), pp. 1726.
[80] A. D. Rosso, C. A. Conizares, and V. M. Dona,
A Study of TCSC Controller Design for Power
System Stability Improvement, IEEE Trans.
PWRS, 18(4)(2003), pp. 14871496.
[81] Gyugyi, L.; Sen, K.K.; and Schauder, C.D., The
Interline Power Flow Controller Concept: A new
approach to power in transmission systems,
IEEE Trans. on Power Delivery ,Vol. 4, No. 2,
2009, pp.1115 -1123.
[82] B.K. Panigrahi, M.K. Mallick, S.S. Dash, A
novel fuzzy logic controller for STATCOM to
improve power system stability, International
Journal of Automation and Control Volume 1,
Number 1 , 2007,pp.4-15.
[83] K. N. Shubhanga, and Anil M. Kulkarni,
Application of Structure Preserving Energy
Margin Sensitivity to Determine the
Effectiveness of Shunt and Series FACTS
Devices, IEEE Trans. on Power Systems, Vol.
17, No.3, August 2002.
[84] Dheeman Chatterjee and Arindam Ghosh,
Application of Trajectory Sensitivity for the
Evaluation of the Effect of TCSC Placement on
Transient Stability, International Journal of
Emerging Electric Power Systems, Vol. 8, Issue
1, 2007.
[85] M. H. Haque, Evaluation of First Swing
Stability of a Large Power System with Various
FACTS Devices, IEEE Trans. on Power
Systems, Vol. 23, No. 3, August. 2008,pp. 1144-
1151.
[86] B. Chaudhuri, B. C. Pal, A. C. Zolotas, I. M.
Jaimoukha, and T. C. Green, Mixed-Sensitivity
Approach to H Control of Power System
Oscillations Employing Multiple FACTS
Devices, IEEE Trans. PWRS, 18(3)(2003),pp.
11491156.
[87] B. Chaudhuri and B. C. Pal, Robust Damping of
Multiple Swing Modes Employing Global
Stabilizing Signals with a TCSC, IEEE Trans.
PWRS, 19(1)(2004), pp. 499506.
[88] M. M. Farsangi, Y. H. Song, and K. Y. Lee,
Choice of FACTS Device Control Inputs for
Damping Interarea Oscillations, IEEE Trans.
PWRS, 19(2)(2004), pp. 11351143.
[89] A. M. Kulkarni and K. R. Padiyar, Damping of
Power Swings Using Series FACTS
Controllers, Int. Journal of Electrical Power
and Energy Systems, 21(1999), pp. 475495.
[90] M. A. Abido, Analysis of Power System
Stability Enhancement via Excitation and Facts-
Based Stabilizers, Electric Power Components
and Systems, Volume 32, Issue 1 January 2004 ,
pages 75 9.
[91] Ahad Kazemi
,
and Mahmoud Vakili
Sohrforouzani, Power system damping using
fuzzy controlled facts devices, International
Journal of Electrical Power & Energy Systems,
Volume 28, Issue 5, June 2006, Pages 349-357.
[92] M. Noroozian, M. Ghandhari, G. Andersson, J.
Gronquist, and I. Hiskens, " ARobust Control
Strategy for Shunt and Series Reactive
Compensators to Damp Electromechanical
Oscillations," IEEE Trans. On Power Delivery,
Vol. 16, No. 4, October 2001, pp: 812-817.
[93] M. Noroozian and G. Andersson, "Damping of
Inter-Area and Local Modes by use Controllable
Components," IEEE Trans. On Power Delivery,
Vol. 10, No. 4, October 1995, pp: 2007-2012.
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

66


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
[94] M. Noroozian and G. Andersson, "Damping of
Power System Oscillations by use of
Controllable Components," IEEE Trans. On
Power Delivery, Vol. 9, No. 4, October 1994, pp:
2046-2054.
[95] D. J. Hanson, M. L. Woodhouse, C. Horwill, D.
R. Monkhouse, and M. M. Osborne,
STATCOM: A New Era of Reactive
Compensation, Power Engineering Journal,
June 2002, pp. 151160.
[96] Jungsoo Park, Gilsoo Jang, and Kwang M. Son,
Modeling and Control of VSI type FACTS
controllers for Power System Dynamic Stability
using the current injection method, International
Journal of Control, Automation, and Systems,
vol. 6, no. 4, pp. 495-505, August 2008.
[97] J. E. Candelo, N. G. Caicedo, and F.Castro
Aranda, Proposal for the Solution Voltage
Stability Using Coordination of FACTS
Devices, 2006, IEEE PES Transmission and
Distribution Conf. and Exposition Latin
America, Venezuela.
[98] Claudio A. Canizares, and Zeno T. Faur,
Analysis of SVC and TCSC Controllers in
Voltage Collapse, IEEE Trans on Power
Systems, Vol. 14, No. 1, February 1999.
[99] Hai Feng wang, H. Li, and H. Chen,
Coordinated Secondary Voltage Control to
Eliminate voltage Violations in Power System
Contingencies, IEEEE Trans on Power
Systems, Vol. 18, No.2, May 2005.
[100] Gabriela Hug-Glanzmann, and Goran
Andersson, Decentralized Optimal Power Flow
Control for Overlapping Areas in Power
Systems, IEEE Trans Power Systems, Vol.24,
No.1, February 2009.
[101] Hong, Ying-Yi, and Wu Wen-Ching, A
New Approach Using Optimization for Tuning
Parameters of Power System Stabilizers, IEEE
Trans on Energy Conversion, Vol. 14, No. 3,
September 1999.
[102] Zhihong Feng, Ven Kataramana Ajjarapu,
and Dominic J. Maratukulam, A
Comprehensive Approach for Preventive and
Corrective Control to Mitigate Voltage
Collapse, IEEE Trans on Power Systems, Vol.
15, No.2, May 2000.
[103] L. I. Yan Jun, Hill David J. , and W. U.
Tie-Jun, Optimal Coordinated Voltage Control
of Power Systems, Journal of Zhejiang
University Science A, Vol. 7, No.2, pp. 257-262,
2006.
[104] Gabriela Hug-Glanzmann, and Goran
Anderson, Coordinated Control of FACTS
Devices in Power Systems For Security
Enhancement, IERP Symposium, Bulk Power
System Dynamics and Control, VII, Revitalizing
Operational Reliability, Charleston, SC, USA,
August 19-24, 2000.
[105] P. Zhang and A. H. Coonick,
Coordinated Synthesis of PSS Parameters in
Multi-Machine Power Systems Using the
Method of Inequalities Applied to Genetic
Algorithms, IEEE Trans. on Power Systems,
Vol. 15, No.2, May 2000.
[106] Pavel Etingov, Alexandre Oudalov,
Nikolai Voropai, Rachid Cherbaoui, and Alain
Germond, Power System Stability
Enhancement Using ANN Based Coordinated
Emergency Control System, In Proc. Of the
IEEE Power Tech. 2007, Lauzanne, Switzerland,
July 1-5, 2007.
[107] Sadegh, Mahmoud Outkati, Lo. K. L.,
Decentralized coordination of FACTS for
Power System Stability enhancement Using
Intelligent Programming, International Journal
for Computation and Maths in Electrical Engg.,
Vol. 24, No. 1, 2005, pp. 179-201(23).
[108] T. Hiyama, M. Mishiro, H. Kihara, and T.
H. Ortmeyer, Coordinated Fuzzy Logic Control
for Series Capacitor Modules and PSS to
Enhance Stability of Power System, IEEE
Trans. PWRD, 10(2)(1995), pp. 10981104.
[109] J. M. Ramirez, R. J. Davalos, and I.
Coronado, Use of an Optimal Criterion for
Coordinating FACTS-based Stabilizers, IEE
Proc. Genet. Transm. Distrib., 149(3)(2002), pp.
345351.
[110] J. M. Ramirez and I. Castillo, PSS and
FDS Simultaneous Tuning, Electric Power
Systems Research, 68(1)(2004), pp. 3340.
[111] H. F. Wang, Modeling Multiple FACTS
Devices into Multi machine Power Systems and
Applications, Int. Journal of Electrical Powers
& Energy Systems, 25(3)(2003), pp. 227237.
[112] Yoke Lin Tan and Youyi Wang, Design
of series and shunt FACTS controllers using
Adaptive nonlinear coordinated design
techniques, IEEE Trans on Power Systems, vol.
12, no. 3, August 1997.
[113] Youyi wang, Yoke Lin Tan, and Guoxiao
Guo, Robust Non-linear Coordinated Excitation
and SVC Control for Power Systems, In Proc.
of the 4
th
International Conf. on Advances in
Power System Control , Operation and
Management, APSCOM97, Hong Kong, Nov.
1997.
[114] J. W. Park, R. G. Harley, and G. K.
Vanayagamoorthy, Power System Optimization
and Coordination of Damping Controllers by
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

67


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
Series FACTS Devices, Power Engineering
Society Inaugural Conference & Exposition in
Africa 2005, IEEE, 11-15 July, 2005, pp293-
298.
[115] Siddhartha Panda and Narayana Prasad
Padhy, Coordinated Design of TCSC
Controllers and PSSS Employing Particle Swarm
Optimization Technique, International Journal
of Computer and Information Science and
Engineering, Vol.1, No. 1, 2006.
[116] H. F. Wang, Selection of Operating
Conditions for the Coordinated Setting of Robust
Fixed-Parameter Stabilizers, IEE Proc. Genet.
Transm. Distrib., 145(2)(1998), pp. 111116.
[117] Cong, L. Wang, Y. Co-ordinated control
of generator excitation and STATCOM for rotor
angle stability and voltage regulation
enhancement of power systems, Generation,
Transmission, Distribution, IEE Proceedings,
vol.149, issue 6, Nov 2002, pp, 659-666.
[118] F. P.Demello, P. J. Nolan, T. P.
Laskowski, and J. M. Undrill, Coordinated
Application of Stabilizers in Multi-machine
Power Systems, IEEE Trans. on Power
Apparatus &Systems, Vol. PAS-99, No.3,
May/June 1980.
[119] Juan M. Ramirez, Isidro Castillo, PSS
and FDS simultaneous tuning, Electric Power
Systems Research, Vol.68, pp. 33-40, 2004.
[120] Mao-Xiaoming, Zhang Yao, Guan Lin,
and Wu Xiao-chen, Coordinated Control of
Inter-area Oscillation in the China Southern
Power Grid, IEEE Trans on Power Systems,
Vol. 21, No.2, May 2006.
[121] C.L. Chen and Y. Y. Hsu, Coordinated
Synthesis of Power System Stabilizers Using An
Efficient Decentralized Modal Control (DMC)
Algorithm, IEEE Trans. on Power Systems,
Vol. PWRS-2., No.3, pp. 543-551, August 1987.
[122] R. M. Hamouda, M. R. Iravani, and R.
Hacham, Coordinated Static VAR
Compensators for Damping Power System
Oscillations, IEEE Trans. on Power Systems,
Vol. PWRS-2, No.4, November 1987.
[123] A Elices, L. Rouco, H. Bourles, and T.
Margotin, Design of Robust Controllers for
Damping Inter-area Oscillations : Application to
the European Power System, IEEE Trans on
Power Systems, Vol. 19, No. 2, May 2004.
[124] J. J. Sanchez- Gasca and J. H. Chow,
Power systems Reductions to Simplify the
Design of Damping controllers for Inter-area
Oscillations, IEEE Trans on Power Systems,
Vol. 11, No. 3, pp. 1342-1349, August 1996.
[125] Sami Ammari, Yuon Besanger, Nourdine
Hadjsaid, and Dider Georges, Robust Solution
for the Interaction Phenomena between Dynamic
loads and FACTS controllers, IEEE Trans on
Power Systems, Vol. 15, No. 2, 2000.
[126] P Shrikant Rao, and I. Sen , Robust Pole
Placement Stabilizers Design Using Linear
Matrix Inequalities, IEEE Trans on Power
Systems, Vol. 15, No.1, February 2000.
[127] S.S. Choi and X. M. Jia, Coordinated
Design of Under Excitation Limiters and Power
System Stabilizers, IEEE Trans on Power
Systems, Vol. 15, No.3, August 2000.
[128] K Bollinger, A. Laha, R. Hamilton, and T.
Harras, Power Stabilizer Design Using Root
Locus Methods, IEEE Trans on Power
Apparatus & Systems , Vol. PAS-94, No. 5,
September/ October 1975.
[129] J.J. Sanchez-Gasca, Coordinated Control
of two FACTS devices for Damping Inter-area
Oscillations, IEEE Trans. on Power Systems,
Vol.13, No.2, pp. 428-434, May 1998.
[130] Yu. T. and So. P. L., Coordinated
Control of TCSC and SVC for System Damping
Improvement, Proc. Int. Cont on Electric Utility
Deregulation and Restructuring and Power
Technologies (DRPT) London UK, 2000, pp.7-
12.
[131] Ping Lam So, Yun Chung Chu, and Tao
Yu, Coordinated Control of TCSC and SVC for
system Damping Enhancement, International
Journal of Control Automation and Systems,
Vol. 3, No.2, (special edition), pp. 322-333, June
2005.
[132] A. J. A. Simoes Costa, F. D. Freitas, and
A. S. Silva, Design of Decentralized Controllers
for Large Power Systems Considering Sparsity,
IEEE Trans on Power Systems , Vol,12, No.1,
February 1997.
[133] J. V. Milanovic, and I. A. Hiskens,
Damping Enhancement by Robust Tuning of
SVC Controllers in the Presence of load
Parameters Uncertainty, IEEE Trans on Power
Systems, Vol.13, No.4, November 1997.
[134] G. Li, T.T. Lie, G. B. Shrestha and K.
L.Lo, Design and Application of Coordinated
multiple FACTS Controllers, IEE Proc. Gener.,
Transm., Distrib., Vol. 147, No. 2, March 2000.
[135] Rajat Majumder, Bikash C. Pal, Christan
Dufour, and Petr Korba, Design and Real Time
Implementation of Robust FACTS Controller for
Damping Inter-area Oscillation, IEEE Trans on
Power Systems, Vol. 21, No.2, May 2006.
[136] G. Li, T. T. Lie, G. B. Shrestha and K. L.
Lo., Implementation of Coordinated multiple
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

68


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
FACTS Controllers for Damping Oscillations,
Electrical Power and Energy Systems, Vol.22,
pp. 79-92, 2000.
[137] Shen J., Liu C., Yokoyama R., and
Ishimaru M., Coordinated Control of PSS and
FACTS for Poor Damping long-term
Oscillations in Multi-machine Power Systems,
39
th
International Universities Power
Engineering Conference, University of the West
of England(UWE), Bristol, UK, 6-8 September
2004.
[138] O. Zhao, and Jin Jiang ,Robust SVC
Controllers Design for Improving Power System
Damping, IEEE Trans on Power Systems, Vol.
10, No.4, November 1995.
[139] B. Chaudhuri, and B. C. Pal, Robust
Damping of Multiple Swing Modes Employing
Global Stabilizing Signals with a TCSC, IEEE
Trans on Power Systems, Vol. 19, No.1,
February 1999.
[140] X. Yu, M. Khammash, and V. Vittal,
Robust Design of a Damping Controller for
Static Var Compensators in Power Systems,
IEEE Trans on Power Systems, Vol. 16, No.3,
August 2001.
[141] M.Yue, and R. A. Schlueter,
Synthesis Power System Stabilizer Design Using
a Bifurcation Subsystem Based Methodology,
IEEE Trans on Power Systems, Vol. 18, No.4,
November 2003.
[142] G.E. Boukarim, S. Wang, Joe H. Chow,
G. N. Taranto, and N. Martins, A Comparison
of Classical, Robust, and Decentralized Control
Designs for Multiple Power System Stabilizers,
IEEE Trans on Power Systems, Vol. 15, No.4,
November 2000.
[143] D. J. Trudnowski, J. R. Smith, T. A.
Short, and D. A. Pierre, An Application of
Prony methods in PSS Design for Multi-Machine
Power Systems, IEEE Trans on Power Systems,
Vol. 6, No.1, February 1991.
[144] Y. Chang, Design of HVDC and SVC
Coordinate Damping Controller Based on Wide
Area Signal, International Journal of Emerging
Electric Power Systems, Vol. 7, Issue 4, 2006.
[145] X. Zhou and J. Liang, Non-linear
Adaptive Control of the TCSC to Improve the
Performances of Power Systems, IEE
Proceedings on Generation, Transmission, and
Distribution, Vol. 146, No.3, May 1999, pp. 301-
305.
[146] Rodrigo A Ramos, Andre. C. P. Martins,
and Newton G. Bretas, An Improved
Methodology for the Design of Power System
Damping Controllers, IEEE Trans. on Power
Systems, Vol. 20, No.4, November 2005.
[147] L. J. Cai, and I. Erlich, Simultaneous
Coordinated Tuning of PSS and FACTS
Damping Controllers in Large Power Systems,
IEEE Trans. on Power Systems, Vol. 20, No. 1,
February 2005.
[148] A. M. Simoes, D. C. Savelli,P. C.
Pellanda, N. Martins, and P. Apkarian ,Robust
Design of a TCSC Oscillation Damping
Controller in a Weak 500-kV Interconnection
Considering Multiple Power Flow Scenarios and
External Disturbances, IEEE Trans on Power
Systems, Vol. 24, No.1, February 2009.
[149] A.J. Urdanata, N. J. Bacalao, B. Feijoo, L.
Flores, and R. Diaz, Tuning of Power System
Stabilizers Using Optimization Techniques,
IEEE Trans on Power Systems, Vol. 6,
No.1,February 1991.
[150] T. T. Nguyen, and R. Gianto,
Optimization-based Control Coordination of
PSSs and FACTS Devices for Optimal
Oscillations Damping in multi-machine power
system, IET Gener. Transm. Distrib, 2007, Vol.
1, No. 4, pp564-573.
[151] T. T. Nguyen, and R. Gianto, Stability
Improvement of Electromechanical Oscillations
by Control Co-ordination of PSSs and FACTS
Devices in Multi-machine Power Systems,
Power Engineering Society General Meeting
2007, IEEE 24-28 June 2007, pp. 1-7.
[152] J. W. Park, R. G. Harley, and G. K.
Vanayagamoorthy, Power System Optimization
and Coordination of Damping Controllers by
Series FACTS Devices, Power Engineering
Society Inaugural Conference & Exposition in
Africa 2005, IEEE, 11-15 July, 2005, pp293-
298.
[153] M. A. Abido, Simulated Annealing
Based Approach to PSS and FACTS Based
Stabilizers Tuning, Electrical Power and Energy
Systems, Vol. 22, pp. 247-258, 2000.
[154] Juan M. Raminrez, Ricardo J. Davalos,
Abraham, Valenzuela, and Ixtlahuate Coronado,
FACTS Based Stabilizers Coordination,
Electrical Power and Energy Systems, Vol. 124,
pp. 233-243, 2002.
[155] L. J. Cai, and I. Erlich, Fuzzy
Coordination of FACTS Controllers for
Damping Power Oscillations, IEEE Trans. on
Power Systems, Vol. 21, No.3, 2006.
[156] Ping Lam So, Yun Chung Chu, and Tao
Yu, Coordinated Control of TCSC and SVC for
system Damping Enhancement, International
Journal of Control Automation and Systems,
International Journal of Reviews in Computing
15
th
July 2011. Vol. 6
2009 - 2011 IJRIC & LLS. All rights reserved
.

ISSN: 2076-3328 www.ijric.org E-ISSN: 2076-3336

69


Publication of Little Lion Scientific R&D, Islamabad PAKISTAN
IJRIC
Vol. 3, No.2, (special edition), pp. 322-333, June
2005
[157] S. Khannan, Shesha Jayaram, and M.M. A
Salama, Real and Reactive Power
Coordination for a Unified Power Flow
Controller, IEEE Trans on Power Systems,
Vol.19, No. 3, August 2004.
[158] X. Lei, E. N. Lerch, and D. Povh,
Optimization and Coordination of Damping
Controls for Improving System Dynamic
Performance, IEEE Trans. on Power Systems,
Vol. 16, pp. 473-480, August 2001.
[159] M. Najafi, and A. Kazemi, Coordination
of PSS and FACTS Damping controllers in
Large power Systems for Dynamic Stability
Improvement, Power System Technology,
2006, POWERCON2006, International
Conference , 22-26 Oct.,2006, pp.1-6.
[160] Karim Sebaa, and Mohamed Boudour,
Power System Dynamic Stability Enhancement
via Coordinated Design of PSSs and SVC
based Controllers Using Hierarchical Real Coded
NSGA-II, Power &Energy Society General
Meeting Conversion & Delivery of Electrical
Energy in the 21
st
Century 2008, IEEE, 20-24
July, 2008, pp1-8.
[161] Juan M. Raminrez, Ricardo J. Davalos,
Abraham, Valenzuela, and Ixtlahuate Coronado,
FACTS Based Stabilizers Coordination,
Electrical Power and Energy Systems, Vol. 124,
pp. 233-243, 2002.
[162] J.M.Ramirez, R. J. Davalos, A.
Valenzuela, and I. Coronado, FACTS-based
Stabilizers Coordination, International Journal
of Electrical Power & Energy Systems, Vol. 24,
Issue 3, March 2002, pp. 233-243.
[163] H. W. Ngan W. Fang, Coordinated
Power Control Strategy for Flexible Ac
Transmission System, Power Electronics &
Drive Systems, 1999, PEDS99 Proceedings of
the IEEE 1999 International Conference, Vol.2,
27-29 July,1999,pp.677-682.







AUTHOR PROFILES:

Bindeshwar Singh was born in
Deoria, U.P., India, in 1975. He
received the B.E. degree in
electrical engineering from the Deen
Dayal of University of Gorakhpur, Gorakhpur,
U.P., India, in 1999, and M. Tech. in electrical
engineering (Power Systems) from the Indian
Institute of Technology (IITR), Roorkee,
Uttaranchal, India, in 2001. He is now a Ph. D.
student at Uttar Pradesh Technical University,
Lucknow, U.P., India. In 2001, he joined the
Department of Electrical Engineering, Madan
Mohan Malviya Engineering College, Gorakhpur,
as an Adoc. Lecturer. In 2002, he joined the
Department of Electrical Engineering, Dr. Kedar
Nath Modi Institute of Engineering & Technology,
Modinagar, Ghaziabad, U.P., India, as a Sr.
Lecturer and `subsequently became an Asst. Prof.
& Head in 2003. In 2007, he joined the Department
of Electrical & Electronics Engineering, Krishna
Engineering College, Ghaziabad, U.P., India, as an
Asst. Prof. and subsequently became an Associate
Professor in 2008. Presently, he is an Assistant
Professor with Department of Electrical
Engineering, Kamla Nehru Institute of Technology,
Sultanpur, U.P., India, where he has been since
August2009. His research interests are in
Placement and Coordination of FACTS controllers
in multi-machine power systems and Power system
Engg.
Mobile: 09473795769
Email: bindeshwar_singh2006@rediffmail.com ,
bindeshwar.singh2025@gmail.com