review paper on facts devices

7/23/2019 Review Paper on FACTS Devices

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A Review Paper on Various FACTS Devices For Enhancing Power System

Stability

Bakhtiar Khan, Sajid ul Haq, Abdul Wahab, Ghulam Hafeez, Hanan Ahmad, Muhammad Waqar, Sajid ul Haq,

Department of Electrical Engineering

Comsats Institite of Information Technology, Islamabad.

Abstract AC power control has been major problem since its invention. With increasing gap in demand and supply and

economic constraint, transmission lines are loaded to their neck. FACTS controller have been in use for power flow control

for some time but recently it has also being in use to enhance power system stability. This paper reviews on research and

development (R&D) on stability enhancement of power system using FACTS devices. In addition with review FACTS devices

installation and impact on power quality is summarized.

Keywords FACTS, UPFC, SVC, STATCOM, transient stability, TCSC, SSSC

1. Introduction

Flexible AC transmission systems (FACTS) technology is the application of power electronics in transmissionsystems. Flexible AC transmission systems (FACTS) controllers have been mainly used for solving various

power system steady state control problems and could be employed to enhance power system stability in

addition to their main function of power flow control. Power quality problems such as voltage regulation, power

flow control, low power factor, shortage of reactive power, poor voltage, voltage and current harmonics due to

sudden change in field excitation of synchronous alternator, sudden increased in load, sudden fault occur in thesystem and transfer capability enhancement are solved by FACTS controller.

The main purpose of this technology is to control and regulate the electric variables (voltage, phase angle and

transmission line impedance) and such effectively mitigate voltage sag in the power systems and to enhance the

power system stability. Facts Devices are also used for improving operation, control, planning & protection

from different performance point of view such as increasing the load ability, improve the voltage profile,

minimize the active power losses, increased the available power transfer capacity, enhance the transient and

steady-state stability, and flexible operations of power systems.

There are two generations for realization of power electronics-based FACTS controllers: the first generationemploys conventional thyristor-switched capacitors and reactors, and quadrature tap-changing transformers, the

second generation employs gate turn-off (GTO) thyristor-switched converters as voltage source converters

(VSCs).The first generation has resulted in the Static Var Compensator (SVC), the Thyristor- Controlled Series

Capacitor(TCSC), and the Thyristor-Controlled Phase Shifter (TCPS) . The second generation has produced the

Static Synchronous Compensator (STATCOM), the Static Synchronous Series Compensator (SSSC), the

Unified Power Flow Controller (UPFC), and the Interline Power Flow Controller (IPFC). The two groups of

FACTS controllers have distinctly different operating and performance characteristics. The thyristor-controlled

group employs capacitor and reactor banks with fast solid-state switches in traditional shunt or series circuit

arrangements. The thyristor switches control the on and off periods of the fixed capacitor and reactor banks and

thereby realize a variable reactive impedance. Except for losses, they cannot exchange real power with thesystem. The voltage source converter (VSC) type FACTS controller group employs self-commutated DC to AC

converters, using GTO thyristors, which can internally generate capacitive and inductive reactive power form

transmission line compensation, without the use of capacitor or reactor banks. The converter with energy storagedevice can also exchange real power with the system, in addition to the independently controllable reactive

power. The VSC can be used uniformly to control transmission line voltage, impedance, and angle by providingreactive shunt compensation, series compensation, and phase shifting, or to control directly the real and reactive

power flow in the line. The devices which are discussed in this paper are as follows.

1. Unified Power Flow Controller (UPFC)1

2. Stativ Var Compenator (SVC)2

3. Static Synchronous Compensator (STATCOM)3

4. Thyristor Controlled Series Capacitor (TCSC)4

5. Static Synchronous Series Compensator (SSSC)5

1 Studied and discussed by Bakhtiar Khan2 Studied and discussed by Sajid ul Haq3 Studied and discussed by Abdul Wahab and Ghulam Hafeez (including Introduction to the topic of review paper)4 Studied and discussed by Hanan Ahmad5 Studies and discussed by Muhammad Waqar



2.

FACTS Devices

2.1 Unified Power Flow Converter (UPFC)

2.1.1 Introduction

Years ago, eletric power systems were relatively simple and self sufficeint in their design. The transmission of

power to distant locations was rare and the systems were designed with generous stability margins with respectto the power needs of that time. Moreover, it was a general view that the transients are of so short time and are

so fast that it couldn’t be controlled and the main focus was given to the steady state conditions. Since, the

control of power flow through transmissin lines require the control of following three transmission line

parameters.

1. Magintude of sending and receiving end voltage

2. Phase angle between the receving and sending end voltages

3. Transmission line impedace

Therefore, to control power flow, optimise system impedance and minimise voltage variation in steady state

conditions, mechanically-switched series and shunt compensators were employed in the design of transmissionline along with voltage regulating and phase shifting transformers tap-changers.

However, recent years have seen much more demand of electric power as well as the power system has become

more complex and deregulation in every industry including power industry has made the power system

vulnerable to much more other threats that were not observable years ago. The generation facilities and new

transmission lines are also not constructed with the same pace. Consequently, it put an urge to explore ways to

obtain better operating flexibility and utilization of existing power systems.

Recent advancement in the field of power electronics has already made significant impact on AC transmission

system via the increasing use of thyistor-controlled static Var Compensators (SVCs). However, SVCs only

control the magnitude of the bus voltage on the selected terminals of transmission line while for complete

control on the power flow through transmission line, impedance and phase angle are also required to be under

control. Similarly, thyristor-controlled tap-changing phase shift transformers are also in use for control over phase shift and thyristor-controlled series compensators are employed for impedance control. But all these

different techniques combined, to give a complete control over the power flow through the transmission line, is

rather custom-designed, bulky in size and are of substancial cost with significant labour installation. Therefore,

they are not considered as an economic, flexible and volume-based solution for the objective of flexible AC

transmission systems.

2.1.2 UPFC: An overview

Unified Power Flow Controller (UPFC) is the most versatile and robust device among the FACTS devices. It is

able to control all the three parameters of power flow i.e. voltage of the bus, reactance of transmission line and

phase angle between two buses, either simultaneously or independently. These parameters are controlled by

controlling shunt compensation, in-phase voltage and quadrature voltage.

The UPFC is represented by the block diagram as shown in Figure 1. It is comprised up of two voltage source

converters (VSCs) coupled through a common DC link. The first VSC (Converter 1) is connected to the line

through a shunt coupling transformer whose primary winding is connected from line to ground and secondary

winding is conected with the converter 1 and the second VSC (Converter 2) is connected in series with the line

through a series coupling transformer whose primary winding is connected in series with the transmission line

and secondary winding is connected with converter 2. Both the converters are supplied DC voltage from a

capacitor bank connected as a common DC link between the two converters.



Figure 1 Basic Circuit of UPFC

2.1.3 Operating Principle of UPFC

The basic operation of UPFC for power flow control is such that a voltage V pq is injected in series with the

transmission line by controlling the series converter (converter 2). This series injected voltage can be varied

from 0 to V pqmax. Moreover, this series converter can also vary the phase angle of the phasor V pq independently

from 0o to 360o. In this way, the series converter exhanges both the real and reactive power with the

transmission line. In the process, the series converter generates/absorbs the reactive power internally while the

real power is generated/absorbed by the dc energy storage device i.e. the capacitor.

The main purpose of the shunt connected Converter (Converter 1) to supply the real power demand of Converter

2. Converter 1 obtains this real power from the transmission line and maintains the voltage of the dc bus

constant. Thus, the losses of the two converters and that of the coupling transformers makes the net real power

drawn from the ac system. In addition to all this, the shunt converter also works like a STATCOM and it hasthe abillity to regulate the terminal voltage of the interconnected bus independently, by generating/absorbing

requisite amount of reactive power.

2.1.4 Literature Review

All the three parameters of transmission line can be controlled with UPFC. It was proved experimently that the

parameters for power flow control i-e voltage, phase angle and transmission line impedance can be controlledeither individually or in appropriate combinations at the series-connected output of UPFC while maintaining

reactive power support at its shunt-connected input [1]. To enhance the damping of power system, the

mechanism of the three control methods of a UPFC was also investigated [2]and it was shown that using simple

propotional feedback of rotor angle deviation of machine, transient swing can be reduced significantly. High

frequency power fluctuations induced by a UPFC were also investigated [3].

Various techniques and methodologies are used in literaure to study the steady-state and transient state response

of UPFC. A small-signal linearized dyanmic model, a steady-state model a state-space large-signal model of a

UPFC was developed assuming the power system to be symmetrical and operating under three-phase balanced

conditions [4]. Two other UPFC models were also developed that were incorporated in the Phillips – Heffron

model after linearizing [5], [6]. It was noticed that their are chances of negative interaction between the voltagecontrol of DC link capacitor of UPFC and PSSs in the power system, unless UPFC is equipped with a proper

damping controller [6]. Another effort in modeling UPFC was made by injecting current to improve dynamicresponse of power system [7]. In this model, a shunt current source and a series voltage source was used to

represent the equivalent circuit of UPFC. The property of symmetry of Ybus matrix was featured in the

presented model.

It was a general view that by adding a supplementary controller to the UPFC, power system damping can be

enhanced to a greater extent. Therefore, various control schemes were introduced for the purpose of damping

the oscillations. To damp the interarea mode of oscillations, an attempt was made to design a lead-lag controller

having conventional fixed-parameter for the UPFC installed in the tie-line of a two-area system [8]. With the

use of H ∞ control, much more robust control schemes were also presented [9], [10]. A PI controller having

multiple input and multipel output was also proposed [11]. It has been illustrated that if more than one UPFC

controller, such as a power flow controller, an AC voltage controller, and a DC voltage controller, weredesigned separately, the dynamic interactions among the various control channels may have a detrimental effect

on the system stability. A nonlinear control strategy for phase angle of the series branch of a UPFC and linearcontrol strategies for the other channels have been hybridized for stability enhancement of a multimachine



system [12]. The adverse effect of DC voltage regulator on the damping characteristics of UPFC has been

addressed in [13]. In addition, different control channels of the UPFC have been evaluated using a

controllability index. Different intelligent damping controllers were also developed for a UPFC to damp both

local and interarea modes of oscillation for a multimachine system. The effectiveness of such controllers has

been demonstrated and reported with satisfactory success. [14] – [17]

2.1.5

Mathematical Modeling

The equivalent electrical model for UPFC in steady state is shown in figure 2 [18]. This model is developed for

a transmission line of 300 Km where the UPFC is placed just at the center of the transmission line. This model

was derived to study the characteristics of transmission line and UPFC in steady state and to derive a

mathematical model for the steady state case.

Figure 2 Electrical Equivalent of UPFC

According to [19], UPFC can be represented as voltage sources representing the fundamental component of the

two converters while impedances as the leakage impedances of the two coupling transformers. Based on theoperating principle of UPFC and using some knowledge of network theory, the real and reactive power flow

between bus-i and bus-j can be written as [20]

2 2( ) 2 cos( ) [ cos( ) sin( )] ( cos sin )ij i T ij i j ij T j j T ij T j ij T j i j ij ij ij ij P V V g V V g V V g b V V g b ( 1 )

2 ( / 2) [ sin( ) cos( )] ( sin cos )ij i T ij i T ij T j ij T i i j ij ij ij ijQ V I V b B V V g b V V g b ( 2 )

Where1

ij ij

ij ij

g jbr jx

andq

I is the reactive current flowing into the shunt transformer to improve the shunt

connected bus of the UPFC.

Similarly, the real and reactive power flows from bus-j to bus-i in the transmission line with UPFC installed on

it is written as

2 [ cos( ) sin( )] ( cos sin ) ji j ij j T ij T j ij T j i j ij ij ij ij P V g V V g b V V g b ( 3 )

2 ( / 2) [ sin( ) cos( )] ( sin cos ) ji j ij j T ij T j ij T j i j ij ij ij ijQ V b B V V g b V V g b ( 4 )

The real and reactive power injections at bus-i with system loading ( ) can be written as

0 (1 )b

i Gi Di ij

j N

P P P P

( 5 )

0 (1 )b

i Gi Di ij

j N

Q Q Q Q

( 6 )

Where 0

Di P and 0

DiQ are the initial real and reactive power demands. Gi P and GiQ are the real and reactive power

generations on the bus-i respectively. b N is the number of system buses and is the sensitivity of system

loading. In equation (5), uniform loading with the same power factor at all the load buses has been considered

and the increase in the loading is assumed to be taken care by the slack bus whereas any sharing of generationamongst the generators can be easily incorporated in this model.



2.1.6 Conclusion

In this study, the most versatile member of FACTS family, UPFC, was briefly discussed. The study includes the

working principle of UPFC, literature review and a mathematical model for steady state. From the literature

review, it is deduced that UPFC is very efficient and robust in enhancing power system transient and steady

state stability. It was noticed in the introductory section that complete control over the flow of power through a

transmission line is possible only if the the voltage magnitude, phase angle and transmission line impedance areunder control simultaneously and later on, it was observed that UPFC is able to control all these parameters

independently or in possible combinations. Therefore, UPFC is a very favourite option for power system

engineers to control power flow over designated transmission line and to enhance power system stability. To

summarize, transient stability is improved and faster steady state is achieved when UPFC is used at an

approprate location in the transmission lines.

2.2 Static Var Compensator (SVC)

2.2.1 Introduction

Static var Compensator (SVC) is a flexible AC transmission system (FACTS) controller. SVC is the latest

technology in power electronics switching devices.[21] It mostly used in the transmission of electric power

system to control the voltage and power flow of the system. it also regulate the voltage level of transmission

line. Both capacitive and inductive shunt reactive power sources is controlled by SVC and improve the overall

system efficient. SVC is made from the following components showen in figure 3 [22].

Figure 3 Basic model of SVC

1. Coupling transformer2. Thyristor valves

3. Reactors

4. Capacitors

The voltages is regulated by SVC at its terminals by controlling the amount of reactive power injected into orabsorbed from the power system [23].The SVC generates reactive power (SVC capacitive) When system

voltage is low. It absorbs reactive power (SVC inductive) When system voltage is high. Static VAR

Compensator is a shunt connected FACTS controller, and enhance stability dynamic and transient disturbances

in power systems. When a three phase fault occur in power system.[24]the damping of power system

oscillations is analyzed with the analyzation of the effects of SVC on transient stability performance of a power

system. SVC is installed in midpoint power system and also may be installed at the end of line.

2.2.2 Literature review

For the purpose of review paper from literature we carried out two most important and database which is named by two different categories called the IEEE/IEE electronic library and Science Direct electronic databases. This

survey is stared from1990 tan complete in 2004.the overall survey period is divided into three stages. 1990 –

1994, 1995 – 1999, and 2000 – 2004 [25]. The number of publications discussing FACTS applications to different

power system studies has been recorded. The results of the survey are shown in Figure 4. It is clear that the

applications of FACTS to different power system studies have been drastically increased in last five years. This

observation is more pronounced with the second generation devices as the interest is almost tripled. This shows

more interest for the VSC-based FACTS applications. The results also show a decreasing interest in TCPS whilethe interest in SVC and TCSC slightly increase. Generally, both generations of FACTS have been applied to



different areas in power system studies including optimal power flow, economic power dispatch, voltage

stability, power system security, and power quality.

Figure 4 Classification of power system stability

2.2.3 Types of SVCs

There are two basic types of SVCs, each having a different combination of the Components.

1) SVC of the TCR-FC type

2) SVC of the TCR-TSC type.

2.2.3.1 SVC of the TCR-FC type

The SVC of the TCR-FC type consists of a TCR, which absorbs reactive power from the ac power system to

which the SVC is connected, and several FCs, which supply reactive power to the system connected to theSVC[26]. The simplified single-wire circuit diagram of an SVC of the TCR-FC type is illustrated in Figure 5.

Figure 5 Simplified single-wire circuit diagram of an SVC of the TCR-FC type.

2.2.3.2 SVC of the TCR-TSC type

The SVC of the TCR-TSC type consists of a TCR, which absorbs reactive power from the ac power system

connected to the SVC, and several TSCs, which supply reactive power to the ac power system connected to the

SVC. The simplified single-wire circuit diagram of an SVC of the TCR-TSC type is illustrated in Figure 6.



Figure 6 Simplified single-wire circuit diagram of an SVC of the TCR-TSC type.

2.2.4 Methodology

2.2.4.1

Development of Transient Stability Analysis

When sudden change in disturbance is occur in power system, the transient stability analysis investigate the

stability of the power system. The transient stability analysis having two combine solution to solve this problem

one is algebraic equations which is performed by numerical solution and other one is differential equations

solution [27]. Although significant improvements have been made in the application of numerical andcomputational methods to the transient stability calculation, the computational demands are rising rapidly at the

same time. Therefore there is a continual search for faster and accurate solutions to the transient stability

problem.

2.2.4.2 With and without SVC Transient Stability Evaluation

The following steps are involves for algorithm of the transient stability studies with FACTS (SVC) devices

1. Read the data for lines, transformers and shunt capacitors.

2. Make matrix of admittance ,YBUS

3. Show and write generator data (Ra,XdXq, H, D etc).

4. From the load flow results, write steady state bus data. ([V], [δ], [Pload], [Qload

], [Pgen], [Qgen

]).

5. Calculates and write the number of steps for different conditions of fault such as fault existing time, line

outage time before auto-reclosing, simulation time etc

6. Modify,YBUS admittance matrix by adding the load and generator admittances.

For generator admittance matrix of bus ‗i‘

Yii = Yli + Ygi

Ygi =

1

Rgi + jXdi

For load admittance matrix bus ‗i‘

Yii = Yli + YLi

Where

YLi =PLi + jQ

Li

|V2|

7. Calculate fault impedance and also show bus impedance with modify from.

8. Initial conditions should be calculated and constants needed in solving the DAEs of generators, AVR etc. is

also known.

9. Calculate the network equation iteratively in each time step of the problem.

10. For Xd − Xq models calculates Vd − Vq using the obtained voltages and rotor angles.

11. Calculates electric power outputs of the generator.



12. The time step is advanced by the current time step.

13. Keeping generator mechanical power output as constant and Solves the generator swing equations using by

trapezoidal rule of integration

14. Solves the AVR equations

15. Solves the SVC. The bus current injection vector is modified with SVC injection currents. Then network

equation is again solved using[28] [YBUS] [V] = [ Iinj ].

2.2.5 Different purpose of SVC:

The unsymmetrical load is balance by SVC and to support the railway voltage in the case of a feeder station trip

when two sections have to be fed from one station which is primary working. The second purpose of the SVCs

is to maintaining unity power factor during normal operation [29]. Thirdly, the SVCs alleviate harmonic

pollution by filtering the harmonics from the traction load.

2.2.6 V-I characteristics of SVC

Figure 7 VI characteristics of SVS

2.2.7 Design of SVC by Adaptive Control

The SVC, which comprises a fixed capacitor and a thyristor-controlled inductor, which improve generator

damping without deterioration in the voltage profile under severe disturbance conditions. We obtained betterdynamic performance, a supplementary proportional-integral (PI) controller, of which the parameters are find by

eigenvalue assignment, is incorporated in the static VAR compensator. By further improving the damping

characteristics over a wide range of operating conditions [30], an adaptive controller using model reference

adaptive control (MRAC) is also developed.

2.2.8 Conclusion

Instabilities in power system are created due to long length of, interconnected grid, transmission lines, changing

system loads and line faults in the system. These instabilities causes in reduced line flows or even line trip. SVC

FACTS controller stabilize transmission systems with increased transfer capability and minimize risk of line

trips. Financial benefit from SVC FACTS controller comes from the additional sales due to increasedtransmission capability, excesses wheeling charges due to increased transmission capability and due to delay in

investment of high voltage transmission lines or even provide new power generation facilities [31]. Also, in a

deregulated market, the improved stability in a power system substantially reduces the risk for forced outages,

thus reducing risks of lost revenue and penalties from power contracts.



2.3

Thyristor Controlled Series Capacitor (TCSC)

There has been a considerable increase in electrical power generation harnessing wind energy. To ensure bulktransfer of power smoothly, the large electrical stations generating power would be connected to the power

system using series compensation. The subsynchronous resonance issues arise due to induction generator effect(

IG) and the possible torsional interactions ( IR). A thyristor controlled series capacitor (TCSC) which in the

first place is used to enhance the capability of the power transferred through the transmission line also mitigates

the sub synchronous resonance issues greatly. The TCSC helps to damp out the sub synchronous

oscillations[32].

Due to limited resources and some environmental issues some of the transmission lines are heavily loaded and

as a consequence the transfer of power is limited through the line to ensure the system stability. Using a

thyristor controlled series capacitor (TCSC) in a power system enhances the power carrying capacity and the

control of a transmission line by changing the impedance of a transmission line. Moreover the application of a

TCSC reduces the oscillations of active power, enhances voltage transient and increases dynamic stability and

overcome the issue of SCR issue ( Sub synchronous issue). Before the application of a TCSC in a power system

it is necessary to carry out a thorough power flow analysis of a power system and carrying out a thorough

analysis of TCSC [33].

The compensation employing fixed series compensation is an economically possible way of improving power

carrying capacity of a transmission line. The issues associated with a fixed capacitance can be avoided by

employing a TCSC which consists of a series capacitor connected with a parallel thyristor controlled reactor

(TCR). The firing angle of a thyristor is changed to change the voltage across the series capacitor and thus in

this way the capacitance is varied . Using a line current as a reference, a TCR offers a different reactance of a

TCSC for a specific firing angle as compared with a voltage referencing of a capacitor [34].

A TCSC is a variable capacitor that is connected in series with a line. The insertion response test of a TCSC

reveals that when it is switched in a vernier mode into a transmission line then then switching transients are

damped out quickly. When TCSC is simply connected as a capacitor then voltage transient has a fairly large

component of oscillation that damps out slowly. Vernier firing helps to achieve steady state with in few cycles

after insertion and the oscillations are also less severe. Thus the control of a TCSC is quite effective and deals

with many types of faults [35].

TCSC mitigates the SSR ( sub synchronous reactance ) issue by changing the series capacitance continuously.

In other words TCSC has a variable capacitance. The thyristor controlled series capacitor at sub synchronousfrequency would reveal characteristics impedance of an inductor provided that middle of firing angles or

conduction angles lie at zero crossing of the voltage across the capacitor. The relationship developed between

the voltage called as sub synchronous voltage across the TCSC and the sub synchronous current flowing

through it reveals that if the firing angles of the valves of thyistors is symmetrical with respect to the zero

crossing of the capacitor voltage then TCSC doesnot lead to SSR issue. If the magnitude of the subsynchronous

frequency is relatively small as compared to the system frequency then the magnitude of the voltage across thecapacitor i.e subsynchronous voltage is approximately equal to zero. The application of TCSC is safe to use. But

if the magnitude of the subsynchronous frequency is comparable to the system frequency then the role of

subsynchronous voltage appearing across the TCSCR cannot be neglected any further. Hence the use of TCSC

requires a careful consideration [36].

FACTS devices are employed in a power system to use our transmission infrastructure effectively. A TCSC

offers a flexible control of the power flowing through the lines. It enhances the power transfer capability and

improves the stability of our system. There are two approaches for synchronization of TCSC. One way is to

synchronize a TCS I,e firing angles or conduction angles of the valves of a thyristor with respect to the zeros of

the capacitor voltage of a TCSCR. And the second method employs the synchronization with zero of the line

current [37].

In case of voltage synchronization the conduction angle varies from 90 to 180 degree and in case of current

synchronization the firing angles increases from 90 to 270. For step change in conduction angles the transient

response is faster with current synchronization as compared with voltage synchronization of TCSC. Irrespective

of which method of synchronization of TCSC was used, experiments indicates that instability occurs under each

scheme of synchronization.



TCSC is connected in series with a line. It consists of a series capacitor shunted by a reactor. The use of TCSC

is more effective as compared with fixed capacitance. The use of thyristors provides more flexibility whena

TCSC is connected in series with a line and TCSC helps to counterbalance the inductance of a transmission line.

Voltage stability is increased and the voltage dips in a power system are reduced to a great extent. The

application of a TCSC in a power system is of significant importance in operation and control of power system.

Besides that TCSC reduces the fault current and improving the dynamic and transient stability of a power

system to a great system. It enhances the power flow through the transmission lines. The values of inductanceand the capacitance of a TCSC should be carefully chosen in order to avoid negative effects on the power

system. Before actually applying a TSCS in a system it is necessary to study the steady state behavior of aTCSC. The mathematical model can be established by employing the firing angles or conduction angles of a

thyristor to enhance the power flow through the transmission lines. The desired value of the parameter in order

to determine the operating performance of a TCSC “w” should lie in between 2.2 and 2.7 [38].

A thyristor controlled series capacitor has a number of benefits to offer. The TCSC alters the reactance of a

transmission line. Inshort it changes the apparent impedence of line. In this way it effects and changes the power

flow through a network. If the parameters of TCSC are set up correctly then the performance of the system is

better with TCSC than it was before the installation of TCSC in power system. The effects of TCSC on the

reliability of power system can be investigated by making a model. The model can be simplified using statespace approach. In order to determine system reliability when a TCSC is connected in power system it is

necessary to operate the TCSC in various operational conditions. Some of the possible conditions includedifferent locations of installation of a TCSC and different thermal limits of the transmission line. The difference

between the TCSC in working conditions and in failure mode indicates that ideal model of TCSC can be used to

determine the reliability of a power system provided that TCSC is reliable enough also [39].

The problems associated with long distribution can be resolved effectively using a variable series capacitance i.e

a TCSC. A TCSC can be operated as current limiter in case of short circuit. The installation of TCSC would notallow the voltage sag on the lines where the sensitive loads are connected to a nearby substation in case of

occurrence faults . EMTDC ( electromagnetic transients for DC) package can be used to stimulate the benefits

of a connection of a TCSC. So the capacity to carry power by a transmission line is comparably increased,

power swings can be damped out and TCSC could be used a fault current limiter. The voltage dips due to

fluctuating loads can be lowered considerably by changing the series capacitance. When TCSC is operated in

an inductive region it limits the fault current and the voltage can be kept constant at the loads. The high power

quality issues could be oversome to some extent by using TCSC in power system [40].

A thyristor controlled series capacitor can be used for closed loop control of power flow in a constant power and

constant angle modes. The transient stability and small signal characteristics of a power system are influenced

by the controller of power flow. The constant angle mode has negative impacts on the first swing stability and

damping of the system. On the other hand the constant power mode has positive impacts on the damping of

system and first swing stability [41].

With the integration of renewable energy and market deregulation the electromechanical stability of power

system is challenged. A thyristor controlled series capacitor can be used to control the stability of a system

during large disturbances during the time of transients. The TCSC can be used to dynamically control the

impedance of a line. In short the TCSC can provide the dynamic series compensation to overcome the transients

in a power system. This remedial action in turn increases the security and stability of a power system [42].

The region known as signal stability region van be greatly enhanced by employing FACTS devices in our power

system. Even on the lower portion of the PV curve the system tends to remain stable. Using a TCSC to keep the

voltage stable i.e constant at the loads the ratio of load time constant to time constant of a thyristor controlled

series capacitor does not has a significant impact on voltage stability region of the power system [43].

The thyristor controlled series capacitor can be used to develop an inductive reactance with in subsynchronous

frequency. The TCSC is able to enhance the transmission power capacity and at the same time reduce the fault

levels [44].

Using angle stability enhancement like TCSC can increase the stability of the voltage in case of occurrence of

faults [45].



2.4 Static synchronous Compensator:

STATCOM is a shunt type FACTS device which is used in power system primarily for the purpose of voltage

and reactive power control. In [46], a current source converter (CSC) based static synchronous compensator

(STATCOM) which is a shunt flexible AC transmission system (FACTS) device; impact is described for small

and large transient stability in an interconnected power system.

That paper investigates the impact of a noveland robust pole-shifting controller for CSC-STATCOM to improve the transient stability of the multi machine

power system. The proposed algorithm utilizes CSC based STATCOM to supply reactive power to the test

system to maintain the transient stability in the event of severe contingency. Below the CSC based STATCOM

representation is shown.

Figure 8 STATCOM

In emerging electric power systems, enlarged communication often lead to the situations where the structure nolonger remains in secure operating region. In [47], the author presents an application of fuzzy control to

determine the control signal of static compensator (STATCOM) for improvement of power system stabilityA

fuzzy logic based supplementary controller for Static Compensator (STATCOM) is developed which is used for

damping the rotor angle oscillations and to improve the transient stability of the power system. Generator speedand the electrical power are chosen as input signals for the fuzzy logic controller (FLC). A Standard 3-phase, six

bus system is taken as test system to evaluate the FACTS device (STATCOM) performance for proposed

controllers PI and fuzzy with Power System Stabilizer in multi machine System.

Damping of low frequency electromechanical oscillations is very important for a safe system operation. To

solve this problem, [48] presents a novel methodology for tuning STATCOM based damping controller in order

to enhance the damping of system low frequency oscillations. The design of STATCOM parameters are

considered an optimization problem according to the time domain-based objective function solved by a Honey

Bee Mating Optimization (HBMO) algorithm that has a strong ability to find the most optimistic results.

In [49], paper presents seeker optimization algorithm (SOA) to design the parameters of PSS and STATCOMcoordinately to improve more stability of power system. The SOA is used to achieve the best optimal results to

minimize the objective function of the optimization problem. Simulations are carried out on a two-area Kundur

and 39-bus New England power systems, and simulation results confirm the efficiency of the proposed method

to stabilize power system oscillations.

In [50], paper the issues related with distance protection of transmission lines with STATCOM connected atmid-point are addressed used to improve the power transfer capability of transmission lines. Use of FACTS

devices in transmission lines affects protection system very drastically. To mitigates the problems associated

With distance protection, a novel algorithm based on synchronized measurement for adaptive Relay setting is

proposed.



Owing to the constantly increased electricity demands and transactions, power systems are becoming more

vulnerable to voltage instability generally incurred by over-utilized transmission facilities or any contingency. In

order for transmission networks to accommodate more power transfers with less expansion cost, proper

installation of Flexible AC Transaction Systems (FACTS) is a promising way. The power system loading

margin enhancement problem to determine an optimal Static Synchronous Compensator (STATCOM)

installation scheme can be formulated as a mixed discrete – continuous nonlinear optimization problem (MDCP).

In [51], to improve the efficiency of solving the MDCP, an ordinal optimization (OO) STATCOM installationstrategy is proposed to seek a good enough solution rather than the Optimal solution.

With increase in electric power demand, transmission lines were forced to operate close to its full load and due

to the drastic change in weather conditions, thermal limit is increasing and the system is operating with less

security margin. To meet the increased power demand, a doubly fed induction generator (DFIG) based wind

generation system is a better alternative. For improving power flow capability and increasing security

STATCOM can be adopted. As per modern grid rules, DFIG needs to operate without losing synchronism

called low voltage ride through (LVRT) during severe grid faults. A STATCOM is coordinated to the system forobtaining much better stability and enhanced operation during grid fault. In [52], author mitigates voltage and

limits surge currents to enhance the operation of DFIG during symmetrical and asymmetrical faults. The system

performance with different types of faults like single line to ground, double line to ground and triple line to

ground was applied and compared without and with a STATCOM occurring at the point of common coupling

with fault resistance of a very small value at 0.001 Ω.

In [53], author presents singular value decomposition (SVD)-based approach to assess and measure the

controllability of the poorly damped electromechanical modes by STATCOM different control channels. Powersystem stability enhancement via STATCOM-based stabilizers is thoroughly investigated in this paper. The

coordination among the proposed damping stabilizers and the STATCOM internal ac and dc voltage controllers

has been taken into consideration. The design problem of STATCOM-based stabilizers is formulated as an

optimization problem. For coordination purposes, a time domain-based multi objective junction to improve the

system stability as well as ac and dc voltage regulation is proposed.

In [54], the optimal location of a static synchronous compensator (STATCOM) and its coordinated design with

power system stabilizers (PSSs) for power system stability improvement are presented in this paper. First, thelocation of STATCOM to improve transient stability is formulated as an optimization problem and particle

swarm optimization (PSO) is employed to search for its optimal location. Then, coordinated design problem ofSTATCOM-based controller with multiple PSS is formulated as an optimization problem and optimal controller

parameters are obtained using PSO. A two-area test system is used to show the effectiveness of the proposed

approach for determining the optimal location and controller parameters for power system stability improvement

.In [55], author proposes and validates models to accurately represent static synchronous shunt compensators

(STATCOM) in voltage and angle stability studies of powers systems. The proposed STATCOM stability

models are justified based on the basic operational characteristics of this flexible AC transmission system

(FACTS) controller for both phase and PWM control strategies. These models are first validated by means of

EMTP simulations on a test system, and then are implemented into two different programs used to study voltage

and angle stability issues in the system.

In [56], author deals with the stability problem at the inverter end of a HVDC link with STATCOM (Static

Compensator), when connected to a weak AC system which has the stability enhancement for power instabilityand commutation failures. The HVDC stability problem is tackled with a STATCOM which not only provides a

rapid recovery from power, harmonic stability and commutation failures but also offers a lower cost filter design

for the HVDC system.

The electric power infrastructure that has served huge loads for so long is rapidly running up against many

limitations. Out of many challenges it is to operate the power system in secure manner so that the operation con-

straints are fulfilled under both normal and contingent conditions. Smart grid technology offers valuable

techniques that can be deployed within the very near future or which are already deployed nowadays. Flexible

AC Transmission Systems (FACTS) devices have been introduced to solve various power system problems. In

[57], author presents a technique for determining the proper rating/size of FACTS devices, namely the StaticSynchronous Compensator (STATCOM), while considering contingency cases. The paper also verifies that the

weakest bus determined by eigenvalue and Eigen- vectors method is the best location for STATCOM. The

rating of STATCOM is specified according to the require reactive power needed to improve voltage stability



under normal and contingency cases. Two case system studies are investigated: a simple 5-bus system and the

IEEE 14-bus system.

The [58], presents the design of a non-linear controller to prevent an electric power system losing synchronism

after a large sudden fault and to achieve good post fault voltage level. By Direct Feedback Linearization (DFL)

technique robust non-linear excitation controller is designed which will achieve stability enhancement and

voltage regulation of power system. By utilizing this technique, there is a possibility of selecting various controlloops for a particular application problem. This method plays an important role in control system and power

engineering problem where all relevant variables cannot be directly measured.

Wind power injection into an electric grid affects the power quality due to the fluctuation nature of the wind and

the comparatively new types of its generators. The power arising out of the wind turbine when connected to a

grid system generates power quality problems. The concerned power quality measurements are: active power,

reactive power, voltage sag, voltage swell, flicker, harmonics, and electrical behavior of switching

operation. For the control of these problems a FACTS device STATIC COMPENSATOR (STATCOM) isconnected at a point of common coupling [59]. The STATCOM will reduce the harmonics in the grid current

by injecting superior reactive power in to the grid. This is because of reactive power drops off STA TCOM is

linear with voltage. Here a bang-bang control scheme has been implemented with the STATCOM to achieve

fast dynamic response for the reduction of harmonics in grid current. Bang-bang controller is simple and

reliable. A STATCOM can improve power system performance in such areas as the following: thedynamic voltage control in transmission and distribution systems, the power-oscillation damping in powertransmission systems, the transient stability, the voltage flicker control and the control of not only reactive

power but also (if needed) active power in the connected line.

Main factor causing voltage instability is the inability of the power system to maintain a proper balance of

reactive power and voltage control. The driving force for the voltage instability is the load. Using the shunt

compensating devices, the reactive power balance of the power system can be maintained. In [60], author

compares the performance of shunt capacitor, SVC and STATCOM in the improvement of static voltage

stability. Issues related to shunt compensation, namely rating of the compensating device and its location are

also considered.

Figure 9 Equivalent Electrical Model

In [61], investigations are carried out to explore the impact of a midpoint static synchronous compensator

(STATCOM) on the coordination between the generator distance phase backup protection (function 21) and the

generator capability curves. The results of these investigations have shown that the midpoint STATCOM has an

adverse effect on such coordination Such an impact varies according to the fault type, the fault location, and the

generator loading. This paper proposes the use of the support vector machines’ classification technique for

generator phase backup protection to enhance the coordination between such protection and generator capability

curves in the presence of a midpoint STATCOM.

In [62], presents a new technique for improving the fault ride through (FRT) capability of self-excited induction

Generator (SEIG)-based wind parks by implementing fault current limiters (FCLs) using the electromagnetic

transient program simulation program (PSCAD/EMTDC). A non-inductive high-temperature superconducting

coil of an FCL is developed comprising its major components, operation control algorithm, sequence of events

and fault detection techniques. The test system is adopted with an integrated 80 MW SEIG-based wind park that

comprises a static synchronous compensator (STATCOM) at each wind turbine. A novel damping voltagecontrol algorithm for the STATCOM is presented for improving the FRT and damping the power system

oscillation. FCLs are installed in series with the high voltage (HV) side of the substation transformers of the

wind park. The operation of the FCLs is tested in the proposed system to demonstrate its superior performance

for reducing the high fault currents and improving the FRT capability.



2.5 Static Synchronous Series Compensator:

2.5.1 Introduction

Initially power system is controlled by mechanical system like switchgears [63]. Mechanical system is slow as

switchgear takes very large time as compared power electronic based circuits. In order to control power system

efficiently, flexible AC transmission line (FACTS) are devised so that flow of power can be controlled. If

transmission system is loaded at their near full capability, generating reserve can be decreased. By decreasing

reserves, capital investment made for these reserves can be decreased.

2.5.2 Overview

Two generation of FACTS base controller have been existed. Fixed capacitors and inductors or thyristor

controlled capacitors and inductors form the first batch of FACTS controller. Static Var Compensator (SVC),

Thyristor Controlled Series Capacitor (TCSC) and Thyristor Controlled Phase Shifter(TCPS). The thyristor

switch converter also known as voltage source converter form the second generation. Static Synchronous Series

Compensator in addition with Static Synchronous Compensator (STATCOM), Unified Power Controller(UFPC) and Interline Power Flow Converter (IPFC) form the second generation of FACTS controller. Both first

and second generation devices are different in their operation, but are used for power flow control [64].

Usage of power electronic based converter for reactive power shunt compensation is being studied for long time.

In 1989, Synchronous Voltage Source for series reactive power compensation is proposed [65].

Power flow depends directly upon sending and receiving end voltages, the angle difference between them and

inversely proportional to impedance between them. Inductance and capacitance is added in order to increase or

decrease the reactance as per given circumstances [66]. Conventionally reactance is controlled by capacitors and

inductors. Now power electronic based solid state devices are proposed. One of them is Static Synchronous

Series Compensator (SSSC), produces nearly sinusoidal voltage in series of transmission line. Voltages injected

by SSSC are nearly in quadrature with line current. A part of voltage in phase with series current is used

compensate for losses by compensator. Voltage in quadrature of line current depicts inductive and capacitive

nature of compensator in series with line. When voltage leads line current, compensator behaves capacitive

nature and when voltage lags line current, compensator behaves inductive nature of reactance.

2.5.3 SSSC Installation

Different controllers are in commercial use for power flow control especially STATCOM but SSSC is only intesting stage. Convertible Static Compensator (CSC) is commissioned at Marcy 345 kv substation of New York

Power Authority. Although it is configured in STATCOM, it has been tested in SSSC configuration. In SSSC

configuration it was designed to produce constant voltage in series with line current [67].

Two 160 Mvar United Power Flow Converter (UPFC) is also installed by American Electric Power in

Kentucky. One of them is also operated as SSSC, while other one as STATCOM [68].

2.5.4 Power System Stability Enhancement

Kumkratug and Haque propose control strategy to increase stability region in power system using SSSC.Comparison is made between this nonlinear Control and Linear Control by others. Results are drawn to show

increase in power system stability [69].

Mihalic studied the mathematical model of SSSC and compared it with controllable series compensation (CSC).

Results from time based detailed simulation confirmed the superiority of SSSC based on theoretical

assumption[70].

SSSC is applied on IEEE bus systems for power flow analysis in steady state. In power flow analysis one of the

following parameters can be used for steady state control: (1) real power; (2) reactive power; (3) bus voltage;

and (4) impedance [71].

Frequency oscillation in inter-area mode is one of basic dynamic problem. SSSC is extended its use to damp the

frequency oscillation in interconnected power system [72].



2.5.5 Voltage Enhancement

Static voltage stability margin is studied is assessed using STATCOM, TCSC and SSSC respectively and their

results are compared [73].

Heavy loaded system leads to voltage instability. In loaded system power demand increases which consequently

drop the voltage on bus. This drop may be cascaded to other busses. Cascaded voltage drop causes black out ofwhole system. Kumar and Easwarlal studied effect of SSSC in controlling reactive power hence voltage drop in

system. In addition to reactive power, damping on system is also studied [74].

2.5.6 FACTS and Market

With each passing day demand in electrical energy is increasing. Industrialization and commercialization of power system has broken the monopoly of single utility provider. Laws have been passed to deregulate the

system and make market open. Utilities are in ever struggle to make the best from existing system without

investing extra penny to generation. FACTS provided itself for better managed transmission and distribution

system. Kazemi and Andami have discussed extensively impacts of FACTS devices on competitive power

market and their benefits [75].

2.5.7

Stability of RES

Renewable energy sources comprise of solar parks, wind farms and tidal based electric generation. Renewable

energy sources produce green energy but has great impact on stability of power system.Offshore wind farm fed

synchronous generator using SSSC is studied. Logic was proposed for damping synchronous generator. After

performing different disturbances it was evaluated that SSSC provide damping in offshore wind farm fed

synchronous generator [76].

2.5.8 Power Quality Improvement using FACtS

Power quality problems are voltage sags, voltage swell, flicker and harmonics. FACTS devices can also be used

to improve power quality by removing harmonics. Harmonics are one of the core problems of power quality.

Current Harmonics are produced non-linear load [77]. Current harmonics when come in contact with system

impedance form voltage harmonics. Both current and voltage harmonics cause problem in power system. Normally SVR is used for power quality improvement but has limitation because of low voltage. In this studySTATCOM is used at point of common coupling (PCC). By injecting var in line STATCOM reduces harmonics

in system. Renewable energy sources especially wind power generator affects power quality due to natural

constraint depend upon air speed. Power quality of wind turbine using STATCOM is measured and results

confirmed betterment of power quality.

Facts devices have been in use on high voltage side but customer is on lower side. DVR injects voltage in series

with a distribution feeder in order to increase the level of power quality. Results are analyzed using

DSTATCOMS for protection of voltage sags [78].

2.5.9 Conclusion

In this review power system stability enhancement is extensively studied. Salient features of SSSC and impacton power system is addressed. Utility experience is also summarized and power quality enhancement is also

discussed.



References

[1] T. Makombe and N. Jenkins, “Investigation of a unified power flow controller,” IEE Proc. - Gener. Transm. Distrib., vol. 146, no. 4,

p. 400, 1999.

[2] S. Limyingcharoen, U. D. Annakkage, and N. C. Pahalawaththa, “Effects of unified power flow controllers on transient stability,” IEE Proc. - Gener. Transm. Distrib., vol. 145, no. 2, p. 182, 1998.

[3] H. Fujita, Y. Watanabe, and H. Akagi, “Control and Analysis of a Unified Power Flow Controller,” IEEE Trans. Power Electron., vol.

14, no. 6, pp. 1021 – 1027, 1999.[4] A. Nabavi- Niaki and M. R. Iravani, “Steady-state and dynamic models of unified power flow controller (upfc) for power system

studies,” IEEE Trans. Power Syst., vol. 11, no. 4, pp. 1937 – 1943, 1996.

[5] H. F. Wang, “Damping function of unified power flow controller,” IEE Proc. - Gener. Transm. Distrib., vol. 146, no. 1, pp. 81 – 87,1999.

[6] H. F. Wang, “Applications of modeling UPFC into multi-machine power systems,” IEE Proc. - Gener. Transm. Distrib., vol. 146, no.

3, pp. 306 – 312, 1999.[7] Z. . Meng and P. . So, “A Current Injection UPFC Model for Enhancing Power System Dynamic Performance,” IEEE Power Eng.

Soc. Winter Meet., vol. 2, pp. 1544 – 1549, 2000.

[8] Z. Huang, Y. Ni, C. Shen, and F. Wu, “Application of unified power flow controller in interconnected power systems-modeling,interface, control strategy, and case study,” IEEJ Trans. Power Syst., vol. 15, no. 2, pp. 817 – 824, 2000.

[9] M. Vilathgamuwa, X. Zhu, and S. S. Choi, “A robust control method to improve the performance of a unified power flow controller,”

Electr. Power Syst. Res., vol. 55, no. 2, pp. 103 – 111, 2000.[10] B. C. Pal, “Robust damping of interarea oscillations with unified power -flow controller,” IEE Proc. - Gener. Transm. Distrib., vol.

149, no. 6, p. 733, 2002.

[11] H. F. Wang, “Interactions and multivariable design of multiple control functions of a unified power flow controller,” Int. J. Electr. Power Energy Syst., vol. 24, no. 7, pp. 591 – 600, 2002.

[12] H. XIE, Y. H. SONG, A. YOKOYAMA, and M. GOTO, “Integrated Linear and Nonlinear Control of Unified Power Flow Controllers

for Enhancing Power System Stability,” Electr. Power Components Syst., vol. 31, no. 4, pp. 335 – 347, 2003.

[13] N. Tambey and M. L. Kothari, “Damping of power system oscillations with unified power flow controller (UPFC),” Gener. Transm.

Distrib. IEE Proceedings-, vol. 150, no. 2, pp. 129 – 140, 2003.

[14] G. P. S.Mishra, P.K.Dash, “TS-fuzzy controller for upfc in a multimachine power system,” IEE Proc. - Gener. Transm. Distrib., vol.147, pp. 15 – 22, 2000.

[15] P. K. Dash, S. Mishra, and G. Panda, “A Radial Basis Function Neural Network Controller for UPFC,” IEEE Trans. Power Syst., vol.

15, no. 4, pp. 1293 – 1299, 2000.[16] P. K. Dash, S. Morris, and S. Mishra, “Design of a nonlinear variable-gain fuzzy controller for FACTS devices,” Control Syst.

Technol. IEEE Trans., vol. 12, no. 3, pp. 428 – 438, 2004.

[17] S. Mishra, “Hybrid-Neuro-Fuzzy UPFC for Improving Transient Stability Performance of Power System,” Electr. Power ComponentsSyst., vol. 33, no. 2, pp. 73 – 84, 2005.

[18] S. N. Singh and I. Erlich, “Locating unified power flow controller for enhancing power system loadability,” 2005 Int. Conf. Futur.

Power Syst., p. 5 pp. – 5, 2005.[19] A. M. Vural and M. Tümay, “Mathematical modeling and analysis of a unified power flow controller: A comparison of two

approaches in power flow studies and effects of UPFC location,” Elsevier Int. J. Electr. Power Energy Syst., vol. 29, no. 8, pp. 617 – 629, 2007.

[20] S. N. Singh and A. K. David, “Optimal location of FACTS devices for congestion management in Deregulated Power Systems,” vol.

58, no. 6, pp. 71 – 79, 2001.

[21] M. Biswas and K. K. Das, “Voltage Level Improving by Using Static VAR Compensator (SVC),” vol. 11, no. 5, 2011. [22] S. Keskes, W. Bahloul, M. Ben, and A. Kammoun, “Improvement of Power System Stability by Static Var Compensator and Tuning

Employing Genetic Algorithm,” no. July, pp. 113– 123, 2014.[23] K. Oyeniyi, “MODELING AND SIMULATION STUDY OF THE USE OF STATIC VAR COMPENSATOR ( SVC ) FOR

VOLTAGE CONTROL IN NIGERIA TRANSMISSION NETWORK,” vol. 5, no. 05, 2014.

[24] P. Bisen and A. Shrivastava, “Comparison between SVC and STATCOM FACTS Devices for Power,” vol. 4, no. 2, pp. 101– 109,2013.

[25] R. Das and D. K. Tanti, “Transient stability of 11-bus system using SVC and improvement of voltage profile in transmission line

using series compensator,” vol. 3, no. 4, pp. 76– 85, 2014.[26] C. Sample, Electricity and New Energy Static Var Compensator ( SVC ). .

[27] A. Kumar and S. B. Dubey, “Enhancement of Transient Stability in Transmission Line Using SVC Facts Controller,” no. 2, pp. 51– 56,

2013.[28] S. V. R. Kumar and S. S. Nagaraju, “Transient stability improvement using upfc and svc 1,” vol. 2, no. 3, pp. 38– 45, 2007.

[29] I. Paper, “Reactive Power Compensation Technologies , State- of-the-Art Review,” no. 1.

[30] Electric power system research volume 13, oct 1987[31] “power electronics in electric utilities static var compensator.pdf.”

[32] R. K. Varma, S. Auddy, and Y. Semsedini, "Mitigation of Subsynchronous Resonance in a Series-Compensated Wind Farm Using

FACTS Controllers," Power Delivery, IEEE Transactions on, vol. 23, pp. 1645-1654, 2008.

[33] Shankar, C.U.; Thottungal, R.; Priya, C.S., "Enhancement of transient stability and dynamic power flow control using Thyristor

Controlled Series Capacitor," in Intelligent Systems and Control (ISCO), 2015 IEEE 9th International Conference on , vol., no., pp.1-

6, 9-10 Jan. 2015

[34] Raju, R.; Shubhanga, K.N., "Laboratory implementation of a thyristor controlled series capacitor," in Signal Processing, Informatics,

Communication and Energy Systems (SPICES), 2015 IEEE International Conference on , vol., no., pp.1-5, 19-21 Feb. 2015



[35] Nyati, S.; Wegner, C.A.; Delmerico, R.W.; Piwko, R.J.; Baker, D.H.; Edris, A., "Effectiveness of thyristor controlled series capacitor

in enhancing power system dynamics: an analog simulator study," in Power Delivery, IEEE Transactions on , vol.9, no.2, pp.1018-1027, Apr 1994

[36] Tae Kyoo Oh; Zhi Zhong Mao, "Analysis on thyristor controlled series capacitor for subsynchronous resonance mitigation,"

in Industrial Electronics, 2001. Proceedings. ISIE 2001. IEEE International Symposium on , vol.2, no., pp.1319-1323 vol.2, 2001[37] Matsuki, J.; Hasegawa, S.; Morioka, Y.; Abe, M., "Synchronization schemes for a thyristor controlled series capacitor," in Industrial

Technology 2000. Proceedings of IEEE International Conference on , vol.1, no., pp.536-541 vol.2, 19-22 Jan. 2000

[38] Anele, A.O.; Agee, J.T.; Jimoh, A.A., "Investigating the steady state behavior of thyristor controlled series capacitor," in Energytech,

2012 IEEE , vol., no., pp.1-5, 29-31 May 2012[39] Huang, G.M.; Li, Y., "Impact of thyristor controlled series capacitor on bulk power system reliability," in Power Engineering Society

Summer Meeting, 2002 IEEE , vol.2, no., pp.975-980 vol.2, 25-25 July 2002

[40] M.N. Moschakis, E.A Leonidaki and N.D Hatziargyriou "Considerations for the application of Thyristor controlled series capacitors

to radial power distribution circuits", Power Tech Conference Proceedings, 2003 IEEE Bologna, vol. 3, pp.23 -26

[41] Ally, A.; Rigby, B.S., "An investigation into the impact of a thyristor controlled series capacitor-based closed-loop power flowcontroller under fault conditions," in AFRICON, 2004. 7th AFRICON Conference in Africa , vol.2, no., pp.675-681 Vol.2, 15-17 Sept.

2004

[42] Bruno, S.; De Carne, G.; La Scala, M., "Transmission Grid Control Through TCSC Dynamic Series Compensation," in PowerSystems, IEEE Transactions on , vol.PP, no.99, pp.1-10

[43] Xiaolu Li; Lixin Bao; Xianzhong Duan; Yangzan He; Mingyan Gao, "Effects of FACTS controllers on small-signal voltage stability,"

in Power Engineering Society Winter Meeting, 2000. IEEE , vol.4, no., pp.2793-2799 vol.4, 2000[44] Gama, C.; Tenorio, R., "Improvements for power systems performance: modeling, analysis and benefits of TCSCs," in Power

Engineering Society Winter Meeting, 2000. IEEE , vol.2, no., pp.1462-1467 vol.2, 2000

[45] Huang, G.; Tong Zhu, "TCSC as a transient voltage stabilizing controller," in Power Engineering Society Winter Meeting, 2001. IEEE , vol.2, no., pp.628-633 vol.2, 2001

[46] Sandeep Gupta and Ramesh Kumar Tripathi, “Transient Stability Enhancement of Multimachine Power System Using Robust and

Novel Controller Based CSC-STATCOM,” Advances in Power Electronics, vol. 2015, Article ID 626731, 12 pages, 2015.doi:10.1155/2015/626731

[47] A.S.Kannan and R.Kayalvizhi, “Implementation of PSS and STATCOM Controllers for Power System Stability Enhancement”International Journal of Engineering Research and Development, Volume 9, e-ISSN: 2278-067X, p-ISSN: 2278-800X,

www.ijerd.com, Issue 7 (January 2014), PP. 01-08

[48] A. Safari, A. Ahmadian, M.A.A. Golkar, Controller Design of STATCOM for Power System Stability Improvement Using Honey BeeMating Optimization, Journal of Applied Research and Technology, Volume 11, Issue 1, February 2013, Pages 144-155, ISSN 1665-

6423

[49] Ehsan Afzalan, Mahmood Joorabian, Analysis of the simultaneous coordinated design of STATCOM-based damping stabilizers andPSS in a multi-machine power system using the seeker optimization algorithm, International Journal of Electrical Power & Energy

Systems, Volume 53, December 2013, Pages 1003-1017, ISSN 0142-0615

[50] Arvind R. Singh, Nita R. Patne, Vijay S. Kale, Adaptive distance protection setting in presence of mid-point STATCOM usingsynchronized measurement, International Journal of Electrical Power & Energy Systems, Volume 67, May 2015, Pages 252-260,

ISSN 0142-0615

[51] Y.C. Chang, Transmission system loading margin enhancement with ordinal optimization based STATCOM installation strategy,International Journal of Electrical Power & Energy Systems, Volume 55, February 2014, Pages 503-510, ISSN 0142-0615

[52] Fault ride-through enhancement using an enhanced field oriented Control technique for converters of grid connected DFIG and

STATCOMfor different types of faults[53] M.A. Abido, Analysis and assessment of STATCOM-based damping stabilizers for power system stability enhancement, Electric

Power Systems Research, Volume 73, Issue 2, February 2005, Pages 177-185, ISSN 0378-7796

[54] Sidhartha Panda, Narayana Prasad Padhy, Optimal location and controller design of STATCOM for power system stability

improvement using PSO, Journal of the Franklin Institute, Volume 345, Issue 2, March 2008, Pages 166-181, ISSN 0016-0032

[55] Claudio A. Cañizares, Massimo Pozzi, Sandro Corsi, Edvina Uzunovic, STATCOM modeling for voltage and angle stability studies,

International Journal of Electrical Power & Energy Systems, Volume 25, Issue 6, July 2003, Pages 431 -441, ISSN 0142-0615[56] M. Ramesh, I. Swathi, A Jaya Laxmi, Stability Enhancement of HVDC System using Fuzzy based STATCOM, AASRI Procedia,

Volume 2, 2012, Pages 205-215, ISSN 2212-6716

[57] H. Hassan, Z. Osman and A. Lasheen, "Sizing of STATCOM to Enhance Voltage Stability of Power Systems for Normal andContingency Cases," Smart Grid and Renewable Energy, Vol. 5 No. 1, 2014, pp. 8 -18. doi: 10.4236/sgre.2014.51002

[58] R. Chaudhary and A. Singh, "Transient Stability Improvement of Power System Using Non-Linear Controllers," Energy and Power

Engineering, Vol. 6 No. 1, 2014, pp. 10-16. doi: 10.4236/epe.2014.61002.[59] Sunil, T.P.; Loganathan, N., "Power quality improvement of a grid-connected wind energy conversion system with harmonics

reduction using FACTS device," in Advances in Engineering, Science and Management (ICAESM), 2012 International Conference on

, vol., no., pp.415-420, 30-31 March 2012

[60] Kumar, Y.P.; Raju, H.B.P., "Static voltage stability margin enhancement using shunt compensating devices," in Research &Technology in the Coming Decades (CRT 2013), National Conference on Challenges in , vol., no., pp.1-7, 27-28 Sept. 2013

[61] Elsamahy, M.; Faried, S.O.; Sidhu, T.S.; Ramakrishna, G., "Enhancement of the Coordination Between Generator Phase BackupProtection and Generator Capability Curves in the Presence of a Midpoint STATCOM Using Support Vector Machines," in Power

Delivery, IEEE Transactions on , vol.26, no.3, pp.1841-1853, July 2011

[62] El-Moursi, M.S., "Fault ride through capability enhancement for self-excited induction generator-based wind parks by installing faultcurrent limiters," in Renewable Power Generation, IET , vol.5, no.4, pp.269-280, July 2011

[63] N. G. Hingorani, "Flexible ac transmission," IEEE Spect. vol. 30, no. 4, pp. 40-45, 1993

[64] Yong Hua Song and Allan T. Johns, Flexible AC Transmission Systems (FACTS). London, UK: IEE Press, 1999.

[65] L. Gyugyi, "Solid-State Control of Electric Power in AC Transmission Systems", International Symposium on "Electric EnergyConversion in Power systems, 1989



[66] K. K. Sen "SSSC- Static Synchronous Series Compensator: Theory. Modeling and Application", IEEE Trans. Power Delivery, vol.

13, no. 1, pp.241 -246 1998[67] B. Fardanesh, A. Edris, B. Shperling, E. Uzunovic, S. Zelingher, L. Gyugyi, L. Kovalsky, S. Macdonald, and C. Schauder, “NYPA

Convertible Static Compensator Validation of Controls and Steady State Characteristics”, CIGRE 14-103, France, August 2002.

[68] A. S. Mehraban, A. Edris and C. D. Schauder "Installation, commissioning, and operation of the world's first UPFC on the AEPsystem", Proc. IEEE Int. Conf. Power Syst. Technol., pp.323 -327 1998

[69] 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, 13 – 17 July 2003, vol. 3, pp. 1417 – 1421.

[70] R. Mihalic and I. Papic, “Static Synchronous Series Compensator – A Mean for Dynamic Power Flow Control in Electric PowerSystems”, Electric Power Systems Research, 45(1)(1998), pp. 65– 72.

[71] Xiao-Ping Zhang, “Advanced modeling of the Multicontrol Functional Static Synchronous Series Compensator (SSSC) in Newton

Power Flow”, IEEE Trans. on PWRS, 18(4)(2003), pp. 1410– 1416.

[72] I. Ngamroo and W. Kongprawechnon, “A Robust Controller Design of SSSC for Stabilization of Frequency Oscillations in

Interconnected Power Systems”, Electric Power Systems Research, 67(2)(2003), pp. 161 – 176.[73] A. Kazemi and H. Andami, “FACTS Devices in Deregulated Electric Power Systems: A Review”, 2004 IEEE International

Conference on Electric Utility Deregulation, Restructuring and Power Technologies (DWT2004), Hong Kong , April 2004, pp. 337 –

342[74] D.-N. Truong and L. Wang, "Application of a static synchronous series compensator to improve stability of a SG-based power system

with an offshore wind farm," in Proc. 2012 IEEE PES General Meeting, 22-26 July 2012, San Diego, CA, USA.

[75] A. Sode-Yome, N. Mithulananthan, "Static Voltage stability Margin Enhancement using STATCOM, TCSC and SSSC," iEEEIPESTransmission and Distribution Conference &Exhibition: Asia and Pacific Dalian, China, 2005.

[76] S Arun Kumar, C Easwarlal and M Senthil Kumar "Multi Machine Power System Stability Enhancement Using Static Synchronous

Series Compensator (SSSC)", Computing, Electronics and Electrical Technologies, Conference on,[77] T. Sunil and N. Loganathan, "Power quality improvement of a grid-connected wind energy conversion system with harmonics

reduction using FACTS device," in Advances in Engineering, Science and Management (ICAESM), 2012 International Conference

on, 2012, pp. 415-420.[78] Woo Sung-Min, Dae-Wook Kang, Woo-Chol Lee and dong-Seok Hyun "The Distribution STATCOM for Reducing the Effect of

Voltage Sag and Swell", IEEE IECO;V'2001 Conference Record , pp.1132 -1137

review paper on facts devices

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