IACSIT International Journal of Engineering and Technology, Vol. 4, No. 5, October 2012
Enhancing Power System Security by Proper Placement of
Thyristor Controlled Series Compensator (TCSC)
P. S. Vaidya and V. P. Rajderkar
considered for the intact system. Very limited efforts have
been made to study the impact of TCSC and their placement
under contingencies. J.G.Singh et al [1] has been suggested
the optimal placement of TCSC and UPFC for enhancement
of power system security. M.K.Verma et al [2] deals with the
location of FACTS controllers under contingencies. A.
Kazemi et al [3] proposed the comprehensive load flow
model for UPFC combined with ESS. S.N.Singh [4] have
proposed the sensitivity based approach for the location of
FACTS devices for enhancing the security. Teoman et al [5]
suggested the location of FACTS devices based on line
outage distribution factor.
The main objective of this paper is to locate the TCSC for
enhancing the security of power system under contingencies.
A real power flow performance index sensitivity based
method & line outage distribution factor has been suggested
to optimally locate the TCSC for enhancing the power system
security. The effectiveness of the proposed method has been
demonstrated on modified IEEE 30 bus system by using
Power World Simulator Software version 12.0.
Abstract—In stressed electric power systems, due to
increased loading or due to severe contingencies often lead to
situation where system no longer remains in the secure
operating region. FACTS devices can play very important role
in power system security enhancement. Due to high capital
investment, it is necessary to locate these devices optimally in
the power system. The scope of this paper is to decide optimal
location of Thyristor controlled series compensator (TCSC) by
a real power flow performance index sensitivity based approach
& line outage distribution factor. The effectiveness of the
proposed controller has been tested on modified IEEE 30 bus
system using Power world simulator software version 12.0.
Index Terms—Line outage distribution factor, power system
security, power world simulator software, real power flow
performance index, sensitivity analysis, TCSC.
I. INTRODUCTION
Electric utilities are forced to operate the system close to
their thermal & stability limits due to major hurdles such as
enviournmental, right of way and cost problems limit the
expansion of the transmission networks. The security of
power system can be defined as its ability to withstand a set
of severe but credible contingencies & to survive transition to
an acceptable new steady state condition[1]. As power
systems have become more heavily loaded due to increased
load and larger interconnection, there will be ,an increase in
number of situations where power flow equation have either
no real solution (unsolvable case) or solution with violating
operating limits such as voltage limit (insecure
case),particularly, in contingency analysis & planning
application. The solution of the power flow problem has
received much attention over the last several decades. This is
due to its fundamental importance to power system analysis.
However, little attention has been focused on how to handle
situations where power flow equations have no real solutions
& any attempt to operate the system there, probably results in
the system instability & voltage collapse. [4]
Hence there is an interest in better utilization of available
capacities by installing Flexible AC Transmission System
Devices such as Thyristor controlled series compensator
(TCSC). These devices can help in reducing the power flows
in heavily loaded lines, resulting increased system
lodability,less system loss & improved security of the system.
It is important to locate such devices optimally because of
their cost.
In most of the work, the placement of TCSC has been
II. MODELING OF TYRISTOR CONTROLLED SERIES
COMPENSATOR( TCSC)
The model of TCSC is developed to be used for steady
state conditions. This device may take a fixed number of
discrete values. TCSC are connected in series with the lines.
The effect of a TCSC on the network can be seen as a
controllable reactance inserted in the related transmission
line that compensates reactance of the line. It may have one
of the two possible characteristics: capacitive or inductive to
decrease or increase the reactance of the line
respectively.
Their values are functions of the line where the device is
located [6]. Moreover, to avoid over compensation of the line,
the working range of the TCSC is considered to be [-0.39XL,
0.39XL].
So as to increase the maximum power transfer in that line
and also improves voltage profile. It is assumed that only one
TCSC per lines is allowed.
Fig. 1 shows a simple transmission line represented by its
lumped π equivalent parameters connected between bus i
and bus j. Gij is the series conductance and Bij is the series
susceptance of a transmission line. Bsh is the shunt
susceptance of a transmission line. The model of a
transmission line with a TCSC connected between bus- i and
bus- j is shown in Fig. 2.
Manuscript received July 25, 2012; revised August 23, 2012.
The authors are with the G. H Raisoni Collage of Engg, Nagpur, India
(e-mail:prajakta.vaidya@yahoo.co.in, vedashri_raj@yahoo.com).
DOI: 10.7763/IJET.2012.V4.446
622
IACSIT International Journal of Engineering and Technology, Vol. 4, No. 5, October 2012
Bus i
However in the study, the value of exponent has been taken
as n=2 and wm =1 for all m. The real power flow PI
Bus j
Yij=Gij+Bij
sensitivity factors with respect to the parameter of TCSC can
be defined as
∂PI
= PI sensitivity with respect to TCS placed in
Cc =
jBsh
jBsh
line k (k=1,...........Nl)
Using Eq (2), the sensitivity of PI with respect to FACTS
device parameter Xk (xck for TCSC) connected between bus i
and bus j for case n=2 can be written as
Fig. 1. Model of transmission line.
Bus i
∂xck⎟ xck =0
k
Xc
Bus j
Yij=G ij+Bij
4
XL
Nl
⎛ 1 ⎞ ∂Plm
∂PI
= ∑ wm Plm3 ⎜ max ⎟
∂X k m =1
⎝ Plm ⎠ ∂X k
jBsh
jBsh
(3)
The real power flow in a line m ( Plm ) can be represented
Fig. 2. Model of TCSC.
in terms of real power injections using DC power flow
equation [1] where s is a slack bus, as
⎧ N
⎪ ∑ S mn Pn
⎪ n =1, n ≠ s
Plm = ⎨ N
⎪
S mn Pn + P j
⎪⎩ n =∑
1, n ≠ s
III. METHODS OF OPTIMAL LOCATION OF TCSC
A. Line Outage Distribution Factor
Linear sensitivities are popular methods of approximating
the power system states after a change occur in the system.
They are based on reducing the nonlinear power flow
equations in to a linear system using the dc assumption. Line
outage distribution factors (LODFs) are the sensitivities of
line flows to line outages.LODFs tell how the flow changes
on a line when some other line in the system is outage. They
are used to quickly predict the change in line flows for the
outage of another line. For example, flow gates are used in an
online capacity to monitor the post contingency state of
critical elements in the system.[5]
LODF is the change in flow on a line as a percentage of the
pre outage on another line. Thus, the LODF on line l for the
outage of line k is defined as
LODFl , k =
where
Δp1,k
additional flow, at bus-j, in the line containing the TCSC
device, due to the presence of the device. Using equation (10),
the following relationship can be derived.
∂ Plm
∂X k
line k.
⎧⎛
⎪⎜ S mi
⎪⎝
=⎨
⎪⎛ S
⎪ ⎜ mi
⎩⎝
The terms
B. Real Power Flow Performance Index Sensitivity
Approach
The severity of the system loading under normal and
contingency cases can be described by a real power line flow
performance index [1] as given below.
w
PI = ∑ m
m =1 2n
where Plm
⎛ Plm ⎞
⎜ max ⎟
⎝ Plm ⎠
(2)
is the real power flow and P
∂ Pj ⎞
∂ Pi
+ S mj
⎟
∂X k
∂X k ⎠
∂ Pj ⎞ ∂ Pj
∂ Pi
+ S mj
⎟+
∂X k
∂X k ⎠ ∂X k
for m ≠ k
(5)
for m=k
∂P
∂Pi
|xck =0 , j |xck =0 can be obtained using
∂xck
∂xck
equation are given below.
2n
max
lm
for m= k
line flow with power injections at the buses without TCSC
devices and N is the number of buses in the system. Observe
that line k, from bus-i to bus-j, is the line containing the
TCSC device, as illustrated in Fig. 2. Pj , therefore is the
LODFl ,k is the sensitivity on line l for the outage of
N1
(4)
where Smn is the mnth element of matrix [S] which relates
(1)
pk
for m ≠ k
Pic = Pij − Pijc = Vi 2 ΔGij − VV
i j ⎡
⎣ΔGij cos δij + ΔBij sin δij ⎤⎦
(6)
Pjc = Pji − Pjic = Vj2ΔGij −VV
i j ⎡
⎣ΔGij cosδij −ΔBij sinδij ⎤⎦
(7)
∂Pi
∂x ck
=
x ck = 0
∂Pic
∂x ck
(
x ck = 0
is the rated
∂Δ G ij
) ∂x
= V i 2 − V i V j cos (δ ij )
∂Δ B ij
− (V i V j sin (δ ij ))
∂x ck
capacity of line m, n is an exponent and wm a real non∂P j
negative weighting coefficient which may be used to reflect
the importance of lines. PI will be small when all the lines are
within their limits and reach a high value when there are
overloads. Thus, it provides a good measure of severity of the
lines overloads for a given state of the power system.
∂ x ck
=
x ck = 0
∂ P jc
∂ x ck
(
(8)
∂ Δ G ij
) ∂x
∂Δ B ij
+ (V i V j sin (δ ij ))
∂ x ck
623
x ck = 0
x ck = 0
= V j2 − V i V j cos (δ ij )
x ck = 0
ck
ck
x ck = 0
x ck = 0
(9)
IACSIT International Journal of Engineering and Technology, Vol. 4, No. 5, October 2012
V. CONCLUSION
where
∂ΔGij
∂xck
|xck =0 = 2Gij Bij and
∂ΔBij
∂xck
For enhancing the security of power system, line outage
distribution factor and sensitivity based approach has been
developed for finding the optimal placement of TCSC. The
test results obtained on modified IEEE 30 bus system by
using power world simulator software .The TCSC should be
placed on the most sensitive lines. Line 2-6 is the best
location for TCSC.
|xck =0 = B − G
2
ij
2
ij
c
The sensitivity factor Ck can be found by substituting
equation (8) and (9) in equation (5).
The criteria for optimal location is to placed the TCSC [1]
in a line having most negative sensitivity index. Additional
criteria can also be used
while deciding the optimal
placement of TCSC should not be placed with generating
transformer even though the sensitivity is the negative
highest.
4 MW
-29 Mvar
1 Mvar
187 MW
s la c k
3
1
A
A
91%
40 Mvar
40 MW
Amps
40 MW Amps
50 Mvar
80 MW
14 Mvar
94 MW
19 Mvar
5
8 MW
2 Mvar
2
A
A
Amps
23 MW
7
A
2-4
1.2195
0
Amps
-1.21951
Amps
9 MW
7 Mvar
4.0 Mv
Amps
3 Mvar
10 MW
19
A
A
Amps
Amps
24
A
Amps
1 Mvar
2 MW
10
A
18 MW
11 Mvar
20
21
25
22
A
Amps
A
A
MVA
Amps
Amps
A
A
A
Amps
Amps
4 MW
2 Mvar
Amps
A
A
Amps
Amps
26
27
2 MW
1 Mvar
28
11 MW
2 Mvar
29
30
A
A
Amps
A
Amps
Amps
Fig. 3. 30-Bus with line12-14 is open ( outage).
4 MW
-29 Mvar
s la c k
1 Mvar
188 MW
3
1
A
93%
40 Mvar
40 MW
PI Sensitivity
40 MW
50 Mvar
A
8 MW
2 Mvar
14 Mvar
2
A
Amps
23 MW
Amps
40 Mvar
30 MW 30 MW
30 Mvar
A
Amps
A
18
23
A
A
Am ps
Am ps
4 MW
2 Mvar
6 Mvar
9 MW
3 Mvar
10 MW
17
5 Mvar
3 MW
2 Mvar
A
Am p s
Am p s
8
6
A
Amps
3 MW
1 Mvar
3 Mvar
Amps
15
14
A mps
M VA
85% 8 MW
6 MW
2 Mvar
95%
A
A
A
Am ps
Am p s
16
9 MW
7 Mvar
4.0 Mvar
19
24
A
A
25 MW
4.25685
13
A
7
2.842161
12
A
A
A
Amps
1.051722
11 MW
8 Mvar
4
A
-2.45807
2 Mvar
30 MW
Amps
A mps80 MW
5
-4.48697
Amps
Am ps
Am ps
9
11
A
A
Am ps
Am ps
6 MW
2 Mvar
1 Mvar
18.4 Mvar 2 MW
A
5-7
A
Amps
6 MW
2 Mvar
18.4 Mvar
A
9
11
11 Mvar
1-3
A
A
Amps
2.409
23
A
16
Amps
94 MW
19 Mvar
1-2
A
Amps
4 MW
2 Mvar
A
25 MW
A
2.439
A
17
5 Mvar
18
Amps
6 Mvar
9 MW
Amps
3 MW
2 Mvar
A
Amps
Amps
8
6
A
3 MW
1 Mvar
3 Mvar
Amps
15
14
40 Mvar
30 MW 30 MW
30 Mvar
TABLE I: LODF AND PI SENSITIVITY FOR TCSC ON IEEE 30-BUS WHEN
LINE12-14 IS OUTAGE.
2-6
6 MW
2 Mvar
Amps
MVA
86% 8 MW
Amps
109%
A
Amps
Amps
% LODF
13
12
A
A
A
11 Mvar
The proposed method for optimal location of TCSC has
been tested on modified IEEE -30 bus system by using power
world simulator software 12.0. In 30 bus system, line 12-14 is
a outage line. To obtain the critical line outages were
computed by line outage distribution factor for a single line
outage case & sensitivity were calculated for TCSC placed in
every line one at a time. The real power flow performance
index with respect to TCSC for line outage are presented in
Table I.
11 MW
8 Mvar
4
A
IV. SIMULATION RESULTS
2 Mvar
30 MW
Amps
Amps
LINE
A
Amps
10
A
Am p s
18 MW
11 Mvar
21
20
22
A
Am ps
A
25
A
M VA
Am ps
A
Am ps
From Table I, it can be seen that line 4-6 is getting
overloaded when the line 12-14 outage. The placement of
TCSC in a line having most positive line outage distribution
factor & a line having most negative sensitivity factor. When
the TCSC is placed in line 2-6 validates the effectiveness in
the security enhancement.
Fig. 3 shows the outage state of a part of an interconnected
power system network, where line 12-14 connected between
bus- 12 and bus- 14 is to be considered for the outage study.
The power flow in this fictitious line is considered as the
pre-outage power flow in the actual line. The power injected
due to fictitious sources has been taken to be same as the line
flows at the two ends in order to make the net power flow to
be zero and thus simulating the line outage condition.
Fig. 4 shows the one TCSC is placed in line 2-6 and it
removes the congestion present in line 4-6 from 109% to
95%. Hence the system is operated within the limit. After 2-6,
1-2, 1-3 will be the best location giving a line loading limit of
99% as shown in Fig. 5 & Fig. 6.Then, 2-4 gives line loading
limit of 104% and line 5-7 gives 108% as shown in Fig.7 &
Fig. 8 which is not good location for enhancing power system
security.
624
A
A
A
Am ps
Am p s
4 MW
2 Mvar
A
A
Am ps
Am ps
Amps
26
27
2 MW
1 Mvar
28
11 MW
2 Mvar
29
30
A
A
Am p s
A
Am ps
Am ps
Fig. 4. 30-Bus with one TCSC placed in line 2-6.
4 MW
-35 Mvar
s la c k
1 Mvar
188 MW
1
98%
94 MW
19 Mvar
40 MW
50 Mvar
3
A
A
40 Mvar
40 MW
Amps
A
8 MW
2 Mvar
14 Mvar
2
5
11 MW
8 Mvar
12
4
13
A
A
A
A
A
Amps
A
A
Amps
Amps
23 MW
Amps
40 Mvar
30 MW 30 MW
30 Mvar
7
6
A
A
Amps
Amps
3 Mvar
Amps
15
14
A mps
M VA
86% 8 MW
6 MW
2 Mvar
99%
11 Mvar
3 MW
2 Mvar
18
A
A
Am ps
Am ps
23
A
A
4 MW
2 Mvar
6 Mvar
9 MW
3 Mvar
10 MW
16
17
6 Mvar
3 MW
1 Mvar
A
Am ps
Am ps
8
A
Am p s
Am p s
9 MW
7 Mvar
4.0 Mvar
19
24
A
A
25 MW
Am ps
Am ps
9
A
A
Am ps
Am ps
6 MW
2 Mvar
1 Mvar
18.4 Mvar 2 MW
A
11
3 Mvar
30 MW
Amps
A mps80 MW
Amps
10
A
Am ps
18 MW
11 Mvar
20
22
21
A
Am ps
A
25
A
A
M VA
Am ps
Am ps
A
A
A
Am ps
Am ps
4 MW
2 Mvar
A
A
Am ps
Am ps
Amps
27
28
2 MW
1 Mvar
26
11 MW
2 Mvar
29
30
A
A
Am ps
Am ps
A
Am ps
Fig. 5. 30-Bus with one TCSC placed in line 1-2.
IACSIT International Journal of Engineering and Technology, Vol. 4, No. 5, October 2012
4 MW
-28 Mvar
s la c k
1
3
A
A
97%
40 Mvar
40 MW
2 Mvar
30 MW
A
Amps
8 MW
2 Mvar
2
5
11 MW
8 Mvar
4
13
12
[2]
A
A
A
A
A
Amps
A
Amps
23 MW
Amps
6
A
Amps
Amps
23
A
[3]
A
Am ps
Am ps
4 MW
2 Mvar
6 Mvar
9 MW
3 Mvar
10 MW
A
A
Am ps
Am ps
9 MW
7 Mvar
4.0 Mvar
19
16
17
5 Mvar
18
Am ps
A
Am ps
8
A
3 MW
2 Mvar
A
15
40 Mvar
30 MW 30 MW
30 Mvar
7
3 MW
1 Mvar
3 Mvar
Amps
14
A mps
11 Mvar
M VA
85% 8 MW
6 MW
2 Mvar
99%
A
Amps
[1]
Amps
40 MW
50 Mvar A mps80 MW
14 Mvar
94 MW
19 Mvar
REFERENCES
1 Mvar
188 MW
24
A
A
25 MW
Am ps
A
A
Am ps
Am ps
Am ps
6 MW
2 Mvar
1 Mvar
18.4 Mvar 2 MW
A
9
11
Amps
18 MW
11 Mvar
10
A
20
25
22
21
A
Am ps
[4]
A
Am ps
A
A
M VA
Am ps
Am ps
A
A
A
Am ps
Am ps
4 MW
2 Mvar
A
A
Am ps
[5]
Am ps
Amps
26
27
2 MW
1 Mvar
28
11 MW
2 Mvar
29
30
A
A
[6]
Am ps
A
Am ps
Am ps
Fig. 6. 30-Bus with one TCSC placed in line 1-3.
-29 Mvar
s la c k
1 Mvar
187 MW
3
1
A
A
90%
40 Mvar
40 MW
94 MW
19 Mvar
Amps
Amps
8 MW
2 Mvar
2
11 MW
8 Mvar
4
13
12
A
A
A
A
A
Amps
Amps
Amps
23 MW
14
7
6
A
18
Am ps
A
A
Am ps
Am ps
P. S. Vaidya received M. Tech from G. H. Raisoni
College of Engineering, Nagpur, India in 2011. She is
presently working as Assistant Professor in the
Department of Electrical Engineering at Nagpur
University (India). Her reaserch interest includes
power system restructuring, FACTS.
23
A
Am ps
8
A
Amps
3 MW
2 Mvar
A
15
30 Mvar
4 MW
2 Mvar
6 Mvar
9 MW
17
Amps
5 Mvar
3 MW
1 Mvar
8 MW
3 Mvar
Amps
40 Mvar
Amps
30 MW 30 MW
11 Mvar
M VA
86%
6 MW
2 Mvar
104%
A
A
Amps
2 Mvar
30 MW
A
40 MW
50 MvarA mps 80 MW
14 Mvar
5
[7]
4 MW
J. G. Singh, “Enhancement of power system security through optimal
placement of TCSC and UPFC,” Power Engg Society General Meeting,
2007, IEEE, vol. 24-28, pp. 1-6, June 2001.
M. K. Verma and S. C. Srivantava, “Enhancement of voltage stability
margin under contingencies using FACTS controllers,” ICPSODR
2006, pp. 139-149.
N. G. Hingorani and L. Gyugyi, “Understanding FACTS: Concepts and
technology of flexible AC transmission systems,” IEEE Power
Engineering Society, IEEE press, Delhi 2001.
A. Kazemi, A. Esmaielie, M. T. Hassanzade, and R. Rezaiepour, “A
comprehensive load flow model for UPFC and its combination with
ESS,” International conference on Electrical and Elecronics Engg.
ELECO-2008, Aug 26, 2008.
S. N. Singh, “Location of FACTS devices for enhancing power
systems’ security,” Power Engineering 2001,’LESCOPE’01, 2001
Engg Large Engg System Conference on 2001. pp. 162-166.
T. Giiler, G. Gross, and M. Liu “ Generalised line outagedistribution
factor,” IEEE Transcations on Powersystems, vol. 22, no. 2, May 2007
N. G. Hingorani and L. Gyugyi, “Understanding FACTS: Concepts
and technology of flexible AC transmission systems,” IEEE Power
Engineering Society, IEEE press, Delhi 2001.
A
A
3 Mvar
10 MW
Am ps
16
9 MW
7 Mvar
4.0 Mvar
Am ps
19
24
A
A
A m ps
25 MW
A
A
Am ps
Am ps
Am ps
6 MW
2 Mvar
1 Mvar
18.4 Mvar 2 MW
A
9
11
Amps
10
A
A
Am ps
18 MW
11 Mvar
20
21
25
22
A
A
Am ps
A
M VA
Am p s
Am ps
A
A
A
A m ps
Am ps
4 MW
2 Mvar
A m ps
A
A
A m ps
Amps
26
27
2 MW
1 Mvar
28
11 MW
2 Mvar
29
30
A
A
Am ps
A
Am p s
Am ps
Fig. 7. 30-Bus with one TCSC placed in line 2-4.
1 Mvar
187 MW
3
1
A
A
91%
40 Mvar
40 MW
94 MW
19 Mvar
Amps
Amps
8 MW
2 Mvar
2
A
A
A
Amps
14
6
A
18
A
A m ps
23
A
Am ps
4 MW
2 Mvar
6 Mvar
9 MW
8
A
Amps
17
Amps
5 Mvar
3 MW
2 Mvar
A
Am ps
A
Am ps
30 Mvar
7
3 MW
1 Mvar
8 MW
3 Mvar
15
40 Mvar
Amps
30 MW 30 MW
11 Mvar
M VA
86%
6 MW
2 Mvar
108%
A
Amps
23 MW
13
12
A
Amps
A
Amps
11 MW
8 Mvar
4
A
Amps
2 Mvar
30 MW
A
40 MW
50 MvarA mps 80 MW
14 Mvar
5
V. P. Rajderkar completed her M. Tech from G. H.
Raisoni College of Engineering, Nagpur, India in
2006. In 2007, she joined the Electrical Engineering
Department of G. H. Raisoni college of Engineering,
Nagpur, India as Assistant Professor. her area of
interest are Power system & FACTS technology.
4 MW
-29 Mvar
s la c k
A
A
3 Mvar
10 MW
Am ps
16
9 MW
7 Mvar
4.0 Mvar
Am ps
19
24
A
A
Am ps
25 MW
A
A
A m ps
Am ps
Am ps
A
6 MW
2 Mvar
1 Mvar
18.4 Mvar 2 MW
A
11
9
Amps
10
A
Am ps
18 MW
11 Mvar
20
21
25
22
A
A
Am ps
A
M VA
Am ps
A m ps
A
A
A
Am ps
Am ps
4 MW
2 Mvar
Am ps
A
A
Am ps
Amps
27
28
2 MW
1 Mvar
26
11 MW
2 Mvar
29
30
A
A
Am ps
A
Am ps
Am ps
Fig. 8. 30-Bus with one TCSC placed in line 5-7.
625