congestion management using facts devices
TRANSCRIPT
ORIGINAL ARTICLE
Congestion management using FACTS devices
Anwar S. Siddiqui • Tanmoy Deb
Received: 27 August 2013 / Revised: 17 November 2013
� The Society for Reliability Engineering, Quality and Operations Management (SREQOM), India and The Division of Operation and
Maintenance, Lulea University of Technology, Sweden 2013
Abstract With power system restructuring going on the
world over, there are increased power transactions due to
wheeling, unscheduled flows, higher contractual needs etc.
This results in heavy flows in transmission lines causing
higher losses with possibility of loss of stability and security.
This results in congestion on transmission lines. FACTS
device can provide a solution to mitigate the effect of con-
gestion in heavily loaded lines. This paper investigates the
effect of SVC, TCSC and UPFC devices on power flows and
bus voltages with increased line loadings. The effectiveness
of these FACTS devices are demonstrated on two test sys-
tems viz. IEEE-14 bus system and WSCC 9 bus system.
Keywords Congestion � FACTS � SVC � TCSC � UPFC
1 Introduction
Restructuring of power system has thrown open a variety
of challenges such as pricing of energy and services,
ancillary service management, market power, congestion
management, available transfer capacity calculations, price
volatility etc. Although different models are followed by
different markets but some issues are common to all.
Congestion management is one such issue affecting all
including markets players and consumers.
Congestion can be tackled by several methods such as
technical methods, market based methods and non-market
based methods. In technical methods, FACTS devices
promises a solution to the congestion problem. These devices
control transmission line impedance, bus voltage magnitude
and angle so that there is enhancement of line flows, system
reliability and dynamic behaviour. Using these devices,
higher loading can be achieved on the network without
violating operating limits. Congestion is dependent upon the
network constraints which ultimately limits the transmission
capacity and hence restricts contracted flows (Singh et al.
2011). So, FACTS devices can be used as a solution to ATC
enhancement (Mandala and Gupta 2010). These devices can
control both steady state power flow and dynamic stability
without generation re-scheduling or topological changes
improving performance considerably (Galina et al. 1996).
High loading of power network in de-regulated elec-
tricity markets motivates the use of FACTS controllers
(Hingorani and Gyuygi 2001). Use of these devices such as
static var compensator (SVC) and STATCOM for reactive
power and voltage control is discussed in Gupta et al.
(1999), Rao et al. (2000) and Liu et al. (2000).
FACTS devices can enhance power flow by providing
quick response to control voltage and power flow (Nelson
et al. 1996). Congestion is a serious concern for system
operator in deregulated markets as it increases the price and
hinders free trade of electricity. FACTS devices such as
thyristor controlled series capacitor (TCSC), TCPAR, uni-
fied power flow controller (UPFC) etc. can help to reduce
congestion (Singh and David 2001; Verma et al. 2001).
Three FACTS devices viz. SVC, TCSC and UPFC have
been implemented on IEEE-14 bus and WSCC 9 bus sys-
tem to check the effectiveness of these devices in man-
agement of congestion.
Section 2 deals with static modelling of SVC, TCSC and
UPFC. Section 3 deals with simulation results and dis-
cussion. Conclusion is drawn in Sect. 4.
A. S. Siddiqui � T. Deb (&)
Department of Electrical Engineering, Jamia Millia Islamia,
New Delhi, India
e-mail: [email protected]
123
Int J Syst Assur Eng Manag
DOI 10.1007/s13198-013-0212-3
2 Static modelling of FACTS devices
2.1 Modelling of static var compensator (SVC)
The equivalent circuit of SVC is shown in Fig. 1. This is
used to determine non-linear power equations and the lin-
earized equations required by Newton’s method.
The current drawn by SVC is given by ISVC = j BSVC Vk
Reactive power injected at bus k
QSVC ¼ QK ¼ �V2KBSVC
Linearized equation is given below where equivalent
susceptance BSVC is taken as state variable.
DPk
DQk
� �i
¼ 0 0
0 Qk
� �i DQk
D Bsvc
Bsvc
" #i
At the end of iteration (i), the variable susceptance BSVC
is updated according to following equation:
Bisvc ¼ Bi�1
svc þDBsvc
Bsvc
� �i
Bi�1svc
The variable susceptance represents the total SVC
susceptance necessary to maintain nodal voltage at specified
voltage. After determination of level of compensation,
susceptance can be calculated.
2.2 Modelling of thyristor controlled series
compensator (TCSC)
The TCSC power flow model is based on concept of a vari-
able series reactance. The value of reactance is adjusted to
constrain power flow across the branch to a specified value.
The value of reactance can be determined using Newton’s
method (Fig. 2).
The transfer admittance matrix of variable series com-
pensator is given by
IK
IM
� �¼ jBKK jBKM
jBMK jBMM
� �VK
VM
� �
For inductive operation
BKK ¼ BMM ¼ �1
XTCSC
BKM ¼ BMK ¼1
XTCSC
For capacitive operation, signs are reversed. The active
and reactive power equations at bus K are given by
PK ¼ VKVMBKM Sin £K �£Mð Þ ð1Þ
QK ¼ �V2KBKK��VKVMBKM Cos £K�£Mð Þ
For power equation at bus M, the subscripts K and M are
interchanged.
In Newton–Raphson solution, these equations are line-
arised with respect to series reactance.
DPK
DPM
DQK
DQM
DPXTCSC
KM
266664
377775
i
¼ A:B:
A ¼
oPK
o£K
oPK
o£M
oPK
oVKVK
oPK
oVMVM
oPK
oXTCSCXTCSC
oPM
o£K
oPM
o£M
oPK
oVKVK
oPM
oVMVM
oPM
oXTCSCXTCSC
oQK
o£K
oQK
o£M
oQK
oVKVK
oQK
oVMVM
oQK
oXTCSCXTCSC
oQM
o£K
oQM
o£M
oQM
oVKVK
oQM
oVMVM
oQM
oXTCSCXTCSC
oPXTCSCKM
o£K
oPXTCSCKM
o£M
oPXTCSCKM
oVKVK
oPXTCSCKM
oVMVM
oPXTCSCKM
oXTCSCXTCSC
2666666664
3777777775
i
B ¼
D£K
D£M
DVKDVK
VK
DVM
VM
DXTCSC
XTCSC
266666664
377777775
i
Fig. 1 Equivalent circuit of
SVC
Fig. 2 Equivalent circuit of
TCSC a inductive and
b capacitive operation region
Fig. 3 Equivalent circuit of UPFC
Int J Syst Assur Eng Manag
123
where DPXTCSC
KM is given by
DPXTCSC
KM ¼ PregKM � PXTCSC:cal
KM
which is the active power mismatch for series reactance.
DXTCSC is given by
DXTCSC ¼ XðiÞTCSC � X
ði�1ÞTCSC
DXTCSC is the incremental change in series reactance.
PXTCSC:cal
KM is the calculated power given by Eq. 1
The state variable XTCSC is updated at the end of each
iterative step, given by
XiTCSC ¼ X
ði�1ÞTCSC þ
DXTCSC
XTCSC
� �i
Xði�1ÞTCSC
2.3 Modelling of unified power flow controller (UPFC)
The schematic representation of UPFC is given below. It
consists of a two back to back, self commutated voltage
source converters sharing a shunt capacitor on DC side.
One converter is coupled to the AC system via a series
transformer and the other is coupled to the AC system via a
shunt transformer.
The equivalent circuit is used to derive the steady-state
model (Fig. 3). The equivalent circuit consists of two ideal
voltage sources representing the fundamental Fourier series
component of switched voltage waveforms at the AC
converter terminals. The source impedances in the model
represent the positive sequence leakage inductances and
resistances of the coupling UPFC transformers.
The UPFC voltage sources are
EVR¼ VVRðcosdVRþ j sin dVRÞECR¼ VCRðcosdCRþ j sin dCRÞ
where VVR and dVR are the controllable (VVR
min B VVR B VVR max) magnitude and phase angle
(0 B dVR B 2p) of the ideal voltage source representing
the shunt converter. The magnitude VCR and angle dCR of
the voltage source representing the series converter are
controlled between limits (VCRmin B VCR B VCRmax)
and (0 B dCR B 2p) respectively.
The active and reactive power equations of the equiva-
lent circuit of UPFC are given below
At bus K
PK¼V2KGKKþVKVM½GKM cosð£K�£MÞ
þBKM sinð£K�£MÞ��VKVCR½GKM
�cosð£K�dCRÞþBKM sinð£K�dCRÞ�þVKVvR ½GVR cosð£K�dVRÞþBVR sinð£K�dVRÞ�
QK¼�V2KBKKþVKVM½GKM sinð£K�£MÞ
�BKM cosð£K�£MÞ�þVKVCR½GKM sinð£K�dCRÞ�BKM cosð£K�dCRÞ�þVKVvR ½GVR sinð£K�dVRÞ�BVR cosð£K�dVRÞ�
Table 1 Power flow results for SVC in IEEE-14 bus system
Bus. no. Base case
voltage (pu)
With SVC
Voltage
(pu)
Reactive power
supply by SVC (pu)
SVC
susceptance
(pu)
Total
PQ loss
(pu)
11 0.9679 1.0 -0.1732 0.1732 0.1521 - j 0.1473
12 0.9703 1.0 -0.1233 0.1233 0.1528 - j 0.1506
13 0.9642 1.0 -0.2696 0.2696 0.1527 - j 0.1497
14 0.9417 1.0 -0.2398 0.2398 0.1527 - j 0.1435
Table 2 Power flow result for SVC in WSCC-9 bus system
Bus. no. Base
case
voltage (pu)
With SVC
Voltage
(pu)
Reactive
power supply
by SVC (pu)
SVC
susceptance
(pu)
Total
PQ
loss (pu)
4 0.9870 1.0000 -0.2927 0.2927 0.0491 ? j 0.8241
5 0.9876 1.0000 -0.4677 0.4677 0.0473 ? j 0.8625
6 0.9755 1.0000 -0.2654 0.2654 0.0492 ? j 0.8300
7 0.9962 1.0000 -0.0854 0.0854 0.0493 ? j 0.8096
8 0.9856 1.0000 -0.1971 0.1971 0.0488 ? j 0.8226
9 1.0034 1.0000 -0.0796 -0.0796 0.0497 ? j 0.7954
Int J Syst Assur Eng Manag
123
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34
9–
60
.60
89
?j
0.1
24
31
.00
.66
97
?j
0.1
11
80
.99
20
,0
.36
83
0.1
07
1,
-8
6.7
26
10
.04
95
?j
0.8
02
6
91
.00
34
9–
80
.24
11
-j
0.0
45
41
.00
.26
52
-j
0.0
49
90
.99
35
,1
.60
12
0.0
43
4,
-1
00
.73
38
0.0
49
8?
j0
.79
83
50
.95
76
7–
50
.86
50
?j
0.0
25
31
.00
.96
51
?j
0.0
22
71
.00
14
,1
.16
72
0.1
68
6,
-8
3.5
42
00
.05
11
?j
0.7
96
9
Int J Syst Assur Eng Manag
123
Ta
ble
9P
ow
erfl
ow
resu
ltfo
rU
PF
Cin
WS
CC
-9b
us
syst
em
Bu
sn
o.
Bas
eca
se
vo
ltag
e(p
u)
Bra
nch
fro
m–
to
Bas
eca
se
po
wer
(pu
)
Wit
hU
PF
C—
20
%in
crea
sein
Psp
ecifi
ed
Vo
ltag
e(p
u)
Po
wer
(pu
)S
hu
nt
sou
rce
vo
ltag
em
agn
itu
de
and
ang
le(p
u),
(deg
)
Ser
ies
sou
rce
vo
ltag
em
agn
itu
de
and
ang
le(p
u),
(deg
)
To
tal
PQ
loss
(pu
)
91
.00
34
9–
60
.60
89
?j
0.1
24
31
.00
.73
06
?j
0.0
99
40
.99
08
,-
1.2
22
40
.15
42
,-
89
.56
09
0.0
50
3?
j0
.80
08
91
.00
34
9–
80
.24
11
-j
0.0
45
41
.00
.28
93
-j
0.0
54
40
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36
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18
0.0
62
7,
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59
60
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01
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97
9
50
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76
7–
50
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0.0
25
31
.01
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0.0
30
00
.99
52
,-
0.7
59
30
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98
,-
82
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0.0
54
3?
j0
.77
55
Ta
ble
10
Po
wer
flo
wre
sult
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FC
inW
SC
C-9
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ssy
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sn
o.
Bas
eca
sev
olt
age
(pu
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ran
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om
–to
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eca
se
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ed
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un
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ang
le(p
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(deg
)
Ser
ies
sou
rce
vo
ltag
e
mag
nit
ud
ean
d
ang
le(p
u),
(deg
)
To
tal
PQ
loss
(pu
)
91
.00
34
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60
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89
?j
0.1
24
31
.00
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15
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00
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,-
2.8
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10
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91
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58
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52
0?
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32
91
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34
9–
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11
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45
41
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34
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59
00
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37
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12
0.0
82
1,
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6.8
67
60
.05
06
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0.7
96
6
50
.95
76
7–
50
.86
50
?j
0.0
25
31
.01
.12
45
?j
0.0
32
80
.98
75
,-
3.0
98
40
.30
20
,-
44
2.5
75
90
.05
98
?j
0.7
40
1
Int J Syst Assur Eng Manag
123
Similarly for bus M.
For series converter
PCR¼ V2CRGMMþ VCRVK½GKMcosðdCR�£KÞ
þ BKMsinðdCR�£KÞ� þ VCRVM½GMMcosðdCR�£MÞþ BMMsinðdCR�£KÞ�:
QCR¼�V2CRBMMþ VCRVK½GKMsinðdCR�£KÞ
�BKMcosðdCR�£KÞ� þ VCRVM½GMMsinðdCR�£MÞ�BMMcosðdCR�£MÞ�:
Shunt converter
PVR ¼ �V2VRGVR þ VVRVK½GVRcosðdVR � £KÞ
þ BVRsinðdVR�£KÞ�:QVR ¼ V2
VRBVR þ VVRVK½GVRsinðdVR � £KÞ� BVRcosðdVR � £KÞ�:
Assuming loss–loss converter valves, the active power
supplied to shunt converter PVR equals the active power
demanded by series converter PCR, that is PVR ? PCR = 0
Further, if the coupling transformer is assumed to have
no resistance then active power at bus K is equal to active
power at bus M. Hence
PVR þ PCR ¼ PK þ PM ¼ 0
The UPFC equation in linearized form is combined with
AC network. For the case when UPFC controls the
following parameters
1. Voltage magnitude at the AC shunt converter terminal
(bus K).
2. Active power flowing from bus M to bus K.
3. Reactive power injected at bus M and taking bus M as
PQ bus.
The linearized system of equations are given below
DPK
DPM
DQK
DQM
DPMK
DQMK
DPbb
2666666664
3777777775¼ A:B:
B ¼
D£K
D£M
DVVR
VVR
DVM
VM
DdCR
DVCR
VCR
DdVR
26666666666664
37777777777775
i
where DPbb is the power mismatch given by
PVR þ PCR ¼ 0
3 Simulation result and discussion
IEEE-14 bus system and WSCC-9 bus system have been
used. MATLAB codes are written using models of FACTS
devices in Newton–Raphson load flow. The results are
tabulated showing bus voltage, line flow, line losses,
reactive power flow etc. Then, effect of FACTS devices on
the performance is evaluated. Two basic objectives are
kept in mind viz.—first to control and maintain bus voltage
A ¼
oPK
o£K
oPK
o£M
oPK
oVVRVVR
oPK
oVMVM
oPK
odCR
oPK
oVCRVCR
oPK
odVR
oPM
o£K
oPM
o£MO oPM
oVMVM
oPM
odCR
oPM
oVCRVCR O
oQK
o£K
oQK
o£M
oQK
oVVRVVR
oQK
oVMVM
oQK
odCR
oQK
oVCRVCR
oQK
odCR
oQM
o£K
oQM
o£MO oQM
oVMVM
oQK
odCR
oQM
oVCRVCR O
oPMK
o£K
oPMK
o£MO oPMK
oVKVM
oPMK
odCR
oPMK
oVCRVCR O
oQMK
o£K
oQMK
o£MO oQMK
oVMVM
oQMK
oVCR
oQMK
oVCRVCR O
oPbb
o£K
oPbb
o£M
oPbb
oVVRVVR
oPbb
oVMVM
oPbb
odCR
oPbb
oVCRVCR
oPbb
odVR
266666666666664
377777777777775
Int J Syst Assur Eng Manag
123
to 1 pu for the load buses by different FACTS devices.
Secondly, to control and enhance power flow in the lines to
specified value by different FACTS devices. Purpose is to
reduce/eliminate congestion in the power network by using
these FACTS devices.
3.1 Location of SVC in revised model
SVC is connected to bus no. 11, 12, 13 and 14 in IEEE-14
bus system. While SVC has been connected to bus no. 4, 5,
6, 7, 8 and 9 in WSCC-9 bus system.
3.2 Location of TCSC in revised model
TCSC is connected to branch no. 2–4, 12–13, 13–14 and
2–3 in IEEE-14 bus system. While it is connected to branch
no. 4–6, 7–5, 9–6 and 9–8 in WSCC-9 bus system.
3.3 Location of UPFC in revised model
UPFC is connected to bus and branch no. 2, 2–4; 12,
12–13; 13, 13–14; 2, 2–3 respectively.
Tables 1 and 2 show the implementation of SVC in IEEE
14 and WSCC-9 bus system. It is observed that for both sys-
tems, the desired voltage (i.e. 1.0 pu) is achieved by SVC. In
WSCC-9 bus system, it is seen that bus 9 base voltage is
1.0034 (higher than 1 pu) and SVC susceptance becomes
negative that is—it operates in inductive mode and brings
down the voltage to 1.0 pu. In other buses, SVC raises bus
voltage to 1.0 pu and operates in capacitive mode showing
positive susceptance. The influence of SVC on real power
flow is negligible. The total real power losses with SVC in a
particular line are minimum for a specific value of SVC rating.
Tables 3 and 4 show implementation of TCSC in IEEE-14
and WSCC-9 bus system. The objective of TCSC is to
increase base case active power in different branches by 10,
20 and 30 %. The TCSC reactance increases to bring the base
power to P specified for higher power flow. The total real
power losses increase with TCSC to raise base case real
power of branches to P specified. For a fixed value of degree
of compensation, TCSC in general improves voltage profile
of the line under heavy loadings. The real powers losses may
increase or decrease depending upon location of TCSC.
Tables 5, 6, 7, 8, 9 and 10 show implementation of
UPFC for both systems. The objective of UPFC is to bring
the branch voltage to 1.0 pu and improve real power flow
by 10, 20 and 30 % from base values. The higher loadings
indicate congestion on the line. The total losses increases
with implementation of UPFC.
The study of implementation of various devices suggests
that because of simultaneous control of voltage, active and
reactive power, UPFC is one of the best controllers for
congestion mitigation.
4 Conclusion
Simplified models of SVC, TCSC and UPFC have been
suggested and developed suitably for steady state analysis.
The effect of variations in parameters of these models is
studied on test system to evaluate effect on mitigation of
congestion. Congestion is introduced by increasing line
loading from 10 to 30 % in steps of 10 %.
The benefits of FACTS devices in congestion management
is evident from the observation that in IEEE-14 bus system,
bus voltages in bus no. 11, 12, 13 and 14 (Table 11) have very
low voltage profile. After connection of SVC to these buses,
voltage profile has reached 1 pu level due to reactive power
supplied by SVC. If SVC is not used, further loading of buses
will deteriorate the voltage profile of the system. This not only
endangers system stability and security but also prevents
further loading. Hence, due to these reasons a condition of
congestion is created. This is also demonstrated in WSCC-9
bus system where bus voltages at buses 4, 5, 6, 7 and 8 are
Table 11 Bus voltages without using FACTS devices IEEE-14 bus
system
Bus no. Bus voltage magnitude
1 1.0600
2 1.0128
3 1.0000
4 0.9898
5 0.9974
6 0.9875
7 0.9780
8 1.0000
9 0.9595
10 0.9563
11 0.9679
12 0.9703
13 0.9642
14 0.9417
Table 12 Bus voltages without using FACTS devices WSCC-9 bus
system
Bus no. Bus voltage magnitude
1 1.0000
2 1.0000
3 1.0000
4 0.9870
5 0.9576
6 0.9755
7 0.9962
8 0.9856
9 1.0034
Int J Syst Assur Eng Manag
123
below 1 pu and in bus 9 above 1 pu (Table 12). Due to con-
nection of SVC to these buses, voltage profile improves to
1 pu thereby strengthening system stability and security and
allowing higher loadings or reducing congestion.
In case of TCSC (Tables 3 and 4, by altering the branch
reactance, the branch power flow could be increased to
110, 120 and 130 % of base case power respectively (base
case means no FACTS are connected).
In case of UPFC (Tables 5, 6 and 7), the bus voltages of
bus no. 2, 12 and 13 are improved to 1 pu level and power
flow in branches 2–3, 2–4, 12–13 and 13–14 could be
increased to 110, 120 and 130 % of base case value. Similar
findings could be reached at by analysing Tables 8, 9 and 10.
Hence, all above observations indicate that shunt (SVC),
series (TCSC) and combined series-shunt (UPFC) devices
help to improve bus voltages and branch flows thereby
improving line loadability or reduce congestion. The series
device (TCSC) improves active power flow by altering line
reactance thereby improving power flow and reducing con-
gestion. The shunt device (SVC) improves bus voltage
thereby improving reactive power flow. While, combined
series and shunt (UPFC) device improves both active power
flow and reactive power flow.
The studies show different FACTS devices reduce
congestion. But, UPFC is best for congestion reduction due
to simultaneous control of active and reactive power.
Appendix 1
See Fig. 4.
Appendix 2
See Fig. 5.
References
Galina GD et al (1996) Assessment and control of the impact of
FACTS devices on power system performance. IEEE Trans
Power Syst 11(4):1931–1936
Gupta CP, Srivastava SC, Varma RK (1999) Enhancement of static
voltage stability margin with reactive power dispatch using
FACTS devices. In: 13th PSCC in Trondheim, 28 June–2 July
1999
Hingorani NG, Gyuygi L (2001) Understanding FACTS: concept and
technology of flexible ac transmission systems. IEEE Press, New
Delhi
Liu JY, Song YH, Mehta P (2000) Strategies for handling UPFC
constraints in steady state power flow and voltage control. IEEE
Trans Power Syst 15(2):566–571
Mandala M, Gupta CP (2010) Congestion management by optimal
placement of FACTS device. In: Power electronics, devices and
energy system, 2010, power India, pp 1–7
Nelson RJ et al (1996) Transient stability enhancement with FACTS
controllers. In: Sixth international conference on AC and DC
power transmission, 29 April–3 May 1996
Rao R, Crow ML, Zhang Z (2000) STATCOM control for power
system voltage control applications. IEEE Trans Power Deliv
15(4):1311–1313
Singh SN, David AK (2001) Optimal location of FACTS devices for
congestion management. Electr Power Syst Res 58:71–79
Singh K, Padhy NP, Sharma J (2011) Influence of price responsive
demand shifting bidding on congestion and LMP in pool based
day ahead electricity markets. IEEE Trans Power Syst
26(2):886–896
Verma KS, Singh SN, Gupta HO (2001) Location of unified power
flow controller for congestion management. Electr Power Syst
Res 58:89–96
12
13
14
1011
9
87
4
5
2
3
1
6
Fig. 4 IEEE-14 bus system
3
5 6
27 8
9
4
1
Fig. 5 WSCC-9 bus system
Int J Syst Assur Eng Manag
123