application of multiple facts devices of similar type for congestion mitigation

ORIGINAL ARTICLE

Application of multiple FACTS devices of similar typefor congestion mitigation

Anwar S. Siddiqui • Tanmoy Deb

Received: 8 March 2014 / Revised: 28 April 2014

� The Society for Reliability Engineering, Quality and Operations Management (SREQOM), India and The Division of Operation and

Maintenance, Lulea University of Technology, Sweden 2014

Abstract FACTS (flexible AC transmission system)

devices can increase line loadability by altering transmis-

sion line parameters. Use of multiple FACTS devices can

reduce congestion in heavily loaded lines, reduce system

loss, improve stability and hence reduce cost of energy

delivery. This paper examines the effect of multiple

FACTS devices of similar type on congestion mitigation.

The system has been tested with a series FACTS device

(TCSC), a shunt FACTS device (STATCOM) and a com-

bined series & shunt FACTS device (UPFC). The proposal

has been demonstrated on IEEE-14 bus system.

Keywords Congestion � Multiple FACTS devices �Deregulated power system

1 Introduction

In deregulated electricity markets, congestion management

is more complex than vertically integrated electricity

markets. The management of congestion is easier in latter

case as it is under a single market player. However, pre-

sence of large number of players in deregulated market not

only makes operation complicated but also leads to dis-

putes. The variety of contractual obligation and require-

ment of delivering power over wider geographical area

necessitates optimum utilization of transmission

infrastructure.

FACTS devices have the potential to operate power

system near the thermal limit in flexible, secure and eco-

nomic way. The present paper investigates the effect of

multiple FACTS devices viz TCSC, STATCOM and UPFC

on congestion management. The effect is studied by using

one type of FACTS devices at a time. Up to a maximum of

three such devices are placed simultaneously. The effect of

multiple FACTS devices of series, shunt & combined

series & shunt are studied separately. The proposal is tested

on IEEE-14 bus system.

The following Sect. 2 gives literature review in this

field. Sect. 3 gives steady state modelling of FACTS

devices used. Section 4 gives simulation result. This is

followed by conclusion in Sect. 5.

2 Literature review

Use of single FACTS device such as TCSC, STATCOM,

UPSC, TCPST etc. enhances power flow in transmission

lines. Use of multiple FACTS device such as TCSC

increases line loadability further. Rasheed et al. (2007)

used multiple TCSC on IEEE-6 & 14 bus using genetic

Algorithm and particle swarm optimization technique to

increase power flow. Thermal limit of lines and voltage

limit of buses were taken as constraint. Azadani et al.

(2008) used multiple STATCOMs on IEEE-57 bus sys-

tem to improve power flow using PSO technique. Sar-

avanan et al. (2007) used PSO technique to find optimal

location of FACTS devices such as SVC, TCSC &

UPFC for minimum installation cost on IEEE-6, 30 &

118 bus system. They observed that loadability of line

increases with multiple FACTS devices. UPFC gave

maximum loadability with higher cost. While TCSC

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/s13198-014-0262-1

offered relatively good loadability with lesser cost,

however, SVC gives lowest cost but minimum loada-

bility improvement. Esmeli et al. (2013) used multi type

FACTS devices for improvement. They used STAT-

COM, SSSC & UPFC on IEEE-30 bus system under

normal & contingency condition. They concluded multi

type (of dissimilar type) are more advantageous than

single type FACTS. Tabatabaei et al. (2011) used SVC

& TCSC to find optimal location & size of these devices

to increase voltage stability & reduced real power loss.

Cases considered were- single type FACTS devices of

similar type and multi type FACTS devices of dissimilar

type (SVC & TCSC) on IEEE-14 bus system. Chakr-

aborty et al. (2011) used three TCSC and one TCPST to

improve active power flow. Rahimadeh et al. (2010) used

STATCOM and SSSC together to find optimal location

& number. While Mohammed Idris et al. (2010) used

four different types of FACTS devices viz TCSC,

TCPST, SVC and UPFC to enhance available transfer

capacity on IEEE-118 bus system. They observed that in

all cases power flow and voltage profiles were improved.

With multi type FACTS, increment of ATC is better

than single type FACTS. However, single type FACTS

are cheaper. Gitizadeh (2010) used combination of TCSC

and SVC to reduce active power loss, voltage deviation

and increase security margin against voltage collapse. He

used sequential quadratic programming to optimize

location & sizing of devices on IEEE-14 bus system.

Gerbex (2001) used simultaneous combinations of TCSC,

TCPST, TCVR and SVC on IEEE-118 bus system to

increase line loadability. He observed that loadability can

not be increased beyond a point.

In all above literature, there is no in depth study of

simultaneous application of similar type of FACTS devices

i.e. shunt (STATCOM), series (TCSC) and combined series

& shunt (UPFC). This paper explores effect of these indi-

vidual devices in multiple configuration.

3 Modeling of FACTS devices

3.1 Modeling of of TCSC

TCSC being a series device is modelled as variable series

reactance which controls the amount of power flow in a

branch. The value of reactance can be found using Newton-

Raphson algorithm. For branch a–b, the transfer admittance

matrix of series compensator is given by-

Ia

Ib

� �¼ j Baa j Bab

j Bba j Bbb

� �Va

Vb

� �ð1Þ

For inductive operation-

Baa ¼ Bbb ¼�1

XTCSC

ð2Þ

Bab ¼ Bba ¼�1

XTCSC

ð3Þ

For capacitive operation-

Baa ¼ Bbb ¼1

XTCSC

ð4Þ

Bab ¼ Bba ¼1

XTCSC

ð5Þ

Active and reactive power bus a are given by-

Pa ¼ VaVbBab sinðha�hbÞ ð6Þ

Qa ¼ �V2aBaa� VaVbBab cosðha � hbÞ ð7Þ

When series reactance controls value of active power from

bus a to bus b at magnitude Pabreg, the linearzed power flow

equations can written as-

DPa

DPb

DQa

DQb

DPXTCSCab

266664

377775 ¼

oPa

oha

oPa

ohb

oPa

oVa

Va

oPa

oVb

Vb

oPa

oXTCSC

� XTCSC

oPb

oha

oPb

ohoPb

oVa

Va

oPb

oVb

Vb

oPb

oXTCSC

� XTCSC

oQa

oha

oQa

ohb

oQa

oha

Va

oQa

ohb

Vb

oQa

oXTCSC

� XTCSC

oQb

oha

oQb

ohb

oQb

oVa

Va

oQb

oVb

Vb

oQb

oXTCSC

� XTCSC

oPXTCSC

ab

oha

oPXTCSC

ab

ohb

oPXTCSC

ab

oVa

Va

oPXTCSC

ab

oVb

Vb

oPXTCSC

ab

oXTCSC

� XTCSC

26666666666666666664

37777777777777777775

Dha

DhbDVa

VaDVb

VbDXTCSC

XTCSC

26666666664

37777777775

ð8Þ


123

DPXTCSC

ab ¼ PRegab � PXTCSC:Cal

ab ð9Þ

This is active power mismatch for series reactance.

At the end of each iteration, state variable XTCSC is

updated as given below-

XiTCSC ¼ Xi�1

TCSC þDXTCSC

XTCSC

� �i

Xi�1TCSC ð10Þ

4 Modelling of STATCOM

STATCOM can be represented as voltage source VVR

\hVR with series impedance ZVR at bus voltage Va\ha.

Assuming a voltage source representation as given below-

EVR ¼ VVRðcos dVR þ j sin dVRÞ ð11Þ

We know,

SVR ¼ I�VRVVR ¼ VVRY�VR V�VR � V�a� �

ð12Þ

Following equations are obtained, after complex transfor-

mation at bus a.

PVR ¼ V2VR GVR þ VVRVa½GVR cosðdVR � haÞ

þ BVR sinðdVR � haÞ� ð13Þ

QVR ¼ �V2VR GVR þ VaVVR½GVR cosðha � dVRÞ

þ BVR sinðha � dVRÞ� ð14Þ

Pa ¼ V2a GVR þ VaVVR½GVR cosðha � dVRÞ

þ BVR sinðha � dVRÞ� ð15Þ

Qa ¼ �V2a BVR þ VaVVR½GVR sinðha � dVRÞ

� BVR cosðha � dVRÞ� ð16Þ

Using all above equations, the linearzed model is given

below. VVR and dVR are chosen as state variable.

DPa

DQa

DPVR

DQVR

26664

37775

¼

oPa

oha

oPa

oVa

Va

oPa

odVR

oPa

oVVR

VVR

oQa

oha

oQa

oVa

Va

oQa

odVR

oQa

oVVR

VVR

oPVR

oha

oPVR

oVa

Va

oPVR

odVR

oPVR

oVVR

VVR

oQVR

oha

oQVR

oVa

Va

oQVR

odVR

oQVR

oVVR

VVR

2666666666664

3777777777775

Dha

DVa

Va

DdVR

DVVR

VVR

26666664

37777775

ð17Þ

5 Modeling of UPFC

UPFC is a back to back self commutated, voltage source. It

has one converter coupled to AC system through a series

transformer and other is connected to AC system through a

shunt transformer. It can be represented by two ideal

voltage sources given by following equations.

EVR ¼ VVRðcos dVR þ j sin dVRÞ ð18ÞECR ¼ VCRðcos dCR þ j sin dCRÞ; ð19Þ

where VVR represents voltage and dVR represents angle of

shunt converter. Similarly, VCR & dCR represent voltage

and angle of series converter. Both dVR & dVR can vary

from 0 to 2 p. Active and reactive power equations at bus a

are given by-

Pa¼ V2aGaaþ VaVb½Gab cosðha�hbÞ þ Bab sinðha�hbÞ�þVaVCR½Gab cosðha�dCRÞ þ Babsinðha�dCRÞ�þVaVVR½GVRcosðha�dVRÞ þ BVR sinðha�dVRÞ�

ð20Þ

Qa¼ �V2aBaaþ VaVb½Gab sinðha�hbÞ � Bab cosðha�hbÞ�

þVaVCR½Gab sinðha�dCRÞ � Bab cosðha�dCRÞ�þVaVVR½GVR sinðha�dVRÞ � BVR cosðha�dVRÞ�

ð21Þ

Similarly at bus b-

Pb ¼ V2bGbb þ VbVa½Gba cosðhb � haÞ þ Bba sinðhb

� haÞ þ VbVCR� ½Gbb cosðhb � dCRÞ� þ Bbb sinðhb

� dCRÞð22Þ

Qb ¼ �V2bBbb þ VbVa½Gba sinðhb � haÞ � Bba cosðhb

� haÞ þ VbVCR� ½Gbb sinðhb � dCRÞ� Bbb cosðhb

� dCRÞ�ð23Þ

Active and reactive power equations for series converter is

given below-

PCR ¼ V2CRGbb þ VCRVa½Gab cosðdCR � haÞ

þ Bab sinðdCR � haÞ þ VCRVb� ½Gbb cosðdCR � hbÞþ Bbb sinðdCR � hbÞ�

ð24Þ

QCR ¼ �V2CRBbb þ VCRVa½Gab sinðdCR � haÞ

� Bab cosðdCR � haÞ þ VCRVb� ½Gbb sinðdCR

� hbÞ� Bbb cosðdCR � hbÞ�ð25Þ

Active and reactive power equations for shunt converter is

given by-

PVR ¼ �V2VRGVR þ VVRVa½GVR cosðdCR � haÞ

þ BVR sinðdCR � haÞ� ð26Þ

QVR ¼ V2VRBVR þ VVRVa½GVR sinðdCR

� haÞ� BVR cosðdCR � haÞ� ð27Þ


123

Active power supplied to shunt converter PVR is equal to

active power demanded by series converter PCR, if con-

verter values are assumed to b e lossless.

So,

PVR þ PCR ¼ 0 ð28Þ

Again, if the coupling transformer has no resistance, active

power at bus l is equal to active power at bus n.

So,

PVR þ PCR ¼ 0 ¼ Pa þ Pb ð29Þ

Furthermore, if UPFC controls voltage magnitude at AC

shunt converter terminal (bus a) active power flow from

bus b to bus a and reactive power injected at bus b

(assuming bus a as PQ bus) then after simplification, the

linearzed system of buses is given by following-

DPa

DPb

DQa

DQb

DPab

DQba

DPtt

2666666664

3777777775¼

oPa

oha

oPa

ohb

oPa

oVa

Va

oPa

oVb

Vb

oPa

odCR

oPa

oVCR

VCR

oPa

odVR

oPb

oha

oPb

ohb

oPb

oVa

Va

oPb

oVb

Vb

oPb

odCR

oPb

oVCR

VCR O

oQa

oha

oQa

ohb

oQa

oVa

Va

oQa

oVb

Vb

oQa

odCR

oPa

oVCR

VCR

oQa

odVR

oQb

oha

oQb

ohb

oQb

oVa

Va

oQb

oVb

Vb

oQb

odCR

oQb

oVCR

VCR O

oPba

oha

oPba

ohb

oPba

oVa

Va

oPba

oVa

Vb

oPba

odCR

oPba

oVCR

VCR O

oQba

oha

oQba

ohb

oQba

oVa

Va

oQba

oVa

Vb

oQba

odCR

oQba

odCR

VCR O

oPtt

oha

oPtt

ohb

oPtt

oVK

Vk

oPtt

oVb

Vb

oPtt

odCR

oPtt

oVCR

VCR

oPtt

odVR

2666666666666666666666666664

3777777777777777777777777775

Dha

DhaDVa

VaDVn

VnDdCRDVCR

VCRDdVR

26666666666664

37777777777775

Table 1 Base case power flow

result (IEEE-14 bus system)Bus no. Bus voltage (pu) Bus voltage

angle (deg).

Branch (from-to) PQ send (Pu) PQ loss

1 1.0600 -0 1–2 1.5732-j 0.3287 0.0453-j 0.0248

2 1.0128 -4.5715 1–5 0.7608-j 0.1130 0.0292-j 0.0163

3 1.0000 -13.732 2–3 0.7433?j 0.0997 0.0254-j 0.0185

4 0.9898 -10.2542 2–4 0.5554?0.0579 0.0175?j 0.0151

5 0.9974 -8.7373 2–5 0.4122?j 0.0654 0.0095?j 0.0410

6 0.9875 -15.2057 3–4 -0.2241-j 0.1416 0.0050?j 0.0127

7 0.9780 -13.7583 4–5 -0.6130-j 0.0241 0.0051-j 0.0162

8 1.0000 -13.7583 4–7 0.2829-j 0.0647 0.0000-j 0.0180

9 0.9595 -15.6592 4–9 0.1608-j 0.0616 0.0000-j 0.0168

10 0.9563 -15.9144 5–6 10.4403-j0.0641 0.0000-j 0.0501

11 0.9679 -15.7048 6–11 0.0720-j 0.0630 0.0009-j 0.0019

12 0.9703 -16.1963 6–12 0.0786-j 0.0289 0.0009-j 0.0018

13 0.9642 -16.2518 6–13 0.1777-j 0.0871 0.0027-j 0.0052

14 0.9417 -17.1206 7–8 0.0000?j 0.1224 0.0000-j 0.0028

7–9 0.2829-j 0.1691 0.0000-j 0.0125

9–10 0.0543-j 0.0158 0.0001-j 0.0003

9–14 0.0944-j 0.0196 0.0013-j 0.0027

10–11 -0.0358?j 0.0425 0.0003-j 0.0006

12–13 0.0168 - j 0.0111 0.0001-j 0.0001

13–14 0.0567 - j 0.0348 0.0008-j 0.0017

Total = 0.1440-j 0.1216


123

The magnitude of VVR is maintained within prescribed

limits (between Vmin & VMax)

6 Simulation result and discussions

6.1 Implementation of multiple TCSC

Table 1 shows power flow result on IEEE-14 bus system

(without FACTS devices). Table 2 shows implementation

result of single, double and triple TCSCS on IEEE-14 bus

system. The objective is to increase power flow Lines 9, 10

and 14 are chosen for TCSC implementation. Single TCSC

is connected between line 9–14 with a reactance setting of

-0.1354 pu. Another single TCSC connected between line

9–10 &4–9. The reactance setting of TCSC connected

between line 9–10 is -0.1335 pu & that connected

between line 4–9 is -0.0788 pu. Figure 1 shows higher

power flow compared to base case [without TCSC]. The

double TCSC is connected between lines 9–14 and 9–10;

between 9–14 and 4–9; between 9–10 and 4–9.

Table 2 Power flow result for multiple TCSC implementation (IEEE-14 bus)

No. of TCSC Base case active power flow (pu) Power flow with TCSC (pu) TCSC reactance (pu)

Branch 9–14 Branch 9–10 Branch 4–9 Branch 9–14 Branch 9–10 Branch 4–9 X9–14 X9–10 X4–9

Single TCSC 0.0944 0.0543 0.1608 0.1043 0.0605 0.1806 -0.1354 -0.1335 -0.0788

Double TCSC 0.0944 0.0543 – 0.1097 0.0620 – -0.1935 -0.2552 –

0.0944 – 0.1608 0.1075 – 0.1844 -0.1097 – -0.0699

– 0.0543 0.1608 – 0.0618 0.1846 – -0.0759 -0.0734

Triple TCSC 0.0944 0.0543 0.1608 0.1128 0.0644 0.1933 -0.1615 -0.1926 -0.0521

Fig. 1 Improvement in power

flow with single TCSC


flow with double TCSC


flow with Triple TCSC


123

Table 3 Power flow result for multiple STATCOM (IEEE-14 bus)

No. of STATCOM Base case bus voltage

(pu)

Bus voltage with

STATCOM

STATCOM parameter

Voltage magnitude (pu) and angle (deg.) Reactive power (pu)

V12 V13 V14 V12 V13 V14 12 13 14 12 13 14

Single STATCOM 0.9703 0.9642 0.9417 1.0 1.0 1.0 1.0122 &

-16.9271

1.0270 &

-17.0216

1.024 &

-18.1899

-0.1238 -0.2768 -0.2455

Double STATCOM 0.9703 0.9642 – 1.0 1.0 – 1.0038 &

-16.6462

1.0249 &

-16.9965

– -0.0380 -0.2551 –

– 0.9642 0.9417 – 1.0 1.0 – 1.016 &

-16.8612

1.0203 &

-18.1920

– -0.1628 -0.2069

0.9703 – 0.9417 1.0 – 1.0 1.0081 &

-16.6272

– 1.0203 &

-18.1659

-0.0813 – -0.2350

Triple STATCOM 0.9703 0.9642 0.9417 1.0 1.0 1.0 1.0038 &

-16.5071

1.0139 & -16.8361 1.0203 & -18.1787 -0.0385 -0.1412 -0.2069

Fig. 4 Improvement of voltage

profile with single STATCOM


profile with double STATCOM


profile with Triple STATCOM


123

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123

Two TCSCs are connected at a time and response is noted.

Again, two TCSCs are connected in other two branches &

the response is noted and so on. The Fig. 2 shows increase in

power flow using double TCSC as compared to base case.

Similarly, three TCSCs are connected to branches 9–14,

9–10 and 4–9 simultaneously with reactances of 0.1615, -

0.1926 and -0.0521 pu respectively. Figure 3 shows higher

power flow with triple TCSC.

6.2 Implementation of multiple STATCOM

Table 3 shows implementation of single, double and triple

STATCOM in IEEE-14 bus system. The objective here is

to bring the voltage of the buses to 1 pu. Single STAT-

COM is connected to bus 12,13 and 14 one at a time. The

reactive power to achieve 1 pu bus voltages are -0.1283,

-0.2768 and 0.2455 pu respectively. Double STATCOMS

were implemented between buses 12&13; buses 13 & 14

and buses 12 & 14 respectively. The reactive power sup-

plied are -0.0380 and -0.2551 pu for bus 12–13; -0.1628

and -0.2069 pu for bus 13–14 and -0.0813 and

-0.2350 pu for bus 12–13 respectively.

In all these cases, objective of bus voltage of 1 pu

(±10 %) was achieved. This is shown in Figs. 4, 5, 6 in

which single, double & triple STATCOM are

implemented.

Fig. 7 Active power flow with

Single UPFC


double UPFC


Triple UFPC


123

6.3 Implementation of multiple UPFC

Table 4 shows implementation of single, double and triple

UPFC. The objective was to bring bus voltages to 1 pu and

increase 10 % both active and reactive power flow in

branches. Single UPFC is connected between branch 12-

13 and bus 12; branch 13–14 and bus 13 and branch 9–10

and bus 9-one at a time. When UPFC is connected between

branch 12–13 & bus 12, the bus voltage and active and

reactive power flows are 1 pu, 0.0183pu (active power)and

-0.0122 pu (reactive power). The bus voltage increased

from 0.9703 to 1 pu. The active and reactive power

increased 10 %. Similar effect can be seen for other buses

& branches. Figure 7 shows increase in power flow with

single UPFC. The double UPFC is connected in bus 12&

branch 12–13 and bus 13 and branch 13–14. Again, in bus

9 & branch 9–10 and bus 12 and branch 12–13. Similarly,

in bus 13 and branch 13–14 and bus 9 and branch 9–10. As

can be seen voltages of the buses are 1 pu and power flow

has increased. The corresponding series source voltage and

shunt source voltages are shown in Table 4. Figure 8

shows increase in power flow with double UPFC. The

triple UPFC is connected to buses 12, 13 & 9 and branches

12–13, 13–14 and 9–10 respectively. It is observed that

Fig. 10 Position of TCSC in

IEEE-14 bus system


123

equivalent series & shunt voltages of UPFC in multiple

operations is reduced in comparison to single unit. Figure 9

shows increase in power flow with triple TCSC.

7 Conclusion

Multiple FACTS devices viz. STATCOM, TCSC and

UPFC were implemented in IEEE-14 bus system. Single,

double and triple devices were implemented individually.

It was observed that multiple FACTS devices reduce

congestion considerably. However, cost of the system also

increases.

It was observed that instead of using a single device of

large rating, multiple devices offer better congestion relief.

With single TCSC, the increase in active power flow ran-

ged from 10.53 to 12.35 %. With double TCSC, the

increase ranged from 13.53 to 16.23 % while with triple

configuration, it ranged from 18.67 to 20.22 %. With

STATCOM, voltages uniformly achieved 1 pu level. With

single UPFC, active power flow improved by about 12 %,

with double UPFC active power flow improved up to 20 %.

With triple configuration, the increase was up to 24 %.

UPFC provides better congestion relief compared to

other FACTS devices due to simultaneous control of both

active & reactive power. Compared to other congestion

Fig. 11 Position of STATCOM

in IEEE-14 bus system


123

management techniques i.e. market based approaches,

FACTS offers a better approach as it is not dependent upon

uncertainties of market forces & type of market model

followed.

References

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Fig. 12 Position of UPFC in

IEEE-14 bus system (series and

shunt element of each UPFC

shown seperately)


123

application of multiple facts devices of similar type for congestion mitigation

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