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PERFORMANCE OF TRANSMISSION SYSTEM USING FIRING

ANGLE MODEL OF SVC BY CONVENTIONAL METHOD

A. HEMA SEKHAR1 & A. LAKSHMI DEVI2

1Research Scholar, Department of EEE, S.V.University College of Engineering, Tirupati, Andhra Pradesh, India 2Professor & HOD, Department of EEE, S.V.University College of Engineering, Tirupati, Andhra Pradesh, India

ABSTRACT

In modern power system network , due to continuously increased load demand the transmission losses

reduction and the voltage profiles improvement are the major tasks and moreover the power system networks are imposed

to more stressed. These factors are very much important in analyzing the power system network. With the rapid

improvement of power electronic technology has made FACTS for the solution of future power system. Among these

Flexible AC Transmission Ssystem devices, Shunt device i.e SVC is one of the most effective device for increasing the

transfer capability of the transmission system, voltage profile improvement and transmission losses reduction power

system. However, to achieve the above mentioned advantages, the SVC should be properly located in the network with

suitable parameters. In this present paper Voltage collapse Prediction Index (VCPI) is described for the purpose of

finding suitable placement of SVC in the network and for reducing the losses,, suitable firing angles are calculated for

determine the size of the SVC device The proposed work is applied to two test cases which are IEEE 30 and IEEE 118

bus systems

KEYWORDS: Flexible AC Transmission System (FACTS), Voltage collapse Prediction Index (VCPI), Static VAR

Compensator (SVC) and Newton Raphson Method

Received: Sep 08, 2016; Accepted: Sep 30, 2016; Published: Oct 13, 2016; Paper Id.: IJEEEROCT20165

INTRODUCTION

The power demand is substantially increased by day by day. The increase in generation is not only the

solution for reaching the demand but the reduction of losses which are majorly in transmission system also add on

to serve the increase in the demand. The FACTS devices are play the same role to reduce the losses. The reduction

of reactive power losses are improving the voltage profile and increase the stability of the power system. The shunt

compensation play the similar role which is mentioned above. In this paper a firing angle control of the shunt

compensating FACTS device which is called SVC is proposed for reducing the reactive power losses and increases

the stability of the power system.

LITERATURE SURVEY

In the literature [14] several authors presens different concepts about the optimum location of the Static

VAR Compensators.

Hadi Saadat Presented the simple two bus system for the calculating the Real and Reactive Power flow

equations in polar form [1]. Hingorani N.G et.al presented the advancement of power electronics introduces the

uasage of flexible ac transmission system (FACTS) controllers in power systems. [2. Ref[3]-[4] papers proposes

Existing model and the novel Firing angle model for Static VAR Compensator (SVC) FACTS devices. Kumar, G.R

Original A

rticle

International Journal of Electrical and Electronics Engineering Research (IJEEER) ISSN(P): 2250-155X; ISSN(E): 2278-943X Vol. 6, Issue 5, Oct 2016, 33-46 © TJPRC Pvt. Ltd

34 A. Hema Sekhar & A. Lakshmi Devi

Impact Factor (JCC): 6.1843 NAAS Rating: 2.40

et.al presented about the FACTS controllers in multimachine power systems from different operating conditions view

point. [5] .B. Venkateswara rao et.al explains the Implementation of Static VAR Compensator for Improvement of Power

System Stability[6] Sahoo et.al (2007) proposed the basic modeling of the FACTS devices for improving the system

performance[7]. Gotham.D.J and G.T Heydt (1998) detailed about the optimal location of FACTS devices allows

controlling its power flows and thus enhances the reliability of the power systems [8].Povh.D(2000) proposed the nice

concepts of the modeling of the power systems and the impact of the FACTS devices on the transmission network [9]. Ref

[10] paper presented on prediction and it is is based on voltage collapse prediction index [VCPI] have been used to identify

the bus which is more prone to voltage instability. Ref [11] presented the Modelling of the FACTS devices with various

techniques with complete computer programming and the operating state determine the maximum power carrying

capability of the network elements . Radman.G and R.S Raje presents about the Power Flow Model for Power Systems by

using Multiple FACTS Controllers [12]. Ref [13] explains the important concepts of the power systems with different load

flow. A.Hema sekhar explains the concepts of load flow and advanced SVC models [14].

LOAD FLOW ANALYSIS

Generally power system problems can be easily solved iteratively by several load flow methods in which Newton

Raphson algorithm method is very popular in use. These Newton Raphson equations are the solutions for the non linear

alzebraic equations and it converts into linear alzebraic equations. For a particular load demand, The load flow analysis

gives steady state solutions of voltages at all the busses. For different operating points, different steady steady state

solutions can be obtained. The generators produce power that can be travel in the transmission line and the power

consumed by the loads then power losses are occured and these losses are travel from sending end to receiving end and so

on are solved iteratively by power flow analysis.

The foloowing Figure 1 shows the a simple two bus system of buses k and m. From the Figure it can easily solved

the power equations [14] in polar form.

Figure 1: A Simple Two Bus Power System

The current entering bus k is given by

Ik = Vk

n

m 1

ykm -

n

m 1

ykmVm m = k (1)

This equation can be written in terms of the bus admittance matrix as

Performance of Transmission System using Firing Angle Model of SVC by Conventional Method 35


Ik =

n

m 1

Ykm Vm (2)

In the above equation, m includes bus k. expressing this equation in polar form, we have

Ik =

n

m 1

|Ykm| |Vm|∟θkm+ δm (3)

The complex power at bus k

Pk-j Qk = Vk*

Ik ` (4)

Substituting from 2.3 for Ik in 2.4

Pk-j Qk =|Vk|∟δ

n

m 1

|Ykm| |Vm|∟θkm+ δm (5)

Separating real and imaginary parts

P = ∑ |V | |V ||Y |Cos(θ + δ − δ ) = P (|V|, δ) (6)

Q = ∑ |V | |V ||Y |Sin(θ + δ − δ ) = Q (|V|, δ) (7)

The power mismatch equations ΔP and ΔQ are expanded around a base point (θ(0),V(0)) and, hence, the power

flow equations are expressed by the following relationship.

VV

VVQQ

VVPP

QP

(8)

Where

P is the change in real power at the bus.

Q is the change in reactive power at the bus.

V is the change of voltage at the bus

is the change of angle at the bus

SHUNT COMPENSATION

Au In shunt compensation, power system is connected in shunt (parallel) with the FACTS. It works as a

controllable current source. Shunt compensation is of two types:

Shunt Capacitive Compensation

By using shunt capacitive compensation the power factor can be improved. Most of the loads are inductive in

nature and due to this voltage are lagging behind the currents. so that poor power factor occurs.To eliminate this problem a

shunt capacitor is connected to transmission line which draws currents leading the sending end voltage.then the power



factor can be automatically improved.

Shunt Inductive Compensation

Normally, the shunt inductive compensation is used when the receiving end voltage is very minimum or when the

trasmission line at charging condition. Because of these problem slow currents are pssed through the transmission line and

due to this receiving end voltage is higher than the sending end voltage . this is called Ferranti effect. To reduce these

problems a shunt inductor is connected across the line.

The Examples of shunt compensation are Thyristor controlled reactor (TCR), Static Synchronous Compensator

(STATCOM), Thyristor Switched reactor (TSR), Thyristor Switched Capacitor (TSC) and etc.

STATIC VAR COMPENSATOR(SVC)

The devices which can receive or produce the outputs for the purpose of controlling the specific parameters in the

Transmission system are called as Static VAR Compensators (SVCs) [3]. These devices are shunt connected devices. Here

the word static means that there are no rotating devices unlike synchronous compensators. Thus an SVC consists of static

VAR generator or absorber devices and a suitable control device. A typical SVC consists of Thyristor-Switched Reactors

(TSRs) and Thyristor-Switched Capacitors (TSCs) or a fixed Capacitor in parallel. By operating the devices TCRs and

TSCs in step wise then the SVC output can be controlled.. The need for harmonic filtering as part of the compensator

scheme could be eliminated by stepwise switching of reactors rather than continuous control.. The figure shows the basic

construction model of SVC device.

Figure 2: The Basic Construction Model of SVC Device

FIRING ANGLE MODEL OF STATIC VAR COMPENSATOR (SVC)

The SVC consists of a group of shunt-connected capacitors and reactors banks with fast control action by means

of thyristor switching. The firing angle model for SVC is shown in figure 3.

Figure 3: The Firing Angle Model of SVC



In this advanced model, according to the control algorithm , The firing angles ( 0 to 180 degress) of the thyristors

are controlled the active power flow for the line where the SVC is installed and also to adjust the SVC reactance, then the

net reactance in the transmission line is reduced. As a result the power transfer capability can be increased. Here, in this

case firing angles and SVC reactance are nonlinearly related.

The formula for XLeq,, at fundamental frequency, is given by [14]

= . ( ) ( ) (9)

Where α is the firing angle of Thyristors

The SVC effective reactance Xeq is determined by the parallel combination of XC and XLeq,

= .

.( ( ) ( )) (10)

In general, the transfer admittance equation for the variable shunt compensator is,

)()( iVjBiI svcsvc (11)

Where

The SVC equivalent susceptance is given by (4) whilst its profile, as function of firing angle,

])2sin)(2[(1

cL

LcTCRcsvc

XX

XXBBB (12)

Voltage Collapse Prediction Index(VCPI)

The Voltage Collapse Prediction Index (VCPI) was proposed by Balamourougan et al [10] and this is calculated

from network admittance matrix and measured voltage phasor of participating buses in the system. The basic load flow

equation is necessary for obtaining this technique and which can be applied for any no of buses in the system. Newton

Raphson method is best for the solution of these load flow equations ,which create a partial matrix.

By adjusting the determinant of the network admittance matrix to zero, the index at bus j is written as follows

p

N

pqq

q

p V

V

VCPI

,1

'

1 (16)

Where,

′ = ∑ , (17)

Vp is the voltage phasor at bus p

Vq is the voltage phasor at bus q



Ypq is the admittance between bus p and q

Ypj is the admittance between bus p and j

p is the monitoring bus

q is the other bus connected to bus p

N is the bus set of the system

The value of Voltage Collapse Prediction Index (VCPI) varies between 0 and 1. If the VCP Index is zero, the

voltage at bus p is taken as stable and if the VCP Index is 1, a voltage collapse occurs.

SIMULATION RESULTS

The proposed system is applied is two different test cases which are IEEE 30 and IEEE 118 bus systems by using

MATLAB software.

Test Case 1: IEEE 30 Bus System

The single line diagram of IEEE 30 bus system is shown in the Figure 4 and the voltage profile for IEEE 30 bus

system without SVC is shown in Figure 5.

Figure 4: Single line Diagram of IEEE 30 Bus System

Figure 5 : Voltage Profile of IEEE 30 Bus System without SVC

Single SVC Placement

The single SVC is placed at optimum location on the highest value of VCPI and this is performed on IEEE 30 bus

0 5 10 15 20 25 300.96

0.965

0.97

0.975

0.98

0.985

0.99

0.995

1

1.005

busnumbers

volta

ge m

agni

tude

in p

.u

Voltage profile without SVC device



system. In this 30 bus system 27th bus having highest value of VCPI so the single SVC is placed on this 27th bus. The real

and reactive power losses are reduced to 1.952 MW and 7.76 MVar. The voltage profile, total real and reactive power

losses without with the placing of single SVC are shown in the figure 6, 7 and 8 respectively.

Figure 6: Voltage Profile of IEEE 30 Bus with and without SVC

Figure 7: Total Real Power Losses of IEEE 30 Bus with and without Single SVC

Figure 8: Reactive Power Losses of IEEE 30 Bus with and without Single SVC

Placement of Two SVC’s

By placing two TCSc’s on IEEE 30 bus system i.e one SVC is at 27th bus and second SVC at 18th bus then the

0 5 10 15 20 25 300.96

0.97

0.98

0.99

1

1.01

1.02

1.03

busnumbers

volta

ge m

agni

tude

in P

.U

voltage profile with and without SVC

without SVCwith SVC

1 20

0.5

1

1.5

2

2.5

without SVC with SVC

real

pow

er lo

sses

(Mw) w

ith a

nd w

ithou

t svc

TOTAL REAL POWER LOSSES WITH AND WITHOUT SVC

1 20

1

2

3

4

5

6

7

8

9


reac

tive

power

loss

es(M

Var

) with

and

with

out s

vc

TOTAL REACTIVE POWER LOSSES WITH AND WITHOUT SVC



power system losses and voltage profiles are 1.706 MW and 5.12 Mvar which are shown in the table 1. The voltage profile,

total real and reactive power losses without and with placing two SVC’s are shown in the figure 9,10 and 11 respectively.

Figure 9: Voltage Profile of IEEE 30 Bus with and without two SVCs

Figure 10: Total Real Power Losses with and without two SVCs

Figure 11: Total Reactive Power Losses with and without Two SVCs

0 5 10 15 20 25 300.96

0.97

0.98

0.99

1

1.01

1.02

1.03

busnumbers

volta

ge m

agni

tude

in P

.U


without SVCwith SVC

1 20

0.5

1

1.5

2

2.5


real

pow

er lo

sses

(Mw

) with

and

with

out s

vc


1 20

1

2

3

4

5

6

7

8

9


reac

tive

pow

er lo

sses

(MV

ar) w

ith a

nd w

ithou

t svc




Table 1: Comparative System Parameters of IEEE 30 bus with and without SVC

Parameters Without SVC with Single SVC with Two SVC’s Minimum Voltage(p.u) 0.966 at bus8 0.956 at bus 8 0.964 at bus 8 Maximum Voltage(p.u) 1.00 at bus1 1.005 at bus 1 1.003 at bus 1 Real power losses(Mw) 2.44 1.952 1.706 Reactive power losses(Mvar) 8.99 7.76 5.12

Location of SVC ---------- 27th bus 27th bus 18th bus

SVC 1firing angle(deg) ---------- 142.3 144.3 SVC2 firing angle(deg) ---------- ------- 104.8 Size of SVC1(Kvar) ----------- 2.82 1.94 Size of SVC2(Kvar) ---------- ------- 1.35

From the above table, it is shown that without SVC the Real and Reactive power losses are 2.44 MW and 8.99

MVar.In case placing single SVC the losses are Reduced i.e Real and Reactive power losses are 1.952 MW and 7.76 MVar

and for two SVC’s 1.706 MW & 5.12 MVar.

Test case 1: IEEE 118 bus system

The single line diagram of the IEEE 118 bus system is shown in the figure 12.

Figure 12: Single Line Diagram of the IEEE 118 Bus System

8.2.1 Single SVC Placement

The placement of single SVC by using VCPI is implemented on IEEE 118 bus system. By placing single SVC at

113th bus location of the transmission network, the real and reactive power losses are reduced.. The real and reactive power

losses are reduced to 130.631 MW and 778.21 MVar from 132.83 MW and 783.79 MVar. The voltage profile, total real

and reactive power losses without placing of SVC and with the placing of single SVC are shown in the figure 13,14 and 15

respectively.



Figure 13: Voltage Profile of IEEE 118 Bus with and without Single SVC

Figure 14: Total Real Power Losses of IEEE 118 Bus with and without Single SVC

Figure 15: Total Reactive Power Losses of IEEE 118 Bus with and without Single SVC

Placement of Two SVC’s

With the inclusion of two SVC’s in the bus system i.e one SVC is locate at 113th bus and second SVC is locate at

93rd bus then the power flows are further improved and losses further are reduced which is shown in the table 2.

The voltage profile, total real and reactive power losses without placing of SVC and with the placing of two SVC’s are

shown in figures 16,17 and 18 respectively.

0 20 40 60 80 100 1200.94

0.96

0.98

1

1.02

1.04

1.06

1.08

busnumbers

volta

ge m

agni

tude

in P

.U


without SVCwith SVC

1 20

20

40

60

80

100

120

140


real

pow

er lo

sses

(Mw

) with

and

with

out s

vc


1 20

100

200

300

400

500

600

700

800


reac

tive

pow

er lo

sses

(MV

ar) w

ith a

nd w

ithou

t svc




Figure 16: Voltage Profile of IEEE 118 Bus with and without Two SVCs

Figure 17: Total Real Power Losses of IEEE 118 Bus with and without Two SVCs

Figure 18: Total Reactive Power Losses of IEEE 118 Bus with and without Two SVCs

Table 2: Comparative System Parameters of IEEE 118 Bus with and without Single & Two SVCs

Parameters without SVC with SINGLE SVC with TWO SVC’S Minimum Voltage(p.u) 0.943 at bus 76 0.957 at bus 55 0.955at bus 55 Maximum Voltage(p.u) 1.05 at bus10 1.055 at bus 66 1.053 at bus 66 Real power losses(MW) 132.83 130.631 129.515

Reactive power losses(MVar) 783.79 778.21 768.91

Location of SVC ---------- 113th bus 113th bus, 93rd bus

0 20 40 60 80 100 1200.94

0.96

0.98

1

1.02

1.04

1.06

1.08

busnumbers

volta

ge m

agni

tude

in P

.U


without SVCwith SVC

1 20

20

40

60

80

100

120

140


real

pow

er lo

sses

(Mw) w

ith a

nd w

ithou

t svc


1 20

100

200

300

400

500

600

700

800


reac

tive

powe

r los

ses(

MVa

r) wi

th a

nd w

ithou

t svc




Table 2: Contd., SVC 1firing angle(deg) ---------- 148.3 134.3 SVC2 firing angle(deg) ---------- ------- 154.3

Size of SVC1(kVar) ----------- 4.82 2.94 Size of SVC2(KVar) ---------- ------- 2.18

From the above table, it is shown that without SVC the Real and Reactive power losses are 132.83 MW and

783.79 MVar.In case placing single SVC the losses are Reduced i.e Real and Reactive power losses are 130.631 MW and

778.21 MVar and for two SVC’s 129.515 MW & 768.91 MVar.

CONCLUSIONS

In this paper, IEEE 30 and 118 bus systems are used to analyzed the performance of the transmission line with

and without placing single and double Advanced model of Static VAR Compensator (SVC) devices.As compared to

without placing SVC and single SVC , The losses are greatly reduced and voltages are highly improved with placing of

two SVC’s which are shown in tables 1 & 2 respectively..thse results are obtained with the help of Newton Raphson

method of load flow. As compared to Reactance method and power injection methods ,The Advanced model of SVC with

N.R method is much easier and it is best for calculating the performance of the transmission line.

REFERENCES

1. Power System Analysis - Hadi Saadat , Tata MC Graw Hill, Edition 2002.

2. Hingorani, N.G. and L. Gyugyi. 2000. Understanding FACTS: Concepts and Technology of Flexible AC Transmission

Systems. Wiley–IEEE Press: New York, NY. ISBN: 0-7803-3464-7.

3. Amit Debnath, Joseph Rualkima Rante, Champa Nandi,” Stability Enhancement with SVC”, International Journal of

Computer Applications (0975 – 8887) Volume 72– No.5, May 2013.

4. H. Amhriz-PBrez, E. Acha, and C. R. Fuerte-Esquivel,” Advanced SVC Models for Newton-Raphson Load Flow and Newton

Optimal Power Flow Studies”, IEEE TRANSACTIONS ON POWER SYSTEMS. VOL. 15. NO. 1, FEBRUARY 2000 PP.129-

136

5. Kumar, G.R.; Rao, R.K.; Ram, S.S.T., Power Flow Control and Transmission Loss Minimization model with TCSC and SVC

for Improving System Stability and Security” Industrial and Information Systems, 2008. ICIIS 2008. IEEE Region 10 and the

Third international Conference on 8-10 Dec. 2008 Pages:1 – 5.

6. B. Venkateswara Rao, G.V. Nagesh Kumar, M. Ramya Priya and P.V.S. Sobhan, "Implementation of Static VAR Compensator

for Improvement of Power System Stability", Advances in Computing Control & Telecommunication Technologies 2009. ACT

'09. International Conference on, pp. 453-457, 2009.

7. Sahoo, A.K., S.S. Dash, and T. Thyagarajan. 2007. “Modeling of STATCOM and UPFC for Power System Steady State

Operation and Control”. IET-UK International Conference on Information and Communication Technology in Electrical

Sciences (ICTES 2007).

8. Gotham, D.J. and G.T. Heydt. 1998. Power Flow Control and Power Flow Studies for Systems with FACTS Devices. IEEE

Trans. Power Syst. 13(1): 60–66.

9. Povh, D. 2000. Modeling of FACTS in Power System Studies. Proc. IEEE Power Eng. Soc. Winter Meeting. 2:1435–1439.

10. V. Balamourougan, T. S. Sidhu, M. S. Sachdev, “Technique for online prediction of voltage collapse”, IEE Proc. on

Generation, Transmission and Distribution, Vol. 151, No. 4, pp. 453-460, Jul. 2004.



11. Acha, E., C.R. Fuerte-Esquivel, H. Ambriz-Pe´rez, and C. Angeles-Camacho. 2004. FACTS: Modelling and Simulation in

Power Networks. John Wiley and Sons: West Sussex, UK.

12. Radman, G. and R.S. Raje. 2007. Power Flow Model/Calculation for Power Systems with Multiple FACTS Controllers.

Electric Power Systems Research. 77:1521–1531.

13. Stagg, G.W. and A.H. Ei-Abiad. 1968. Computer Methods in Power Systems Analysis. McGraw-Hill: New York, NY.

14. A. Hema Sekhar & Dr A.Lakshmi Devi ,” Firing Angle SVC Model for Analyzing the Performance of Transmission Network

using Newton Raphson Load Flow”, International Journal of Electrical Engineering & Technology (IJEET) Volume 7, Issue

5, September–October, 2016, pp.44–61

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