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International Journal of Scientific & Engineering Research Volume 8, Issue 8, August-2017 1514
ISSN 2229-5518
IJSER © 2017
http://www.ijser.org
Performance Evaluation of Reactive Power
Compensation of TCSC and SVC on Voltage
Profile Enhancement and Power System Loss
Minimization Using Firefly Algorithm
Olakunle Elijah Olabode, Oluwasegun Dayo Ayantunji, Victor Uchenna Nwagbara
Abstract--FACTS devices are alternative means of controlling active and reactive power loss with a view to lower system
loss, enhanced system voltage profile, increased transfer capability and improvedsteady state and dynamic performance
of power system. The optimal placement, locations and sizes of these devices influence its performance on the grid. This
paper presentsperformance evaluation of reactive power compensation of TCSC and SVC on voltage profile enhancement
and power system loss minimization using Firefly Algorithm. The results of the analysis showed that with the system
reinforced with TCSC, the total system loss reduced from 13.3674MW to 13.2890MW which is about 0.586% reduction.
Also the reduction in active power loss with the optimal location of SVCs is 13.2400MW which amount to 0.95 %
reduction. An appreciable voltage enhancement occurred at bus 4, 5, 10 and 14 as a result of system reinforcement with
TCSCs and SVCs. In all SVC gives better result than TCSC in term of active power reduction and voltage profile
enhancement.
Index Terms:Active Power Loss, Firefly Algorithm, Reactive PowerCompensation, SVC, TCSC, Voltage Profile
Enhancement
————————————————————
1.0 INTRODUCTION
Effective management of reactive compensation on
weak nodes is one of the major challenges in power
sector industry and this is largely due to ever-increasing
demand for electricity, the environmental constraints in
expansion of transmission networks and transmission
open access in a restructured power market [1, 2].
Adequate reactive compensation on power system
enhances voltage profile, minimizes power loss and it as
well improves steady state and dynamic performance of
power system [4].
The progressive advancement in the field of power
electronics paved way for emergent of FACTS devices
whose technologies solely depend on power electronic
————————————————
• Olakunle Elijah Olabode is currently rounding off his M.Tech Degree in
Electrical & Electronics Engineering (Power & Machine),Ladoke Akintola
University of Technology, P.M.B 4000, Ogbomoso, Oyo State, Nigeria.
Email: 095082@gmail.com
• Oluwasegun Dayo Ayantunji holds B.Tech Degreein Electrical & Electronics
Engineering (Telecommunication option),Ladoke Akintola University of
Technology, P.M.B 4000, Ogbomoso, Oyo State, Nigeria.
Email: segunayantunji@gmail.com
• VictorUchenna Nwagbaraworks with Ibadan Electricity Distribution
Company, Ibadan, Oyo State, currently finishing his M.Tech Degree in
Electrical& Electronics Engineering (Power & Machine),Ladoke Akintola
University of Technology, P.M.B 4000,Ogbomoso, Oyo State, Nigeria
E-mail: nwagbaravictor@gmail.com
Devices[1, 4].FACTS devices are solid-state converters
endowed with the ability to rapidly and smoothly inject
or absorb reactive power by controlling the firing delay
angles of thyristors (Valves). With these, it is possible to
control the phase angle, the voltage magnitude at chosen
buses and /or line impedances of a transmission system
[1, 5].
FACTS devices most frequently find in literature for
these functions are Static Var Compensator (SVC),
Thyristor Controlled Series Capacitor (TCSC), Static
Synchronous Series Compensator (SSSC), Static
Synchronous Compensator (STATCOM), Unified Power
Flow Controller (UPFC) and Interlink Power Flow
Controller (IPFC) [6-8]. These FACTS controllers are
classified as Series (TCSC and SSSC), Shunt (SVC and
STATCOM) and combined Series-Shunt (UPFC) devices
based on their existence in the system [9, 10].
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International Journal of Scientific & Engineering Research Volume 8, Issue 8, August-2017 1515
ISSN 2229-5518
IJSER © 2017
http://www.ijser.org
In the recent time, swarm intelligence, population based
optimization algorithms are widely employed by
researchers in finding the optimal sizes of these devices
while load flow techniques still remain the potential tool
for finding the exact location for sitting of these devices
[11]. Power system loss minimization and voltage profile
enhancement has been attempted by quite a number of
researchers using these population based algorithms
which includes Genetic Algorithm (GA) [12], Particle
Swarm Optimization (PSO) [13], Hybrid Binary Genetic
Algorithm and Particle Swarm Optimization
[14],Bacterial Swarming Algorithm (BSA) [15] and
Firefly Algorithm (FA) [16] among others.
In the last one decade, Dr. Xin-She Yang brings to birth
firefly algorithm (FA) at Cambridge University, the
algorithms was modeled to mimic the inherent flashing
characteristics of fireflies [17]. It is one of the newest
members of metaheuristic, nature-inspired, optimization
algorithms having many similarities with Particle
Swarm Optimization (PSO), Artificial Bee Colony
optimization (ABC) and Bacterial Foraging Algorithms
(BFA) except that it is relatively easier both in concept
and implementation and this make this algorithm
superior in performance relative to others when it comes
to solving complex optimization problems [16, 18-19].
In this paper, the researchers carried outperformance
evaluation of reactive power compensation of TCSC and
SVC on voltage profile enhancement and power system
loss minimization using Firefly Algorithm. The
proposed approach identifies the optimal location and
the parameters of TCSC and SVC, the depth of loss
minimized and the extent of voltage profile
enhancement was used as the performance metric. One-
line diagram of IEEE 14-bus system used as test system
is as shown in Figure 1 below, basically it interconnects
five generator buses, nine load buses and twenty
transmission lines.
2.0 MATHEMATICAL MODEL OF THYRISTOR
CONTROLLED COMPENSATOR (TCSC)
TCSC a series-type reactive power support usually
connected in series with the transmission line with the
aim of decreasing or increasing the overall lines effective
series transmission impedance either by injecting a
capacitive or inductive reactance accordingly.
Figure 1: One-line diagram of IEEE 14 bus system
TCSC reactance is within the range of 0.8
0.2 to keep the size minimum in a bid to
reduce the cost of TCSC to be incorporated into the
power system.
The TCSC modelled by the reactance is expressed
as follows;
= + (1)
= (2)
The variable series compensator expressed in transfer
admittance matrix form is as follows;
=
(3)
For inductive operation we have;
= =1
(4a)
= =1
(4b)
The incremental change in the reactance is given as;
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International Journal of Scientific & Engineering Research Volume 8, Issue 8, August-2017 1516
ISSN 2229-5518
IJSER © 2017
http://www.ijser.org
=
()
(1) (5)
At each iteration run, the reactance () is updated
thus;
()=
(1) +
()()
(1) (6)
2.1 MATHEMATICAL MODEL OF STATIC VAR
COMPENSATOR (SVC)
SVC is a shunt-type variable reactive power support
usually connected to a bus in a power system either to
inject or absorb reactive power with the aim of raising or
lowering the voltage magnitude at that bus within a
specified value. The reactive power generation of SVC
for this work is confined within the range
of 50 50 to keep the size
minimum so as to reduce the cost of SVC to be
incorporated into the power system.
The transfer admittance equation for the variable shunt
compensator is given as;
= (7)
The reactive power injected by SVC at bus is given as;
==2 (8)
The linearized equation representing the total
susceptance as state variable is given as;
=0 0
0
(9)
At the end of iteration(), the variable shunt
susceptance is updated as;
+1 =
+
(10)
It should be noted that this changing susceptance stands
for the total SVC susceptance needed to maintain the
nodal voltage magnitude at the specified value.
2.2 MATHEMATICAL MODEL OF FIREFLY
ALGORITHM
The firefly algorithm being one of the newest members
of nature inspired, meta-heuristic is based on three
idealized rules as detailed in [16]. The light intensity of
firefly is given as;
=() (11)
The attractiveness function of a firefly is represented by
the equation (12) below;
()=(0) ×() 1 (12)
The distance between any two fireflies is
represented , (0)is the initial attractiveness at =0,
and is an absorption coefficient which controls the
decrease of the light intensity.
The distance (r) between fireflies is given as;
,=||=,,2
=1 (13)
The movement of a firefly () when is attracted by a
brighter firefly()is as expressed by the equation;
= +,
2()+1
2
(14)
Where the current is position of a firefly,
,
2 () is the firefly’s attractiveness to light
intensity seen by adjacent fireflies and 1
2
is the random movement of a firefly in case there are no
any brighter ones.
3.0 PROBLEM FORMULATION
With the proposed algorithm, SVCs and TCSCs are
installed at appropriate locations in the test system
independently with the aim of minimizing the real
power losses and raising the voltage at defective buses
within the acceptable range without any special
attention on the installation cost.
3.1 OBJECTIVE FUNCTION
The mathematical model that minimized real power loss
is defined as;
=2+22cos ,
=1 (15)
3.2 SYSTEM CONSTRAINTS
The equalityconstraints are the power balanced
equations given as;
=(,) (16)
=(,) (17)
The inequality constraints are the limitation imposed on
the system and SVC and TCSC limits;
Voltage constraints on the generator (PQ) - bus is given
by the equation (18);
(18)
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International Journal of Scientific & Engineering Research Volume 8, Issue 8, August-2017 1517
ISSN 2229-5518
IJSER © 2017
http://www.ijser.org
The reactive power generation limit on the load (PV)-bus
is thus;
(19)
By transforming the power loss function of equation (15)
and the voltage constraints of equation (18), we obtain
the light intensity of FA thus;
.=1
1+ + 2
(20)
The power system and optimal values of FA parameters
is as shown in table one below;
Table 1: Power System and Optimal Values of FA
Parameter
Minimum Maximum
Power
System
Variables
Voltage
Magnitude
(p.u)
0.950 1.500
(MVAR) -50 50
(p.u) -0.8 0.2
Firefly
Algorithm
Parameters
α
(Randomness)
0.0 0.6
β
(Attractiveness)
0.4 1.0
ɤ (Absorption) 0.1 1.0
(d)No of
dimension
0.0 0.2
Population Size 30 50
No of iterations - 100
4.0 RESULTS AND DISCUSSION
This section shows the result of power flow calculations
coded in MATLAB (R2013a, Version 8.1.0.64) on IEEE
14- bus system using the proposed FA for optimal
placement of TCSC and SVC devices without any special
consideration for the cost of installation. The objective is
to compare the effectiveness of reactive power
compensation of TCSC and SVC using transmission loss
and voltage profile enhancement as performance
metrics. Table 2 and Table 3 present the optimal location
and parameters of TCSCs and SVCs respectively.
Table 2: The Optimal Location and Parameters of TCSCs
Proposed
Approach
Line Location of m
th
TCSC
(Lm)
(p.u)
Firefly
Algorithm
8 - 0.114
15 -0.799
17 - 0.790
18 -0.666
Table 3: The Optimal Location and Parameters of SVCs
Proposed
Approach
Location (Bus No)
()
Firefly
Algorithm
4 11.101
5 6.021
10 9.780
14 8.606
The effect of optimal placement TCSCs and SVCs on
voltage profile enhancement of the system is presented
in Table 4 and Table 5 below using the proposed
approach. Places where significant improvements were
observed were marked with yellow colour.
Table 4: Voltage Profile Enhancement with TCSC and
SVC using Firefly Algorithm (FA)
Bus
No
Voltage Magnitude (p.u)
Base Voltage With TCSC With SVC
1 1.060 1.060 1.060
2 1.045 1.045 1.045
3 1.010 1.010 1.010
4 0.967 0.976 1.001
5 0.974 0.984 1.041
6 1.070 1.070 1.070
7 1.035 1.035 1.035
8 1.090 1.090 1.090
9 0.973 0.973 0.973
10 0.974 0.986 1.027
11 1.035 1.035 1.035
12 1.046 1.046 1.046
13
1.017 1.017 1.017
14 0.951 0.958 1.045
The percentage voltage profile enhancement observed
on the test case system is presented in the Table 5 below;
Table 5: % Voltage Profile Enhancement with TCSC and
SVC using Firefly Algorithm (FA)
Bus No
Voltage magnitude (p.u)
% increase with
TCSC
% increase with
SVC
4 0.93 3.51
5
1.02
6.88
10 1.23 5.44
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International Journal of Scientific & Engineering Research Volume 8, Issue 8, August-2017 1518
ISSN 2229-5518
IJSER © 2017
http://www.ijser.org
14
0.74
9.88
The effect of the system reinforced with SVCs and
TCSCs bring about an appreciable reduction in the
active power loss of the system and these are presented
in table 6 below;
Table 6: Active Power Loss with the system reinforced
with TCSCs and SVCs using Firefly Algorithm
(FA)
Base Case
TCSC
SVC
Active Power Loss
(MW)
13.3674
13.2890
13.2400
Reduction in Active
Power Loss (MW)
------
0.0784
0.1274
% Reduction in Active
Power Loss
-----
0.59
0.95
A bar chart showing voltage profile enhancement
capabilities of TCSC and SVC with the proposed
techniques is presented in figure I below;
Figure 1: Comparison of Voltage Magnitude in (p.u)
Figure 2: Comparison of Active Power Loss in (MW)
Figure 3: Comparison of Active Power Loss in % (MW)
5.0 CONCLUSION
Performance evaluation of reactive power compensation
of TCSC and SVC on voltage profile enhancement and
power system loss minimization using Firefly Algorithm
was presented in this paper. The results of the analysis
showed that with the system reinforced with TCSC, the
total system loss reduced from 13.3674MW to
13.2890MW which is about 0.586% reduction. Also the
reduction in active power loss with the optimal location
of SVCs is 13.2400MW which amount to 0.95 %
reduction.
It was also found that the identified location and
parameters of both SVCs and TCSCs using Firefly
algorithm raised the voltage magnitude of defective
buses within acceptable limits. However, from the
analysis above, application of SVCs were found to bring
appreciable improvement in system’s voltage profile in
addition to significant reduction in total active power
losses compared with what was observed when the
system was reinforced with TCSCs.
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