Optimal Location of Multi-types of FACTS Devices using Genetic Algorithm

International Journal of Research in Computer Science
eISSN 2249-8265 Volume 2 Issue 3 (2012) pp. 11-15
© White Globe Publications
www.ijorcs.org

OPTIMAL LOCATION OF MULTI-TYPES OF FACTS
DEVICES USING GENETIC ALGORITHM
Jigar S.Sarda1, Manish J. Chauhan2, Viren B. Pandya3, Dhaval G. Patel4
1,2,4
Electrical Engineering Department, Gujarat Technological University, India
1
Email: jigarsunrise@gmail.com
2
Email: manish_20176@rediffmail.com
4
Email: pateldhaval_prem@yahoo.co.in
3
Asst. Prof. Electrical Engineering Department, Gujarat Technological University, India
3
Email: virenbpandya@gmail.com

Abstract: The problem of improving the voltage profile conventional OPF algorithms have to be modified such
and reducing power loss in electrical networks is a that power system analysis is possible for modern
task that must be solved in an optimal manner. power industry with FACTS devices. For last two
Therefore, placement of FACTS devices in suitable decades researchers develop algorithms to solve OPF
location can lead to control in-line flow and maintain incorporating FACTS devices. Still research is in
bus voltages in desired level and reducing losses is progress to meet the present congestion management
required. This paper presents one of the heuristic problem with help of FACTS devices efficiently.
methods i.e. a Genetic Algorithm to seek the optimal Taranto et al.[6] have proposed decomposition method
location of FACTS devices in a power system. to solve OPF dispatch problem incorporating FACTS
Proposed algorithm is tested on IEEE 30 bus power devices. This method deals with the representation of
system for optimal location of multi-type FACTS series compensators and phase shifters but this method
devices and results are presented. did not consider the specified line flow constraints.
Linear Programming (LP) based security constrained.
Keywords: FACTS Devices; Genetic Algorithm;
OPF method has been successfully used to determine
Optimal location;
the FACTS parameters to control the power flow in the
I. INTRODUCTION specific lines [7]. Ambriz-Perez et al.[8] have solved
OPF problem incorporating FACTS devices using
In the present day scenario private power producers Newton's method, leading to highly robust iterative
are increasing rapidly to meet the increase demand of solutions. Chung and Li [9] have presented GA to
electricity. In this process, the existing transmission determine the parameters of FACTS devices. Ongsakul
lines are overloaded and lead to unstable system. and Bhasaputra [10] have proposed hybrid Tabu
Overloading may also be due to transfer of cheap Search and Simulated Annealing (TS/SA) technique to
power from generator bus to load bus. New solve OPF problems with FACTS devices. For
transmission lines or FACTS devices on the existing Optimal location of different types of FACTS devices
transmission system can eliminate transmission in the power system has been attempted using different
overloading, but FACTS devices are preferred in the techniques such as GA, hybrid tabu approach and
modern power systems based on its overall Simulated Annealing (SA). The best location for a set
performance [1]. The benefits brought about FACTS of phase shifters was found by GA to reduce the flows
include improvement of system dynamic behaviour in heavily loaded lines resulting in an increased
and enhancement of system reliability. FACTS devices loadability of the network and reduced cost of
provide strategic benefits for improved transmission production. The best optimal location of FACTS
system management through: better utilization of devices in order to reduce the production cost along
existing transmission assets; increased transmission with the device's cost using real power flow
system reliability and availability; increased dynamic performance index was reported [11]. In this paper, an
and transient grid stability and enabling environmental approach to find the optimal location of thyristor-
benefits. However their main function is to control the controlled series compensator (TCSC), static var
power by controlling the parameters such as compensator (SVC) and unified power flow controller
transmission line impedances, terminal voltages and (UPFC) in the power system to improve the loadability
voltage angles. Power flow is electronically controlled of the lines and minimize the total loss using GA is
and it flows as ordered by control center and presented. Examination of the proposed approach is
consequently the cost and losses will be optimized. It carried out on IEEE 30-bus system. The Genetic
has been observed that installation of FACTS devices Algorithm tool (ga-tool) of MATLAB is implied to
increases the network's controllability but the existing solve the problem.

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12 Jigar S.Sarda, Manish J. Chauhan, Viren B. Pandya, Dhaval G. Patel

TCSC reactance is chosen between -0.7𝑋 𝑙𝑖𝑛𝑒 to 0.2
𝑋 𝑙𝑖𝑛𝑒 .
II. FACTS DEVICES MODEL
A. FACTS Devices
In this paper, three different FACTS devices have SVC:- SVC can be used for both inductive and
been selected to place in suitable location to improve capacitive compensation.
security margins in power system. These are: TCSC
(Thyristor Controlled Series Compensators), SVC
(Static VAR Compensator) and UPFC (Unified Power
Flow Controller). These are shown in Fig. 1.Power
flow through the transmission line i-j namely Pij is
depended on line reactance Xij, bus voltage magnitudes
Vi, Vj, and phase angle between sending and receiving
buses δi-δj. This is expressed by Eq.1. Fig.2 SVC structure

Vi *Vj sin(δι − δj ) In this paper SVC is modelled as an ideal reactive
Pij = (Eq.1) power injection at bus i:
Xij
∆Qi =
Qsvc (Eq.4)
TCSC can change line reactance and SVC can be
used to control reactive power in network. UPFC is the UPFC:- Two types of UPFC models have been
most versatile member of FACTS devices family and reported . One is coupled model and other is decoupled
can be applied in order to control all power flow model. In the first type, UPFC is modelled with series
parameters. Power flow can be controlled and combination of a voltage source and impedance in the
optimized by changing power system parameter using transmission line. In decoupled model, UPFC is
FACTS devices. So, optimal choice and allocation of modelled with two separated buses. First model is
FACTS devices can result in suitable utilization in more complex compared with the second one because
power system. modification of Jacobian matrix in coupled model is
inevitable. While decoupled model can be easily
B. Mathematical Model of FACTS Devices implemented in conventional power flow algorithms
In this paper steady state model of FACTS without modification of Jacobian matrix elements, in
devices are developed for power flow studies. So this paper, decoupled model has been used for
TCSC is modelled simply to just modify the reactance modelling UPFC in power flow study (Fig. 3) UPFC
of transmission line. SVC and UPFC are modelled controls power flow of the transmission line where is
using the power injection models. Models integrated installed. To obtain UPFC model in load flow study, it
into transmission line for TCSC and UPFC and SVC is is represented by four variables: Pu1, Qu1, Pu2,
modelled and incorporated into the bus as shunt Qu2.Assuming UPFC to be lossless, and real power
element of transmission line. Mathematical models for flow from bus i to bus j can be expressed as[12]:
FACTS devices are implemented by MATLAB
programming
language.
TCSC: TCSC acts as the capacitive or inductive
compensator by modifying reactance of transmission
line. This changes line flow due to change in series
reactance. In this paper TCSC is modelled by changing
transmission line reactance as below:

Fig.3 Modelling of UPFC

Pij = Pu1 (Eq.5)
Fig.1 TCSC structure. Although UPFC can control the power flow, but
cannot generate the real power. So:
= Xline + Xt csc
Xij (Eq.2)
Xt csc = rt csc* Xline Pu1 + Pu 2 =
0 (Eq.6)

where 𝑋 𝑙𝑖𝑛𝑒 = reactance of transmission line,
(Eq.3)

𝑟 𝑇𝐶𝑆𝐶 =compensation factor of TCSC.
Each reactive power output of UPFC Qu1, Qu2 can
be set to an arbitrary value depends on rating of UPFC
to maintain bus voltage.

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Optimal Location of Multi-Types of Facts Devices using Genetic Algorithm 13

III. GENETIC ALGORITHM As with any search algorithm, the optimum solution
is obtained only after much iteration. The speed of the
The GA is a search algorithm based on the
iterations is determined by the length of the
mechanism of natural selection and natural genetics. In
chromosome and the size of the populations. There are
a simple GA, individuals are simplified to a
two main methods for the GA to generate itself,
chromosome that codes for the variables of the
namely generational or steady state. In the case of
problem. The strength of an individual is the objective
generational, an entire population is replaced after
function that must be optimized. The population of
iteration (generation), whereas in steady state, only a
candidates evolves by the genetic operators of
few members of the population are discarded at each
mutation, crossover, and selection. The characteristics
generation and the population size remains constant
of good candidates have more chances to be inherited,
[14].
because good candidates live longer. So the average
strength of the population rises through the Fitness calculation:- In this work, the fitness function

𝐹𝑖𝑡𝑛𝑒𝑠𝑠 = 𝐵𝑢𝑠 𝑙𝑜𝑎𝑑𝑖𝑛𝑔 ∗ 100000000;
generations. Finally, the population stabilizes, because is bus overloading consider.

𝐵𝑢𝑠 𝑙𝑜𝑎𝑑𝑖𝑛𝑔 = 𝑂𝑉𝐿(𝑘) + 𝑝𝑐𝑜𝑠𝑡_𝑓 + 𝑝𝑐𝑜𝑠𝑡_𝑣
no better individual can be found. At that stage, the
algorithm has converged, and most of the individuals

+ 𝑝𝑐𝑜𝑠𝑡_𝑞𝑔 + 𝑝𝑐𝑜𝑠𝑡_𝑠;
Where,
in the population are generally identical, and represent

𝑂𝑉𝐿(𝑘) = exp(𝑙𝑎𝑚𝑑𝑎 ∗ 𝑎𝑏𝑠(1 − 𝑎𝑏𝑠(𝑠𝑝𝑞(𝑘))′ )/
a suboptimal solution to the problem. A GA is

𝑠𝑝𝑞𝑚𝑎𝑥(𝑘))));
governed by three factors: the mutation rate, the
crossover rate, and the population size. The
implementation of the GA is detailed in. GAs is one of
pcost_f=calculating penalty for violation of line flow
the effective methods for optimization problems
limits;
especially in non-differential objective functions with
discrete or continuous decision variables. Figure 4 pcost_v= calculating penalty for violation of load bus
shows the way that the genetic algorithm works. A voltage limits;
brief description of the components of Figure 4 is as pcost_qg= calculating penalty for violation of
below: generator reactive power limits;
pcost_s= calculating penalty for violation of slack bus
1. Initialize a population of chromosomes. active power limits;
2. Evaluate each chromosome in the population.
3. Create new chromosomes by mating current Selection Operator:--
chromosomes. Key idea: give preference to better individuals,
4. Apply mutation and recombination as the parent allowing them to pass on their genes to the next
chromosomes mate. generation. The goodness of each individual depends
5. Delete a member of the population to on its fitness. Fitness may be determined by an
accommodate room for new chromosomes. objective function or by a subjective judgement.
6. Evaluate the new chromosomes and insert them
into the population. Crossover Operator:-
7. If time is up, stop and return the best Prime distinguished factor of GA from other
chromosomes; if not, go to 3. optimization techniques. Two individuals are chosen
from the population using the selection operator .A
Chromosome
Reproduction Alteration
crossover site along the bit strings is randomly chosen.
The values of the two strings are exchanged up to this
Children
point. If S1=000000 and S2=111111 and the crossover
Altered point is 2 then S1'=110000 and S2'=001111. The two
Parents
new offspring created from this mating are put into the
next generation of the population .By recombining
Population of Chromosome portions of good individuals, this process is likely to
Chromosome Evaluation create even better individuals.
Evaluating
Discarded Mutation Operator:-
hild With some low probability, a portion of the new
h
individuals will have some of their bits flipped. Its
Dustbin purpose is to maintain diversity within the population
and inhibit premature convergence. Mutation alone
induces a random walk through the search space;
Fig.4 Working of Genetic algorithm.

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14 Jigar S.Sarda, Manish J. Chauhan, Viren B. Pandya, Dhaval G. Patel

4
IV. CASE STUDY AND RESULT x 10
14
In order to verify the effectiveness of the proposed
12
method, IEEE 30 bus system is used. Different
operating conditions are considered for finding the 10

FITNESS VALUE
optimal choice and location of FACTS controllers.
8
Maximum Generation=200;
Maximum no. of iteration=100; 6
Population size=60;
4
Elitism probability=0.150000;
Mutation probability=0.001000; 2
Crossover probability=0.950000.
0
1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2

0.2
LOSSES COMPERISON FITNESS NUMBER
Fig.8 Fitness value plot with overloading condition.
0.15
0.1
0.05
0
witout with FACTS with
FACTS overloading

Fig.5 Total losses of the IEEE 30 bus system before and
after FACTS insertion.

Fig.6 Voltage profile of the IEEE-30 bus at different
conditions Fig 9. IEEE30 Bus test system
5
x 10
6

V. CONCLUSION
5
In this paper a genetic algorithm based approach is
proposed to determine the suitable type of FACTS
4
controllers, its optimal location and rating of the
FITNESS VALUE

parameter of the devices at different loading condition
3 in power system and also minimizes the total losses of
the system. The proposed algorithm is an effective and
2 a practical method for the allocation of FACTS
controllers.
1

0
1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2
FITNESS NUMBER
Fig.7 Fitness value plot without overloading condition.

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Optimal Location of Multi-Types of Facts Devices using Genetic Algorithm 15

Table.I Optimal Location, Type, and Parameter value of FACTS Controllers.
Cases Location of Device Para-meter Fitness Line losses
FACTS name value value of (p.u.)
devices bus loading
Normal loading LINE-14 UPFC 1.04045 811.093610 0.090742
LINE-25 SVC 0.019245
LINE-32 TCSC -0.28943
Increasing 30% load LINE-2 TCSC -0.30755 2537.82020 0.190164
bus loading LINE-5 UPFC -0.04970 5
LINE-13 TCSC -0.03952
LINE-31 SVC 0.994853

VI. REFERENCES Engineering Sciences Research-IJESR Vol 01, Issue 02,
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New York, 2001. Algorithms Based Method" IEEE Bucharest Power
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[2] Tjing T. Lie and Wanhong Deng, “Optimal Flexible
AC Transmission Systems (FACTS) Devices [14] N.P.Padhy. "Artificial Intelligence and Intelligent
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[3] K. Habur, and D. Oleary, “FACTS - Flexible AC
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[4] D. Gotham and G.T. Heydt, “Power Flow control and
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[5] H. A. Abdelsalam, etal, “ Optimal location of the
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[6] Taranto GN, Pinto LMVG, Pereira MVF,
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Optimal Location of Multi-types of FACTS Devices using Genetic Algorithm

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