Page 1 of 7
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online: https://ejbss.org/ P a g e | 2025
Enhancement of Contingency Constrained Economic
Load Dispatch Using Particle Swarm Optimization
SARAN KUMAR .S
M.Tech – Power System Engineering,
PRIST Deemed University, Madurai, Tamilnadu
Abstract - The power system security is mostly
influenced by several contingencies.. Under
contingency the system might get into insecure.
Determination of system state that is whether the
system is working under secure condition or not that
can be deal by security analysis. Insecure of the
system means all the components in the system are
Operating out of the specified limits. During the
contingency the transmission line power flows will
get affected and it might cross the maximum power
flow limit. So we have to control the power flows in
the transmission lines during the contingency. The
power flows in the transmission line can be control by
rescheduling of the generators in the system. In this
work the particle swarm optimization technique has
been utilized to reschedule the generators for getting
optimum cost. While rescheduling the generators
under contingency the power flows in the
transmission line will get control and they will come
within the specified limits and security will get
enhance under contingency.
I.INTRODUCTION
The security Assessment (SA) is also called as
Security Evaluation, determines the robustness of the
system (security level) to a set of preselected
contingencies in its present or future state. It is the
analysis carried out to determine whether, and to what
extent, a power system is reasonably
safe from serious interference to its operation. A
power system may face contingencies like outage of
transmission line, outage of a generating unit, loss of
a transformer, sudden increase in demand, etc.
Although many contingencies can occur, only those
contingencies with high probability of occurrence are
to be considered and such contingencies are called
credible contingencies. A set of credible
contingencies needs to be given first priority for
security analysis.The contingency analysis involves
the simulation of individual contingency for the
power system model. In order to make the analysis
easier, it consists of three basic steps. Contingency
Creation: It comprises of a set of possible
contingency that might occur in a power system. The
process consists of creating the contingencies list.
Contingency evaluation: The necessary preventive
actions needed to be taken by the operational
engineers. Thus the power system security assessment
is an important aspect for power system engineers.
Objectives of The Work:
Obtain the power flows in transmission lines
under the contingencies using Newton- Raphson load flow method.
Obtain the severity index of each contingency.
Page 2 of 7
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online: https://ejbss.org/ P a g e | 2026
Reduce the over flow in transmission lines by
rescheduling the generation to enhance system
security.
Obtain the optimal dispatch of generators with
minimum fuel cost along with the
minimization severity index
II.POWER SYSTEM SECURITY
In recent times major blackouts has been
occurred due to this some million number of
peoples were affected. The most reason for this is
that not having good security treatment for power
system network under the different contingencies. As
demand is goes on increasing besides of transmission
capacity the power system security also get
importance for power system operation. Security of a
power system network deals with weather the
network is withstanding the contingencies without
any limit violation or not. Contingency means any
outage of transmission line, generator, transformer
etc. from power system network. If the present
condition of power system network is found to be
insecure then the action must be taken to bring the
network into the secure condition. If any transmission
line get outage from the network then the power flows
in the remaining lines will get affect and it might
cross the transmission line power flow limits also. So
because of flowing the unsafe power in that
transmission lines that lines also might get outage.
This process will continue and lead to complete black
out if we will not control the power flows in
transmission lines under contingency. So the power
system security is essential under the contingency to
operate the power system network in safe mode. The
security of a power system network can be enhance
by rerouting of power flows in the transmission lines.
The rerouting of power flows in transmission lines
can be done by rescheduling of generators.
III.CONTINGENCY ANALYSIS
Any outage of equipment from power system
network is called contingency. Due to the
contingency very severe problems can occur within
short time. Security assessment is essential under
contingency. Contingency analysis is needed for any
power system network because there is no chance to
extensive development of power stations for
increasing load demand. Contingency analysis should
be performed for different and unexpected faults
which are occurring in power system network to take
particular remedy prior to the fault occur in power
system network. The contingency analysis for
considered power system network has been divided
into three basic steps. They are as given below.
i. Contingency creation: This is the first step of
contingency analysis and it consists of different
contingencies which are having most chance to occur in
power system network. So finally this process gives the
list of different contingencies which are regularly
happened in power system network.
ii. Contingency Selection: This is the second step of
contingency analysis and in this process we will select
severe contingency from the list made in contingency
creation process. Severe contingency means the
contingencies for which the bus voltage and power limit
violates. The severity of each contingency can calculate
in terms of severity index and we can filter the very
sever contingencies and least
sever contingencies in this process.
iii. Contingency evaluation: This is the third step of
contingency analysis and in this process we have to
take the particular control action or security action for
Page 3 of 7
European Journal of Business &
Social Sciences
Available at https://ejbss.org/
ISSN: 2235-767X
Volume 07 Issue 04
April 2019
Available online: https://ejbss.org/ P a g e | 2027
sever Contingencies to keep the bus voltage and power
within specified limits
IV.CONTINGENCY CONSTRAINED ECONOMIC
LOAD DISPATCH USING PSO
Under the contingency the power system security
can be enhance by rescheduling the generating units.
While rescheduling the generators different constraints
should take into consideration. The minimum and
maximum limits of power flow and nodal voltages of
different transmission lines are the main constraints during
the rescheduling under contingency. In this work the
rescheduling has been done by using an optimization
technique called Particle Swarm Optimization (PSO).
V.PARTICLE SWARM OPTIMISATION
PSO is a population based optimization technique and
it is adopted from the simulation of the fish schooling
and birds flocking. PSO having some inherent
capability so that it will take less time to compute and
require less memory space. The basic consideration
behind the PSO technique is that birds are finding
their food by flocking as a group. The PSO is also
same as some other evolutionary algorithms. The
problem is first initialised with stochastic solutions
(swarm). The potential solution of each stochastic
solution can call as particle (agent) and it is associated
with stochastic velocity and it is flying through the
problem space. Each particle have some amount
knowledge with that they will move around the
problem space. All the particles have memory and
each particle keeps track with its previous best
position (Pbest) and corresponding the fitness value.
The best of all particles of Pbest will be global best
position (Gbest). The position of each particle will be
updated by updating their velocity by following
equation.
V =WV +c * rand ()* (P best1 S )+c * rand ()* (G best - S
)
PSO ALGORITHM:
Algorithm steps for PSO technique.
• Initialise the population with random values and
velocities.
• Computing the fitness of each agent (particle) and assign
the position of particles to Pbest
position and fitness of particle to P-best fitness.
• Identify the best value among the P-best and store the
fitness value as a G-best.
• Update the Velocity and position of each particle (agent)
by using below equations.
k+1 k k k
1 1 1 1 best1 - 1 2 2 best 1 V =WV +c * rand ()* (P S
)+c * rand ()* (G - S )
k+1 k k+1
1 1 1 S = S +V
• Check the velocities and positions whether it will be
within the range or not then again find the fitness of each
particle (agent).
• Compare the current fitness value with its previous P- best. If present value is better than the P-best then update
the P-best as a current value.
• Now compare the present value with the G-best. If
present value is better than the Gbest then update the G- best as a present value.
• Repeat the above steps until to get sufficiently good G- best or until to reach maximum number of iterations
VII.CONTINGENCY CONSTRAINED ELD:
In Chapter 2 we have discussed the different
contingency analysis. In Table No:1(Severity
indexes for different contingencies for IEEE-30 bus
system) shown that the severity of each
contingency and also shown that which lines are getting
overload under different contingencies. Because of
overloaded lines the total power system may get effect. So
we have to reduce the loading effect in overloaded lines
for that we have to reschedule the generating units. While
rescheduling the generators we have taken the severity
index also one of the constraint so that the power flow in
overloaded lines will come under specified limits. During
the rescheduling the generation by utilising PSO
optimisation technique will be as
