Background:
Increasing power demand forces the power systems to operate at their
maximum operating conditions. This leads the power system into voltage instability and causes
voltage collapse. To avoid this problem, FACTS devices have been used in power systems to increase
system stability with much reduced economical ratings. To achieve this, the FACTS devices
must be placed in exact location. This paper presents Firefly Algorithm (FA) based optimization
method to locate these devices of exact rating and least cost in the transmission system.
Methods:
Thyristor Controlled Series Capacitor (TCSC) and Static Var Compensator (SVC) are
the FACTS devices used in the proposed methodology to enhance the voltage stability of power
systems. Considering two objectives of enhancing the voltage stability of the transmission system
and minimizing the cost of the FACTS devices, the optimal ratings and cost were identified for the
devices under consideration using Firefly algorithm as an optimization tool. Also, a model study
had been done with four different cases such as normal case, line outage case, generator outage
case and overloading case (140%) for IEEE 14,30,57 and 118 bus systems.
Results:
The optimal locations to install SVC and TCSC in IEEE 14, 30, 57 and 118 bus systems
were evaluated with minimal L-indices and cost using the proposed Firefly algorithm. From the
results, it could be inferred that the cost of installing TCSC in IEEE bus system is slightly higher
than SVC.For showing the superiority of Firefly algorithm, the results were compared with the
already published research finding where this problem was solved using Genetic algorithm and
Particle Swarm Optimization. It was revealed that the proposed firefly algorithm gives better optimum
solution in minimizing the L-index values for IEEE 30 Bus system.
Conclusion:
The optimal placement, rating and cost of installation of TCSC and SVC in standard
IEEE bus systems which enhanced the voltage stability were evaluated in this work. The need of
the FACTS devices was also tested during the abnormal cases such as line outage case, generator
outage case and overloading case (140%) with the proposed Firefly algorithm. Outputs reveal that
the recognized placement of SVC and TCSC reduces the probability of voltage collapse and cost
of the devices in the transmission lines. The capability of Firefly algorithm was also ensured by
comparing its results with the results of other algorithms.
Analysis of Voltage Stability Index under Stressed Operating Conditions in Bus Power Systems