This paper aims to study distribution system operations by the ant colony search algorithm (ACSA). The objective of this study is to present new algorithms for solving the optimal feeder reconfiguration problem, the optimal capacitor placement problem, and the problem of a combination of the two. The ACSA is a relatively new and powerful swarm intelligence method for solving optimization problems. It is a population-based approach that uses exploration of positive feedback as well as ldquogreedyrdquo search. The ACSA was inspired from the natural behavior of ants in locating food sources and bring them back to their colony by the formation of unique trails. Therefore, through a collection of cooperative agents called ldquoants,rdquo the near-optimal solution to the feeder reconfiguration and capacitor placement problems can be effectively achieved. In addition, the ACSA applies the state transition, local pheromone-updating, and global pheromone-updating rules to facilitate the computation. Through simultaneous operation of population agents, process stagnation can be effectively prevented. Optimization capability can be significantly enhanced. The proposed approach is demonstrated using two example systems from the literature. Computational results show that simultaneously taking into account both feeder reconfiguration and capacitor placement is more effective than considering them separately.
I. INTRODUCTION
GENERALLY, capacitors have been commonly employed
to provide reactive power compensation in distribution
systems. They are used to reduce power losses and to maintain
the voltage profilewithin acceptable limits. The benefits of com-
pensation depend greatly on how the capacitors are placed in the
system, specifically on the location and size of the added capac-
itors.
Distribution systems consist of groups of interconnected
radial circuits. The configuration of the system may be varied
by switching operations to transfer loads among the feeders.
Two types of switches are applied in primary distribution
systems, which are normally closed switches (sectionalizing
switches) and normally open switches (tie switches). Both
types of switches are designed for protection configuration
management. Feeder reconfiguration is the process of changing
Manuscript received July 16, 2007; revised February 24, 2008. Current ver-
sion published October 22, 2008. Paper no. TPWRS-00014-2007.
The author is with the Department of Electrical Engineering,WuFeng Insti-
tute of Technology, Chiayi 621, Taiwan, R.O.C. (e-mail: cfchang@mail.wfc.
edu.tw).
Digital Object Identifier 10.1109/TPWRS.2008.2002169
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