Optimal Allocation and Sizing of Shunt Capacitors in Unbalanced Radial Distribution Systems: A Comparative Study

A comparative study on the problem of optimal capacitor allocation and sizing in unbalanced radial distribution systems (URDSs) is presented in this paper. The comparison is performed between three different sensitivity-based indices, which are utilized for selecting the optimal locations of the three-phase capacitors. Those indices are: index vector (IV), combined loss sensitivity factor (CLSF) and voltage stability index (VSI). For the comparison purpose, the capacitors' sizes are obtained by implementing particle swarm optimization algorithm (PSO). Two main aspects are considered in this comparison: (i) the number of locations for capacitors to be installed at, and (ii) the type of the three-phase capacitors (balanced or unbalanced three-phase capacitors). The optimization problem is basically a minimization of three objective functions, namely: power loss, voltage deviation and voltage unbalancing. The comparative analysis is executed on the 25 bus unbalanced system and then simulation results are discussed and evaluated.