Optimal capacitor placement in distribution system considering mutual coupling, load unbalancing and harmonics

One of the most effective and useful methods in reducing the power losses of distribution networks is utilization of optimal capacitor placement. To do this, real modelling of the system is required. This paper investigates the effect of mutual coupling, load unbalance and harmonics on the capacitor placement. A binary Particle Swarm Optimization Algorithm has been proposed for solving this problem. The objective function includes the cost of power losses and capacitor banks with constraints which include limits on voltage, total harmonic distortion and sizes of installed capacitors. The proposed method has been applied to a distorted 9 bus distribution system to demonstrate the significant differences in results of capacitor placement studies when unbalanced system approximated by their positive sequence single phase equivalents and ignoring the effects of harmonics.