Abstract

The necessity for flexible electric systems, changing regulatory and economic
scenarios, energy savings and environmental impact are providing impetus to the development of
Distributed Generation (DG), which is predicted to play an increasing role in the electric power
system of the future. The optimal placement and sizing of generation units on the distribution
network has been continuously studied in order to achieve different aims. This paper describes
planning of distribution systems in two scenarios. In the first scenario, optimal distributed
generation allocation for voltage profile improvement, loss and Total harmonic Distortion (THD)
reduction in distribution network has been implemented. Whereas, DG cannot reduce THD to the
optimum range, in the second scenario an active filter and a capacitor is used to reduce THD as
much as possible. Because of THD and Losses are based on different objective function, a
“compromise programming” model that attains the “best compromise” among the conflicting
objectives is introduced to overcome on this problem. Harmony Search Algorithm (HSA) was used
as the solving tool, which referring two determined aim; the problem is defined and objective
function is introduced according to losses, security and THD indices. The applied fast harmonic
load flow method is based on the equivalent current injection that uses the bus-injection to
branch-current (BIBC) and branch-current to bus-voltage (BCBV) matrices which were developed
based on the topological structure of the distribution systems. This method is executed on 12 bus
harmonic unbalanced distribution system and show robustness of this method in optimal and fast
placement of DG, efficiency for improvement of voltage profile, reduction of power losses and
THD.