عنوان مقاله [English]
In this paper, an optimization method is proposed to determine the optimal placement and size of Distributed Generation (DG) resources and capacitors simultaneously in radial distribution systems. Improvement of active and reactive power losses, voltage deviation, line load balancing and voltage stability indices of the network are objectives of this optimization problem. A multi-objective function with appropriate constraints has been proposed. In order to robust the location of DGs and capacitors against load variations, different load levels have been incorporated into the objective function simultaneously, while the generated power of DGs and reactive power of capacitors are assumed to be variable for each load level. In this study, light, nominal and heavy load levels have been considered for network. Also, the loads are considered to be voltage dependent. The optimization problem has been solved by TLBO algorithm. The proposed method has been implemented on the 33 and 69 bus radial distribution standard systems and the results have been compared with the methods based on single-level and loss sensitivity factor. The obtained results show superiority of the proposed method.