Mohammad Kazeminejad - Department of Electrical Engineering, Aliabad Katoul Branch, Islamic Azad University, Aliabad Katoul, Iran
Saheb Khanabdal - Faculty of Electrical Engineering, Shahrood University of Technology, Shahrood, Iran
Mozhdeh Karamifard - Department of Physics, Aliabad Katoul Branch, Islamic Azad University, Aliabad Katoul, Iran

Improving voltage stability is one of the most critical issues in evaluating the performance of power systems. Whereas the use of distributed generation resources in distribution networks plays an important role, the optimal sitting and sizing of these units are vital for improving voltage stability and reducing losses. Distribution systems are known to be substantially unbalanced, so a three-phase power flow is required as an efficient tool for unbalanced network analysis. This paper presents a new voltage stability index with simple updating that can update just by active and reactive power demand in each iteration of power flow. Also, in order to find the optimal siting and sizing of distributed generation units (DGs), the voltage stability is analyzed by considering the Imperialist Competition Algorithm (ICA). The obtained results show the improvement of voltage profile and voltage stability as well as the reduction of total losses in the IEEE ۳۴ bus multiphase distribution system.

Voltage stability, Backward/forward load flow, Imperialist competition algorithm, distributed generation, Multiphase distribution systems