Mehrdad Moghaddam - M.Sc. Student, Department of Electrical Engineering, Ashtian Branch, Islamic Azad University, Ashtian, Iran
Mohammad Reza Alizadeh Pahlavani - Associate Professor, Department of Electrical Engineering, Malek-Ashtar University of Technology (MUT), Tehran, Iran

Recently emerged developments in the field of renewable energies disclose that wind turbines and photovoltaic, as modern distributed generation systems in distribution network, are growing in popularity as new energy sources. One of the most prominent criteria relied upon traditional network is that its protection and planning in case of connecting a distributed generation source to power network, is insufficient; therefore, this interconnected electric power system, constantly makes the power system stability confronted with new challenges. This paper investigates the effects of distributed generation, specifically variable-speed wind turbines on distribution network and is particularly focused on the stability of power network during fault conditions and includes voltage dips, transients, and line short circuit fault currents in cases both single-phase and three-phase faults. Furthermore, solutions to overcome miscoordinations resulted from the integration of distributed generators (DGs) into power network have been brought into focus. This paper also investigates how influentially the integration of variable-speed wind turbines into power system enhances the whole system s operation affecting in several ways such as lessening power losses, betterment of voltage, and injecting current. Modeling and simulations have been performed in DigSILENT PowerFactory and the results are analytically presented

voltage stability, wind turbine, renewable energy integration, microgrids, miscoordination, short circuit, variable-speed, distribution network, DG integration