I. Introduction
In the beginning of 21st century, the world electricity demand is increasing very rapidly because of the advanced technology and industrial growth. The major part of these electricity demands is fulfilled through the conventional energy. In general, the conventional energy is dependent on the fossil fuels-coal, oil, and gas, which are very limited as well as air is also polluted by using of conventional energy sources. Therefore, due to the environmental concerns and inadequacy of fossil fuel resources, the electric power industries are placing more emphasis on the renewable energy resources or green energy sources with respect to economical and availability prospects. Among the various viable renewable energy sources including hydro, wind, solar, and geothermal resources, wind energy becoming the most prominent energy resources and fastest growing power generation technologies in comparison to others renewable energy sources due to its low maintenance cost, high production capability, no air pollution and availability in several parts of the world. Moreover, wind energy is endless energy resources in the power network. In [1], it is reported that throughout the world, total 760 GW of the wind power will generated by the end of year 2020.