A wind turbine is a complex electromechanical system. It is important to know how to control it, particularly if high performance and good efficiency are needed. Understanding the rules of nature and the behavior of a wind turbine, especially in its operation, is a subject that requires a number of types of specialized knowledge. We also need to know how to work on them, and then carry out further research and development on their functionality. In this thesis we have studied in different aspects of wind turbine. There are two types of wind turbines (Horizontal axis & Vertical axis). In our thesis we have only focused on the horizontal-axis type.