The yaw system is one component of the unique system of wind turbine. The function of yaw system is automatic for wind, automatic untwisting and wind wheel protection. The yaw system of wind turbine is generally divided into active yaw system and passive yaw system. Passive yaw is the yaw mode based on wind force to direct the wind. Active yaw is to use the electric or hydraulic drag to conduct the action of wind yaw.

     Active yaw is adjusting the motor to wind impeller position. It can control and determine the turbines direction according to the wind direction and the normal direction of the impeller plane, but the structure is complex. It has great significance to extend to the turbines life and improve power generation.