Modeling and semi-active control for a low power and free-yaw drive HAWT

Nowadays, wind power is being widely used as a renewable source of energy. The major disadvantage is the dependence of the wind's velocity and direction to maximize the power production. Actually, wind is unpredictable and the availability of wind energy is not constant. Once it's possible to deal with the wind velocity on the blades by controlling the pitch angles, is also possible to deal with the wind direction deviation by controlling the yaw angle, which is already done in every wind-turbine with a yaw-drive system. For those who are free-yaw drive, vertical-axis wind turbines (VAWT) and low power horizontal-axis wind turbines (HAWT), it's important to maximize its production at least until the nominal conditions, since its power is already lowest and the production almost never reach the nominal condition. This paper analysis the differences between the real power production and the ideal power production, based on two low-power HAWT models, with the objective of showing the power that is being lost. To maximize the production of the free-yaw drive turbine a semi-active control system magnetorheological based will be implemented to brake it when its need and to perform the wind's direction tracking, with the objective of concluding the influences of control systems in its power produced and to demonstrate how a brake model of magnetorheological fluid can perform a track on the wind direction.