Combined maximum power point and yaw control strategy for a horizontal axis wind turbine

In this paper, a combined maximum power point tracking (MPPT) and active yaw control strategy for a wind energy conversion system (WECS) is presented. The proposed control system provides maximum power point operation of the wind turbine combined with fast and reliable alignment of the nacelle to the wind direction and therefore, maximization of the captured power from the incident wind. For the implementation of the MPPT control, the rotor speed is required, while for the implementation of the yaw control, only the measurement of the wind speed is needed because the wind direction, and therefore the yaw angle, can be estimated from the error between the optimum and the real mechanical power at the shaft. The drive train of the WECS comprises a three blade horizontal axis wind turbine coupled to a three-phase squirrel cage induction generator (SCIG) driven by two back-to-back converters operating with space vector modulation. The active yawing is implemented by utilizing a position controlled squirrel cage induction motor (SCIM) drive. Simulation results are presented for the validation of the theoretical considerations and the demonstration of the effectiveness of the proposed control scheme.