Effective capture of wind gusts in small wind turbines by using a full active rectifier

Small wind turbines have difficulties to start rotating at low wind speeds due to their relatively large rotor inertia and small starting torque. In case a permanent magnet generator is used, the rotor magnets will cause an additional cogging torque which makes starting even more difficult. By using the generator as motor from the moment a wind gust is detected, the turbine is able to accelerate much faster to reach the maximum power point. A maximum power point tracking algorithm is used to locate the optimal working point. At sufficiently large rotor speeds, the controller switches to the generator mode where the energy used for acceleration is recuperated, together with the additional energy captured from the wind gust. To control the generator power in both directions, an active rectifier is used in a back-to-back converter topology. In this paper, this wind capture strategy is simulated. The results show that the power output during a wind gust can be largely increased compared to common MPP-tracking.