This paper presents a comparative study of several speed estimators to implement a torque control loop, in a wind generation system with a three-phase boost rectifier operating in discontinuous conduction mode. The electrical variables measured for speed estimation contain low frequency harmonics of the fundamental frequency of the wind generator, as well as switching frequency components due to the boost rectifier. In this noisy environment the linear Kalman filter estimator is the best among the options under study, because of its faster response time and lower estimation error.