I. Introduction
In most of wind-energy generation systems, anemometers are used to measure the wind speed for the maximum-power-point-tracking (MPPT) control [1]. The anemometer installed on the top of nacelle may be a source of inaccurate measurement of the wind speed. In wind farms, several anemometers are often placed at some locations to measure the average wind speed [2]. The use of anemometers raises a problem of calibration and measurement accuracy, as well as increasing the initial cost of the wind generation systems. For these reasons, it is desirable to replace the mechanical anemometers by the digital wind-speed estimator based on the turbine characteristics.