In this paper a novel electrically controlled power splitting drive train for variable speed wind turbines is presented. A variable speed wind turbine has many advantages, mainly it can increase the power yield from the wind, alleviate the load peak in the electrical-mechanical drive train, and posses a long life time, also, it can offer the possibility to store the briefly timely wind-conditioned power fluctuations in the wind rotor, in which the rotary masses are used as storages of kinetic energy, consequently, the variable speed wind turbines are utilized in the wind power industry widely. In this work, on the basis of a planetary transmission a new kind of drive train for the variable speed wind turbines is proposed. The new drive train consists of wind rotor, three-shafted planetary gear set, generator and servo motor. The wind rotor is coupled with the planet carrier of the planetary transmission, the generator is connected with the ring gear through an adjustment gear pair, and the servo motor is fixed to the sun gear. By controlling the electromagnetic torque or speed of the servo motor, the variable speed operation of the wind rotor and the constant speed operation of the generator are realized, therefore, the generator can be coupled with the grid directly. At the nominal operation point, about 80% of the rotor power flow through the generator directly and 20% through the servo motor and a small power electronics system into the grid. As a result, the disadvantages in the traditional wind turbines, e.g. high price of power electronics system, much power loss, strong reaction from the grid and large crash load in the drive train will be avoided.
