W-CVT continuously variable transmission for wind energy conversion system

This paper investigates the possibility to use a power split electric driven continuously variable transmission as the core of a wind energy conversion system. The proposed power split transmission for WECS, called W-CVT allows to control the speed of the turbine rotor by keeping constant the speed of the electric generator. The W-CVT is constituted by a planetary gear set integrated with a small size electric machine. This device is installed between the step-up gearbox and a fixed speed fixed frequency electric generator. The limitation of the transmissible torque between the rotor and generator due to the introduction of the W-CVT could be preserve the system components during wind-gusts or electric faults on the grid side. This paper introduces the W-CVT concept, the dynamic model of a complete WECS transmission based on the W-CVT, a design criteria for sizing the CVT and some preliminary results obtained with this system.