CIRCUIT ARRANGEMENT FOR USE IN A VARIABLE SPEED WIND TURBINE SYSTEM COMPRISING A DOUBLE-FED INDUCTION GENERATOR AND A BACK-TO-BACK CONVERTER

摘要

A circuit arrangement in a grid-connected variable speed wind turbine system comprising a double-fed induction generator (G) connected on the stator side to the grid and on the rotor side to a back-to-back converter connected for transferring energy between the rotor of the double-fed induction generator (G) and the grid, is provided with means (S2) for disconnecting at least one normally grid-connected terminal of the back-to-back converter from the grid and means (S1) for connecting an impedance for allowing controlled power transfer from the intermediate DC circuit to said impedance. The control is performed by one or more power-switching elements of the normally grid-connected converter (GC), which has been disconnected from the grid. This makes it possible to keep the generator (G) connected to the grid during grid faults and take active part in the reestablishment of the grid voltage.