Design specifications for series connected power transformer in DFIG driven wind turbines

This paper presents some topological solutions for the connection to the grid of a wind turbine using a DFIG, in order to increase the reliability of the gearbox. The so called crowbar system is studied to demonstrate its contribution to the gearbox mechanical stress. Analytical models are used to present the advantages of inserting a series voltage to the DFIG stator during voltage dips in order to decrease the oscillating mechanical torque applied to the gearbox. A global approach is used to propose the specifications of such kind of transformer.