Transient behaviour and active damping of vibrations in DFIG-based wind turbines during grid disturbances

This paper investigates a drive system control strategy for grid-connected wind energy conversion systems with doubly-fed induction generator and its behavior under grid fault operation. During grid faults there is a possibility for undefined load situations in the mechanical drive system. These loads are able to start oscillations in the drive system not only in the shaft but in the blades as well due to the fact that the specific weight of wind energy converter decreases. The combination of the grid fault strategy and the control of the drive system is essential for minimizing the loads in the drive system during and after grid faults. In this paper, a new control scheme for drive system is developed with the focus on oscillation reduction in drive systems of wind energy converters. The controller design procedure is presented in detail. The proposed controller is verified through time domain simulations and its performance is compared against an optimal controller.