Power Quality of Variable Speed Wind Turbines with DFIG and their Interaction with the Grid/Netkvalitet ved hastighedsstyrede vindmøller.

The project concentrates on study of flicker emission and mitigation of variable speed wind turbines with doubly fed induction generator (DFIG) during continuous operation, and voltage recovery of two different kinds of variable speed wind turbines, respectively with dynamic slip control and with DFIG, after the clearance of a short circuit fault in the grid. The project is mainly carried out with the following parts: * Modelling of variable speed wind turbines with DFIG; * Control systems design for wind turbines with DFIG; * Flicker emission of wind turbines with DFIG and the influence factors; * Flicker mitigation of wind turbines with DFIG using wind turbine output power control and STATCOM; * Control strategies for voltage recovery of wind turbines with dynamic slip control after the clearance of an external short-circuit fault; * Control strategy for voltage recovery of wind turbines with DFIG after the clearance of an external short-circuit fault. The project intends to investigate the power quality issues of variable speed wind turbines with DFIG and propose some control strategies that help to maintain the voltage stability of grid connected wind turbines. The project is partly sponsored by the Danish Academy of Wind Energy (Tao Sun; Z Chen; Frede Blaabjerg)