Improvement of voltage quality in connection of wind farms to transmission network using VSC-HVDC

This paper studies possible improvements of voltage quality in connection of 40 MW wind farm to transmission network using VSC-HVDC link. The 40 MW wind farm includes 20 individual 2 MW permanent magnet synchronous generators. The voltage at the transmission network terminal should be re-established with minimized power losses during wind speed fluctuations and after the clearance of grid side faults. This paper emphasizes on a modified decoupling control strategy which is implemented in VSC-HVDC converters to obtain variable speed operation and voltage stabilization in wind farm network and transmission network respectively. Simulations using PSCAD/EMTDC are performed to study behavior of wind farm, transmission voltage and dc voltage for different changes in wind speed and three-phase fault and a 20% voltage sag on transmission network. The simulation results confirm the connection method and the modified decoupling control strategy.