Reactive power coordination in DFIG based wind farms for voltage regulation & flicker mitigation

The deployment of modern DFIG or full converter turbine technologies on a large scale into distribution networks is raising issues for electric utilities with regard to voltage rise and flicker amongst other power quality issues. This paper proposes an real-time reactive power coordination scheme employed with the voltage control technique, the concurrent means for achieving both voltage regulation and flicker mitigation at the wind farm point of common coupling (PCC). Noting that each wind turbine generator (WTG) comprising the wind farm operates in a different state, wind condition dependant, the instantaneous reactive power capabilities of each WTG differ. Based on the estimated real-time instantaneous reactive power available from each WTG, a wind farm Q dispatcher is proposed to fully utilize the DFIG turbine power converter capabilities in order to avoid active power curtailment and maximize energy production. Exploiting the reactive power capabilities of the rotor side converter (RSC) and grid side converter (GSC), the proposed control strategy regulates the voltage level within acceptable bands and reduces the flicker level by up to 90%. The real-time simulation results presented in this paper focus on a 6 MW wind farm being connected to a rural 25 kV distribution feeder, considering the applicable utility grid code requirements.