Reactive power control strategy of DFIG wind farms for regulating voltage of power grid

If a wind farm is weakly connected to a power grid, then the voltage of the connection point fluctuates frequently due to the changeable wind speed. The active and reactive power of a doubly-fed induction generator (DFIG) can be decoupling controlled and the grid-side converter (GSC) of a DFIG can also generate some reactive power by adjusting the power factor, thus a DFIG can be considered as a reactive power resource to stabilize the voltage of the connection bus. Based on the power relationship of a DFIG, the up and down reactive power limitations of DFIG stator and GSC are analyzed. Then a reactive power control strategy of a DFIG wind farm is proposed, in which, a certain number of DFIGs are selected to support reactive power to the power grid when the voltage of the connection point drops. The control strategy aims at bringing the reactive power capability of DFIG into play and cutting down the investments in the reactive power compensation devices which are used less. The simulation model of a grid-connected DFIG wind farm is developed on the PSCAD/EMTDC platform, and the simulation results demonstrate the effectiveness of the control strategy proposed.