Enhanced Flicker Mitigation in DFIG-Based Distributed Generation of Wind Power

Abstract

Upon the connection of wind generators to distribution grids, significant flicker emission can appear, due to the low $X/R$ ratios and low short-circuit levels at the points of connection. This paper proposes a reactive-power-based control scheme that aims for accurate cancellation of voltage flicker resulting from the grid connection of DFIG-based wind power. The control scheme operation is based on constructing the two-bus equivalent network of the detailed power system, via local measurements of voltage and active and reactive power flows at the DFIG terminals. The reactive power flow at the DFIG terminals is adjusted accordingly to cancel voltage flicker, based on the constructed equivalent network equations. The proposed control scheme avoids the use of power flow approximations at the connection point, and hence is free of the inaccuracies implicated in the conventional reactive-power-based flicker mitigation approaches (based on power factor control and voltage control). The proposed control scheme is shown, by comparative results, to provide superior performance to those conventional flicker mitigation approaches, as well as flicker mitigation capability independent of the connection point parameters.