Collective Impact of Multiple Doubly Fed Induction Generators With Similar Dynamics on the Oscillation Stability of a Grid-Connected Wind Farm

This paper examines the small-signal oscillation stability of a grid-connected wind farm affected collectively by multiple doubly fed induction generators (DFIGs) with similar dynamics. An analysis of this issue, which is referred to as the collective impact of similar DFIGs, revealed that the interconnection of a standalone DFIG with the rest of the wind farm determines whether the collective impact of similar DFIGs is beneficial or detrimental to the oscillation stability of the wind farm. The network topology and parameters of the wind farm affect the scale of the collective impact in several respects. First, increasing the length of the transmission line connecting the wind farm to the AC grid leads to an increase of the collective impact. Second, when the transmission line is much longer than the cables within the farm, the collective impact is approximately proportional to the number of DFIGs. Accordingly, increasing the transmission line length and/or number of DFIGs may magnify the detrimental collective impact, resulting in growing oscillations in the wind farm in the worst case. The analysis of the collective impact of similar DFIGs in this study revealed a new mechanism through which grid-connected DFIG wind farms can lose oscillation stability.