Voltage stability analysis and control of wind farms connected to weak grids

Weak AC grids can pose serious interconnection problems by limiting the amount of wind power that can be integrated. Weak AC grids have high transmission impedance compared to strong AC grids. The connection of more wind power generators into weak AC grids may be constrained by voltage instability on the AC grids. This paper analyses and compares the power transfer characteristics of wind farms connected to weak and strong AC grids, and investigates the factors affecting the grid voltage stability. Additionally, using an appropriate control strategy, the relationship between the strength of the grid and the rating of the reactive power compensation device(s) is investigated. The effectiveness of an AC voltage versus reactive power droop fitted to static compensators (STATCOM) is demonstrated to improve voltage regulation on weak grids during wind power variation.