A Two-Stage Method for Assessment of Voltage Stability in Power System with Renewable Energy

This paper presents a novel method to evaluate the impact of uncertain power injections on voltage stability assessment. For power grids with large renewable generation, the uncertainty needs to be explicitly accounted for; making the voltage stability assessment a stochastic problem. A two-stage method is proposed to evaluate the impact of uncertain power injections on the voltage stability load margin. The approximate probabilistic distribution of load margin is assessed with a minimum number of samples by use of a stochastic response surface method implementation in the first stage. And severe scenarios are then screened and then ranked by the proposed Scenarios Screening method. The first stage gives preliminary information whether uncertainty of power injections leads to voltage collapse while the second stage finds severe scenarios which lead to voltage collapse. The proposed two-stage method is illustrated on the IEEE24-bus and the IEEE 118-bus system considering stochastic wind generations.