An improved voltage stability index and its application

After some damaging blackouts, voltage stability and collapse have become worldwide concerned problems. In this paper, we focus on the aspect of voltage stability. An improved voltage stability index named L_I is presented, which can give an accurate indication to power system voltage instability with considering the influence of load model. An appropriate external equivalent method is also presented to speed-up the calculation. So index-L_I can be used in regional operating centers of the interconnection power systems. Applications of index-L_I are also discussed in the end. Some systems are used to illustrate the accurateness and effectiveness of oUMLur methods.