Probabilistic Static Voltage Stability Security Assessment for Power Transmission System

A probabilistic static voltage stability security assessment model based on stochastic load flow (SLF) and static voltage stability region in cut-set space (CVSR) is presented. Uncertainties in loads and generation power injections, probabilities of critical contingencies can be considered in the model. The probabilistic distribution functions (PDFs) of line flows of key cut-set are obtained by stochastic load flow, and the PDFs of linear combination of line flows in CVSR are deduced by Gram-Charlier progression and Cumulants. Then the probability of static voltage instability is calculated by hyperplane equation of CVSR. By analysis of probability index, faults making the most contribution to the system static voltage insecurity probability are obtained. The results of probabilistic static voltage stability security assessment can be applied in making decision of preventive control. Test results on the New England 10-genarator 39-bus system are presented and the effectiveness of this approach has been proved.