Robust and efficient voltage stability margin computation using synchrophasors

Results from two practical and fast methods to estimate systems´ Maximum Loading Point (MLP) using Phasor Measurement Units (PMUs) are used in this paper as initial values for a robust and very efficient method that takes advantage of the geometric characteristics of the maximum loading hyperplane and uses the load flow with step size optimization (LFSSO) technique to estimate the system´s proximity to the MLP. Both initializing methods are based on estimated Thévenin Equivalents (TEs) as seen from load buses using only local measurements. On the other hand, the latter method is based on successive load flow calculations of multiple operating points until the MLP is reached within a certain threshold defined by the user. The performance of the complete method (combination between the initializing methods and the LFSSO based method) was tested for some IEEE test systems and for a realistic Brazilian transmission system with more than 4,500 buses.