Real time voltage stability margin estimation using auto-regressive models and PMUs

This paper presents results about the development of a tool for real time monitoring of the voltage stability margin of transmission systems. With the advent of Phasor Measurement Units (PMU), it becomes easier to obtain the system´s state in real time for both the voltage magnitude and phase angle of the buses. A parametric linear estimation method of discrete dynamic systems called ARX (Auto-Regressive eXogenous inputs) and a nonlinear ARX were used to determine the parameters from a database obtained in an offline stage. The proposed method allows the estimation of the voltage stability margin value in real time using the measures of PMUs installed on the system. Two criteria for the allocation of the PMUs in the network were tested: the voltage variance and the modal participation factor.