PMU measurement-based voltage stability indicators by modified multi-port equivalent models

This paper presents a method for voltage stability assessment using local synchrophasor measurements. The maximum power transfer theorem of the single-port system provides a theoretical basis for local load margin estimations at load buses. Extensions to the multi-port model have been explored recently. However, some inaccurate under-estimations have been founded in our extensive simulation studies. To tackle out this problem, a modified multi-port equivalent model is proposed in this paper. The extended Ward equivalent is adopted to upgrade the voltage profile by appending an additional conductance in the equivalent impedance of the multi-port model. By exploring such modifications in the L indicator, more accurate detection of voltage collapse can be achieved. Quasi-steady state time-domain simulations conducted in IEEE 14-bus test system validate the feasibility and the accuracy of the proposed method for on-line voltage stability assessment.