Online voltage stability monitoring based on PMU measurements and system topology

This paper presents a new approach to estimate the Thevenin impedance and the maximum power transfer at load buses, which are criteria for voltage stability assessment. The proposed algorithm utilizes system topology, load impedances and phasors from phasor measurement unit (PMU) as means of estimation, in which load impedances are integrated into the admittance matrix of the power system to compute Thevenin equivalent parameters and phasors at monitored load buses are used to identify the maximum loadability point. The proposed method shows good performance on monitoring voltage stability. It is also applicable for online applications since PMUs are required at buses of concern and other information is available from existing state estimator. In case study section, the proposed methodology is demonstrated and validated by simulation on IEEE test systems.