Performance assessment of PMU-based estimation Methods of Thevenin Equivalents for real-time voltage stability monitoring

This paper investigates the performance of different methods for calculating the Thevenin equivalent parameters based using only data obtained from real-time synchrophasor measurements. Estimating the parameters from data affected by noisy measurements, transients, and continuously varying power system parameters may yield Thevenin equivalents that do not reflect the actual voltage stability of the system. The paper proposes using a total least squares method to take into account errors in the model from time-varying Thevenin parameters and noise. The paper reviews two different methods for Thevenin equivalent estimation proposed in the literature. The suitability of the three methods described in the paper is tested in case studies, where the performance of the methods are tested with both noise-free and noisy data. The papers also investigates effect of changes in the power consumptions at other buses on the Thevenin parameters seen from the monitored load bus.