Thevenin equivalent parameter tracking for on-line voltage stability assessment

This paper demonstrated a method for online voltage stability assessment of a load bus using bus phasor measurements. The power system is represented by Thevenin equivalent model, which parameters are estimated by applying new methods based on discrete Kalman filter (DKF) and unscented Kalman filter (UKF). Voltage stability index is calculated based on the impedance matching concept. Several measurement base methodologies are proposed to assess long-term voltage stability using the advantage of PMU measurements. Current methods are facing accuracy problem on capturing system dynamics due to limitations in power system representation model. The proposed methods use a new model to represent power system dynamics for long-term voltage stability. The methods performance is tested on WSCC, 9-bus system and compared with recursive least square algorithm. The result shows that the proposed methods can track Thevenin equivalent parameters with better accuracy and can capture the change of system dynamics quickly.