A new hybrid approach to thevenin equivalent estimation for voltage stability monitoring

Voltage instability may be predicted by the Thevenin equivalent based approach using only local measurements taken at the monitored buses. This paper focuses on reliable estimation of Thevenin parameters from measurements, which are crucial in judging voltage stability. Two parameter estimation methods (least squares and Kalman filter) and a proposed new hybrid method are tested on the NPCC 140-bus power system for monitoring real-time margin of the power transferred to a load area against voltage instability.