An On-line Thévenin Equivalent Estimation Algorithm and its Application to Condition Monitoring

Abstract

A simple and reliable voltage stability analysis method is to use a Thevenin equivalent model to represent the electrical connection to a load center. Assuming fixed values of the Thevenin voltage and reactance during some interval, a power-voltage (PV) curve analysis can be performed to find the voltage collapse point and stability margin during the observation period. In this paper, an on-line estimation method is proposed to repeatedly compute the Thevenin equivalent voltage and reactance of a power system at regular intervals or on demand using measured values and forgetting factors. The method is validated with simulated PMU data and with 24-hour SCADA data at a wind hub on a medium voltage transmission system in the U.S. western interconnection.