Power System Thévenin Equivalent Estimation Based on Phasor Measurements

This paper presents a novel algorithm based on phasor measurements to online estimation of power system Thévenin Equivalent (TE) from a generator terminal. Three consecutive phasor measurements of generator terminal voltage and current are used to estimate the system TE. In a real network, system frequency deviation from its nominal value will produce some phase drift in consecutive phasors reported by Phasor Measurements Units (PMUs). To correct the phase drift and synchronizing the reported phasors to the same reference, an improved triangulation method is developed. The improved method uses a virtual vector in its structure. Using this vector alleviates the negative impacts of improper data resulting from noise or disturbances which make the simple triangulation method to be useless. The algorithm is tested on standard NE-39 network and is implemented in Shahid Beheshti University (SBU) protection laboratory to verify the results in a practical area. The obtained results show that the new method can efficiently estimate the in online mode in steady-state and transient conditions.