Power System Thévenin Equivalent Estimation Based on Phasor Measurements

Abstract

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.

State Estimation in Unbalanced Distribution Networks by Symmetrical Components

“…In Line 1, we form the SE analysis positive sequence measurement vector  z which consist of pseudo and µPMU measurements. In Line 2, using the SDP SE formulation, we relax the nonconvex rank-one constraint (9e) and solve (9) for the positive sequence component. We next form () s  W to derive normalized residuals in Line 4 using (16).…”

“…As a result, it is inevitable to use full ac power flow equations. In recent years, the distribution network SE analysis has attracted lots of research interests [7,8,9].…”