An Observer-Based Composite Identifier for Online Estimation of the Thevenin Equivalent Parameters of a Power System

TL;DR

This paper introduces a novel observer-based method for real-time estimation of Thevenin equivalent parameters in power systems using local measurements and grid frequency, enhancing grid monitoring accuracy.

Contribution

It presents a new composite identifier that requires only local measurements and grid frequency, with an extension ensuring exponential convergence under certain conditions.

Findings

The proposed method accurately estimates Thevenin parameters in simulations.

It outperforms conventional gradient descent algorithms.

The approach requires minimal measurement data.

Abstract

We consider a Th\'evenin equivalent circuit capturing the dynamics of a power grid as seen from the point of common coupling with a power electronic converter, and provide a solution to the problem of online identification of the corresponding circuit parameters. For this purpose, we first derive a linear regression model in the conventional abc coordinates and next design a bounded observer-based composite identifier that requires local measurements and knowledge of the grid frequency only. An extension that guarantees exponential convergence of the estimates, under the additional assumption of knowledge of the grid X/R ratio, is further provided. The performance of the proposed identifier, which subsumes a conventional gradient descent algorithm, is illustrated via detailed computer simulations.