Uncertainty in real-time voltage stability assessment methods based on Thévenin equivalent due to PMU's accuracy

Abstract

This article studies the influence of PMU's accuracy in voltage stability assessment, considering the specific case of Thévenin equivalent based methods that include wide-area information in its calculations. The objective was achieved by producing a set of synthesized PMU measurements from a time domain simulation and using the Monte Carlo method to reflect the accuracy for the PMUs. This is given by the maximum value for the Total Vector Error defined in the IEEE standard C37.118. Those measurements allowed to estimate the distribution parameters (mean and standard deviation) of the studied voltage stability indices and grid transformation coefficients which have applications in voltage stability assessment. The obtained distributions have a direct impact in the number of samples needed for estimating system parameters and compromise between timescale and uncertainty in those estimations is shown.

Evaluation of Factorization Methods for Thévenin Equivalent Computations in Real-Time Stability Assessment

“…Thereby this paper focus on computational performance only. For studies on the impact of measurement uncertainty the reader is referred to [7].…”

Considering wind speed variability in real-time voltage stability assessment using Thévenin equivalent methods

“…It is expected that a higher percentage of power generation will come from wind energy in Denmark [1] and its variability will impose challenges in the power system control and stability, where some of those concerns are aimed to be addressed by the SOSPO project 1 . For this purpose, a set of algorithms have been developed to produce a fast stability assessment, in real-time, by using PMU (Phasor Measurement Units) and wide-are information [2][3][4][5][6][7][8][9][10].…”

“…In the specific case of voltage stability, two methods were identified as suitable for real-time assessment [5]: sensitivities and Thévenin Equivalent methods, and a review of existent approaches can be found in [11]. The real-time voltage stability assessment in this paper is based on Thévenin equivalent method [2,5,11], which offers advantages in its computational complexity [5] and its element-wise nature is used to consider the limits in the generators as described in [6]; the improvements described in [9] make it suitable for considering wind farms limits.…”

“…The forecast and the associated uncertainty allows to compute the Thévenin equivalent parameters and its uncertainty. This is achieved by using the work developed, which considers the PMU accuracy in real-time stability assessment [6] as a framework to study the variability of the voltage stability index. The main objective was to show the possibility of considering the variability of the wind as an uncertainty of the estimated Thévenin Equivalent, and the associated implications it has on the index.…”

Detecting topological errors with pre-estimation filtering of bad data in wide-area measurements

“…Every measurement has some noise component. While PMUs are capable of measuring state variables directly it has been shown that the noise component can reduce the accuracy of system monitoring to undesirable levels [2]. A state estimator may filter the noise component from the measurements.…”