Voltage Stability Analysis and Online Monitoring Method Based on Fixed-Point Principle and Spectrum Calculation

Abstract

Accurate voltage stability analysis and online monitoring are essential to ensure a secure operation of the power system. To this end, researchers have proposed a variety of voltage stability indicators and analysis methods, of which, the voltage stability analysis method based on Thévenin equivalent has been widely concerned. However, due to the lack of simple and effective online identification method for Thévenin equivalent parameters, this method is still difficult to apply online. In this paper, the fixed point principle is applied to voltage stability analysis, and a new voltage stability criterion is proposed. Furthermore, in order to determine the physical correspondence between the spectral distribution and each specific load, this paper derives a numerical method for quickly estimating the spectral distribution. Based on the above, this paper proposes a new online analysis and monitoring method for voltage stability. The proposed method was tested on 3-machines and 10-bus system, and compared with the voltage stability analysis method based on Thévenin equivalent. The results show that the proposed method in this paper is effective. Introduction Since the 1990s, great progress has been made in the study of voltage stability in power systems. So far, researchers have proposed a variety of voltage stability indicators and analysis methods[1-9], of which, the voltage stability analysis method based on Thévenin equivalent has been widely concerned[10-13]. Thévenin equivalent is an important concept in linear circuit theory, which has wide application value. For time-varying non-linear circuits, in principle, at any time section, the non-linear circuit can be simplified to a Thévenin equivalent circuit of a node. Therefore, the voltage stability analysis method based on Thévenin equivalence not only has the advantages of clear physical concept, simple model, and can clearly characterize the voltage stability of the power system, but also has good practical application prospects. In 1999, Khoi Vu and other scholars took the lead in putting forward the online identification of Thévenin equivalent parameters and voltage stability monitoring method based on local measurement[6]. Since then, scholars in various countries have continuously improved and improved on this basis and put forward various improved Thévenin equivalent parameter calculation models and methods[12]. However, existing methods for identifying Thévenin equivalent parameters based on in-situ measurements are based on the assumption that the Thévenin equivalent parameters between two adjacent state points or time sections remain unchanged. Obviously, this assumption is not strictly valid, because every operating point of the system should correspond to a unique set of deterministic Thévenin equivalent parameters. Therefore, how to accurately track and estimate the dynamic Thévenin equivalent parameters is still an unsolved problem[7-9]. In order to avoid the above problems, the paper [11] proposes a method of tracking Thévenin equivalent parameters based on time domain simulation and develops a corresponding program for calculating Thévenin equivalent parameters in FDS system[12]. In theory, this method of calculating Thévenin s equivalent parameters based on time domain simulation is accurate and reliable, but the results of literature [14] show that different Thévenin s equivalent methods can get different 2nd International Conference on Electrical and Electronic Engineering (EEE 2019) Copyright © 2019, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Advances in Engineering Research, volume 185