Contingency ranking method for voltage security assessment based on critical eigenvalue trajectory

Abstract

In voltage security assessment it is of great importance to determine the most critical contingencies of the system. However, most of the contingency ranking methods fail to capture the nonlinear behavior of the system, which is more pronounced in the proximity of the system to the voltage collapse point. This paper proposes a contingency ranking method that considers the trajectory of the critical eigenvalue of the jacobian matrix of the power flow equations when the load grows as an indicator of the closeness of the power system to the voltage collapse point. The proposed critical eigenvalue trajectory (CET)-based method utilizes a linear extrapolation of the eigenvalue trajectory. Therefore, for each analyzed contingency, two equilibrium points are obtained and associated with their respective critical eigenvalue, which leads to a linear extrapolation of each critical eigenvalue trajectory. The contingency ranking method is applied on the IEEE 57-bus test system. The results analysis show a good accuracy of the method, specially for the most critical cases. Besides the performance analysis, CET-based method presents good results when compared to the results of two other ranking methods, implemented according to the literature and tested on the same test system.