A general index for voltage stability assessment of power system

Abstract

Nowadays, due to the expansion and increase of loads in transmission and distribution (T&D) networks of power systems, the importance of voltage stability has increased. Also, by increasing the penetration of distributed generation (DG) resources, the interaction between these two networks cannot be ignored. So far, several indicators have been proposed to evaluate the voltage stability of power systems. However, these indices have shortcomings, including the following: Most of them are not able to be used at both the distribution and transmission levels, and they are also unable to consider the interaction between the transmission and distribution network. Most of these indices do not model the effect of line length on voltage stability. In this article, a general index is presented to evaluate the voltage stability in power systems, which can accurately evaluate the voltage stability by considering the effect of line length. In the equation provided for this index, some parameters are determined according to the line length (long line, medium line, and short line). The proposed index can assess the voltage stability of the T&D networks, both separately and together. As a result, it can consider the effect of the T&D networks on each other. Also, it is expanded to consider the effect of DGs and tap-changers. Evaluation of this index in different case studies shows its better performance compared to other well-known indices. So, this index alone can be a good alternative to the multiplicity of indices that the operator must use in different cases.