A comparison of voltage collapse point prediction capabilities of voltage stability index and inherent structural characteristics

Modern power systems are highly interconnected and heavily loaded. The continuous load increase may drag the whole systems to a condition of voltage instability and this may result in voltage collapse. Prediction of the proximity of the system to voltage collapse is therefore an important task in power system operation and planning. Presented in this paper is the application of two techniques that can be used to determine the voltage collapse point in a power system network. At first, the conventional approach of voltage stability index, which is solely based on running repetitive load flow solutions while finding the point susceptible to system voltage collapse, is considered. The inherent structural characteristic of the power system network, which is the structural interconnections between the nodes governed by the impedances or admittances between them, is also presented. The formulation of which is done based on the basic circuit theory laws. Simulations are done using MATLAB software package. Results obtained show that voltage collapse point is easily and quickly detected and predicted with the approach of inherent structural characteristic without necessarily going through the rigor of a time consuming and repetitive load flow based voltage stability index (L-index).