Accuracy Analysis of Static Voltage Stability Indices Based On Power Flow Model

There are some voltage stability indices for voltage security assessment and calculating stable margin from operating point to voltage instability at each load bus. Most of those indices are based on static analyses using power flow model. This paper aims to verifying the accuracy of representative power flow model based indices by small signal stability analysis and dynamic time domain simulation. It briefly reviews some representative indices invented in the past several decades, and draws the conclusion that the voltage stability critical point calculated from those indices is in essence the maximum transfer limit from electric network to loads for constant MVA load. A small signal stability analysis mathematical model of single induction motor and infinite bus system is presented in order to reckon for the dynamic behaviors of loads. The mathematical model is used for analyzing small signal stability of a simple system. Dynamic simulation is performed for verifying the results obtained from static indices and small signal stability analysis. Those results show that static indices based on the power flow model is sometimes inaccurate. It is recommended to research new indices considering dynamic components