Developing New Thevenin Impedance Determination Technique and Voltage Stability Assessment Index for Online Application

In Thevenin impedance determination techniques, which are used for voltage stability assessment, approximations are common. The approximations produce erroneous results during critical operating times. This paper has solved the approximation problems and comes up with new Thevenin impedance determination technique suitable for online voltage stability assessment. The Technique is tested on a simple three bus test system, and produced results that match with the actual values. Using this new Thevenin impedance determination Technique, a new voltage stability index is also developed. The index is tested on IEEE 14 bus system and it has, effectively, identified weakest and strongest buses. The test is also compared with the result from other methods, and its effectiveness for online voltage stability assessment is shown.