Buffer system selection of a steady-state external equivalent model for real-time power flow using an automated sensitivity analysis procedure

A steady-state external equivalent model of a large interconnected power system for a real-time power flow use, incorporating a properly selected buffer system, is presented. The particular problem of how to select the buffer (or inner external) system is the author´s primary focus. The elements of the buffer system selected from the external system by the automated procedure are key transmission lines, transformers, load, and generators. The external equivalent model presented can be described as a modified Ward P2m-V model. The impact of a condition change in each of these elements on the voltage magnitudes and line flows at the boundary is determined by an automated sensitivity method using the decoupled P- theta and Q-V power flow models. The method has the capability of identifying the important elements for the buffer system based upon a normalized level-of-impact index. Tests were performed on specific areas and the equivalent model was found to provide very accurate results.<>