Zonal Dynamic Equivalents Based on the Concept of Relative Electrical Distance

Abstract

Abstract: This article presents a systematic approach to construct the zonal dynamic equivalents of a large-power system based on the concept of relative electrical distance (RED). The task of dynamic equivalencing is to eliminate the full model of the external system and replace it with an equivalent model, which has dynamic characteristics close enough to the full model. The dynamic equivalent models are used for large-scale power system offline transient stability analysis with large disturbance. Dynamic equivalencing also helps in reducing the computation burden and memory requirements in wide area monitoring system (WAMS) for online stability assessment. The procedure is illustrated on IEEE 39 bus system and on a practical 205 bus system consisting of three zones of Indian Southern grid, where an equivalent of a zone has been constructed. The simulation results of the original system and equivalent system are compared. The proposed approach is also compared with the existing Ward equivalent method and the results are found to be similar. The simulation results show that the developed equivalent system has close accuracy in representing the dynamic characteristics of the original system.