Development of AC Network Dynamic Equivalents for Large Scale Power System

Electromagnetic transient studies of large scale power system including FACTS and HVDC requires modeling of complicated transmission networks, at the same time modeling the details of complete system requires great amount of computer memory and computation time. The complete Indian power system network of northern, eastern, western, north-eastern and southern region consists of more than 1200 buses and more than 2500 transmission interconnecting lines. The complete power system network cannot be represented in the electromagnetic transient studies. Therefore, it is required to derive a power system equivalent to the Complete Network containing relevant network buses and power system components. The main objective of power system equivalent is to approximate the behavior of the complete network in both steady states and transient state. The aim of this paper is twofold: on one hand, it presents a discussion about importance of power system equivalents and step by step procedure for constructing the equivalents for electromagnetic transient studies; on the other hand, it proposes the methodology to validate the derived equivalents with full system with the help of a case study. Finally, the results of derived Dynamic Equivalent Network behavior is matched with the Complete Network behavior both in terms of steady state and in transient conditions which are illustrated through the simulation results, discussion and interpretation. The power system equivalent is developed using PSS/E, a software tool for power transmission systems simulations.