Three-phase voltage stability analysis in an integrated transmission-distribution network

Abstract

The transmission–distribution interaction is not generally considered in the voltage stability analysis of power systems. Moreover, the load-ability assessment of power system with considering of the penetration level of distributed generation (DG) resources and the performance of on-load tap changers (OLTCs) need to be further analysed. In this study, unstable regions in integrated transmission–distribution networks (ITDNs) were detected in terms of voltage stability and maximum load-ability. A new voltage stability index was also proposed based on the Thevenin equivalent circuit observed from distribution buses. The proposed method was exactly proportional to the active and reactive powers of each bus in the multi-phase distribution system. Accordingly, the static voltage stability of an integrated test system can be accurately analysed. Two IEEE transmission test systems (3 buses and 14 buses) connected to the distribution systems were utilized to simulate the proposed method. The simulation results were analysed in detail to find the maximum load-ability. The results strongly suggested the significance of the voltage stability analysis in ITDNs.