Extended Ward equivalent of external system for on-line security analysis

Today's power systems are more and more intensively interconnected. The monitored part of the power system that these measurements cover normally consists of the energy control centre's own system which is called the internal system, and the neighbouring system which is called the external system. Usually, the external system is far bigger than the internal system and a modern energy control centre for a number of the interconnections is responsible for the control of the internal system. So external network modelling is becoming an important component of on-line security analysis. This paper investigates the extended Ward equivalent method. A new equivalent modelling, with sparsity technique, for on-line power system security analysis is presented. The extended Ward equivalent has been tested by simulation on the IEEE 30-bus, IEEE 118-bus load flow test system, and the 706-bus interconnected power system of the NGC. The results show that extended Ward equivalent has suitable properties for practical use and further development.<
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