Structure-preserving dynamic equivalents for large-scale power systems using border synchrony

Abstract

In general, the existing model reduction methods for power systems use information of the overall system to reduce part of it. This information may not always be available as it may be the case for the studies of interconnection of two power systems. In such situations, when reducing one power system, full data for the other one cannot always be used. However, the reduction should be done such that when connecting the two simplified models, the important cross-border phenomena like, e.g., inter-area modes which involve machines of both sides are preserved. We propose here an approach based on a new definition of the equivalence classes of machines in the zone to be reduced, called border synchrony. The Synchronic Modal Equivalencing (SME) principles of constructing the equivalent are used in this new framework to obtain a structure-preserving reduced system considering that the modes of interest are those observed in the interconnection lines between the two power systems. The feasibility in large-scale systems is studied on a representation of the UCTE power system. However the notion of border synchrony is independent of the effective reduction method and it can thus be exploited with any dynamic model reduction methodology for power systems.