Simple dynamic equivalent for fast online transient stability assessment

The development of a simple dynamic equivalent of an external area containing a group of coherent generators is presented. The formulation of this equivalent is based on decomposition and aggregation of coherent generators. The dynamic equivalent has a power system structure and is connected to the internal area at a set of common boundary buses which separate the two areas. The dynamic equivalent is developed in two stages. A multigenerator dynamic equivalent is first formed, then extended to a single-generator equivalent. Unlike the conventional coherency-based reduction techniques of forming the dynamic equivalents, the proposed technique does not require measurement data at the original generators of the external area to determine the parameters of the resulting dynamic equivalent. This important feature makes the proposed dynamic equivalent attractive and suitable for online transient stability assessment. With the knowledge of only the passive network model of the external area and the total inertia constant of the generators in this area, the parameters of this equivalent are determinable from a set of measurement data taken solely at the boundary buses. The performance of the equivalent has been evaluated. Test results show outstanding quality of the proposed equivalent.