Consideration of controllability and observability of generators in the coherency-based dynamic equivalencing

This paper describes an improved method for developing dynamic equivalents. The method bases on the coherency of generators quantified by the correlation coefficient of the swing curves. For measuring the electromechanical distance of generators from the interesting areas, controllability and observability indices are defined. These are calculated on the base of the linearized system equations. A modified correlation formula is used for considering the controllability and observability. As a result, distance generators will be put together into a coherent group rather then those with large controllability and observability factors.