Generating units aggregation for dynamic equivalent of large power systems

This work describes an improved method for developing dynamic equivalents of coherent groups of generators, which are identified on the basis of a slow coherency approach. The proposed aggregation method is based on the structure preservation of the coefficient matrices in time domain representations of generating units with detailed models. The equivalent parameters of dynamic equivalent including its control devices are identified directly according to the principle of structure preservation and weighted with MVA base. The derived dynamic equivalent can be used with conventional transient stability programs. The proposed method is applied to the well-known New England test system (10-machine, 39-bus) and results of validation test show that the reduced equivalent system retains the dynamic performance of the original system with good accuracy.