Dynamic equivalents for large ac networks using modal analysis for S-domain models

This paper describes a new methodology for the calculation of dynamic equivalents of large ac networks using modal analysis. The representation of system parts by dynamic equivalents is very important when reductions in the computational efforts and in the system dimensions are required. The proposed methodology is based on the calculations of the dominant poles and associated residues of the self-impedances seen from the connection buses and of the transfer-impedances among them. In this paper the electrical network is modeled direct in the s-domain and some theoretical background on this subject is presented. Results of a network composed by two subsystems are also presented. The simulations considering the dynamic equivalent of one subsystem connected to the detailed part of the second subsystem were compared with the original detailed model of the entire network, showing an excellent agreement.