Dynamic reduction, Version 1. 0

This report describes the theoretical background of the EPRI Dynamic Reduction DYNRED V 1.0. EPRI initiated research under project RP763 to develop the original reduction program DYNEQU. This program was the first to be based on the concept of aggregating of coherent groups of synchronous generators into a single equivalent generator model. While technically advanced, DYNEQU proved difficult to use. Since then, the stability problems encountered in power system planning and operations have changed. The emphasis on first swing transient stability has been replaced by emphasis on inter-area oscillations and voltage stability. The method of identification of coherent generators used in DYNEQU is based on the comparison of rotor angle swings, in a linearized system model, following a fault. It has been shown that this method of coherency identification is good for first swing stability. For inter-area oscillation studies, this method of generator aggregation is less accurate. Far better, are identification methods based on the structure of the power system. Because of these changes in the requirements for reduced order power system models, a new dynamic reduction program (DYNRED) has been developed under EPRI project RP2447-1. It is coherency based, as is DYNEQU, but it has structurally based coherency identificationmore » methods in addition to the method used in DYNEQU. This report describes the techniques used in DYNRED, that is: Coherency Identification; Network Reduction; Method of Aggregation, Generator Aggregation, Excitation Aggregation, Primemover/Governor Aggregation. An example of the application of DYNRED to the reduction of a large interconnected power system model is also presented. DYNRED uses the special modeling and network solution techniques developed to enable systems having up to 12,000 bus to be studied. Dynamic data is completely compatible between MASS, PEALS, and the EPRI Extended Transient Midterm Stability Program (ETMSP).« less