Identifying coherent areas in transmission system for transient stability studies in future smart grids

Dynamic equivalencing has been an effective tool for reducing number of generators in transient stability studies of large networks. The problem size can be further reduced if coherent areas in transmission system are located and aggregated. This manuscript presents a new method for identifying coherent areas in transmission system for transient stability studies. Sufficient condition for coherency between two buses along with rigorous mathematical proof are presented to ensure that the final results are reliable and accurate. The proposed method is able to handle different load models and find nearly all coherent areas even if there is no coherency between load and generation buses. Using the proposed methodology, it is possible to keep any desired subsystem while achieving maximum reduction of the remaining system. The IEEE 50-gen 95-bus test system is used to validate and demonstrate the proposed method.