Approximation of Generator Coherency Based on Synchronization Coefficients

Abstract

Dynamically coupled or coherent groups of generators are likely to occur between strongly connected generators connected to the system through weak or strained transmission lines. Establishing which machines in a system are dynamically coupled has shown to be helpful in identifying coherent areas for aggregation, providing insights into system stability, and for showing potential stability limits. Synchronizing coefficients between machines is a well established measure for the level of influence that machines have on each other. The synchronizing coefficients reflect not only the strength of the connections between machines but also include the effects of system loading. This paper proposes a method to approximate dynamic coupling or coherency based on direct evaluation of the synchronizing coefficient magnitudes. It is shown that estimation of the dynamic coupling in this manner has the benefit of being computationally simple without requiring any additional information beyond the load flow data.