On the Sensitivity of Ring-Down Observed Inter-Area Modes in Large-Scale Electric Grids Using a Simulation Approach

This paper presents results on the sensitivity of the inter-area electromechanical modes obtained by ring-down, measurement-based modal analysis for large-scale electric grids. The paper utilizes the Iterative Matrix Pencil Method (IMP) to determine the most significant electro-mechanical modes and their associated mode shapes after the system has been perturbed by generator or load outage contingencies. The paper shows that the resultant values can be dependent on both the applied contingency and the set of signals used in the IMP with this sensitivity due at least in part to the system nonlinearities. The techniques are demonstrated using three synthetic grids ranging in size between 2000 and 70,000 buses. Visualization methods are used to show the mode shapes and compare and contrast how modes manifest themselves on the grid.