Reliable mode-shapes for major system modes extracted from concentrated WAMS measurements processed by a SIMO identification algorithm

This paper presents a technique to identify a single-input multiple-output (SIMO) model and extract from it the approximate dominant poles and associated system mode-shapes. The technique simultaneously identifies all rotor speed deviations, when a mechanical power disturbance is applied to the input of a single generator. The SIMO model has an inherent constraint that is very useful: all poles of the scalar TFs in this system are common. The mode-shapes are identified from the residues of each TF. A technique based on moment-matching in the domain of the z-transform is employed to compute the common poles. Then, the residues of the TFs are determined. The poles in the z domain are then directly converted to the s domain. Tests and results are based on simulations carried out on the 39-bus, 10-generator New England system and include quality estimates for dominant poles, frequency responses and mode shapes.