TIME-SERIES IDENTIFICATION OF INTERAREA AND LOCAL GENERATOR RESONANT MODES

A power system consisting of large generation pools is characterized b y several modes of oscillation. The various modes arise from a group o f generators swinging relative to other groups as well as each machine swinging relative to its local bus. A practical problem that arises i n the design and evaluation of controllers for damping power system os cillations is to measure the appropriate transfer function(s) of the p ower system. The transfer function from the input to the power system to the output signal being fed back to the controller contains eigenva lues that characterize each of the modes embedded in the time-domain t ransients. The number of modes, the range of residues (or amplitudes o f each mode), and the random disturbances that appear on the measured output signals, all conspire to make this a challenging problem. In th is paper the Least Squares and Generalized Least Squares time-domain i dentification algorithms are applied to a simulated power system exhib iting local and interarea oscillatory modes. A comparison in the frequ ency domain is made between the simulated system and the models obtain ed by the two identification techniques. Under the experimental condit ions used in this paper both the local and interarea oscillatory modes are identified by the Generalized Least Squares Identification techni que while the Least Squares parameter estimation method identifies onl y the local mode.