Power System Modal Identification from Large Scale Simulations Using Model Adaptive Reference Control

The major objective of this paper is the identification of the dominant modal responses of large scale power system dynamic simulations. The results of simulations are the angle-time responses of synchronous machine rotors. The rotor inertias coupled via transmission lines produce second order responses, whose damping factors and undamped natural frequencies are identified by a Model Adaptive Reference Control (MARC) system. The MARC identification system is applied successfully to the swing curves of a 1700 bus power system simulation to identify the local and intertie mode parameters. Specifically the sensitivity of modal damping due to power modulation of an HVDC tie is quantified. The low frequency interarea mode damping ratio (¢) is increased from 0.12 to 0.17 by the use of Frequency Sensitive Power Modulation, whereas the other parameters of the two modes were not affected significantly. Thereby the effectiveness of an External Control system on an HVDC transmission line is quantified. Previous evaluations had yielded only qualitative results.