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This paper demonstrates the feasibility of using the system identification method known as the eigensystem realization algorithm (ERA) as a means for computing the subsynchronous torsional modes of turbine-generator sets. Measured data obtained during an out-of-phase synchronization test of a large turbine generator are used to perform the modal computation. Both front and rear standard speeds are used. The results are compared with those obtained using more conventional methods.

The maximum continuous power output of a gas turbine depends on the system frequency and the ambient temperature. The temperature control of a gas turbine limits the exhaust temperature by reducing the fuel flow as the air flow decreases with the shaft speed. This paper addresses the frequency dependency of the gas turbine power output and presents a physically-based model of a gas turbine that may enable parameter estimation of the frequency dependency from the ambient temperature dependency. The model is suitable for long-term simulation of power system dynamic performance involving abnormal frequency conditions.