STABILIZING SUBSYNCHRONOUS RESONANCE USING A SHUNT CONNECTED, CURRENT REFERENCE POWER CONVERTER (POWER SYSTEM CONTROL)
Abstract
In power systems containing series capacitor compensated transmission lines, the natural frequencies of the turbine prime movers in stream turbogenerators may become self excited due to an unstable interaction between the transmission network and the torsional modes of the steam turbine. Such instabilities fall into the general category of subsynchronous resonance (SSR). The research introduces a new countermeasure to SSR using a controlled, shunt connected static power converter. This method involves the measurement of the transmission system currents which are subsequently transformed into a synchronously rotating frame of reference. In the synchronous reference frame, the components of current that give rise to SSR are easily identified using simple active filters. Once extracted, these signals are subsequently amplified by the power converter and injected into the power system so as to prevent SSR. A benchmark system, known to be affected by SSR, is used to demonstrate the effectiveness of this approach. A small displacement analysis of this system has been performed demonstrating the improved stability characteristics of the study system. The generalized Nyquist method is used to characterize the sensitivity of the compensated system to phase and/or gain errors associated with the compensating circuitry and to changes in the operating point of the power system. Moreover, describing function techniques are used to quantify the converter capacity required to stabilize SSR in the presence of system disturbances. Finally, the time domain behavior of the benchmark system is thoroughly explored by computer simulation.
Degree
Ph.D.
Subject Area
Electrical engineering
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