Estimating damping effectiveness of BPA's thyristor controlledseries capacitor by applying time and frequency domain methods tomeasured response

Recently, a 500 kV thyristor controlled series capacitor (TCSC) was installed in the Bonneville Power Administration system in the Northwestern United States. Extensive field testing has included modulation experiments to determine the effect of the TCSC on low-frequency oscillations. This paper discusses modulation procedures, analysis methods, and results for estimating the damping effectiveness of the TCSC. Modulation methods include driving the TCSC with step and random noise, and analysis techniques include time (Prony analysis) and frequency-domain identification. Results indicate that: (1) the TCSC can have significant impact on system dynamics; and (2) under a very small feedback gain, the TCSC provides measurable added damping