Voltage collapse is a critical problem that impacts power system operational security. Timely and accurate assessment of voltage security is necessary to detect post-contingency voltage problems in order to prevent a large scale blackout. This paper presents an online voltage security assessment scheme using synchronized phasor measurements and periodically updated decision trees (DTs). The DTs are first trained offline using detailed voltage security analysis conducted using the past representative and forecasted 24-h ahead operating conditions. The DTs are also updated every hour by including newly predicted system conditions for robustness improvement. The associated synchronized critical attributes are obtained in real time from phasor measurement units (PMUs) and compared with the offline thresholds determined by the DTs to assess security. This approach is tested on the American Electric Power (AEP) system and properly trained DTs perform well in assessing voltage security. Several new ideas to improve DT performance are also introduced.Index Terms-Decision trees, online security assessment, phasor measurement units, voltage collapse.
Abstract-This paper presents analysis results of synchronized phasor data from 10 disturbance events recorded in the US Eastern Interconnection (EI). The phasor data covers a wide region in the EI, allowing for the study of disturbance propagation, interarea modes, and oscillations in voltages and currents. The analysis is not straightforward because the EI is a meshed system with adequate interarea mode damping. Disturbances involving tripping a single large generator unit produce very short interarea swing responses. Islanding events involving regions at the perimeter, however, provide more prominent responses for analysis.
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