Abstract
Under real-time operation, early detection of oscillations that lead to instability is of noteworthy importance for power system operators. This paper demonstrates how the relative angle (RA) obtained with online data from phasor measurement units (PMUs) and predefined thresholds of the relative angle (PTRA) obtained with offline simulations are valuable for the monitoring and prediction of transient stability. Primary features of the method consist of first calculating the maximum and minimum relative angles by offline simulations of different contingencies. Next, the voltage angles at buses that represent areas of the power system are measured to calculate the center of inertia (COI). Finally, the RA of the generators at each area is determined during the online operation to monitor stability behaviors and identify those that lead to a loss of synchronism. The method was validated in the New England 39-bus and the IEEE 118-bus power systems by performing contingencies, finding critical stability angles, monitoring areas and controlling the predicted unstable events with control actions, such as generation and load tripping, with enough time to return to stability.
Highlights
Nowadays, power systems are operated closer to their safety limits and some disturbances can produce instabilities that lead to service interruption or blackouts [1]
We have demonstrated how the predefined thresholds of relative angles obtained
We have how obtained the predefined relative angles obtained with offline anddemonstrated the relative angles duringthresholds the onlineof operation with phasor measurement units (PMUs) are with offline simulations and the relative angles obtained during the online operation with
Summary
Power systems are operated closer to their safety limits and some disturbances can produce instabilities that lead to service interruption or blackouts [1]. In recent years, phasor measurement unit (PMU) installations have increased considerably, allowing the availability of real-time data that show the system’s dynamic operating behavior [2] This opens the possibility to develop an efficient monitoring application for more robust and secure power systems. The first swing could show a stable operation and the subsequent oscillations lead to a loss of synchronism due to small disturbances [4] Those angular behaviors that lead to instability are not detected because some state estimators could be considering unsynchronized data from the supervisory control and data acquisition (SCADA), where the deviation is mainly due to the asymmetrical time between measurements [5]. These anomalies can be removed with the use of synchronized measurements [6], that have time stamps referenced by the global positioning system
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