Motivation and objective (Back to the homepage)
Massive deployment of Phasor Measurements Units (PMU) in power systems has enabled an ability to monitor actual dynamic behavior of the system to the level of details not available before. PMU measurements have helped detect multiple instances of poorly damped oscillations with high pick-to-pick MW magnitude up to hundreds of MW and with wide frequency range from 0.02 Hz to 5-20Hz. These oscillations can be persistent over hours and days time frame or can exist only within few minutes. They could be observed in relatively local area or wide spread in the system. The reason of occurrence and disappearance of these oscillations often remain unknown for the power system operator. Power engineers classify such oscillations as natural (caused by unfavorable combination of equipment or control system parameters) or forced (associated with an external input or malfunctioning apparatus).
Independently of classification, high-magnitude poorly damped oscillations represent the risk for stability and reliable operation of the power systems and should be mitigated as soon as possible. The first step in a mitigation process is the localization of the source of bad damping or forced oscillation. Traditional modeling approach practically cannot help here because the location and nature of the source are typically unknown and cannot be modeled. Localization method should rely on PMU measurements collected from different points in the system.
Localization of the source is understood as localization in the system to a level of power plant or individual generator or substation when the source of oscillation is load or HVDC. If PMU measurements are available on individual generators within a power plant, then localization method should identify specific generator as the source. Localization of the source to a specific module or a piece of hardware is beyond the scope of methods under test here.
Localization of the source of oscillation is not a trivial task and particularly for inter-area oscillations. Research community has proposed several methods but none of these yet have been shown as a robust and efficient tool for practical use with actual PMU measurements. New methods are under development. Effectiveness of these methods is difficult to evaluate by using actual PMU data mainly because the actual source of oscillations is often unknown. Even if the actual source of a certain oscillation event is known and can be used for validation, the applicability of these methods to other situations still remains unclear.
In order to overcome this hurdle, we propose a library of simulated cases and cases of actual events with known sources. Any practically meaningful source location method should be validated using simulated cases and verified with the actual cases.