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Center for Nonlinear Studies |
Fault-Induced Delayed Voltage Recovery (FIDVR) is an observed phenomenon in electric power system that is driven by the stalling of compressor loads. Under certain conditions following a successfully cleared fault, the voltage will depressed for up to a minute after which it will rise to a level exceeding its pre-fault level. This behavior is consistent with the cascaded stalling of compressor motor loads (air conditioners) during the fault, and subsequent unsynchronized tripping of components on local thermal protection. The concern about FIDVR events is that they may lead to larger system-wide cascading outages. In this talk we will review some of the data associated with events and for laboratory tests of air conditioner stall characteristics. We then consider the question of how many compressor motors need to stall before all of them on a feeder must stall. We perform a bifurcation analysis to determine whether there exist solutions for 1, 2, or more stalled motors, leaving the rest running normally. As we will show, a low percentage of motor stalls will necessitate that all will. This makes it difficult to mitigate FIDVR events in the short term. As part of our attempt to construct complete bifurcation diagrams it is necessary to compute all the solutions to the power system equations. These equations may be viewed as a set of coupled multi-variable quadratic equations. The task of finding all solutions scales poorly with the size of the system. We show that a long-standing practical approach to finding all the real-valued solutions to the power flow solutions is flawed. This remains an open question for research.
Host: Misha Chertkov, chertkov@lanl.gov, 665-8119