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Calculating the Distance to the Saddle-Node Bifurcation Set
KTH, School of Electrical Engineering (EES), Electric Power Systems.
2009 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

A power system will experience voltage collapse when the loads increase up to a certain critical limit, where the system physically cannot support the amount of connected load. This point identified as a Saddle- Node Bifurcation (SNB), corresponds to a generic instability of parameterized differential equation models and represents the intersection point where different branches of equilibria meet. At this point the jacobian matrix of the system is singular and the system loses stability bringing the typical scenario of voltage collapse. To prevent voltage instability and collapse, the computation of the closest distance from a present operating point to the saddle-node bifurcation set can be used as a loadability index useful in power system operation and planning. The power margin is determined by applying the iterative or direct method described in [16]. Numerical examples of both methods applied to IEEE 9-bus system and IEEE 39-bus system shows that the iterative method is more reliable although it requires a longer computation time. The stability of the system is negatively affected in two ways when generators reach their reactive power limits: the voltage stability margin

is deteriorated, or immediate voltage instability and collapse is produced.

Place, publisher, year, edition, pages
2009. , 77 p.
EES Examensarbete / Master Thesis, XR-EE-ES 2009:017
Keyword [en]
Voltage stability, voltage collapse, saddle node bifurcation, load power margin, transfer capability, continuation methods, continuation power flow.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-119236OAI: diva2:610010
Educational program
Master of Science - Electric Power Engineering
Available from: 2013-03-12 Created: 2013-03-08 Last updated: 2013-03-12Bibliographically approved

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