• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.27-30
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• 1991

Recently, the phenomena of voltage instability have become major concern in power system, these phenomena are closely related to what are called multiple load flow solutions and calculation methods on these solutions have developed. The multiple solutions concerned with phenomena are pair solutions in heavy loaded contion. But conventional methods require much run time to find this pair solutions and unusual generation patten in the condition of multiple solutions. In this paper, by using concept of existence condition of multiple solutions, calculation method on the multiple load flow solutions is presented which find the pair solutions in light loaded condintion.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.8
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• pp.951-957
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• 1999

The saddle node bifurcation (SNB) and the distance voltage instability are valuable information in power system planning and operation. This paper presents a new efficient, robust and unified strategy to compute the SNB by the combined use of the continuation power flow (CPF), Point of Collapse (PoC) method, and the method of a pair of multiple load flow solutions (PMLFS) with Lagrange interpolation utilizing only their advantages: the approximate nose curves and critical loading are determined fast by Lagrange-interpolating two stable and two unstable solutions obtained by using the robust CPF and PMLFS; the exact SNB is computed by the quadratically converging PoC method. The proposed method has been tested on Klos-Kerner 11-bus, New England 30-bus, IEEE 118-bus and KEPCO 791-bus systems. The method is found to be so efficient that computation time for determining the SNB of the KEPCO 791-bus system is 17.82 sec by a notebook PC with 300 MHz Pentium processor.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.89-91
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• 1995

This paper describes an extension or a pair or multiple load flow solutions and nose curve method developed for voltage stability analysis or AC power systems to AC/DC systems. In this approach the converters are regarded as voltage dependent loads. Assuming that the converters at the unstable (-mode) solution consume the same power equal to the power at the stable (+mode) solution, the unstable solutions or the nose curves arc determined. This method is very efficient since estimating voltage collapse point and voltage stability margin arc determined by a few iterations of multiple load flow solutions. Also the method has the advantages that since the structure or Jacobian matrix is same with that of AC load flow, modal analysis or voltage stability is readily applicable if desired.