• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.10
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• pp.1290-1294
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• 1995

In this paper, a new voltage collapse proximity index (VCPI) based on system apparent power loss sensitivity is proposed. The newly proposed index .lambda.$^{Sloss}$ reaches -.inf. at system voltage collapse point and can be represented by .root..lambda.$^{Ploss}$$^{2}$+.lambda.$^{Qloss}$$^{2}$ where .lambda.$^{Ploss}$ and .lambda.$^{Qloss}$ are the VCPI based on the system active and reactive power loss sensitivity respectively. These indices can be used for the system VAR investment. .DELTA.Q [VAR] is invested, step by step, by the priority of the VCPI index given for each bus. The indices use information from normal power flow equations and their Jacobians. Computation time for deriving .lambda.$^{Sloss}$ is almost same as that for power flow calculation. Two case studies prove the effectiveness of the .lambda.$^{Sloss}$ index and the VAR investment algorithm proposed.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.218-221
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• 1992

Recent years voltage collapse phenomenon have a great attention to power system engineers. As the system size increases the voltage problem shows a very complicated and the reactive power contol problem becomes more difficult. This paper gives an efficient methods for calculating voltage collapse proximity index based on the reactive power loss sensitivity and real power loss sensitivity. The system voltages are tightly associated with the system reactive power, so the proposed voltage collapse proximity index is very usefull for the system voltage control problems. Numerical examples showed a good and reliable results.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.3-5
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• 1994

It is shown that the power flow considering the voltage characteristic of the composite load has some difference comparing with conventional load flow in this paper. When the load flow is used in a study of the static voltage stability, it is necessary to consider the voltage characteristic of load, since the composite load of a typical power system bas constant power, constant current, and constant impedance characteristic. The load is modeled to a polynomial form in here, and used in solving the load flow problem. In this way, the effect which the voltage characteristic of the load has on several voltage collapse proximity indicator based on sensitivities is compared with the conventional load flow, or with another load model having a different voltage characteristic. In this paper, the voltage collapse proximity indicator using the sensitivity of real power for transmission loss is also proposed, and compared with other indicators.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.279-281
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• 2006

A Voltage Instability Predictor(VIP) estimates the proximity of a power system to voltage collapse in real time. Voltage Instability Index(Z-index) from VIP algorithm is estimated using LS(Least Square) method. But this method has oscillations and noise of result due to the system's changing conditions. To suppress oscillations, a larger data window needs to be used. In this paper. I propose the new other method which improves that weakness. It uses RLS(Recursive Least Square) to estimate voltage instability index without a large moving data window so this method is suitable for on-line monitor and control in real time. In order to verify effectiveness of the algorithm using RLS method, the method is tested on HydroQuebec system in real time digital simulator(HYPERSIM).

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.2
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• pp.56-61
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• 2000

In the paper, the system loss sensitivity index that implies the incremental system loss with respect to the change of bus power is derived using optimization technique. The index λ reaches $\infty$ at critical loading point and can be applied to actual power systems for following purposes. 1) Evaluation of system voltage stability 2)Optimal investment of reactive power focused on minimizing system loss and maximizing system voltage stability 3)Optimal re-location of reactive power focused on minimizing system loss and maximizing system voltage stability 4)Optimal load shedding in case of severe system contingency focused on minimizing system loss and maximizing system voltage stability. Case studies for each application have proved their effectiveness.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.255-258
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• 2003

In this paper there are different methods used to study the voltage stability, such as the P-V curve method. Jacobian method and the voltage collapse proximity indicator(L-index) method. The P-V curve method is to check operating margin from the maximum operating point. The Jacobian method is to check the eigenvalue or the minimum singular value of the load flow Jacobian matrix. If the power system is unstable, one of the eigenvalues, at least, has crossed the imaginary axis. The L-index method is to quantify how to close a particular operating point. This paper describes these methods to select the best location of FACTS and demonstrate the effectiveness of STATCOM of voltage stability on the IEEE 9-bus system.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.145-148
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• 1992

The best index should show the margins to the operating limit at the present operating point without much efforts. Such voltage collapse proximity index has been proposed in this study. Differently from the normal procedure in which every bus load is increased at the same propotion, bus load increase toward the direction of T/L loss increase has been applied in this study. Sample studies show the usefulness and the practical applicability in voltage stability analysis.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.77-79
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• 1996

This paper presents an integrated stability analysis by the direct energy function method based on Equivalent Mechanical Model(EMM) which reflects the system behavior related to both angle and voltage stabilities. Actually, angle and voltage stability are intimately related in power system, so complete decoupling of these stability analysis is not possible in general, particularly in stressed power systems. In this paper, it is shown that a identical energy function can be used for angle and voltage stability analysis. The proposed energy function reflects the line resistances and reactive powers under the constraints of the same R/X ratio. The energy margin between UEP and SEP presents a good collapse proximity index in both types of stability analysis.