• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.620-624
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• 2011

This paper propose a new delay-dependent stability criterion of neutral time-delay systems. By employing double-integral terms in augmented states and constructing a new Lyapunov-Krasovskii's functional, a delay-dependent stability criterion is established in terms of Linear Matrix Inequality. Through numerical examples, the validity and improvement results obtained by applying the proposed stability criterion will be shown.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.104-106
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• 2000

Transient Stability of a power systems is its ability to maintain synchronous operation of machine when subjected to a large disturbance. This paper presents a new methodology for speed-up transient stability evaluation in SIME. SIME is a hybrid direct method including time simulation to enhance flexibility. The First features of the proposed method are that generator grouping can be performed even in very stable cases and that the stability of a contingency can be evaluated from a short period of time simulation results. The second features of the proposed method are that using power-angle trajectory and subdividing contingency classification have improved the screening capability.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1387-1392
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• 2012

These days people use a lot of electric power, because industry advancement and a standard of living is elevated. So voltage stability analysis and control problems are very important in these days. U.S.A has already developed voltage stability analysis program, and use it on power transmission scheme such as generator overhaul, transmission line off and so on. So voltage stability analysis is more and more interested in Korea, too. In this paper, we introduce a standard theory of voltage stability analysis and real time voltage stability analysis program that use sPMU(Satellite Phasor Measurement Unit). And we also introduce the calculation result about voltage stability in Jeju power transmission system.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1283-1289
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• 2014

The state transition matrix are obtained by solving state equations in terms of Laplace inverse transformation and Cayley-Hamilton theorem, and an establishment of a precise discrete-iterative mapping of the voltage-fed buck-boost converter operating in discontinuous conduction mode is made. On the basis of the mapping, the converter bifurcation diagrams and Lyapunov exponent diagrams with the input voltage, the resistance, the inductance and the capacitance as the bifurcation parameters are obtained, and the effect of the parameters on the system stability is deeply studied. The results obtained show that they have a great influence on the stability of the system, and the general trend is that the increase of either the voltage-fed coefficient, input voltage or the load resistance, or the decrease of the filtering inductance, capacitance will make the system stability become poorer, and that all the parameters have a critical value, and when they are greater or less than the values, the system will go through stable 1T orbits, stable 2T orbits, 4T orbits, 8T orbits and eventually approaches chaos.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.787-789
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• 1996

This paper describes a Transient Stability Education & Training Software that can make the students or beginners easily be familiar with power system stability problems. The Major objective of this study is to provide, for educational purpose, an interactive computer graphic tool that can facilitate power system study in highly user-friendly environment. The proposed software is designed to have the particular features such as follow : simulation with animation of the rotor, useful interactive scheme, various graphic illustrations related to critical factors of the stability, trace function including revival simulation with different processing speed. With these features, the software could be suitable for educational and training of students/beginners in power system stability engineering field.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.20-28
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• 2016

This paper presents a generation rescheduling method for the enhancement of transient stability in power systems. The priority and the candidate generators for rescheduling are calculated by using the energy margin sensitivity. The generation rescheduling formulates the Lagrangian function with the fuel cost and emission such as NO_x and SO_x from power plants. The generation rescheduling searches for the solution that minimizes the Lagrangian function by using the Newton’s approach. While the Pareto optimum in the fuel cost and emission minimization has a drawback of finding a number of non-dominated solutions, the proposed approach can explore the non-inferior solutions of the multiobjective optimization problem more efficiently. The method proposed is applied to a 4-machine 6-bus system to demonstrate its effectiveness.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.1094-1097
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• 1993

In this paper, the absolute stability criterion of nonlinear plants with sector bounded nonlinear feedback is derived. The result obtained is useful for applications, in particular, stability analysis and design of fuzzy logic controllers.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1611-1624
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• 2017

With the rapid development of microgrid technology, microgrid projects are no longer limited to laboratory demonstrations and pilot platforms. It shows greater value in practical applications. Hence, the smooth interaction between a microgrid and the main grid plays a critical role. In this paper, a control method based on active disturbance rejection control (ADRC) is proposed in order to realize seamless transitions between grid-connected and islanding operation modes and stable operation with variable loads. It is verified by simulations that the proposed ADRC-based method features better performance when compared to conventional proportional-integral-differential (PID) control. Meanwhile, the stability of the third-order extended state observer (ESO) in second-order ADRC is validated by using Lyapunov stability criteria.

• Transactions on Electrical and Electronic Materials
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• v.16 no.6
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• pp.293-302
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• 2015

Degraded data stability, weaker write ability, and increased leakage power consumption are the primary concerns in scaled static random-access memory (SRAM) circuits. Two new SRAM cells are proposed in this paper for achieving enhanced read data stability and lower leakage power consumption in memory circuits. The bitline access transistors are asymmetrically gate-underlapped in the proposed SRAM cells. The strengths of the asymmetric bitline access transistors are weakened during read operations and enhanced during write operations, as the direction of current flow is reversed. With the proposed hybrid asymmetric SRAM cells, the read data stability is enhanced by up to 71.6% and leakage power consumption is suppressed up to 15.5%, while displaying similar write voltage margin and maintaining identical silicon area as compared to the conventional memory cells in a 15 nm FinFET technology.

• Electrical & Electronic Materials
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• v.10 no.9
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• pp.895-900
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• 1997

A Quench in cable-in-conduit (CIC) conductors is often initiated by a disturbance such as strand motion that generates a highly localized normal zone in a strand or a few strands of the CIC conductors. The localized normal zone causes current and heat transfer between a disturbed strand and neighboring strands. Electrical and thermal contact characteristics between strands thus have an effect on the transient stability of the CIC conductors. In this paper the effect of contact characteristics between strands on the CIC conductor stability is presented based on the measured heat transfer characteristics of supercritical helium (SHe) for the local heating. The quench and recovery processes of the strands for the abrupt and highly localized disturbance are analyzed at the boundary between quench and recovery.