• Journal of KIEE
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• v.11 no.1
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• pp.55-61
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• 2001

SIME(Single Machine Equivalent) method has been recognized as a useful tool to determine transient stability of power system. In this paper, SIME method is used to develop the KEPCO transient stability assessment (TSA) tool. A new screening algorithm that can be generators are identified by a new index in the early stage of the time domain simulation. Thus, computational time require to find OMIB(One Machine Infinite Bus) can be reduced significantly. Second, clustering critical machines can be performed even in very stable cases. It enables to be avoid extra calculation of time trajectory that is needed in SIME for classifying the stable cases. This algorithm is applied to the fast TSA of the KEPCO system in the year of 2010.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1614-1622
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• 2014

A novel equivalent flux sliding-mode observer (SMO) is proposed for dual three-phase interior permanent magnet synchronous motor (DT-IPMSM) drive system in this paper. The DT-IPMSM has two sets of Y-connected stator three-phase windings spatially shifted by 30 electrical degrees. In this method, the sensorless drive system employs a flux SMO with soft phase-locked loop method for rotor speed and position estimation, not only are low-pass filter and phase compensation module eliminated, but also estimation accuracy is improved. Meanwhile, to get the regulator parameters of current control, the inner current loop is realized using a decoupling and diagonal internal model control algorithm. Experiment results of 2MW-level DT-IPMSM drives system show that the proposed method has good dynamic and static performances.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.3
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• pp.373-379
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• 2012

This paper presents a fault location algorithm based on the adaptively estimated value of the local sequence source impedance for faults on a parallel transmission line. This algorithm uses only the local voltage and current signals of a faulted circuit. The remote current signals and the zero-sequence current of the healthy adjacent circuit are calculated by using the current distribution factors together with the local terminal currents of the faulted circuit. The current distribution factors consist of local equivalent source impedance and the others such as fault distance, line impedance and remote equivalent source impedance. It means that the values of the current distribution factors can change according to the operation condition of a power system. Consequently, the accuracy of the fault location algorithm is affected by the two values of equivalent source impedances, one is local source impedance and the other is remote source impedance. Nevertheless, only the local equivalent impedance can be estimated in this paper. A series of test results using EMTP simulation data show the effectiveness of the proposed algorithm. The proposed algorithm is valid for a double-circuit transmission line system where the equivalent source impedance changes continuously.

• Journal of Power Electronics
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• v.3 no.1
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• pp.40-48
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• 2003

In this paper, a hybrid power system with photovoltaic/wind/diesel generators is proposed to solve the defect of stand-alone type power system in a remote area. A hybrid power system has a power-balanced controller to equilibrate generation power with a given load demand and which is composed of common DC power system. To execute a power-balanced control, a hybrid power system is assumed that all of power generators have the characteristics of an equivalent current-source and load sharing control technique must be needed at the same time. So this paper discusses the structure of power-balance control for hybrid power system. And through the results of simulation, the proposed scheme was verified.

• Korean Journal of Agricultural Science
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• v.46 no.4
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• pp.723-735
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• 2019

The power-train is the most important component of an agricultural tractor. In this study, the strength of the driving gear transmission of an 82 kW-class tractor was analyzed using equivalent torque during plow tillage. The load measurement system consisted of an engine revolution speed sensor, torque-meters, revolution speed sensors for four axles, and pressure sensors for two hydraulic pumps. The load data were measured during plow tillage for four speed stages: F2 (2.78 km/h), F5 (5.35 km/h), F7 (7.98 km/h), and F8 (9.75 km/h). Aspects of the gear-strength such as bending stress, contact stress, and safety factors were analyzed under two torque conditions: the equivalent torque at the highest plow load for the F8 speed stage and the maximum engine torque. The simulation results using KISSsoft showed that the maximum engine torque conditions had a lower safety factor than did the highest equivalent torque condition. The bending safety factors were > 1 at all gear stages, indicating that gear breakage did not occur under actual measured operating conditions, nor under the maximum torque conditions. However, the equivalent torque condition in the contact stress safety factor was > 1, and the maximum torque condition was < 1 at the first gear pair. The method of analysis using the equivalent torque showed lower stress and higher safety factor than did the method using maximum torque. Therefore, when designing a tractor by applying actual working torque, equivalent torque method would support more reliable product development.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.101-110
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• 1997

The circuit effects due to the transformer primary side series equivalent inductance in the Zero Voltage Switching Pulse Width Modulated Half Bridge DC/DC Converter and its impact on the effective duty are analyzed. The steady state equations and the small signal model of the converter are derived incorporating the effects of the complementary control and the utilization of transformer primary side series equivalent inductance. The open plant dynamics are analyzed on the basis of the model derived. The model predictions are confirmed by experimental measurements.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.512-515
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• 1991

The advantages of poly-phase converter are to be able to reduce the ripple current and to lessen the weight of power inductors. This paper is derived the equivalent circuit, dc of and ac modeling circuit of a 3-phase multiple buck converter by using state space representation and averaging techniche. Futhermore, it is represented the equivalent circuits according to the duty cycle.

• Proceedings of the IEEK Conference
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• 2002.06b
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• pp.49-52
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• 2002

A new method is developed to extract model parameters of SiGe HBT equivalent circuit including the base impedance and base-collector junction capacitance. Using this method, all resistances and capacitances of SiGe HBT are independently determined from measured S-parameters using two-port parameter formula. This method is proposed to reduce possible errors generated from global optimization process, and its accuracy has been verified by finding good agreements between measured and modeled current / power gain up to 18 GHz.

• Coupled systems mechanics
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• v.7 no.1
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• pp.61-77
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• 2018

This paper establish a high concentration ratio approximation of linear elastic properties of materials with periodic microstructure with cubic inclusions. The approximation is derived using first few terms of power series expansion of the solution of the equivalent eigenstrain problem with a homogeneous eigenstrain approximation. Viability of the approximation at high concentration ratios is proved by comparison with a numerical solution of the homogenization problem. To this end some theoretical result of symmetry properties of the homogenization problem are given. Using these results efficient numerical computation on a reduced computational domain is presented.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.592-594
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• 1998

In order to analysis high frequency interference conduction in transformer, this paper constructs a equivalent network based on P.I. Fergested transformers physical model. A method of calculating self and mutual leakage inductance of windings sections is presented and a calculating example is given.