• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.175-178
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• 1996

Power system is becomming more and more complex and large. So system is stressed increasingly. This paper presents a method to select contingency ranking in power systems for EMS operation. Firstly, the proposed method is applied line outage using Thevenin equivalent circuit. Secondly, Contingency harmful to system is selected by loss variation between base case and fault. Thirdly, this paper prescribed simulated line sequence. Therefore this algorithm shows higher computation speed and effective memory use.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.236-240
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• 1988

The simplified equivalent by using the short circuit impedance has been used for analyzing the prospective transient recovery voltage of the large power system. But it sometimes generates untorelable error in the rate-of-rise of TRV when using the Thevenin equivalent source. This paper provides the new equivalent by using the multi-port theory. The application of the new method to the sample system gives satisfactory accuracy compared with the short-circuit equivalent.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.331-333
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• 1998

This paper deals with the analysis of the magnetic circuit of a claw pole type step motor. The air gap flux equation is derived using Thevenin equivalent circuit. On the base of the magnetic circuit analysis, both static torque and the dynamic torque characteristics are presented.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.4
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• pp.86-92
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• 1995

In the analysis of characteristic behaviors of a real transformer with coupling coefficient K is less than 1, this paper presents the more accurate and practical profits than the traditional analysis of the transformer treated as K∼1. This results from the use of the coupling coefficient type equivalent circuit of the transformer which includes K as positive parameter. Furthermore, a leakage transformer is analyzed in a unified method and the results of analysis are consistent with the practical measurements of the transformer. By using the above equivalent circuit, the characteristics referred to the load side are expressed as Thevenin voltage source and the leakage inductor (1-K2)L2. Therefore, these analysis about the output voltage and the damping factor in the transient state which are affected by the leakage inductor are confirmed to be an effective method.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.6 no.3
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• pp.50-56
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• 1992

The coupling coefficient K controls the characteristic behaviors of leakage transformer. The value of coupling coefficient K was obtained from th leakage flux of leakage transformer an ascertained from the variation due to the function of current. Therefore, this paper presented the equivalent circuit of leakage transformer consisting of Thevenin's constant voltage source and inductor as (1-K2)L2 which were proportional to parameter K. The proposed equivalent circuit verified the validity in designing the leakage transformer because it was in good agreements of the behaviors of ideal transformer (K is 1), leakage transformer (K is 0$\leq$K$\leq$1), inductor (K is 0).

• Transactions on Electrical and Electronic Materials
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• v.17 no.1
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• pp.13-17
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• 2016

The ampere-hour integral method and the open circuit voltage method are integrated via the extended Kalman filter method so as to overcome insufficiencies of the ampere-hour integral method and the open circuit voltage method for estimating battery SOC. The process noise covariance and the measurement noise covariance of the extended Kalman filter method are simplified based on the Thevenin equivalent circuit model, with a proposed simplified SOC estimating method. Verification of DST experiments indicated that the battery SOC estimating method is simple and feasible, and the estimated SOC error is no larger than 2%.

• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.7-14
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• 2020

A Battery Monitoring System capable of State-of-Charge(SOC) estimation using the Extended Kalman Filter(EKF) is described in this paper. In order to accurately estimate the SOC of the battery, the battery cells were modeled as the Thevenin equivalent circuit model. The Thevenin model's parameters were measured in experiments. For the Battery Monitoring System, we designed a battery monitoring device that can calculate the SOC estimation using the EKF and a monitoring server that controls multiple battery monitoring devices. We also develop a web-based dashboard for controlling and monitoring batteries. Especially the computation of the monitoring server could be reduced by calculating the battery SOC estimation at each Battery Monitoring Device.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.12
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• pp.209-219
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• 1995

As a new algorithm for RC tree delay estimation, we propose a $\tau$-model of the driver and a moment propagation method. The $\tau$-model represents the driver as a Thevenin equivalent circuit which has a one-time-constant voltage source and a linear resistor. The new driver model estimates the input voltage waveform applied to the RC more accurately than the k-factor model or the 2-piece waveform model. Compared with Elmore method, which is a lst-order approximation, the moment propagation method, which uses $\pi$-model loads to calculate the moments of the voltage waveform on each node of RC trees, gives more accurate results by performing higher-order approximations with the same simple tree walking algorithm. In addition, for the instability problem which is common to all the approximation methods using the moment matching technique, we propose a heuristic method which guarantees a stable and accureate 2nd order approximation. The proposed driver model and the moment propagation method give an accureacy close to SPICE results and more than 1000 times speedup over circuit level simulations for RC trees and FPGA interconnects in which the interconnect delay is dominant.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.4
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• pp.20-28
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• 1998

This study proposes a new method to estimate voltage unbalance more exactly using Thevenin's equivalent circuit. The conventional simple formula were easily applied to evaluate voltage unbalance. Because the formula was derived on the assumption that traction load would be directly connected to the secondary windings of the main transformer, they could not consider the detailed characteristics of traction power supply system, for example, self and mutual impedances of rail, catenary and return feeder. So, the ac쳐racy of the results could not be guaranteed. The proposed algorithm is applied to a standard autotransformer-fed test system to analyze unbalance phenomena. Through simulations, we could evaluate voltage and current unbalance factors and compare the voltage unbalance of the three transformer connection schemes : single phase, V- and Scott-connections which are required for suitable train operation schedules. Additionally, we could determine the combinations of trains which can be operated under the unbalance factor limits.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.15-23
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• 2017

This paper reports a SOC(State-of-Charge) estimation method using the extended Kalman filter(EKF) algorithm, which can allow real-time implementation and reduce the error of the model and be robust against noise, to accurately estimate and evaluate the charging/discharging state of the EV(Electric Vehicle) battery. The battery was modeled as the first order Thevenin model for the EKF algorithm and the parameters were derived through experiments. This paper proposes the changed method, which can have the SOC to 0% ~ 100% regardless of the aging of the battery by replacing the rated capacity specified in the battery with the maximum chargeable capacity. In addition, This paper proposes the EKF algorithm to estimate the non-linearity interval of the battery and simulation result based on Ah-counting shows that the proposed algorithm reduces the estimation error to less than 5% in all intervals of the SOC.