• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.416-418
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• 2001

This Paper presents the 2-step load cycle of daily load curve for representative load pattern of power distribution transformer. We decide the representative load pattern of distribution transformer in domestic using the pattern classification algorithm. The K-mean method is used for the pattern classification algorithm. The acquisition equipment of field load data is utilized for 96-sample distribution transformers and the field data is used in the construction of the database for the creation of daily load pattern.

• KIEE International Transactions on Power Engineering
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• 제5A권2호
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• pp.177-185
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• 2005

This paper proposes an expert system that can enhance the accuracy of real-time bus reconfiguration strategy by adopting the local minimum tree search method and that can minimize the spreading effect of the fault by considering the operating condition when a main transformer fault occurs in an automated substation. The local minimum tree search method is used to expand the best-first search method. This method has the advantage that it can improve the solution performance within the limits of the real-time condition. The inference strategy proposed expert system consists of two stages. The first stage determines the switching candidate set by searching possible switching candidates starting from the main transformer or busbar related to the event. The second stage determines the rational real-time bus reconfiguration strategy based on heuristic rules from the obtained switching candidate set. Also, this paper proposes generalized distribution substation modeling using graph theory, and a substation database based on the study results is designed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1379-1381
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• 2004

This paper presents the AC electric railway system modeling using PSCAD/EMTDC program. This system model is composed of the scott-transformer the auto-transformer. the running rails. the protection wires, the feeders. the catenary and contact wires, etc. After obtaining the models of the fundamental elements describing the AC electric railway system and its behavior, we have analyzed and tested real traction power feeding system focused on the amplification of harmonic current to verify the proposed model. The simulation results from the proposed approach and the measurement data from the test are described in the paper.

• Journal of Power Electronics
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• 제6권3호
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• pp.187-194
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• 2006

A new asymmetrical pulse width modulation (PWM) half bridge converter with improved ZVS performance is proposed. The ZVS operation of the proposed converter can be maintained from no load to full load conditions since the magnetizing current of the transformer contributes to the ZVS operation at light loads without considerable conduction loss of the transformer and switch. Synchronous rectification is employed to reduce the rectification loss. Operational principles, large signal modeling, ZVS analysis and design equations are presented. Experimental results demonstrate that the proposed converter can achieve a large ZVS range and significant improvement in efficiency for a 100W (5V, 20A) prototype converter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.630-633
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• 2001

This paper presents a PSPICE circuit model for the simulation of both static and dynamic characteristics of fluorescent lamps. The model can by utilized for an electric ballast simulation with continuous dimming and transient mode simulation such as step dimming Characteristics of a Rosen-type piezoelectric transformer were analyzed by combining an equivalent circuit with piezoelectric equations and the relation between the characteristics and the dimension of the PT was studied.

• 한국수소및신에너지학회논문집
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• 제17권3호
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• pp.338-346
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• 2006

In this paper, the test results of medium-size(120 kW class) PV system which was installed in the Taeahn thermal power station of Korea Western Power Co., Ltd., were summarized for developing the practical technology to applicate high voltage grid connection PV system. The 120 kW photovoltaic system which was consisted of 1,300 modules, PCS, and 150 kVA transformer station has been operated since Aug. 05, 2005. For verifying the modeling results of PV system, the operation data was compared with modeling results which was executed commercial PSCAD/EMTD and Psim tools. An equivalent circuit model of a solar cell has been also used for solar array modeling. A series of parameters required for array modeling have been estimated from general specification data of a solar module. A PWM voltage source inverter(VIS) and its current control scheme have been analyzed by using P&O (perturbation and Observation) MPPT algorithms technique.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전력기술부문
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• pp.9-11
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• 2008

A protection current transformer (CT) has been widely used for protection devices. When a fault occurs, a CT should provide the faithful reproduction of the primary fault current. However, a CT may saturates due to the magnitude of fault current, dc component primary time constant and the remanent flux of the iron core, and the secondary current of a CT is distorted. The distorted current can cause mal-operation or the operating time delay of a protection relay. This paper provides a modeling of CT saturation using EMTP-RV. The performance of the proposed CT saturation modeling was investigated under various fault conditions varying the fault distance, fault inception angle, and remanent flux of the iron core. The results indicate that the proposed EMTP-RV modeling can operate correctly, and the reasons for CT saturation are verified by EMTP-RV simulations.

• Journal of Power Electronics
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• 제8권3호
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• pp.239-247
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• 2008

This paper presents the design of 1 kW prototype high frequency link boost half bridge inverter-fed DC-DC power converters with bridge voltage-doublers suitable for small scale PEM fuel cell systems and associated control schemes. The operation principle of this converter is described using fuel cell modeling and some operating waveforms. The switching mode equivalent circuits are based on simulation results and a detailed circuit operation analysis at soft-switching conditions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1356-1358
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• 2003

This paper describes the control of grid connected transformerless type PV power conditioning system, which is simple and more efficient than the usual transformer type system. With the modeling and analysis of power system, the validity of control strategy is well verified through the simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.610-611
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• 2007

본 논문은 EMTP-RV를 이용하여 변압기 여자돌입전류를 모델링하는 방법을 제시하였다. 우선, 변압기 여자돌입전류의 특성을 조사하였다. 그 다음으로, EMTP-RV의 변압기의 모델링 방법을 분석하여 변압기 여자돌입전류 모델링을 위한 적절한 방법을 선택하였다. 마지막으로, 다양한 조건에 대하여 여자돌입전류를 모델링하여 그 방법의 적합성을 증명하였다.