• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.548-552
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• 2007

본 논문에서는 연료전지자동차의 저전압 배터리 충${\cdot}$방전을 위한 3상 양방향 DC-DC 컨버터를 제안한다. 제안한 3상 컨버터는 기존의 단상 컨버터에 비해 인터리빙 효과의 증대로 인한 입${\cdot}$출력 필터 사이즈 감소와 변압기의 이용률 증가로 인한 VA정격의 감소가 가능하며, 기존의 위상제어 방식의 3상 컨버터와 달리 입${\cdot}$출력전압이나 부하변동에 따른 무효 전류의 중가 문제가 없다. 또한 MOSFET 스위치를 사용하여 고전압 측에서는 비대칭 소프트 스위칭을 성취할 수 있고, 저전압 측에서는 동기정류 방식을 적용하여 도통손실을 감소시킬 수 있어 효율과 전력밀도를 더욱 향상 시킬 수 있다. 본 논문에서는 제안하는 3상 양방향 DC-DC 컨버터의 동작원리와 기존방식과의 비교분석을 수행하였으며 시뮬레이션을 통해 검증하였다.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.643-645
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• 1996

In order to improve the voltage profile of the system we introduce the reactive power devices. However, it is difficult to know which bus will be the most effective bus when we inject the reactive power supplier in it. This paper systematically determines indices of the system in order to locate reactive power devices in a power system. To prove the validity and effectiveness of the system we apply the proposed method to the 9 bus system.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1358-1360
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• 2005

본 논문에서는 비접촉 전원장치와 같이 누설인덕턴스가 큰 공진형 컨버터에서 스위치단과 공진 탱크 사이에 강압형 매칭 트랜스포머를 삽입하여 스위치의 공진 전류를 줄이는 방법을 제안하였다. 누설인덕턴스가 큰 공진형 컨버터에 강압형 매칭 트랜스포머를 추가함으로써, 일차측의 입력 임피던스를 증가시켜 동일 전압에 대하여 전류의 크기를 작게 하고, 또한 전압과 전류의 위상을 거의 일치시켜 무효 전력 성분을 감소시킬 수 있다. 본 논문에서는 비접촉 트랜스포머의 파라메타 측정을 통하여 비접촉 트랜스포머의 등가화 회로를 구현하였고, 일반 비접촉 트랜스포머와 강압형 매칭 트랜스포머를 추가한 트랜스포머의 전압 이득과 입력 임피던스 특성을 해석하였다. 강압형 매칭 트랜스포머의 특성을 검증하기 위하여 30kW급 비접촉 전원장치를 제작하여 실험하였다.

• Journal of IKEEE
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• v.11 no.4
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• pp.239-246
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• 2007

One of the most serious problems in KEPCO power system is the load centralization in the capital area. The load capacity in the capital area is almost 40% of the total load. However, the generation capacity in this area is just 16% of the total generation. The inequality, between the power demand and supply, in this area needs the power transmission from other regions. The simplest method to solve the problem is the installation of power plants or the addition of high-capacity transmission line in the metropolitan area. However, because of the concentration of human and material resources, there is a difficulty in the installation of the generation and transformer facility. As a result, instead of the installation of large scale facilities, the approach to maximize the application of existing facilities is required. In this research, we will develop a scheme with an HVDC installation for enhancing power transfer capability by utilizing the existing transmission lines.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.10
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• pp.123-130
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• 2016

High-frequency induction heating equipment can heat the metal by applying a High-Frequency power to the resonant circuit. The resonance circuit is composed of the work coil and the conduction-cooled power capacitor, it influences the performance of the heat treatment equipment according to the characteristics of the capacitor. However, dependence on conduction-cooled power capacitor's import is high due to lack of core technology research and development. Minimizing the generation of internal heat transmitted inside during LC resonance, reduce the reactive power loss, there is a need for a capacitor within the voltage characteristic outstanding. To implement localization it is vital that prior study of the analysis on the frequency response characteristic for the finished capacitor advanced manufacturer be implemented. Studying the interpolation method to read the value at any point of the characteristic curve for a given log-log scale was applied to the analysis tool of the capacitor by my proposed algorithm. The simulation for reproducing frequency response curves was attempted by assuming a capacitor in a simplified series equivalent RC circuit to obtain the equivalent series resistance value. It was confirmed that the reproduction rate was the result value above 83% as compared to the simulation of the properties and characteristics on the actual reactive power for Peak value, and that the algorithm can be applicable when analyzing and predicting the characteristic curves of a simpled model capacitor.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.8
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• pp.107-114
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• 2017

In this paper, a novel power factor compensation system based on voltage-controlled method is proposed for 3-phase 4-wire power system. The proposed voltage-controlled power factor compensation system generates a reactive power required for compensation by applying a variable output voltage by a slidac to a capacitor. In conventional power factor compensation system using the capacitor bank method, the power factor compensation error occurs depending on the load condition due to the limited capacity of the capacitors. However, the proposed system compensates the power factor up to 100% without error. In this paper, we have developed a voltage-controlled power factor compensation system and a control algorithm for 3-phase 4-wire power system, and verify its performance through simulation and experiments. If the proposed power factor compensation system is applied to an industrial field, a power factor compensation performance can be maximized. As a result, it is possible to reduce of electricity prices, reduce of line loss, increase of load capacity, ensure the transmission margin capacity, and reduce the amount of power generation.

• Journal of the Korean Society for Railway
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• v.19 no.6
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• pp.727-735
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• 2016

Smart transformers are effective at reducing the weight and increasing the efficiency of traction systems for railroad applications. A smart transformer generally consists of rectifier modules and the Dual-Active-Bridge (DAB) converter modules. The efficiency of the smart transformer depends on not only the electrical characteristics, but also on the control method of the converter modules. Especially, a DAB converter has a high order degree of freedom of voltage modulation to control the power transferred through the high frequency transformer, and a voltage modulation method, are very critical for the efficiency of the DAB converter. This paper proposes a new voltage modulation method for the DAB converter to increase the efficiency in the low/medium power transfer condition. The proposed modulation method controls the reactive power in the high frequency transformer, making it zero. And, the switching loss is dramatically reduced by using the received converter module as a diode rectifier. The feasibility of the proposed modulation method is verified by computer simulation of the 900Vdc DAB converter power control.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1183-1194
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• 2021

Traditionally, electric power systems have been known as the centralized structures, which is organized into placing customers at the end of the supply chain. However, recent decades have witnessed the emergence of distributed energy resources(:DERs) such as rooftop solar, farming PV system, small wind turbines, battery energy storage systems and smart home appliances. With the emergence of distributed energy resources, the role of distributed system operators(:DSOs) will expand. The increasing penetration of DERs could lead to a less predictable and reverse flow of power in the system, which can affect the traditional planning and operation of distribution and transmission networks. This raises the need for a change in the role of the DSOs that have conventionally planned, maintained and managed networks and supply outages. The objective of this research is to designed the future distribution operation system with multi-DERs and the proposed distribution system model is implemented by hardware-in-the-loop simulation(HILS). The test results show the normal operation domain and reduction of distribution line loss.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.746-752
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• 2020

As environmental issues have been taken seriously, the number of solar power generation facilities has rapidly increased in Korea. The voltage at the output stage of an inverter increases in a system that connects a small-capacity photovoltaic power generation to low-voltage power distribution. This degrades the quality of the low-voltage distribution system and adversely affects the load facility. In this study, a solution was obtained to increase the voltage at the output stage of the solar inverter according to the connection of the low-voltage distribution system. The voltage can be controlled by using reactive power factor control inverters. If the secondary tap is adjusted, the voltage can be adjusted to about 15 V, but there is a problem in that the tap is not adjusted unless the KEPCO distribution regulation voltage is out of the range of 220±13V. If the number of inverters is limited, the inverter can be started within the inverter overvoltage range. If it is connected to three phases, the voltage is distributed. The results indicated that power factor control and active voltage control inverters were easy to apply in the field.

• Journal of Korea Port Economic Association
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• v.22 no.4
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• pp.1-17
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• 2006

In the Bill of Lading of The Irbenskiy Proliv is not subject to the Hague-Visby Rules in accordance with paragraphs (A) and/or (E) of cl.1 or to the Hague Rules in accordance with paragraphs (B) and/or (D) of cl.1. The Irbenskiy Proliv is very rare case that is effective to exempt the carrier as literal words of Bill of Lading. The action concerns cargoes of perishable goods shipped from Brazil to Japan, under Bills of Lading each of which contained an extensive carrier's exemption clause. A preliminary issue was ordered to be determined on the question whether c1.4 is effective to exempt the ralliers from any potential liability for the claims in this case. The court held that there is no reason to reject c1.4 as part of each of the contracts contained in or evidenced by the bills of lading; and it protects the carrier where damage to the goods shipped results from such causes. It is therefore effective to exempt the carriers from any potential liability for those claims.