• Journal of IKEEE
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• v.22 no.3
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• pp.738-741
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• 2018

As DC power and DC load increase, unnecessary conversion process occurs in existing system. Due to these problems, interest in DC distribution systems has increased recently. As the importance of DC distribution system becomes higher, it is necessary to analyze the DC current. In this paper, we briefly describe the control method of the converter and describe the DC power flow calculation method. finally, we compared the simulation results of MATLAB and ETAP.

• Journal of the Korean Society of Safety
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• v.25 no.2
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• pp.24-28
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• 2010

The nuclear power Plant onsite AC electrical power sources are required to supply power to the engineering safety facility buses if the offsite power source is lost. Typically, Diesel Generators are used as the onsite power source. The 125 VAC buses are part of the onsite Class 1E AC and DC electrical power distribution system. The DC power distribution system ensure the availability of DC electrical power for system required to shutdown the reactor and maintain it in a safety condition after an anticipated operational occurrence or a postulated Design Base Accident. Recently, onsite DC power supply system trip occurs the loss of system function. To obtain the performance such as reliability and availability, we analyzed the cause of battery charger trip and described the improvement of DC power supply system reliability. Finally, we provide reliability performance criteria of charger in order to ensure the probabilistic goals for the safety of the nuclear power plants.

• Journal of Electrical Engineering and Technology
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• v.5 no.1
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• pp.103-115
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• 2010

This paper discusses a DC distribution system which has been supplied by external AC systems as well as local microturbine distributed generation system in order to demonstrate an overall solution to power quality issue. Based on the dynamic model of the converter, a design procedure has been presented. In this paper, the power flow control in DC distribution system has been achieved by network converters. A suitable control strategy for these converters has been proposed, too. They have DC voltage droop regulator and novel instantaneous power regulation scheme. Also, a novel control system has been proposed for MT converter. Several case studies have been studied and the simulation results show that DC distribution system including microturbine unit can provide the premium power quality using proposed methods.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.353-359
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• 2017

To take advantage of electric propulsion, several large vessel kinds, namely, cruise vessels, icebreakers, drill ships, and warships, have been generally designed with Integrated Power System (IPS). Although most of these vessels have adopted AC distribution IPS, DC distribution IPS ships have recently emerged as a new promising technology thanks to the availability of the products related to the DC distribution system, in which the system's major advantages over AC distribution are reduced weight and fuel consumption. This paper presents the comparison results of a 10-t class fishing boat for the AC distribution and DC distribution cases. By replacing AC distribution system with DC distribution, 31-41% reduction in the weight of the electrical equipment weight and 20-25% reduction in the fuel consumption are expected.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.42-48
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• 2015

DC distribution system is difficult to compose the single-system because of the capacity restriction of power semiconductors. Therefore, DC Distribution system needs parallel operation of AC/DC converters for increase to system capacity. However, this system generates the circulating current. This paper is reducing the circulating current and safely sharing the load using the proposed DC current droop control method when each other 3-phase AC/DC converter connected. This system confirms through the simulation and experiment. Also, when each other converter of parallel operate. it is compared the response characteristics

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.54-61
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• 2015

Recently, DC-based power system is being paid attention as the solution for energy efficiency. As the example, HVDC (High Voltage DC) transmission system is utilized in the real power system. On the other hand, researches on LVDC (Low Voltage DC) distribution system, which are including digital loads, are not enough. In this paper, reliability in LVDC distribution system is analyzed according to the specific characteristics such as the arrangement of DC/DC converters and the number of poles. Furthermore, power quality is also taken account of since LVDC distribution system includes multiple sensitive loads and electric power converters. In order to achieve this, LVDC distribution systems are modeled using ElectroMagnetic Transient Program (EMTP) and both the minimal cut-set method and Customer Interruption Cost (CIC) are used in the reliability analysis.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.4
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• pp.275-286
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• 2019

This paper presents real-time Direct Current (DC) network analysis applications for operation of DC distribution system or DC microgrid. These applications are installed on central Energy Management System (EMS) and provide solutions of DC network operation. To analysis DC distribution network, this paper proposes composition and sequence of applications. Algorithm of applications is presented in this paper. Demonstration tests are performed on DC distribution site in Gochang Power Testing Center of Korea Electric Power Corporation (KEPCO). To verify the performance, developed DC applications installed on EMS. Scenarios for demonstration test of voltage control are presented. Finally, measured data, application output data and simulation data (by PSCAD/EMTDC) are compared and analyze accuracy of applications.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.3
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• pp.209-213
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• 2015

With the increasing popularity of renewable generation systems and the advancement of power electronics, DC distribution systems have recently received considerable research attention. DC distribution has numerous advantages, including reliability, power quality, and efficiency. Owing to these advantages, DC distribution has been applied to data centers and power quality-sensitive electronic load conditions. Because grounding electrodes in DC are much more susceptible to corrosion than in AC, the IT system defined in IEC Standard 60364 may be a good candidate for an earthing method for DC distribution systems. In addition, IEC Standard 61557 specifies the requirements for insulation monitoring devices (IMD) for protection of the IT system, which continuously monitors the insulation resistances between the power lines and the earth. This paper discusses the development and evaluation of IMD to promote the reliability of distribution systems and increase safety of humans and facilities.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1056-1057
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• 2015

A common DC bus is a useful connection for several DC output sources such as photovoltaic (PV), fuel cells, and batteries. Operation of the common DC power system with more than two DC output sources, especially in a stand-alone mode, requires a control scheme for the stable operation of the system. In this paper, a control scheme has been developed for applying DC power sources to the distribution system. The purpose of the control scheme is to make the best use of the DC power sources. The DC power system consists of PV, two energy storage systems and a DC-AC inverter with the control scheme. A distribution system was modeled in PSCAD/EMTDC. As the results, the control scheme is applied to the DC-AC inverter and the DC-DC converter for transfer operations between the grid-connected and the stand-alone mode to keep the DC bus and the AC voltage constant. The results from the simulation demonstrate the stable operation of a grid connected DC power system.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.3
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• pp.219-223
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• 2016

DC microgrid system is attracted attention in the world, because DC distribution system is more energy efficient than AC distribution system. To analyse the contribution effects of distributed generation(DG) in LVDC distribution system through modeling the Rectifier, DC/DC converter, Energy Storage System(ESS) and Photovoltaic(PV). using PSCAD/EMTDC. This paper analyses fault response characteristics in LVDC distribution system according to the interconnection and islanding operation of DG. Based on research results on the paper, direction for development of fault current reduction method for LVDC distribution system is suggested.