• Journal of Power Electronics
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• v.12 no.1
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• pp.157-163
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• 2012

Internet Data Centers (IDCs), which are essential facilities in the modern IT industry, typically have scores of MW of concentrated electric loads. The provision of an Uninterruptible Power Supply (UPS) is necessary for the power feed system of IDCs owing to the need for stable power. Thus, conventional IDC AC power feed systems have three cascaded power conversion stages, (AC-DC), (DC-AC), and (AC-DC), resulting in a very low conversion efficiency. In comparison, DC power feed systems require only a single power conversion stage (AC-DC) to supply AC main power to DC server loads, resulting in comparatively high conversion efficiency and reliability [4-11]. This paper compares the efficiencies of a 220V AC power feed system with those of a 300V DC power feed system under equal load conditions, as established by the Mok-Dong IDC of Korea Telecom Co. Ltd. (KT). Experimental results show that the total operation efficiency of the 300V DC power feed system is approximately 15% higher than that of the 220V AC power feed system.

• Journal of Environmental Science International
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• v.12 no.4
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• pp.503-510
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• 2003

How to plan the energy system is one of the keys f3r constructing the Environment -Friendly City. for this reason, a great number of surveys for utilizing unused energy have conducted by a planner. In regard to unused energy, the heat from incineration plants classify as a unused energy having high-exergy-energy. From this point of view, It is studied about the plant systems providing heat to district heating & cooling(D.H.C) and producing electric power. It is divided four system models as system I (10K [kgf/cm$^2$) vapor as outlet of boiler, supply far 10K vapor and return to 60$^{\circ}C$ as supply condition of district heating), system II (30 K vapor as outlet of boiler, supply for 5t vapor and return to 60f as supply condition of district heating), system 111 (30 K vapor as outlet of boiler, supply for 85$^{\circ}C$ hot water and return to 60$^{\circ}C$ as supply condition of district heating), system IV (30 K vapor as outlet of boiler, supply for 47$^{\circ}C$ hot water and return to 40t as supply condition of district heating). The results from the upper condition of four system, System II got a proper on economical benefits and system IV calculated as benefiting on energy saving effects, and suggest indifference curve as the total evaluation method of both economical benefits and energy saving.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.330-332
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• 2001

This paper reviews technology for power quality differentiated supply in power system. Since price and power quality has been single goods in the light of customer-side view point but hereafter it is essential for power market to introduce multiple goods which is composed of differentiated combination between them. This paper should like to work out strategy for power quality differentiated supply in domestic power system by comparison characteristics of differentiated background and its relevant various theory.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.5
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• pp.611-616
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• 2018

In the cost based pool market in Korea, there is no compensation of reactive power because the fuel cost for reactive power is relatively low compared to that of active power. However, the change of energy paradigm in the future, such as widespread integration of distributed renewable energy source, will prevent the system operator from mandating the reactive power supply without any compensation. Thus, in this study, we propose the reference voltage of the 345 kV transmission system that minimizes the reactive power supply. This is closely related to the economic dispatch of reactive power aiming at minimizing the compensation cost for the reactive power service. In order to verify the effectiveness of the proposed reference voltage, the simulations are performed using the IEEE 14 bus system and the KEPCO real networks. The simulation results show that a voltage lower than the current reference value is recommended to reduce the reactive power supply and also suggest that the current voltage specification for the 345 kV system needs to be reviewed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.80-84
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• 2008

In this paper, we have posed contactless power supply method using the contactless transformer with multiple primary winding. Also, the system uses resonant frequency tracking method for safe power supply at the elevator's car. The proposed system has been verified by the simulation using ICA4 and Maxwell. The contactless power transmission system is designed for 5[kW] rate.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.349-354
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• 2003

Airport facility is infrastructure that become external creditworthiness and linear measure of country competitive power. Among them, receive and supply of electric power facility of airport is very important in peculiarity, trustability, safety side of airport. In this parer, sorted domestic airline as 4 classes by code to accomplish standardization for receive and supply of electric power facility of airport. And established justice and coverage about receive and supply of electric power facility using without any standard present and analyze problem for receive and supply of electric power facility of existing airport and presents standard. Finally, present standard single-line diagram by airport grade and system grade standard of receive and supply of electric power facility of airport.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.202-205
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• 2003

Recently, UPS(Uninterruptible Power Supply) have been largely used to improve power souse quality as well as to protect critical loads such as computer, industrial system, medical equipment, etc, against power outage by providing clean and uninterrupted power under power supply disturbance or interruptions. But UPS is bulky because used battery. So, UPS size issue have received attention in the power electronics industry. Therefore, this paper proposed a implementation of inside of the computer power supply with UPS by the one-chip microprocessor to minimize UPS size. To verify the proposed power supply, the detail simulation and experiment results indicate that high-frequency switching and operation UPS can be achieved.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.5
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• pp.232-237
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• 2002

It is increased for methodology to evaluate distribution power system interruption cost in power supply zones under competitive electricity market. This paper presents algorithms to evaluate system interruption cost in distribution power supply zones taking into consideration failure rate of distribution facilities and composite customer interruption cost. In this paper, it is introduced for weighting factor for each customer failure duration and failure rate of distribution facilities to evaluate reasonable system interruption cost in distribution power supply area. Also, this Paper estimates evaluation results of system interruption cost using a sample model system. Finally, evaluation results of system interruption cost based on failure rate of distribution facilities and composite customer interruption cost are shown in detail.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.11-18
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• 2015

This paper proposes a high-efficiency 3-kW hybrid ESS with emergency power supply. The proposed system enables efficient use of power from photovoltaic (PV) cells and energy storage system (ESS). The proposed system can operate as an uninterruptible power supply (UPS) when grid fault occurs, providing seamless transfer from grid-connected mode to stand-alone mode. The LLC converter for PV achieves ZVS turn-on of switches and ZCS turn-off of diodes, and the isolated bidirectional DC-DC converter for ESS achieves ZCS turn-off regardless of load condition, resulting in high efficiency. The efficiency and performance of the proposed hybrid ESS has been verified by a 3-kW prototype.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.2
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• pp.212-225
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• 2023

This study presents a modularized process of a hybrid renewable energy system that combines photovoltaic power and wind power to supply stable power in a unit area (1 km²). The water electrolysis process and fuel cells process also contributes to the supply of the stable power. The entire system can constantly supply power of 4.39 MW/km². Actual meteorological data is used for simulation.