• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1522-1528
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• 2007

Electric Power cable is the apparatus that receives electric power from the Korea Electric Power Corporation and supplies electric power to electric train and annex facilities of each railway station. With substantial ripple effect during power blackout accidents, such power blackout accidents must be coped with by discriminating the status of insulation deterioration of electric power cable in advance. Discrimination of insulation deterioration of the electric power cable is normally executed while the power is disconnected and it is very difficult to discover, at early stage, the insulation deterioration of the power cable in operational state since the duration of inspection is limited. This research aims to consider method of diagnosing the insulation deterioration of electric power cable in On-Line state rather than diagnosis in Off-Line state in order to secure reliability of power supply by reducing duration of power blackout (accidental blackout and blackout during works) and by seeking reduction in equipment and manpower used in diagnosis of deterioration through prevention of the accident itself prior to occurrence through early restoration of accident due to insulation deterioration of the electric power cable and assessment of performance of the cable under operation.

• 전기학회논문지
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• 제61권3호
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• pp.437-441
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• 2012

In this paper, we have designed and manufactured 10MHz power source for the application of short distance wireless power transmission. The designed power source consists of a DDS(direct digital synthesizer) signal generator, a buffer driver and a balanced power amplifier. Short range wireless power transmission is usually carried out by near-field inductive coupling between source and load. The distance variation between source and load gives rise to the change of load impedance of power amplifier, which has effect on the operation of power amplifier. To overcome this problem due to load variation of power amplifier, we have adopted the balanced power amplifier using the quadrature hybrid implemented by lumped capacitors and a mutually coupled coil. The experiment results show the above 40dBm output power, frequency range of 9 to 11MHz, and total DC power consumption of 36W.

• Journal of Power Electronics
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• 제17권5호
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• pp.1308-1316
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• 2017

The distributed maximum power point tracking (DMPPT) concept is widely adopted in photovoltaic systems to avoid mismatch loss. However, the high cost and complexity of DMPPT hinder its further promotion in practice. Based on the concept of DMPPT, this paper presents an integrated submodule level half-bridge stack structure along with an optimal current point tracking (OCPT) control algorithm. In this full power processing integrated solution, the number of power switches and passive components is greatly reduced. On the other hand, only one current sensor and its related AD unit are needed to perform the ideal maximum power generation for all of the PV submodules in any irradiance case. The proposal can totally eliminate different small-scaled mismatch effects in real-word condition and the true maximum power point of each PV submodule can be achieved. As a result, the ideal maximum power output of the whole PV system can be achieved. Compared with current solutions, the proposal further develops the integration level of submodule DMPPT solutions with a lower cost and a smaller size. Moreover, the individual MPPT tracking for all of the submodules are guaranteed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.488-490
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• 2001

A dispered power system means a little bit of small power generation equipment located near the power-damend areas. Due to no power supply line, such a power source is very favorable for the decrease in loss of electric power supply, in comparison to the giantly focused power source, Because of small power source, this power source also corresponds promptly to the variation of power demend. On the basis of energy saving, environmental reservation, and utilization of natural or unused energy, solar power plants can be introduced into the residence section of cities and small water or wind-power plants near the urban areas. In case of Korea, some wind farm have been introduced into Cheju island, Condensed introduction of several small power sources into an used distribution line may, however, result in a big problem, it is, therefore, necessary that protective-cooporative plans between power quality and distribution line should be introduced for efficient utilization of KEPCO distribution system.

• 한국시스템다이내믹스연구
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• 제4권1호
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• pp.33-53
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• 2003

How to maintain the optimal electric power generation mix is one of the important problems in electric power industry. The objective of this study is to develop a computer model which can be used to forecast the investment in power generation unit by the plant owners after restructuring of electric power industry. Restructuring of electric power industry will make difference in decision making process of investment in power generation unit. After Privatiazation of Power Industry, Gencos will think that profit is the most important factor among all others attracting the investment in the industry. Coal power generation is better than LNG CCGT in terms of profit. However, many studies show that LNG CCGT will be main electric power generation source because the rest of factors other than profit in LNG CCGT are superior than Coal power generation. Because the nst of factors other than profit in LNG CCGT are superior than Coal power generation. The impacts of the various government policies can be analyzed using the computer model, thus the government can formulate effective policies for achieving the desired electric power generation mix.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.384-386
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• 2003

Striking in change that present our country is much by electricity industry reform and the Korea Electric Power Corporation is deciding power distribution system reliability indices every year but power distribution system for reliability evaluation and establishment of investment program are consisting punily. If consider efficient inflection of resources and hereafter power distribution division that is limited for target achievement of schedule level service evaluation and reliability side in operation of the power distribution system, can expect efficient practical use of the power distribution property if gains in electrical side about these change and most suitable investment way consist because there is necessity of electric power plan establishment of area electric power distribution place of business unit. This paper consider proper reliability level and maximum effect through quantitative analysis to gain electrical gains of the power distribution system in reliability side depending on trend DB(Data Base) of data of electric power system composition appliance in this treatise and apply data administration and reliability rate analysis that serve to decide most suitable investment precedence to supply of electric power property to power distribution system present investment algorithm.

• 전력전자학회논문지
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• 제17권1호
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• pp.27-33
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• 2012

Internet Data Centers (IDC), as essential facilities for modern IT industry, typically have scores of MW of concentrated electric loads. Uninterruptible Power Supplies (UPS) are necessary for the power feed system of IDCs because of stable power requirement. Thus, conventional AC power feed systems of IDCs have three cascaded power conversion stages such as (AC-DC), (DC-AC), and (AC-DC), which results in very low conversion efficiency. On the contrary, DC power feed systems need just a single power conversion stage (AC-DC) supplying AC mains power to DC server loads, which gives comparatively high conversion efficiency and reliability. This paper compares the efficiencies between 220V AC power feed system and 300V DC power feed system on equal load conditions which were established in Mok-Dong IDC of Korea Telecom company (KT). Experimental results show that the total operation efficiency of the 300V DC power feed system is around 15% higher than that of the 220V AC power feed system.

• KIEE International Transactions on Power Engineering
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• 제4A권4호
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• pp.262-267
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• 2004

With the advent of electric power systems moving from a vertically integrated structure to a deregulated environment, calculating reactive power service charges has become a new and challenging theme for market operators. This paper examines various methods for reactive power management adopted throughout various deregulated foreign and domestic markets and then proposes an innovative method to calculate reactive power service charges using a reactive power market in a wholesale electricity market. The reactive power market is operated based on bids from the generating sources and it settles on uniform prices by running the reactive OPF programs of the day-ahead electricity market. The proposed method takes into account recovering not only the costs of installed capacity but also the lost opportunity costs incurred by reducing active power output to increase reactive power production. Based on the result of the reactive OPF program, the generators that produce reactive power within the obligatory range do not make payments whereas the generators producing reactive power beyond the obligatory range receive compensation by the price determined in the market. A numerical sample study is carried out to illustrate the processes and appropriateness of the proposed method.

• KEPCO Journal on Electric Power and Energy
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• 제6권3호
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• pp.279-284
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• 2020

This paper presents the conceptual design of a cooperative control with Energy Management System (EMS) and Distribution Management System (DMS). This control enables insufficient reactive power reserve in a power transmission system to be supplemented by surplus reactive power in a power distribution system on the basis of the amount of the needed reactive power reserve calculated by the EMS. This can be achieved, because increased numbers of microgrids with distributed energy resources will be installed in the distribution system. Furthermore, the DMS with smart control strategy by using surplus reactive power in the distribution system of the area has been gradually installed in the system as well. Therefore, a kind of hierarchical voltage control and cooperative control scheme could be considered for the effective use of energy resources. A quantitative index to evaluate the current reactive power reserve of the transmission system is also required. In the paper, the algorithm for the whole cooperative control system, including Area-Q Indicator (AQI) as the index for the current reactive power reserve of a voltage control area, is devised and presented. Finally, the performance of the proposed system is proven by several simulation studies.

• 전기학회논문지
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• 제66권3호
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• pp.593-598
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• 2017

Induction generator is always required reactive power in order to generate a rotating magnetic field as an inductive load. The reactive power must be continuously supplied to the induction generator as well as load of distribution system from the power supply side. So the power factor of the power supply side during the induction generation operation is low. Condenser is installed in order to raise the low power factor of the induction generator. Switching transients occurs when the power supply of the capacitor is turned on in order to ensure the low power factor. When using the reactor in series with the capacitor in order to reduce the influence of switching transient, it can affect the reactive power by the condenser voltage rises. In this study, we analyzed the operating characteristics for power and power factor of induction generator in accordance with the presence or absence of the application of the serial reactors for switching transients reduction of the condenser and the condenser for power factor correction.