• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권5호
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• pp.280-286
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• 2006

The paper proposes a new protection algorithm for reliable operation of grid-interfaced PV system, which can flexibly interact with conventional protective schemes of power utility grid not only to prevent damages to utility or public persons and utility apparatus caused by malfunction or failure in distribution network protection system, but also to protect a PV system itself from faults or abnormal conditions of the network. The proposed algorithm is based on reclosing characteristics of the distribution system. As a network fault occurs, the new scheme determines whether it is momentary or permanent and responds in a pre-programmed way to the fault. For permanent outage, the proposed algorithm shuts down inverter's operations but monitoring system voltage and frequency at the point of common coupling with grid. When it comes to the momentary outage, Inverter starts stand-by operation mode so that it can be automatically connected to the grid without start-up procedures as soon as the system voltage and frequency returns into the normal operation range. In order to investigate' and evaluate the PV system operation, simulation study based on PSCAD/EMTDC has been carried out to verify the performance of the proposed protection scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.400-402
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• 1994

The voltage drop in distribution path of battery-reserved DC power system can affect the total of battery, cable and electricity costs. To determine an optimum voltage drop in distribution path for minimizing the total cost, battery, cable and electricity costs are represented as a function of the voltage drop, respectively, and are summed up to the total cost. An optimum voltage drop is selected as the value giving the minimum total cost. In this paper, a design technique of optimum voltage drop in distribution path of DC power system is proposed to minimize the total of battery, cable and electricity costs. The design procedure is described and design curve for selecting optimum voltage drop is also presented as a function of distribution distance.

• 전기학회논문지
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• 제58권5호
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• pp.898-904
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• 2009

The objective of the present study lies in constructing web-based GIS system providing broad range of information applicable for power/telecommunications distribution facilities through cable. Nowadays, Korea is renowned forits faste sttele communications network across the nation enjoyable for being a test-runbed by worldwide contents providers. It is not too much to say that the trend is caused by the fact that Korea utilizes the cobweb-like power transmission cables applicable for the nationwide telecommunications networking. In particular, the trend has been all the more encouraged by the governmental drive to expedite the telecommunication network by way of the established power transmission facilities deemed as publicutility. Nevertheless, few can deny that the overexcessive competition among telecommunication service providers increasingly gives rise to unauthorized, arbitrary facilitation of distribution devices, which becomes much burden in operating the normal power/telecommunications distribution facilities by a power-generating company. In this regard, the study, to cope with such problems, attempts to develop a web GIS-based information management system compatible with NDIS(New Distribution Information System), a distribution facility management system now under operation by KEPCO, making advantage of GE Energy's SIAS(Smallworld Internet Application) technology. The model provided by this study is expected to get closer into effective operation of distribution facilities along with better sharing of information among conventional telecommunications operators, while getting rid of infringed facilitation cases

• KIEE International Transactions on Power Engineering
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• 제4A권4호
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• pp.207-213
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• 2004

In this paper, the on-line volt/var control algorithms of the Load Tap Changer (LTC) transformer and Shunt Capacitor (SC) are proposed for distribution volt/var compensation. In the existing volt/var control of the distribution substation, the feeder voltage and reactive power demand of the distribution are mainly controlled by the LTC transformer tap position and on/off operation of the Sc. It is very difficult to maintain volt/var at the distribution networks within the satisfactory levels due to the discrete operation characteristics of the LTC and SC. In addition, there is the limitation of the LTC and SC operation times, which affects their functional lifetimes. The proposed volt/var control algorithm determines an optimal tap position of the LTC and on/off status of the SC at a distribution substation with multiple connected feeders. The mathematical equations of the proposed method are introduced. A simple case study is performed to verify the effectiveness of the proposed method.

• 전기학회논문지
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• 제58권10호
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• pp.1835-1841
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• 2009

We analyze the problem of recloser-fuse coordination when a superconducting fault current limiter (SFCL) is installed to a power distribution system. Generally, The recloser is installed to upstream of fuse to protect against both permanent fault and temporary one appropriately. However, in a power distribution system with SFCL, the fault current is decreased by the effect of the impedance value of the SFCL and when a permanent fault occurs, the fuse may not melt during the last delay operation of the recloser because of the insufficient heat from the decreased current. Therefore, when SFCLs are applied into a power distribution system, the rating of the fuse has to be reselected to coordinate recloser to fuse effectively. To solve these problems, this paper analysed the operation of recloser-fuse coordination and presented the improved recloser-fuse coordination method in a power distribution system with SFCL using PSCAD/EMTDC.

• 전기학회논문지
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• 제57권10호
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• pp.1696-1702
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• 2008

This paper proposes a voltage compensation device direct control strategy to realize the distributed, autonomous voltage control of the distribution system, which based on voltage data collected from customers of the remote site under the ubiquitous-based distribution system. In the proposed method, The ULTC and the SVR(Step Voltage Regulator)s compensate autonomously the voltage for self-compensation area based on the voltage data furnished from the ubiquitous device of customers. Also, the SVRs overcome the limit of single-operation of ULTC by the interlocking operation with the ULTC and enhance the voltage compensation capability for the customer. In particular, an optimization design method and a fuzzy design method are compared to determine the effective control method of the voltage compensator under the ubiquitous-based on-line operation environments. In fuzzy method, the tap of voltage compensator is defined as output member. Finally, the proposed two methods are implemented in Visual C++ MFC, the effectiveness is proved by simulation based on the worst virtual voltage data. Also, an optimal voltage compensation strategy is determined under on-line environments based on analyzed results.

• 전기학회논문지P
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• 제56권3호
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• pp.123-128
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• 2007

Hydro power supplies no pollution energy, mainly induction generator has been applied at the small capacity power station. The generating power of small hydro-electric power station connects on the 22.9kV distribution system or low voltage system in the case of three-phase four-wire supply system. There are side effects of various kinds in the 3-three phase 4-wire distribution system mixing 1-phase load and 3-phase load. This system generates the voltage unbalance by unbalanced load operating condition. They have various serious effects on generator and connection system. In this paper, we analyzed what kind of operation characteristic are happened in the induction generator by customer load variation at the 3-three phase 4-wire distribution system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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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.

• 조명전기설비학회논문지
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• 제13권4호
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• pp.127-133
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• 1999

본 논문은 배전계통에 전지전력저장시스템(Battery Energy Storage System: BESS)를 연계하여 운전하는 경우 BESS의 유.무효전력 제어에 대하여 연구하였다. BESS을 배전계통에 연계하는 경우, 이의 유.무효전력 출력을 제어함으로써 배전계통에 일정 전력을 공급, 첨두 부하를 삭감하고 전압을 보상할 수 있다. 본 논문에서는 배전계통과 전지전력저장시스템을 등가 모델링 하였고 전지전력저장시스템의 유.무효 전력제어를 위한 전력 조류 방정식을 제시하였다. 본 논문에서는 BESS의 유.무효전력을 제어하기 위하여 $P-\delta$와 Q-V 제어를 사용하였고 이를 입증하기 위하여 BESS의 유.무효전력 제어를 PSCAD/EMTDC 프로그램을 이용하여 시뮬레이션 하였다.

• 전기학회논문지
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• 제67권8호
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• pp.987-993
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• 2018

In the existing distribution automation system, the database is managed by each distribution office. But there is a high possibility to happened a problem during a fault processing because the representation of the connection switches between distribution offices are complicated. In addition, if a distribution office will be going to collapse due to disaster, for example, a big fire or earthquake, its own database may be lost. In order to solve this problem, it is necessary to have a structure of an integrated database management from an integration center to under the distribution office. To do this, the integration center must store and manage it as the database using the own office code.