• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.958-961
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• 1997

This Paper deals with voltage variation and voltage regulation method in power distribution systems including cogeneration facilities. In order to deliver suitable voltages to many customers at the distribution substations. In this paper, an on-line real time modified voltage regulation method is proposed. The result from a case study show that the proposed method can be practical tool for the voltage regulation in distribution systems including cogeneration facilities.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.1088-1090
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• 1998

The cogeneration facilities (COGN) into the power distribution system can cause operational problems - reenergization of distribution feeders under repair by utility personnel, voltage variation and regulation because of output power of COGN, and lost of coordination at emergency state - on an electrical utility system. This paper deals with momentary voltage dips as the parallel interconnection operation of COGN in the power distribution system. PSCAD/EMTDC simulation tool is used to show the behavior of momentary voltage dips. In addition, restraint solution for momentary voltage variation is presented.

• 조명전기설비학회논문지
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• 제23권2호
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• pp.53-61
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• 2009

현재의 배전계통의 전압은 변전소에서 단방향 조류를 고려하여 LCD에 의한 전압조정방법으로 ULTC 변압기의 탭을 변환하여 공급전압을 적정범위 내에서 유지되도록 운전하고 있다. 그러나 현재의 배전계통 운용은 소용량에서 대규모 용량에 이르기까지 다양한 용량의 PV 시스템이 배전계통에 연계되어 운전되는 것을 반영하지 못하고 있는 실정이다. 때문에 다수의 PV 시스템이 계통에 연계되어 양방향 조류가 발생하고 이로 인해 연계점의 전압변동이 발생하여도 이를 효과적으로 조정하지 못하여 계통의 전압이 적정범위 내에서 운용되지 못하는 경우가 발생할 수 있다. 따라서 본 논문에서는 다수 PV 시스템의 연계에 따른 양방향 조류의 발생을 고려하고 연계점의 전압변동에 따른 계통의 전압을 효과적으로 제어할 수 있도록 실시간 감시가 이루어지는 PV 시스템의 특징을 이용하고 기존의 LDC 전압조정방법을 개선하여 PV 시스템 연계 시에도 변전소에서 계통의 전압을 적정범위 내에서 조정할 수 있는 개선된 전압조정방법을 제안하였다.

• 조명전기설비학회논문지
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• 제21권3호
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• pp.117-124
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• 2007

요즈음과 같은 고유가 시대에 대두되고 있는 분야인 에너지 절감과 관련하여, 본 논문에서는 대단위 전력 수용가 내부의 저압배전 시스템을 특고압으로 변경할 때의 전기에너지의 손실절감에 대해 논하였다. 현재 대수용가에서는 특고압을 수전하여 저압으로 강압하여 각 부하에 전압선로로 전력을 공급하는데, 그 대신에 본 논문에서는 수전한 특고압을 수용가내의 개별 부하 근방까지 직접 가져오고 여기서 저압으로 변환하여 짧은 거리에 위치한 부하들에 전력을 공급할 때 소요되는 대략적인 설비비, 공사비의 증가금액과 선로의 전력손실 감소에 의한 절감 금액을 계산하였다. 또한 초기투자비의 회수 기간을 산정함으로 특고압 배전시스템의 경제성에 대하여 간략히 평가하였다.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.549-558
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• 2017

DC distribution has several differences compared to AC distribution. DC distribution has a higher efficiency than AC distribution when distributing electricity at the same voltage level. Accordingly, power can be transferred further with low-voltage DC. In addition, power flow in a DC grid system is produced by only a voltage difference in magnitude. Owing to these differences, operation of a DC grid system significantly differs from that of an AC system. In this paper, the power flow problem in a bipolar-type DC grid with unbalanced load conditions is organized and solved. Control strategy of energy storage system on a slow time scale with power references obtained by solving an optimization problem regarding the DC grid is then proposed. The proposed strategy is verified with computer simulations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.214-217
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• 1990

The voltage of distribution systems is controlled according to the proper rate of voltage drop and the loss constraints etc.. In modern distribution system it is necessary to supply energy according to the priority of reliabilities of the system. This paper proposes an efficient algorithm of the management of distribution systems considering the system reliabilities and gives a more accurate and economic control of the voltage of distribution systems.

• 조명전기설비학회논문지
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• 제29권7호
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• pp.14-21
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• 2015

Distribution systems are operated in radial structure, but temporal loop structure could be founded the live load transfer. Main purposes of reconfiguration of distribution network are load balancing, loss minimization and voltage drop maintaining. In the loop structure, huge loop current can be flowed between two substations in case of large voltage angle difference. Protection devices of distribution line can be triped by this huge loop current. So, precise calculation of loop current is very important for secure switching. This paper proposes a novel calculation method of loop current using the voltage angle differences measured at the tie switches. Feasibility of the propose method has been verified by various case studies based on Matlab simulation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.177-178
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• 2008

Recently, the concern of PV(Photovoltaic) systems has increased because of an environmental problem and limitation of fossil fuel. In this paper, distribution system of existing one-way power flow and distribution system generating bidirectional power flow analyze voltage variation at distribution system interconnected multiple PV systems. Also, we analyze a supply voltage range of distribution system using LDC and ULTC voltage regulation method by case study.

• 전기학회논문지
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• 제59권7호
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• pp.1242-1247
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• 2010

In this study, the heat source distributions at the end side and the center of the electrode are analyzed to estimate the electrical stress due to the harmonics from the nonlinear loads. The governing equation at the analysis area of low voltage condenser are numerically solved using the finite element software package to analyze the effects of heat source distribution due to the 5th and 7th harmonics, which can exist normally in the distribution network and can be applied to the low voltage condenser. Finally, the heat source distribution from the harmonics is compared and analyzed with the heat source distribution from the fundamental component of the applied voltage.

• Journal of Power Electronics
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• 제12권3호
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• pp.495-502
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• 2012

This paper presents an improved grid voltage control strategy for wind farms with doubly-fed induction generators (DFIGs) connected to distribution networks based on an analysis of the operation limits of DFIG systems. A modified reactive power limit calculation method in different operation states is proposed and a reactive power control strategy during grid voltage dips/rises is further discussed. A control strategy for compensating unbalanced grid voltage, based on DFIG systems, by injecting negative sequence current into the grid through the grid side converter (GSC) is proposed. In addition, the negative current limit of the GSC is discussed. The distribution principle of the negative sequence current among the different DFIG systems in a wind farm is also introduced. The validity of the proposed voltage control strategy is demonstrated by Matlab/Simulink simulations. It is shown that the stability of a wind farm and the power grid can be improved with the proposed strategy.