• 전기학회논문지
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• 제63권2호
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• pp.224-229
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• 2014

This paper presents the novel voltage control method in power distribution system with distributed generators. The voltage in distribution systems is regulated by Under Load Tap Changer(ULTC) of substation and pole transformer of primary feeders. Recently, Step Voltage Regulator(SVR) is getting located at distribution feeders to regulate effectively voltage of primary feeders. But the effectiveness of SVR decreases due to independent operation between SVR and ULTC, and also the existing Line Drop Compensator(LDC) method considering the distributed generators may be not able to regulate the proper voltage in a permissible range. Thus, this paper presents a optimal voltage control algorithm of SVR by using the secondary voltage data of main transformer in substation.

• 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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.212-213
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• 2007

Grid-connected PV(Photovoltaic) power generation system has experienced increasing attention in recent years. But the growing number of non-linear equipments, such as, inverters, has been demanding the compensation for the disturbances caused by them. These non-linear loads may cause poor power factor and high degree of harmonics. Installation of an AF(active filter) can be one of the solutions to mitigate the line distortion, but it requires additional costs. On the other hand, many PV systems have been interconnected to the distribution system. So, the PV system combined with the function of the active filter system can be useful for the application in the power distribution system. In this paper, PV-AF system using DSP (Digital Signal Processing) controller confirmed that it is possible to combine the AF theory to the three phase PV system connected to the utility under various irradiation conditions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.714-716
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• 2004

Owing to the environmental problems as well as increasing energy prices and power plant construction costs, many researches have been made for the safe operation of distributed generations. In order to be more popularly used in parallel with the distribution network, the distributed generation and its correlation with the power system should be exactly monitored at any time. This paper presents a monitoring system which displays the important states of the distributed generation in operation and stores various measurements of the system. The proposed system constructs a data-base for developing algorithms against any faults of the interconnected system, and monitors efficiently at any place with the communication network function.

• 한국초전도ㆍ저온공학회논문지
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• 제15권4호
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• pp.6-9
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• 2013

Korea Superconducting Tokamak Advanced Research (KSTAR) has a helium refrigeration system (HRS) with the cooling capacity of 9 kW at 4.5 K. Main cold components are composed of 300 tons of superconducting (SC) magnets, main cryostat thermal shields, and SC current feeder system. The HRS comprises six gas storage tanks, a liquid nitrogen tank, the room temperature compression sector, the cold box (C/B), the 1st stage helium distribution box (DB#1), the PLC base local control system interconnected to central control tower and so on. Between HRS and cold components, there's another distribution box (DB#2) nearby the KSTAR device. The entire KSTAR device was constructed in 2007 and has been operated since 2008. This paper will present the maintenance result of the KSTAR HRS during the campaign and discuss the operation record and maintenance history of the KSTAR HRS.

• 한국농촌건축학회논문집
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• 제2권2호
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• pp.115-126
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• 2000

Retaining walls are used to prevent excessive movement of retained soils. Typical retaining walls include gravity, reinforced concrete, reinforced earth and tie-back. However, from a practical viewpoint there are still drawbacks among these often constructed retaining walls. New types of retaining walls constructed with precast concrete blocks are proposed. This type of retaining wall is incorporates each blocks interconnected with adjacent block by connecting unit to build up a flexible retaining-wall system. This paper focus to behavior characteristics includes deformation and distribution of lateral earth pressure by loading tests and FEM analysis. For model tests, a 1/10 scale reduce models are manufactured include unevenness part, drainage hole and connecting unit and steel wire used to connect each blocks with adjacent block. To simulate the real retaining walls closely, uneven parts are interconnected each other and the construction type of blocks and wall front inclination are varied to investigate the relative displacement of individual block and the location of maximum deformation of wall as increasing surcharging. Additionally, PENTAGON3D, which solve the geotechnical and other problem, used for verifying and comparing with model tests.

• 조명전기설비학회논문지
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• 제24권6호
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• pp.147-153
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• 2010

소규모 풍력 및 태양광설비가 기존의 배전계통에 연계되어 전압변동, 역률, 주파수, 고조파, 플리커 등의 전원품질 요소에 영향을 줄 것으로 우려하고 있다. 따라서 본 연구에서는 풍력발전설비(AC 링크방식)가 연계된 배전계통의 전력품질에 어떠한 영향을 줄 수 있는지에 대한 조사를 위하여 현재 운영 중에 있는 풍력발전설비의 전력변환장치 앞과 배전선로측 수용가 전원설비 2차측에 각각 전력품질 분석 장치를 설치하여 실측하고 풍력발전기가 가동과 정지 상태에서 배전선로측에 어떠한 영향을 주는지에 대하여 분석하였다. 분석결과 발전기가 가동 및 정지 시 전압변동이 0.34[%] 상승, 전류파형파고율 0.145 정도 상승, 위상차가 가동 중일 때 0.6[$^{\circ}$] 정도의 편차를 발생시켰다.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2245-2253
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• 2018

With the increase of electrical consumption and the unbalance of power demand and supply, power reserve rate is getting smaller and also the reliability of the power supply is getting deteriorated. Under this circumstance, the electrical energy storage (EES) System is considered as one of essential countermeasure for demand side management. This paper proposes efficient evaluation algorithms of multiple functions for EES systems, especially the secondary battery energy storage systems, in the case where they are interconnected with the power distribution systems. It is important to perform the economic evaluation for the new energy storage systems in a quantitative manner, because they are very costly right now. In this paper, the multiple functions of EES systems such as load levelling, effective utilization of power distribution systems and uninterruptible power supply are classified, and then the quantitative evaluation methods for their functions are proposed. From the case studies, it is verified that EES systems installed at distribution systems in a dispersed manner have multiple functions involved with direct and indirect benefits and also they can be expected to introduce to distribution systems with respects to economical point of view.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.712-718
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• 2013

With the development of industry and the improvement of living standards, better quality in power electric service is required more than ever before. This paper deals with the optimal algorithms for voltage regulation in the case where Distributed Storage and Generation (DSG) systems are operated in distribution systems. It is very difficult to handle the interconnection issues for proper voltage managements, because the randomness of the load variations and the irregular operation of DSG should be considered. This paper proposes the optimal on-line real time voltage regulation methods in power distribution systems interconnected with the DSG systems. In order to deliver suitable voltage to as many customers as possible, the optimal sending voltage should be decided by the effective voltage regulation method by using artificial neural networks to consider the rapid load variation and random operation characteristics of DSG systems. The simulation results from a case study show that the proposed method can be a practical tool for the voltage regulation in distribution systems including many DSG systems.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2005년도 하계학술대회
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• pp.382-387
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• 2005

There are many studies on arbitrarily divisible load scheduling problem in a distributed computing network consisting of processors interconnected through communication links. It is not efficient to arbitrarily distribute the load that comes into the system. In this paper, how to schedule in case that arbitrarily indivisible load comes into the system is studied. Also, the cases of the divisible load mixed with the indivisible load that come into network were dealt with optimal load distribution in parallel processing system by scheduling applied to linear programming.