• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1370-1376
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• 2015

Generally, an autotransformer(AT) feeding system consists of double tracks, up and down, with the trolley wire and feeder wire of the up and down tracks connected in the sectioning post(SP). Consequently, load current or fault current flows on two tracks based on catenary impedance characteristics, making it difficult to estimate catenary impedance accurately. This paper presents a technique for the estimation of catenary impedance using boosting current compensation based on the current division characteristics of an AT feeding system to improve the operation performance of impedance relay. To verify the technique, we model an AT feeding system through a power analysis program (PSCAD/EMTDC) and simulate various operation and fault conditions. Through the simulation, we confirmed that the proposed technique has estimated catenary impedance with a similar degree of accuracy to the actual catenary impedance

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.506-507
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• 2008

소규모 풍력에너지, 연료전지 및 태양에너지 등의 신 재생에너지원들이 소규모 분산전원으로 도입되고 있다. 이로 인해, 수용가 측의 전원이 대규모 전력사업자로부터만 공급받던 시스템방식에서, 분산전원과 연계하여 동시에 사용하는 방식으로 바뀌고 있다. 이러한 분산전원이 계통에 도입될 경우 이로 인해 평상시 기존 계통의 보호방식에 미치는 영향의 경우는 상시전압변동, Flicker, 병해열로 인한 순시전압변동, 고조파, 불평형 등이 고려 될 수 있다. 또한 이러한 경우로 인해 보호계전기의 오동작도 초래 할 수 있다. 이에 본 논문에서는 태양광시스템을 분산전원으로 하는 연계 계통을 모델링하여 발생하는 파형에 대해 분석한다. 또한 디지털 보호계전기의 디지털 필터링 기법을 비교하여 빠른 연산 속도와 주파수 응답 특성을 가지는 알고리즘을 선정하고 모델링하여 모델링 된 디지털 필터로 분산전원 연계를 통해 얻어진 파형을 필터링 한다. 본 논문에서 분산전원의 계통 모의는 전력계통에 모의에 높은 신뢰성을 가지는 PSCAD/EMTDC를 기반으로 하였으며, 디지털 보호계전기의 디지털 필터 알고리즘 모델링은 MATLAB을 사용하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.2251-2252
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• 2008

Recently, voltage sag from sudden increasing loads is also one of the major problems inside the utility network. In order to compensate the voltage sag problem, power compensation device systems could be a good solution method. In case of voltage sag, an energy source is needed to overcome the energy loss caused by the voltage sag. Superconducting Magnetic Energy Storage (SMES) is a very promising source of this energy due to its fast response of charging and discharging time. Before constructing the power electronic delivering system for the SMES, it is necessary to simulate the system to understand its behavior. Nowadays, a lot of devices have been developed to compensate voltage sag such as Dynamic Voltage Restorer (DVR), Distribution Static Compensator (D-STATCOM) and Uninterruptible Power Supply (UPS). In this paper, focus is given only on DVR system which will be simulated by using PSCAD/EMTDC software.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1077-1078
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• 2008

The growing number of nonlinear loads such as static power converters has posed a problem on the quality of electric power supply. The active filters (AF) have been rapidly expanding with the advancement of power electronics technology. The purpose of the active filters is to compensate current harmonics and/or current imbalance. The authors have studied and introduced the PV-AF system; the PV power system, which is used widely as a dispersed source, including the function of active filter to compensate the harmonics caused by nonlinear loads. The PV-AF system has merits not only to compensate harmonics caused by nonlinear loads but also to increase the utilization of PCS. This paper describes the grid-connected single phase PV-AF system and the PSCAD/EMTDC simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1081-1082
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• 2008

Photovoltaic (PV) power generation system has been widely studied as a clean and renewable power source. The purpose of this study is to keep the output power of photovoltaic cells maximum under any weather conditions. There are so many MPPT (Maximum Power Point Tracking) methods. P&O method has been used as a key MPPT method, both voltage and current coming out from PV array have to be feedback in the method. Thus, the system has a complex structure, and may fail to track MPP of PV array when unexpected weather conditions happen. In order to reduce the feedback components, POS MPPT control method was proposed by the authors. In this paper, the authors apply the POS MPPT control method to three phase PCS system. And the effectiveness of the proposed control scheme is demonstrated through PSCAD/EMTDC simulation.

• 전기학회논문지
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• 제63권12호
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• pp.1640-1648
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• 2014

This paper proposes a switching frequency reduction method for MMC (Modular Multilevel Converter) utilizing redundancy operation of sub-module, which can offer reduction of voltage harmonics and switching loss. The feasibility of proposed method was verified through computer simulations with PSCAD/EMTDC software. Based on simulation analysis, a hardware scaled-model of 10kVA, DC-1000V MMC was designed and manufactured in the lab. Various experiments were conducted to verify the feasibility of proposed method in the actual hardware system. The hardware scaled-model can be effectively utilized for analyzing the performance of MMC according to the modulation scheme and redundancy operation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.191-192
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• 2015

국내 배전계통은 일반적으로 수지상 계통으로 운영하고 있으며 배전선로 내 과부하 해소 및 배전계통의 유지보수를 위해 상시 개방점과 구분 개폐기를 통해 루프계통으로 운전하는 경우가 있다. 이 과정은 신속한 고장 구간 분리 및 무정전 절체를 위해 루프계통 운전 시 흐르는 루프조류 등을 정확히 고려하여 판단해야 한다. 특히 배전계통 내에 에너지저장장치(Energy Storage System, ESS) 등의 분산전원이 다수 도입된 이후로, 배전계통이 기존의 단방향에서 양방향 전력공급의 특징을 갖게 됨으로 인해 기존의 루프계통 운전에 대한 판단에 추가적인 과정을 필요하게 된다. 따라서 본 논문은 배전계통 내 에너지저장장치가 연계된 경우, 루프계통 운전을 위한 에너지저장장치의 출력변동에 대한 판단을 PSCAD/EMTDC로 모델링하여 수행한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.247-248
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• 2015

Wind turbines causes instabilities on the grid as their penetration increase. To mitigate harmful effects from wind turbines, transmission system operator(TSO) set up some requirements to obligate for wind generation operator for grid connection. So wind farm management system(WFMS) has important role to follow requirement from TSO, WFMS calculates available real power by considering wake effects, and dispatches real power order to each wind turbine in wind farm to optimize for decreasing load fatigue. To verify operation of WFMS, real-time simulator(RTS) is necessary. This paper deals with RTS configuration to verify WFMS operation. RTS includes wind farm model and power flow code. Normally, wind farm equivalent simple model makes wind turbines in wind farm to one wind turbine mode which cannot verify power flow in wind farm and WFMS operation. Thus, this paper makes wind farm model using simple wind turbine model with transfer function. Matlab is used for make power flow code and wind farm model to impose RTS and those model is certified by PSCAD/EMTDC.

• 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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• 제18권3호
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• pp.114-119
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• 2004

차량이라는 특수한 장소에 적용되는 산소 발생 장치는 소형/경량화 및 소음, 충격, 발열에 대한 문제점을 무시할 수 없다. 이러한 문제점을 해결할 방법으로 BLDC를 이용하여 모터의 발열을 줄이고 합성 제올라이트 NaX형을 사용한 베드로 소형에서도 고농도의 산소를 발생시킬 수 있게 하였다. 또한, 합성 제올라이트 NaX형의 특성으로 인한 질소의 강제 탈착을 진공펌프 한 대로 사용하기 위하여 Two Head 진공펌프 Pump Type을 개발하여 소비 전력을 줄이고 소형/경량화 및 저소음, 충격/발열 문제를 해결할 수 있었다.