• 전력전자학회논문지
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• 제22권1호
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• pp.82-88
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• 2017

This study proposes a new topology for the performance test of a valve consisting of a modular multilevel converter (MMC)-based static synchronous compensator (STATCOM). The conventional valve performance test equipment requires high-voltage AC source of several kV rating because the number of submodules to be tested in a valve should be at least six or eight. However, the power source of the proposed scheme is DC and not AC source. The DC power source voltage range of the proposed test circuit is from several volts to several tens of volts. Therefore, the size and cost for the performance test equipment can be reduced considerably compared with the conventional method. The proposed scheme satisfies the requirements of the IEC 62927 standard. Simulations are conducted for a valve of 50[MVA] MMC-based STATCOM. Experimental results with a scale-downed setup show the validity of the proposed performance test topology.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.473-474
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• 2016

최근 신재생에너지의 보급 정책으로 인해 태양광 또는 풍력과 같은 신재생에너지가 전체 전력 계통에서 차지하는 비율이 증가되고 있는 실정이다. 그러나 신재생에너지는 변동 적이기 때문에 계통의 안정성을 저해하는 원인이 될 수 있다. 이에 따라 각 나라에서는 계통 안정성을 위한 기능들을 요구하고 있으며, 그 요구는 점차 강화되고 있다. 이와 같이 신재생에너지 비율의 증가로 인해 계통 안정성에 대한 문제가 강조되고 있지만, 태양광 분산 발전 시스템의 경우에는 일사량에 의존하여 운전하기 때문에 일사량이 낮거나 야간에는 계통 안정성을 위한 기능을 수행하지 못하는 단점이 있다. 본 논문에서는 일사량이 낮거나 야간에도 계통 안정화를 위해 무효전력 지원이 가능한 확장된 무효전력 운전(EF-RPO: Extended feed-in Reactive Power Operation)방법의 제어 전략을 제안하며, 제안한 방식은 1MVA 계통 연계형 인버터의 제작과 실험을 통해 검증하였다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 추계학술대회 논문집
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• pp.225-229
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• 2007

The output voltage of a synchronous generator is regulated constantly by field current control of excitation system. Synchronous generator exciter has two type, first one is Drop control type by thyristor and second one is exciter current control type through power output by PWM control. Control method of the second one prevails, but when the power devices have a breakdown, output voltage of the generator rises rapidly. This exciter must have a protection circuit and system is complicated, so reliability is poor Excitation control type which is drop control type control only 10% of the power, so it can be improved precision. When a trouble come to the controller, output voltage of a generator don't rise excessively and the voltage rise about 10%, so it has a excellent reliability. This paper prove stability of the digital AVR.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.1974-1977
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• 1997

오늘날 철강 냉간압연의 응용분야에서는 고성능의 장력제어와 높은 신뢰도, 역률 개선, 공장의 생산성 향상 등을 요구하고 있다. 기존의 직류전동기를 대체하는 가변속 교류전동기 구동시스템과 고주파 PWM, 그리고 높은 역률을 보장하는 PWM 컨버터에 의해 이러한 요구사항들은 만족될 수 있다. 이 논문에서는 위에서 언급된 제어요건을 보장하는 철강 생산 설비용 1MVA급 압연시스템을 설명한다. 본 시스템은 하나의 ac/dc PWM 컨버터와 각각 700kw 유도전동기를 구동하는 두대의 PWM 인버터로 구성되어 있다. 제어 알고리듬은 TMS320C40 디지탈 신호처리 프로세서(이하 DSP) 시스템을 이용하여 구현하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.107-110
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• 2003

High Temperature Superconductor (HTS) transmission cable can carry more than 2 to 5 times higher electricity and also obtain substantially lower transmission losses than conventional cables. Liquid nitrogen is to be used to cool the HTS power cable and its cost is much cheaper than the liquid helium used for the cooling of metal superconducting wire. In Korea the HTS power cable development project has been ongoing since July, 2001 with the basic specifications of 22.9kV, 50MVA and told dielectric type as the first 3-year stage. The cryogenic system of the HTS cable is composed of HTS cable cryostat termination and refrigeration system. Termination of HTS cable is a connecting part between copper electrical cable at room temperature and HTS cable at liquid nitrogen temperature. In order to design the termination cryostat, it is required that the conduction heat leak and Joule heating on the current lead be reduced, the cryostat be insulated electrically and good vacuum insulation be maintained during long time operation. Heat loads calculations on the copper current lead have been performed by analytical and numerical method and the feasibility study fer the other candidate materials has also been executed.

• 한국산업융합학회 논문집
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• 제14권3호
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• pp.121-125
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• 2011

EMTP-RV is the very powerful program to analyze the dynamic operation of the power system. To use this package in the large complex power system, it is very important to simplify the power system to simple equivalent network. In our study the 100 MVA STATCOM is placed at 345kV "MIGUM" which is the one of the 345kV substations of the Korean Electric Power System that is consist of more than 1000-bus. MIGUM substation is connected with 7 separated transmission lines to main Korean Electric power system. We developed a new method to simplify the network except the substation that we want to analysis. The power system outside the 345kV substation is modeled into the equivalent network. The loop network outside the substation can be modeled to simplified Thevenin equivalent network. The proposed method is applied to IEEE-14 Reliability Test System and the results shows the effectiveness of the method.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2000년도 추계학술대회 및 정기총회
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• pp.113-116
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• 2000

The purpose of this study is to present a method for determining the k most vital arcs in shortest path problem using an evolutionary algorithm. The problem of finding the k most vital arcs in shortest path problem is to find a set of k arcs whose simultaneous removal from the network causes the greatest increase in the total length of shortest path. The problem determining the k most vital arcs in shortest path problem has known as NP-hard. Therefore, in order to deal with the problem of real world the heuristic algorithm is needed. In this study we propose to the method of finding the k-MVA in shortest path problem using an evolutionary algorithm which known as the most efficient algorithm among heuristics. For this, the expression method of individuals compatible with the characteristics of shortest path problem, the parameter values of constitution gene, size of the initial population, crossover rate and mutation rate etc. are specified and then the effective genetic algorithm will be proposed. The method presented in this study is developed using the library of the evolutionary algorithm framework (EAF) and then the performance of algorithm is analyzed through the computer experiment.

• 전기학회논문지P
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• 제64권4호
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• pp.256-260
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• 2015

In this paper, achieved rise temperature distribution about degradation phenomenon of 24 MVA distribution cast resin transformer using CFD(Computational Fluid Dynamics). Usually, life of transformer is depended on temperature distribution of specification region than thermal special quality of transformer interior. Specially, life of transformer by decline of dielectric strength decreases rapidly in case rise by strangeness transformer interior hot spot temperature value permits. Because calculating high-voltage(HV) winding and low-voltage(LV) winding of cast resin transformer and Joule's loss of core for improvement these life, forecasted heat source, and HV winding and LV winding of cast transformer rise temperature distribution of core for supply of electric power and temperature distribution of highest point on the basis of the results. Also, calculated temperature rise limit of cast resin transformer and permission maximum temperature using analysis by electromagnetic heat source. Calculated and forecasted rise temperature distribution by heat source of thermal analysis with calculated result.

• 전기학회논문지
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• 제66권9호
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• pp.1334-1340
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• 2017

In this paper, a tie-plate shape is optimized by using the numerical technique to reduce the stray load loss of the tie-plate which is a mechanical structure for assembling and supporting of the transformer core. The eddy current loss of the structure is calculated by an electromagnetic field FEM program and the results are compared with 4 different shapes of tie-plates. Since the thickness of the tie-plate is very thin, and the skin depth is very small, the number of FE elements for 3-D transformer model is too big to solve. So, the surface impedance boundary condition (SIBC) is used to reduce the system matrix size and its computing time. To verify the method a 2.5 MVA 22,900/380V distribution transformer is simulated using one objective function and three design variables with some constraints. The final optimized tie-plate has three slots of 6 mm width and 23 mm gap, and the loss is reduced by 75 %. Consequently, the proposed algorithm seems to be considerably applicable to electric machinery as well as power transformer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.499-500
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• 2011

국내전력수요의 지속적인 성장과 더불어 전력산업의 대용량화, 고밀도화에 따른 친환경 고신뢰도의 전력계통 구성을 위하여 친환경 녹색기술의 초전도케이블이 실증시험을 통한 실계통 적용 사업이 이천변전소에서 정부지원으로 한전전력공사 주관으로 진행되고 있다. 그래서 향후 초전도 케이블이 실계통에 연계한 계통이 운용되는 것을 고려해야 하기 때문에 기존 전력기기와 협조하여 운영되기 위해서는 계통영향 분석이 필요하다. 특히 초전도케이블은 초전도성이라는 물리적인 특성 때문에 기존 계통해석과정과는 다른 계통 과도현상의 모델링이 필요하다. 따라서 본 논문에서는 초전도케이블의 실계통 적용을 위해서 이천변전소에 시범 적용된 22.9kV 50MVA 500m 초전도케이블 계통을 대상으로 열적특성을 분석하고 안정적인 대규모 전력전송을 위해서 초전도 케이블을 열적특성으로부터 보호하기 위한 열동계전기(Thermal Protection Relay)의 운영방법과 적용방안을 소개하고자 한다. 향후 대용량 초전도케이블의 실계통 적용 확대를 고려한 열동계전기의 운영방법과 적용방안도 제시하고자 한다.