• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.1159-1162
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• 1998

The induced voltage of underground pipelines caused by the stray current not only do harm to workers and instruments. but also cause big accident such as gas explosion. The AC stray current is mainly produced by the grounding system of the 22.9kV distribution power system and the DC stray current is mainly produced by the subway system. The mechanism of AC and DC induction, stray current failure examples of domestic and foreign countries and the countermeasure of the AC and DC induction are described.

• 한국초전도ㆍ저온공학회논문지
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• 제12권4호
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• pp.24-30
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• 2010

The renewable energy source is considered as a good measure to cope with the global warming problem and the fossil energy exhaustion. The construction of electric power plant such as an offshore wind farm is rapidly increasing and this trend is expected to be continued during this century. The bulky and long distance power transmission media is essential to support and promote the sustainable expansion of renewable energy source. DC power cable is generally considered as the best solution and the demand for DC electric power has been rapidly increasing. Especially, the high temperature superconducting (HTS) DC cable system begins to make a mark because of its advantages of huge power transmission capacity, low transmission loss and other environmental friendly aspects. Technical contents of DC HTS cable system are very similar to those of AC HTS cable system. However the DC HTS cable can be operated near its critical current if the heat generation is insignificant, while the operating current of AC HTS cable is generally selected at about 50~70% of the critical current because of AC loss. We chose the specifications of the cable core of 'Tres Amigas' project as an example for our study and investigated the heat generation when the DC HTS cable operated near the critical current by some electric and thermal analyses. In this paper, we listed some technical issues on the design of the DC HTS cable core and described the process of the cable core design. And the results of examination on the current capacity, heat generation, harmonic loss and current distribution properties of the DC HTS cable are introduced.

• Steel and Composite Structures
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• 제22권4호
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• pp.889-913
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• 2016

Vibration analysis of embedded functionally graded (FG)-carbon nanotubes (CNT)-reinforced piezoelectric cylindrical shell subjected to uniform and non-uniform temperature distributions are presented. The structure is subjected to an applied voltage in thickness direction which operates in control of vibration behavior of system. The CNT reinforcement is either uniformly distributed or functionally graded (FG) along the thickness direction indicated with FGV, FGO and FGX. Effective properties of nano-composite structure are estimated through Mixture low. The surrounding elastic foundation is simulated with spring and shear constants. The material properties of shell and elastic medium constants are assumed temperature-dependent. The motion equations are derived using Hamilton's principle applying first order shear deformation theory (FSDT). Based on differential cubature (DC) method, the frequency of nano-composite structure is obtained for different boundary conditions. A detailed parametric study is conducted to elucidate the influences of external applied voltage, elastic medium type, temperature distribution type, boundary conditions, volume percent and distribution type of CNT are shown on the frequency of system. In addition, the mode shapes of shell for the first and second modes are presented for different boundary conditions. Numerical results indicate that applying negative voltage yields to higher frequency. In addition, FGX distribution of CNT is better than other considered cases.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.385-386
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• 2015

This paper analyzes the vulnerable area according to the configuration of Low Voltage DC (LVDC) distribution system. For this study, the various types of system layout are considered and the simulation results are presented.

• 전기학회논문지P
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• 제55권1호
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• pp.47-53
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• 2006

A Voltage Bus Conditioner (VBC) is used to mitigate the voltage transients on a common power distribution bus. The VBC described here utilises inductive storage and unlike its counter part with capacitive storage, it can employ the entire stored energy towards transients' mitigation. The performances of adaptive duty ratio control and sliding mode control have been compared. The simulation results (with the package SABER) indicate that the sliding mode control results in the shortest and the smallest bus voltage excursions.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.158-159
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• 2012

본 논문에서는 3상 AC/DC 컨버터의 병렬 운전 시 발생하는 순환전류를 효과적으로 저감시키기 위한 제어 기법을 제안하였다. 병렬 운전 시스템에서 발생하는 순환전류는 제안 된 제어 기법에 따라 저감되고 또한 각 컨버터가 분담하는 임의의 전력량을 제어 할 수 있다. 제안 된 시스템이 갖는 응답 특성 및 정상상태 동작은 시뮬레이션을 토대로 그 타당성을 검증하였다.

• 한국철도학회논문집
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• 제7권4호
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• pp.412-417
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• 2004

In urban rail transit systems, ground faults in the DC traction power supply system are currently detected by the potential relay, 64P. Though it detects the fault it cannot identify the faulted region and therefore the faulted region could not be isolated properly. Therefore it could cause a power loss of the trains running on the healthy regions and the safety of the passengers in the trains could be affected adversely. Two new ground fault protective relay schemes that can identify the faulted region are presented in this paper. A current limiting device, called Device X, is newly introduced in both system, which enables large amount of ground fault current flow upon the positive line to ground fault. One type of the relaying schemes is called directional and differential ground fault protective relay which uses the current differential scheme in detecting the fault and uses the permissive signal from neighboring substation to identify the faulted region correctly. The other is called ground over current protective relay. It is similar to the ordinary over current relay but it measures the ground current at the device X not at the power feeding line, and it compares the current variation value to the ground current in Device X to identify the correct faulted line. Though both type of the relays have pros and cons and can identify the faulted region correctly, the ground over current protective relaying scheme has more advantages than the other.

• 해양환경안전학회지
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• 제27권7호
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• pp.1124-1128
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• 2021

선박으로부터 발생하는 배출가스에 대한 규제가 강화되고 이를 해결하기위한 대안으로 전기추진시스템의적용이 대형상선에서부터 중·소형선박에 이르기까지 그 사용이 증가되고있다. 전기추진시스템의 효율 향상을 위한 방법으로 발전원의 개선, 배터리·연료전지·태양광 등의 친환경 발전원의 시스템 연계 및 정류기, 전력변환장치, 추진전동기의 개발과 제어방식의 연구를 들 수 있다. 그 중 정류방식에 있어 상천이변압기과 다이오드를 이용하는 방식이 널리 사용되었으나, 직류배전을 이용한 친환경발전원의 계통 연계, 가변속 발전원의 사용, 중·소형 전기추진시스템의 적용을 통해 전력용 반도체 소자를 이용한 AFE정류기에 대한 수요가 증대되고 있다. 이러한 AFE 정류기를 제어하는 방식에 있어 기존의 비례적분제어기가 아닌 신경회로망을 이용한 방식을 본 연구에서는 제안하였다. 기존의 제어기 데이터를 활용하여 Matlab/Simulink를 통해 학습한 신경회로망제어기를 설계하고 PSIM을 통해 설계된 정류시스템에 신경회로망 제어기를 적용하여 부하변동에 따른 직류출력단의 파형과 역률 개선의 유효성을 확인하였다. 이는 공간이 협소한 중소형 친환경 선박의 정류시스템으로써 적용이 가능하다.

• 대한전자공학회논문지SD
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• 제44권2호
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• pp.95-103
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• 2007

동적 전압 조절(Dynamic voltage scaling, DVS) 기법은 가장 효과적이면서 가장 잘 알려진 전력 관리 기법 중 하나이다. DVS가 효율적인 여유 시간(Slack time) 분배 방법, 전압 할당 방법 등 다양한 방면에서 연구되었지만, 전압 변경 가능 프로세서 이외의 장치들에 대한 영향은 제대로 연구되지 못했다. DC-DC 변환기는 오늘날 대부분의 내장형 시스템에서 내부 장치들을 위한 다양한 값의 공급 전압 생성 및 전압 안정화 기능을 제공하는 중요한 역할을 하고 있으며, 특히 공급 전압의 계속적인 변경이 필요한 DVS를 적용하기 위해서는 필수적인 구성 요소이다. 이 논문에서는 DC-DC 변환기의 전력 소모를 포함한 시스템의 에너지 소모에 대해 분석하고 이를 바탕으로 DC-DC 변환기를 포함하는 시스템 또는 이와 유사한 형태의 에너지 소모 특성을 가지는 시스템에서 에너지 소모를 최소화하는 새로운 에너지 최적 오프라인 DVS 스케줄링 알고리즘을 제안하고, 실험 결과를 통해 제안된 알고리즘이 어떤 종류의 설정에서도 기존의 DVS 알고리즘보다 더 적은 에너지 소모의 스케줄을 생성함을 보여준다.

• 대한전기학회논문지:전력기술부문A
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• 제52권2호
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• pp.69-78
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• 2003

This paper presents a voltage analysis method of distribution systems interconnected with DG(Distributed Generation). Nowadays, small scale DG becomes to be introduced into power distribution systems. But in that case, it is difficult to properly maintain the terminal voltage of low voltage customers by using only ULTC(Under Load Tap Changer). This paper presents a voltage analysis method of distribution systems with DC for proper voltage regulation of power distribution systems with ULTC. In order to develop the voltage analysis method, distribution system modeling method and advanced loadflow method are proposed. Proposed method has been applied to a 22.9 kV practical power distribution systems.