• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.355-363
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• 2015

HVDC technology has become popular as an economic mode of bulk power transmission over very long distances. Polymeric insulators in HVDC power transmission lines are affected by surface tracking and erosion problems due to contamination deposit, which pose a greater challenge in maintaining the reliability of the HVDC system. In addition, polymeric insulators are also naturally affected by aging due to various environmental stresses, which in turn accelerates the surface tracking and erosion problems. Research works towards the improvement of tracking and erosion resistance of polymeric insulators by adding nano-sized fillers in the base material are being carried out worldwide. However, surface tracking and erosion performance of nano-filled aged polymeric insulators for HVDC applications are not well reported. Hence, in the present work, tracking and erosion resistance of the nano $Al(OH)_3$ filled silicone rubber insulation material has been evaluated under DC voltages at different filler concentrations and aged conditions, as per IEC 60587 test procedures. Leakage current and contact angle measurements were carried out to understand the surface hydrophobicity. Moving average technique was used to analyze the trend followed by leakage current. Water aged specimen shows less tracking resistance when compared with thermal aged specimen. It is observed that nano-filler concentration of 5% is even sufficient to get better tracking/erosion resistance under DC voltages.

• 한국정밀공학회지
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• 제22권10호
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• pp.218-224
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• 2005

Arthroscopy is a surgical procedure orthopedic surgeons use to visualize, diagnose and treat problems inside a joint. In usual, since the arthroscopic surgery is more accurate and minimally invasive than through 'open' surgery, the surgery of knee, shoulder, and wrist using auto-shaver is increasing in recent. However, repetitive use of arthroscopic-shaver may induce the second infection, hence the disposable arthroscopic-shaver should be developed. In this paper, a unique power transmission mechanism using DC motor, gear trains, and link mechanism is proposed for disposable arthroscopic-shaver and some test results of tissue cutting are introduced.

• 한국전자통신학회논문지
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• 제17권5호
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• pp.815-824
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• 2022

해상풍력발전과 같은 간헐성 재생에너지원의 급격한 성장은 바다를 횡단하는 장거리의 전기에너지의 변환 필요성을 증가시키고 있다. 넓고 깊은 바다에 걸쳐서 장거리 대용량 전력송전을 위한 해법중의 하나는 HVDC 해저 전력케이블을 사용하는 것이다. 그러나 교류자계가 없는 직류전력 케이블의 다양한 해양조건을 갖는 연속허용전류와 관련한 표준이나 연구가 없다. 본 연구에서는 대표적인 두 종류의 해저케이블 모델과 남해안과 서해안 두 지역의 해양 요건을 가정하여 직류케이블의 연속허용전류를 모의하였다. 모의 결과를 보면 직류케이블의 연속허용전류는 해저 지반 깊이에 기반한 감소 구배 특성을 갖고 있는 것을 확인하였다.

• 한국산업융합학회 논문집
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• 제23권1호
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• pp.65-71
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• 2020

Recently, interest in the DC transmission is rapidly increasing worldwide. In many countries and leading companies are prior to the aggressive development of HVDC technology and application. Especially, VSC-HVDC system has been widely applied to transfer power at long distance between power plant and power consumption area. Therefore in this paper, we analyzed the benefit-cost of VSC-HVDC system which has more advantages than existing transmission system. The proposed system is MMC(Modular Multilevel Converter) VSC-HVDC system that have stability of Power Grid, interconnect Large-scale New Power Generation Plants by prevents Blackout. And MMC VSC-HVDC system Reduced the loss importing foreign systems. And the benefits were calculated in four stages, and the costs were applied to the actual project. By evaluating the various avoidance costs compared to the benefit-cost, it was confirmed that MMC VSC-HVDC system was advantageous in system stability and economic and social benefits.

• 한국산업융합학회 논문집
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• 제24권4_1호
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• pp.377-385
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• 2021

High voltage direct current(HVDC) systems has been an alternative method of a power transmission to replace high voltage alternate current(HVAC), which is a traditional AC transmission method. Due to technical limitations, Line commutate converter HVDC(LCC-HVDC) was mainly used. However, result from many structural problems of LCC-HVDC, the voltage source converter HVDC(VSC-HVDC) are studied and applied recently. In this paper, after analyzing the reactive power and output voltage ripple, which are the main problems of LCC-HVDC, the characteristics of each HVDC are summarized. Based on this result, a new LCC-HVDC structure is proposed by combining LCC-HVDC with the MMC structure, which is a representative VSC-HVDC topology. The proposed structure generates lower reactive power than the conventional method, and greatly reduces the 12th harmonic, a major component of output voltage ripple. In addition, it can be easily applied to the already installed LCC-HVDC. When the proposed method is applied, the control of the reactive power compensator becomes unnecessary, and there is an advantage that the cut-off frequency of the output DC filter can be designed smaller. The validity of the proposed LCC-HVDC is verified through simulation and experiments.

• 한국전기전자재료학회논문지
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• 제21권11호
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• pp.977-980
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• 2008

We investigated the effects of power ratio on the electrical and optical properties of Au based Ga-, B- codoped ZnO(GZOB) thin films. GZOB thin films were deposited on Au based poly carbonate(PC) substrate with various power in the range from 60 to 120 W by DC magnetron sputtering. In the result, GZOB films at 100 W exhibited a low resistivity value of $1.12\times10^{-3}\Omega-cm$, and a visible transmission of 80 % with a thickness of 300 nm. This result indicated that the addition of Ga and B in ZnO films leads to the improvement of conductivity and transparent. From the result, we can confirm the possibility of the application as transparent conductive electrodes.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권6호
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• pp.267-272
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• 2002

This Paper deals with the short circuit tests of the three-Phase DC reactor type fault current limiter (FCL) in changing of turns ratio of transformers. The experiment of this paper is a preliminary step to develop the FCL's faculties for an application to high voltage transmission line. So, superconducting coil was made of Nb-Ti, low temperature superconductor, and the ratings of the power system of experimental circuit are 400V/7A class. A three-phase DC reactor type FCL consists of three transformers, six diodes, one superconducting coil and one cryostat. The important point of experimental analysis is transient period, the operating lagging time of circuit breaker. As the results of the experiment, the values are referred to the limitation rate about 77% and 90% when the turns ratio of transformer was 1:1 and 2:1 respectively.

• 한국표면공학회지
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• 제32권3호
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• pp.467-471
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• 1999

BN films were grown on silicon (l00) substrate by magnetically enhanced activated reactive evaporation (ME-ARE) with pulsed DC power instead of r.f. for substrate biasing. The deposited films were analyzed using Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). FTIR results show that the intensity of absorption band of $sp^2$ bond of BN decreased and that of $sp^3$ bond of c-BN increased with increasing pulsed DC bias voltage applied to substrate. The initially grown layer at the interface was observed by TEM and considered to be of$ sp^2$-bonded BN. The cross-sectional and planar TEM micrographs show that the upper layer on the initial layer was the single phase c-BN. It is concluded that cubic boron nitride films could be synthesized by ME-ARE process with pulsed DC biasing.

• 전력전자학회논문지
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• 제8권3호
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• pp.274-284
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• 2003

대용량 전력변환기기인 멀티-레벨 컨버터는 전동기구동시스템 및 유연송전시스템 등에 널리 사용되고 있다. 이중 H-Bridge 컨버터는 캐스캐이드 형태를 사용하여 멀티-레벨로의 확장이 용이한 장점으로 인해 shunt형 기기로 점차 응용이 확대되고 있다. 정상 상태에서 대략 0.7∼0.8의 변조지수 범위에서 작동한다. 고변조지수에서는 부스트 벡터인 zero vector가 인가되지 않아도 DC-link 전압은 일정하게 유지된다. 이것은 3-레벨 컨버터의 여러 벡터 중 zero vector 이외에도 또 다른 boost vector가 존재한다는 것을 의미한다. 본 논문은 boost vector의 원리를 살펴보고 3레벨 컨버터에서 zero vector와 또 다른 boost vector와의 차이점을 고찰하였다. 또한 본 논문은 두 토폴로지의 충전 전류와 커패시터 전압을 해석하고 비교한다 이 전압과 전류는 스위칭 상태와 기준전압과 관련되어 있고 이것을 이용하여 각 커패시터의 충전전류와 전압리플에 대한 계산 방법을 제안하였고 다양한 DC-Link 전압제어 방법을 시뮬레이션을 통해 비교하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1648-1649
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• 2011

본 논문에서는 무선 전력 전송을 위한 10W RF Power Source를 설계 및 제작, 측정 하였다. 제작된 RF Power Source는 9~11MHz의 신호 생성을 위한 DDS와 전력 증폭을 위한 전력 증폭기로 구성되어 있다. 근거리 무선 전력 전송은 전자기 유도 또는 전자기 공진 형태의 무선으로 전력을 전달하게 되므로 전력 증폭기의 부하단의 임피던스가 변하게 되어 전력 증폭기의 특성의 변화가 생기는 단점을 가지고 있다. 이러한 단점을 극복하기 위해 본 논문에서는 부하단의 임피던스 변화에 둔감하도록 평형(Balanced)구조를 이용하여 전력 증폭기를 설계하였다. 제작된 RF Power Source는 입력 전원 DC 24V, 소모 전류 1.5A, 사용가능 주파수범위는 9~11MHz, 최대 출력 전력 10W의 특성을 보였다.