• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.417-421
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• 1996

A new concept of 22.9kV class revenue metering system based on the optical sensing technique was designed and implemented. This paper reports on the performance of a 22.9kV class three phase optical current/voltage metering scheme and three tariff metering system. This optoelectronic system was designed and developed to advance the state of the art in revenue metering. This paper deals with the characteristics of designed optical CPT (Current and Potential Transformer) and optoelectronic demand meter. The extensive field evaluation of the developed system with the existing oil filled transformer and solid state metering pair is undertaking. Upto now the operation of the optical revenue metering system under the field condition compares favorably with the existing system.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1873-1877
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• 2010

In the high-speed EMU, the modularized traction converter produces the significant harmonic currents caused from the switching behavior of a power converter. These harmonic currents bring the interference among the traction equipment. One way to minimize the interference is to design the secondary windings of a power transformer decoupled magnetically as possible. This paper presents a magnetic field analysis on a winding disposition to clarify an impact on magnetic decoupling between secondary windings, under a limited height of a train. Two winding dispositions for a single-phase shell-type transformer are constructed and simulated by a three-dimensional finite elements method (FEM) model. Two different winding dispositions are constructed and simulated by three-dimensional FEM model using Maxwell3D.

• 전기학회논문지
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• 제57권6호
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• pp.938-943
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• 2008

Coupling capacitor voltage transformers(CCVTs) have been used in extra or ultra high voltage systems to obtain the standard low voltage signal for protection and measurement. For fast suppression of the phenomenon of ferroresonance, three winding CCVTs are used instead of two winding CCVTs. A tuning reactor is connected between a capacitor voltage divider and a voltage transformer to reduce the phase angle difference between the primary and secondary voltages in the steady state. Slight distortion of the secondary voltage is generated when no fault occurs. However, when a fault occurs, the secondary voltage of the CCVT has significant errors due to the transient components such as dc offset component and/or high frequency components resulting from the fault. This paper proposes an algorithm for compensating the secondary voltage of a three winding CCVT in the time domain. With the values of the measured secondary voltage of the three winding CCVT, the secondary, tertiary and primary currents and voltages are estimated; then the voltages across the capacitor and the tuning reactor are calculated and then added to the measured voltage. Test results indicate that the algorithm can successfully compensate the distorted secondary voltage of the three winding CCVT irrespective of the fault distance, the fault impedance and the fault inception angle as well as in the steady state.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 추계종합학술대회
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• pp.359-362
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• 2001

전력의 흐름제어와 전원시스템의 과도안정성 개선을 위하여 전압의 위상을 제어할 필요성이 있는 경우가 있다. 이제까지 위상 천이기는 주로 상변압기와 사이리스터 탭변환기를 사용하여 구성하였는데, 이는 응답속응성이 느리고 제어안정성이 떨어지는 단점이 있다. 본 논문에서는 PWM AC/AC 컨버터를 사용한 3상 전압 위상천이기를 제안한다. 제안된 3상 전압 위상천이기는 PWM 제어에 의하여 응답속응성이 우수하고 과도상태에서의 제어안정성을 개선시킬 수 있는 장점이 있다. 본 논문에서는 제안된 시스템의 회로구성, 동작원리와 특성 등을 설명하여 그 특징과 장단점을 나타내고, 이를 PSIM 컴퓨터 시뮬레이션을 통하여 동작과 해석의 타당성을 확인한다.

• 전력전자학회논문지
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• 제18권4호
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• pp.403-411
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• 2013

This paper proposes an isolated bidirectional three-phase push-pull dc-dc converter for high power application such as eco-friendly vehicles, renewable energy systems, energy storage systems, and solid-state transformers. The proposed converter achieves ZVS turn-on of all switches and volume of passive components is small by an effect of three-phase interleaving. The proposed converter has identical switching pattern for both boost and buck mode, and therefore can provide seamless characteristic at the mode transition. A 3kW prototype of the proposed converter has been built and tested to verify the validity of the proposed operation.

• 전력전자학회논문지
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• 제7권4호
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• pp.359-365
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• 2002

최근 상업용 빌딩, 주거용 빌딩 및 공장등의 저전압 3상 4선식 배전계통에서 PC, UPS, 정류기기, 조명장치 및 사무용기기등 비선형 부하의 사용이 증가하고 있으며, 이로 인한 과도한 중성선 전류는 중성선의 고장, 변압기의 과열 및 중성선과 접지사이의 전압강하등 심각한 문제를 야기시키고 있다. 본 논문에서는 3상 4선식 배전계통에서 중성선 전류 제거를 위한 새로운 저감된 용량의 능동전력필터를 제안한다. 제안한 방식은 제어가 간단하고 불평형에 기인하는 기본파 전류만이 인버터 스위치로 흐를 수 있기 때문에 인버터의 VA 정격이 작아진다. 제안한 시스템은 실험에 의하여 그 타당성을 입증한다.

• Journal of Power Electronics
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• 제3권3호
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• pp.151-158
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• 2003

Three-phase four-wire electrical distribution systems are widely employed in manufacturing plants, commercial and residential buildings Due to the nonlinear loads connected to the distribution system, the neutral conductor carries excessive harmonic currents even under balanced loading since the triplen harmonics in phase currents do not cancel each other This may result in wiring failure of the neutral conductor and overloading of the distribution transformer In response to these concerns, a cost-effective neutral current harmonic suppressor system has been proposed. This paper proposes an improved control method for the harmonic suppressor system under unbalanced load conditions The proposed control method compensates for only the harmonic components in the neutral conductor, and the zero-sequence fundamental component due to unbalanced loading is prevented from flowing through the harmonic suppressor system This remedies overloading and power loss of the system The experimental results on a prototype validate the proposed control approach.

• Journal of Power Electronics
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• 제14권6호
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• pp.1166-1177
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• 2014

A new type of topology with medium-frequency-transformer (MFT) isolation for medium voltage wind power generation systems is proposed in this paper. This type of converter is a high density power conversion system, with high performance features suitable for next generation wind power systems in either on-shore or off-shore applications. The proposed topology employs single-phase cascaded multi-level AC-AC converters on the grid side and three phase matrix converters on the generator side, which are interfaced by medium frequency transformers. This avoids DC-Link electrolytic capacitors and/or resonant L-C components in the power flow path thereby improving the power density and system reliability. Several configurations are given to fit different applications. The modulation and control strategy has been detailed. As two important part of the whole system, a novel single phase AC-AC converter topology with its reliable six-step switching technique and a novel symmetrical 11-segment modulation strategy for two stage matrix converter (TSMC) is proposed at the special situation of medium frequency chopping. The validity of the proposed concept has been verified by simulation results and experiment waveforms from a scaled down laboratory prototype.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1215_1216
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• 2009

Most transformer use insulating and cooling fluids derived from petroleum crude oil, but mineral oil is some possibility of environmental pollution and fire with explosion. vegetable oil fluids extracted from seed has superior biodegradation and fire-resistant properties including an exceptionally high fire point enhancing fire safety. In this study, it is aimed at the practicality of substituting natural ester dielectric fluid for mineral oil in liquid insulation system of transformers. As a rise in coil winding temperature has a direct influence on transformer life time, it is important to evaluate the temperature rise of coil winding in vegetable oil in comparison with mineral oil. Three transformers for the test are designed with 10KVA, 13.2KV, one phase unit. The temperature are directly measured in insulating oil of these transformers with the two sorts of natural ester and mineral oil dielectric fluid respectively. Temperature of vegetable oil transformers was similar to temperature of mineral oil transformer in the same design at 80% load and above.

• 한국조명전기설비학회지:조명전기설비
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• 제3권2호
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• pp.63-68
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• 1989

정지형 전원(Static Power Supply) 설계를 위한 다중 PAM 인버터에 관하여 논한다. 인버터의 제어부는 원칩 마이크로 컴퓨터(One-chip Microcomputer)로 구성하여 간단히 제어신호를 얻었고, 종단 구성은 더블 브리지 인버터와 3상 3권선 변압기로 구성하였다. 출력 파형은 제어기와 변압기를 이용하여 1주기당 22 스텝의 전압레벨로 다중 PAM파형을 합성하였으며, 저역 여파기(Low Pass Filter)에 의해 정현파에 가까운 파형을 얻었다.