• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.274-278
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• 2012

Vertical pumps are structurally weak in terms of vibration because of installed heavy motor on top of the pumps in form of cantilever. So high vibration on top of the pumps can occur with low vibration in the bottom. These vibration problems experienced very frequently. Majority of studies have been related to the unbalance of rotating parts or structural resonance. In this paper, we introduce an unusual case, vibration variation caused by VPF(Vane Passing Frequency) according to water level.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2370-2378
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• 2009

The enhanced phase angle estimation algorithm is essential to supply the power stably under synchronizing with grid source. In this paper, we are proposed the novel phase angle estimation algorithm and verified the validity of proposed method as simulation with PSIM and experiments. We sort the harmonics element using high-pass filter(HPF) that have the cut-off frequency below basic element and make reverse d-q transformation. So, it can be restored the harmonics element at stationary axis, and we can get the fundamental voltage element of AC grid. Proposed PLL method have a rapid responsibility and a large margin at controller design than conventional method because it have a small phase delay and a sufficient controller gain margin. And, it can reduce the error of voltage rms value and axis transformation according to robust PLL algorithm against the harmonic and phase unbalance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2072-2077
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• 2007

The primary objective of all power systems is to maintain the reliability and to minimize outage time for fault or the others. The frequency relaying algorithm perceives a variation of system frequency and thereafter detects the unbalance between generation and load. A multi-agent system is composed of multiple interacting computing elements that are known as agents. In this paper, frequency relaying algorithm is designed by multi-agent system and is implemented by EMTP-MODELS. To verify performance of the frequency relaying algorithm based on multi-agent system, simulations by EMTP have been carried out.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.541-546
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• 1998

This paper proposes a new snubber circuit for multilevel inverter and converter. The snubber circuit makes use of Undeland snubber as basic snubber unit and can be regraded as a generalized Undeland snubber. The proposed snubber keeps such good features as fewer number of components, improved efficiency due to low loss snubber, capability of clamping overvoltage across main switching devices, and no unbalance problem of blocking voltage. Furthermore, the proposed concept of constructing a snubber circuit for multilevel inverter and converter can apply to any kind of basic snubber unit such as Holtz nondissipative snubber, McMurray efficient snubber, Lauritzen lossless snubber, etc which have been utilized for two-level inveter.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.332-333
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• 2010

The 5kW SOFC(Solid Oxide Fuel Cell) System is composed to 3kW parallel Fuel Cell. We propose to the parallel control of 5kW PCS in the unbalance condition of fuel cell. The developed 5kW PCS can be found control ability of DC/DC converters in the operating conditions of the unbalanced parallel operation. It is verify to the control characteristics by simulation and experiment.

• 전기의세계
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• v.25 no.4
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• pp.68-72
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• 1976

This study is initiated to solve the problem that the development of an electric machine to drive heavy horse-power load required in the rural district, where only single phase supply is available, is very urgent. As a method for this purpose, the single/three phase converter by single phase induction machine with a tapped auxiliary winding, running unloaded mechanically under single-phase source and supplying three-phase output to a loaded 3-phase induction motor, is devised and the pilot machine is put into test. Analysis based on hybrid equivalent circuit for the phase converter and symmertical component theory for the 3-phase load motor and practical experiment result in that optimum auxiliary winding ratio is to be 1.25 rather than theoretical .root.3/2 in order to keep the voltage unbalance ratio of 3-phase output from the converter as low as possible in both cases of starting and running the load motor.

• Journal of the Korean Society of Safety
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• v.16 no.3
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• pp.45-52
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• 2001

This paper presents a study on the assessment of fuzzy measure possibility for the electromagnetic field of unbalanced system. It takes into account m untransposed transmission line and unbalanced load. A three phase load flow program was developed which employs a Newton-Raphson method as a tool to analyze system unbalanced. This research presents a method of handling two coupled three phase transmission system unbalance analysis and unbalanced power demand as a function of voltages. In assessment of fuzzy measure possibility for the electromagnetic field, this paper use probability of fuzzy and measure of fuzziness technique.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.179-181
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• 2005

PWM(Pulse Width Modulation) 컨버터에서 공급 전압의 품질은 교류 입력전류 및 직류 출력전압의 품질에 큰 영향을 미친다. 공급전압이 불평형 또는 고조파가 포함된 경우에는 평형 전원전압의 경우보다 입력 전류의고조파 및 역률 특성이 저하된다. 또한 컨버터 입력 측의 사용된 인덕턴스의 용량에 따라 입력전류의 고조파 및 역률 특성이 달라진다. 본 논문에서는 입력측 인덕턴스 값의 변화에 따른 단상 및 삼상 PWM 컨버터의 입력전류 고조파와 역률 관계를 해석하였는데, 특히 입력전압에 고조파를 포함한 경우와 불평형인 상태까지 확장하여 성능을 평가하였다. 이러한 결과를 통해 입력 인덕턴스 설계 값을 선정하는데 기준을 제시하였다.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.125-127
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• 2005

In this paper, the control algorithm of DC source device for inverter starting is proposed and the control method for compensating unbalance system source on operating time in the voltage type PWM converter with driving and regenerative faculty is suggested. The maintaining way of balancing condition for converter of AC source is used the compensating unbalanced status by current control loop. Because it is possible that the unbalanced System control is used to leakage transformer not equaled reactance by each phase in rectifier system, the proposed H/W and control algorithm of rectifier system is contributed to minimize of device and rising efficiency.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.343-344
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• 2013

본 논문에서는 바이폴라 타입 DC 마이크로그리드의 전압 불균형을 보상하기 위한 전압 밸런싱 기법과 안정도 향상을 위한 제어기법을 제안하였다. 선로 임피던스와 부하 불균형에 의한 전압 불평형 문제를 해석하고 제안하는 기법을 통해 이를 해결하였으며 과도 상태에 대한 DC 배전계통의 안정도 향상기법을 개발하였다. 제안하는 시스템의 동작 타당성을 체계적으로 분석하기 위해 PSCAD/EMTDC 소프트웨어를 이용한 시뮬레이션 모델을 개발하고 그 성능을 검증하였다.