• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.772-773
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• 2007

This study suggests a modeling of grid-connected wind power generation system that has induction generator, and aims to perform simulations for outputs by the variation of actual wind speed and for fault current of wind generation system by the transformer winding connection. This study is implemented by matlab&simulink. The simulation shall be performed by assuming single line to ground fault generated in the system. Generator power, rotor speed, terminal voltage, system voltage, and fault current shall be observed following the performance of simulation. The fault current change will be dealt through the simulation results for fault current of wind generation system following the grid-connected transformer winding connection and the simulation result by the transformer neutral ground method.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.454-457
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• 2007

This study suggests a modeling of grid-connected wind turbine generation system that has induction generator, and aims to perform simulations for outputs by the variation of actual wind speed and for fault current of wind generation system by the transformer winding connection. This study is implemented by MARTLB & SIMULINK. The simulation shall be performed by assuming single line to ground fault generated in the system Generator power, rotor speed, terminal voltage, system voltage, and fault current shall be observed following the performance of simulation. The fault current change will be dealt through the simulation results for fault current of wind generation system following the grid-connected transformer winding connection and the simulation result by the transformer neutral ground method.

• 소음진동
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• 제9권6호
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• pp.1137-1144
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• 1999

Most of ANC(active noise control) researches are focused on adaptive algorithms, computer simulations and implementations of single-channel system in experimental environments. In this paper, a multi-channel ANC system based on DSP's was developed to obtain global attenuations over wide region and applied to the active control of the humming noise generated by a transformer. The developed ANC system including 24 microphones and 12 spearkers was applied to the real transformer noise reduction problem. Results showed that the control system could successfully control the humming noise over the region of interest.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.200-202
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• 2003

In this paper, 3-D electromagnetic analysis of a single phase 1MVA 22.9kV/6.6kV High Temperature Superconducting(HTS) transformer with double pancake windings by using the OPERA 3D was accomplished. And in order to perform the analysis of leakage impedances of a 1MVA HTS transformer, the energy conservation method was used. The efficiency voltage regulation and ％ impedance voltage drop of a 1MVA HTS transformer were obtained by the analysis of leakage impedances.

• 전기학회논문지
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• 제62권7호
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• pp.1033-1037
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• 2013

Coercion transformer is commonly used in the electrical grid which in three phase of distribution system. The accident of the electrical grid is divided into a single, a double, a third line-to-ground faults and a double, a third line-to-line faults. A single line-to-ground fault accounts for nearly 75[%] among them. In this research, when a Superconducting Fault Current Limiters (SFCL) was applied to the three phase power system, operation in a single line-to-ground fault and limiting characteristics of fault current according to turns ratio of third winding were analyzed. When a single line-to-ground fault happened, secondary winding's circuit was open. Then third winding's circuit with a SFCL was closed. So fault current was limited by diverted circuit. At this time, we could find out that size of the limited fault current could be changed according to third winding rate. We confirmed that limiting operation of the fault current was carried out within one-period. These results will be utilized in adjusting the size of the SFCL.

• 한국초전도ㆍ저온공학회논문지
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• 제13권2호
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• pp.5-8
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• 2011

This paper shows results of a design work of a program that is to develop a large power single phase high temperature superconducting (HTS) transformer. The program forms a part of a national project in Korea. A target of the design work is an HTS power transformer with rated voltages of 154 kV/22.9 kV and material for windings is supposed to be coated conductor. The design results presents in this paper will include: 1)HTS winding structures for high voltage in liquid nitrogen, 2)design result of continuously transposed coated conductor (CTCC), 3)conceptual design of high voltage bushings, 4)cooling system. A feasibility study will succeed to this design work for construction of a prototype HTS power transformer with capacity/voltage of 33 MVA/154 kV.

• 한국전기전자재료학회논문지
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• 제23권10호
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• pp.798-803
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• 2010

This paper describes the characteristics of electromagnetic wave propagation in power transformer. A transformer which is similar to 154 kV single phase on-site transformer unit was provided for the purpose of the experiment. The 12 dielectric windows on the transformer enclosure to install UHF (ultra high frequency) sensors and the full scale mock ups of winding and the core were also equipped in the transformer. Every sensors to be installed to the transformer was tested and verified whether they show same characteristics or not before the experiment. A discharge gap which was used as a PD (partial discharge) source moved to several necessary locations in the transformer to simulate dielectric defects. Propagation times of electromagnetic wave signal from PD source to sensors decided by the routes of both reflection phenomenon and diffraction phenomenon were compared each other. The experimental results showed propagation route of the PD signal makes an effect on the frequency spectrum of front part of the signal and the magnitude of the signal and propagation time of the signal when the signal is captured on the sensor.

• 한국전기전자재료학회논문지
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• 제19권12호
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• pp.1099-1105
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• 2006

In this paper, the equivalent circuit model of a Rosen-type multilayer piezoelectric transformer(MPT) has been proposed based on the Mason's equivalent circuit model and the principle of single layer piezoelectric plate. From the piezoelectric direct and converse effects, the symbolic expressions between the electric inputs and outputs of the MPT have been derived from the equivalent circuit model. A simplified equivalent circuit model of the MPT whose driving part has a single input form has been proposed. The symbolic expressions of the driving part have been derived from the simplified equivalent circuit model and the model was compared with the multi-input equivalent circuit model through the simulation. In the comparisons between the simulation results and the experimental data, output voltage is 630 Vp-p in case of 11-layered MPT and 670 Vp-p for 13-layered MPT over the experiment range. As the load resistance increases, output voltage increases and saturates over $300k{\Omega}$ and the resonant frequency changes from 102 kHz to 103 kHz. The simulation and the experimental results agree well over different load resistances and frequencies.

• 전력전자학회논문지
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• 제12권2호
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• pp.139-148
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• 2007

본 논문에서는 3상 저주파 변압기를 이용한 절연형 멀티레벨 인버터를 제안한다. 제안된 인버터는 3상 절연형 변압기를 이용함으로 비절연형 멜티레벨 인버터와 달리 단일 직류 전원을 사용할 수 있는 장점이 있으며, 기존의 단상 변압기를 이용한 3상 멀티레벨 인버터에 비하여 변압기의 수를 줄일 수 있다. 또한 출력 기본주파수와 동일한 스위칭 주파수로 동작하는 스위칭 각 제어 방식을 통하여 출력 전압의 저차 고조파 성분과 스위치 손실을 줄일 수 있었다. Matlab을 이용한 시뮬레이션 및 실험을 통하여 제안된 방식의 타당성을 검증 하였다.

• 전기학회논문지
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• 제64권11호
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• pp.1543-1550
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• 2015

Ferroresonance is a non-linear vibrational phenomenon that is generated by the electrical interaction of the inductance component with the capacitor component of a certain capacitance as the device of the inductance component such as a transformer is saturated due to the degradation, the waveform distortion of current and voltage, and the oscillation of overcurrent and overvoltage in a system. Recently, ferroresonance was generated from the waveform distortion of current and voltage, or the overvoltage or undervoltage phenomenon caused by the nature of an electrical power system and design technology of the transformer in the three phase transformer system. Hence, in general, ferroresonance analyzed by converting to the LC equivalent circuit. However, in general, the aforementioned analytical method only applies to the resonance phenomenon that is generated by the interaction of the capacitance of bussbar and grounding, and switching as the capacitor component with PT and the transformer as the inductance component in a system. Subsequently, the condition where ferroresonance was generated since overvoltage was supplied as line voltage to the phase voltage and thus the iron core is saturated due to the interconnection between grounded and ungrounded systems could not be analyzed when single phase PT was connected in a ${\Delta}$/Y connection system. In this study, voltage swell in the configuration of grounded circuit of a step-up transformer with the ${\Delta}-{\Delta}$ connection linked to PT for control power and the ferroresonance generated by overvoltage when the line voltage of the ${\Delta}-{\Delta}$ connection was connected to the phase voltage of the grounded Y-Y connection were analyzed using PSCAD / EMTDC through the failure case of the transformer caused by ferroresonance in the system with the ${\Delta}-{\Delta}$/Y-Y connection, and subsequently, the preventive measure of ferroresonance was proposed.