• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.1
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• pp.35-41
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• 2009

This paper proposes a stand alone type single-phase fuel cells micro-source with a voltage sag compensator for compensating the ac output voltage variations (sag or swell) of micro-source. The proposed micro-source is consist of a PEM(polymer electrolyte membrane) fuel cells simulator, a full bridge de converter, a 60Hz PWM(pulse width modulation) VSI(voltage source inverter), and a voltage sag compensator. Voltage sag compensator is similar to the configuration of hybrid series active power filter, and it is directly connected to micro-source through the injection transformer. Compensation algorithm of a voltage sag compensator adopts a single phase p-q theory. Effectiveness of the proposed the system is verified by the PSIM(power electronics simulation tool) simulation in the steady state and transient state which the proposed system is able to simultaneously compensate the harmonic current and source voltage sag or swell.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.36-38
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• 2005

This study is about how to lower the driving voltage that enables to move the micro droplet by the EWOD (Electro Wetting On Dielectric) mechanism. EWOD is well known that it is used ${\mu}-TAS$ digital micro fluidics system. As the device which is fabricated with dielectric layer between electrode and micro droplet is applied voltage, the hydrophobic surface is changed into the hydrophilic surface by electrical property. Therefore, EWOD induces the movement of micro droplet with reducing contact angle of micro droplet. The driving voltage was depended on the dielectric constant of dielectric layer, thus it can be reduced by increase of dielectric constant. Typically, very high voltage ($100V{\sim}$) is used to move the micro droplet. In previous study, we used $Ta_{2}O_{5}$ as the dielectric layer and driving voltage was 23V that reduced 24 percent compared with $SiO_2$. In this study, we used $BZN(Bi_{2}O_{3}ZnO-Nb_{2}O_{5})$ layer which had high dielectric constant. It was operated the just 12V. And micro droplet was moved within Is on 15V. It was reduced the voltage until 35 percents compare with $Ta_{2}O_{5}$ and 50 percents compare with $SiO_2$. The movement of micro droplet within 1s was achieved with BZN (ferroelectrics)just on 15V.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.225-231
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• 2013

Low voltage ride through capability augmentation of a hybrid micro-grid system is presented in this paper which reflects enhanced reliability in the system. The control scheme involves parallel connected multiple ac-dc bidirectional converters. When the micro-grid system is subjected to a severe voltage dip by any transient fault single power converter may not be able to provide necessary reactive power to overcome the severe voltage dip. This paper discusses the control strategy of additional power converter connected in parallel with main converter to support extra reactive power to withstand the severe voltage dip. During transient fault, when the terminal voltage crosses 90% of its pre-fault value, additional converter comes into operation. With the help of additional power converter, the micro-grid system withstands the severe voltage fulfilling the grid code requirements. This multiple converter scheme provides the micro-grid system the capability of low voltage ride through which makes the system more reliable and stable.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1328-1334
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• 2015

A new system for evaluating the voltage management errors of distribution equipment is presented in this paper. The main concept of the new system is to use real distribution live-line voltage to evaluate and correct the voltage measurement data from distribution equipment. This new approach is suitable for a new Distribution Management System (DMS) which has been developed for a distribution power system due to the connection of distributed generation growth. The data from distribution equipment that is installed at distribution lines must be accurate for the performance of the DMS. The proposed system is expected to provide a solution for voltage measurement accuracy assessment for the reliable and efficient operation of the DMS. An experimental study on actual distribution equipment verifies that this voltage measurement accuracy assessment system can assess and calibrate the voltage measurement data from distribution equipment installed at the distribution line.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.999-1002
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• 2002

In this research, the mechanism of micro-ECM was investigated with potentiodynamic method and the optimal condition for micro-ECM was selected by voltage-current-time curve with potentiostatic method. From the experimental result. it was confirmed that anodic voltage curve could be used very effectively for determining the optimal condition of micro-ECM, and the micro part which has extremely fine surface could be fabricated by use of micro-ECM with point electrode method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.9
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• pp.83-89
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• 2013

Power distribution system has been changed from radial system to closed loop or mesh system due to connection of distributed generation growth. Data from distribution equipments which are installed at distribution line is required to be accurate for the performance of DMS(Distribution Management System). This paper analyzes the voltage measurement data from distribution equipment. However, the results of the analysis are confirmed to have some errors in voltage measurement data from distribution equipment. These errors come from aging of voltage sensor in distribution equipment and inaccurate data transfer to FRTU(feeder remote terminal unit) through the controller. The main problem is that the voltage measurement data of distribution equipment can not be assessed after it's first installation at the distribution line. The voltage measurement accuracy assessment system is to assess the voltage measurement data from distribution equipment on hot-line. This study had a field test to verify the performance of system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1571-1574
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• 2005

Generally, the kerosene or the deionized water has been used for dielectric fluid in the electrical discharge machining. The spark occurs when the voltage is over the breakdown voltage and induces high temperature. In this study, the Oxygen gas is used as the dielectric. The voltage behavior in the dry Micro Electrical discharge machining is compared with that of the conventional Micro Electrical discharge machining. The dry Micro EDM has some advantages. The electrode wear isvery smaller than that of the conventional Micro EDM. The contamination in the dry Micro EDM can be drastically reduced comparing to that of the conventional Micro EDM. The Oxygen gas can be replaced as the dielectric successfully.

• New & Renewable Energy
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• v.2 no.3
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• pp.5-9
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• 2006

We have fabricated a micro power generator which changes vibrational energy into useful energy. With vibrating a magnet on the surface of a winding coil, the micro power generator produce alternating voltage. We have changed the vibrational frequency from 0.5Hz to 10Hz. AC voltage of $20{\sim}25mV$ was generated at the frequency of 1Hz. When the vibration was 3Hz, AC voltage of 80mV was obtained. We have rectified and stepped up the input voltage using a quadrupler circuit. The voltage was stepped up to 130mV.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.103-104
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• 2000

Voltage transfer curves have been used for analyzing the micro-discharge characteristics of cells in ac-PDP. This paper deals with the effect of working gas species, pressure and frequency of applied voltage on the micro-discharge characteristics. Using the mixture gases of He+Xe or He+Ne+Xe, wall voltage steeply varied compared with only He gas, and also voltage margin increased. Discharge voltage and voltage margin increased with increasing Xe percentage, and also wall voltage more steeply varied. In addition, the variation of effective wall capacitance which is significantly dependent on the discharge strength is discussed.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.137-139
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• 2003

Micro-Sources arc emerging as a providing environmentally friendly and reliable and effective solution. Micro-Source converter DC voltage of prime mover to AC voltage using voltage source inverter for interjecting with AC grid system. This paper studies optimal series inductance size for interjecting with AC grid system.