• Journal of Power Electronics
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• v.15 no.5
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• pp.1305-1317
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• 2015

Distributed generation systems (DGSs) have been getting more and more attention in terms of renewable energy use and new generation technologies in the past decades. The self-excited induction generator (SEIG) occupies an important role in the area of energy conversion due to its low cost, robustness and simple control. Unlike synchronous generators, the SEIG has to absorb capacitive reactive power from the outer device aiming to stabilize the terminal voltage at load changes. This paper presents a novel static VAR compensator (SVC) called a magnetic energy recovery switch (MERS) to serve as a voltage controller in SEIG powered DGSs. In addition, many small scale SEIGs, instead of a single large one, are applied and devoted to promote the generation efficiency. To begin with, an expandable mathematic model based on a d-q equivalent circuit is created for parallel SEIGs. The control method of the MERS is further improved with the objective of broadening its operating range and restraining current harmonics by parameter optimization. A hybrid control strategy is developed by taking both of the stand-alone and grid-connected modes into consideration. Then simulation and experiments are carried out in the case of single and double SEIG(s) generation. Finally, the measurement results verify that the proposed DGS with SVC-MERS achieves a better stability and higher feasibility. The major advantages of the mentioned variable reactive power supplier, when compared to the STATCOM, include the adoption of a small DC capacitor, line frequency switching, simple control and less loss.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.73-75
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• 2005

In present measurement of moisture contents is used as one of method for estimating degradation of transformer. Most of people use Karl-Fischer titration method for detection moisture contents but this measurement is inconvenient method because we must analyze transformer oil-paper after dismounting transformer and sampling in field. Therefore we don't directly investigate them in field. In this paper we will introduce Recovery Voltage Method(RVM) that is new method for estimating measurement in field though dismounting facility. For measure of moisture contents using RVM in accordance with accelerated thermal aging we have made experimental test cell and aged at a temperature up to 140$^{\circ}C$ for 300 hours. And we have been measured at intervals of 100 hours using RVM 5462 made in fetter company.

• Journal of Bio-Environment Control
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• v.9 no.4
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• pp.212-222
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• 2000

This study was performed to investigate the performance of heat recovery device attached to exhaust gas flue connected to combustion chamber of greenhouse heating system. The experimental heat recovery system is mainly consisted of LPG combustion chamber and two heat recovery units; unit-A is attached directly to the exhaust gas flue, and unit-B is connected with unit-A. Heat recovery performance was evaluated by estimating total energy amounts by using enthalpy difference between two measurement points together with mass flow rate of gas and/or air passing through each heat recovery unit depending on 5 different flow rates controlled by voltage meter. The results of this experimental study, such as heat exchange behavior of supply air tubes and exhaust air passages crossing the tubes, pressure drop between inlet and outlet, heat recovery performance of exchange unit, etc., will be used as fundamental data for designing optimum heat recovery device to be used for fuel saving purpose by reducing heat loss amounts mostly wasted outside of greenhouse through flue.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.79-81
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• 2005

Chemical methods for moisture contents detection of insulation system in transformer must dismount equipment for sampling, and there is shortcoming such as acquiring partial data for measuring. Also the samples can't immediately analyze in field. The Recovery Voltage Method (RVM) will be able to measure a moisture contents at low voltage without dismounting equipment. Therefore, in advanced countries RVM would be used to measure the moisture contents which permeates to the insulation system without weighting additive degradation or mechanical damage. In this paper we have investigated for overcoming these shortcomings using the RVM, and we have measured the moisture contents of transformer insulation with temperature.

• Transactions on Electrical and Electronic Materials
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• v.17 no.3
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• pp.134-138
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• 2016

The fullerene solar cells are becoming a feasible choice due to the advanced developments in donor materials and improved fabrication techniques of devices. Recently, sufficient optimization and improvements in the processing techniques like incorporation of solvent vapor annealing (SVA) with additives in solvents has become a major cause of prominent improvements in the performance of organic solar cell-based devices . On the other hand, the challenge of reduced open circuit voltage (V_oc) remains. This study presents an approach for significant performance improvement of overall device based on organic small molecular solar cells (SMSCs) by following a two step technique that comprises thermal annealing (TA) and SVA (abbreviated as SVA+TA). In case of exclusive use of SVA, reduction in V_oc can be eliminated in an effective way. The characteristics of charge carriers can be determined by the measurement of transient photo-voltage (TPV) and transient photo-current (TPC) that determines the scope for improvement in the performance of device by two step annealing. The recovery of reduced V_oc is linked with the necessary change in the dynamics of charge that lead to increased overall performance of device. Moreover, SVA and TA complement each other; therefore, two step annealing technique is an appropriate way to simultaneously improve the parameters such as V_oc, fill factor (FF), short circuit current density (J_sc) and PCE of small molecular solar cells.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.363-366
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• 1996

A FB-ZVS(Full Bridge Zero Voltage Switching) PWM DC/DC converter for electric vehicles is simulated and implemented in this paper. The converter considered is a step-down DC/DC converter with the ratings of 312/13.5V and 1.35kW. The steady state operation of this converter is divided into six operating modes in case of continuous current mode and eight operating modes in case of discontinuous current mode. Digital simulations using PSpice are carried out to verify the steady-state analysis. A prototype converter was built in the laboratory. MOSFETs were used for swithching devices and fast recovery diodes to reduce the charge storage problem of a pn-junction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.499-502
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• 2004

In order to detect of insulation problems an early, transformer has to be performed the several tests. The ac current and tan6 of transformer winding insulation were investigated by Schering bridge. Partial discharge(PD) tests are used to evaluate the insulation condition of transformer. The moisture content measurement was conducted using RVM(recovery voltage meter). The RVM test can show that the problem is affecting the paper insulation of transformer. The value of moisture content was 2.3% in main transformer. The insulations of four transformers were judged to be in good condition.

• Journal of Sensor Science and Technology
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• v.9 no.3
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• pp.203-207
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• 2000

The sensitivity of ISFET glucose sensor is improved by employing amperometric actuation method. However, this method takes long time to recover the primary output voltage after measurement because of slow migration of the hydrogen ion between internal and external sensing membranes. Consequently, such a recovery-time delaying problem is one of obstacles to a practical use. In this paper, a new method is proposed to control the concentration of hydrogen ion in internal membrane, which applies a reduction potential to the working electrode for supplying hydroxide ion. Experimental results show that the recovery-time was reduced within 2 minute against decades minute of conventional method.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.2
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• pp.39-45
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• 2004

This paper describes the design and implementation of Serial ATA physical layer and performance measurement. It is composed of tranceiver circuit that has the NRZ data stream with +/-250㎷ voltage level and 1.5Gbps data rate, transmission PLL circuit, clock ＆ data recovery circuit, serializer/deserializer circuit and OOB(Out Of Band) generation/detection circuit. We implement the verification of the silicon chip with 0.18${\mu}{\textrm}{m}$ Standard CMOS process. It can be seen that all of the blocks operate with no errors but the data transfer rate is limited to the 1.28Gbps even this should support 1.5Gbps data transfer rate.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.96-99
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• 2005

In this study, we build system and techniques of evaluating the interruption performance of the GCB with experimental method. We constructed a simplified synthetic test circuit of which ability is up to 245kV, 50kA BTF test. And We composed a model test circuit breaker with puffer assisted self blasting type GCB. With this circuit breaker, we carried out the experiment of no load and SLF90. During the tests, we measured the several factors such as stroke, pressure, arc temperature, the voltage and current near the current zero and dI/dt, dV/dt. Arc conductivity before 200ns before current zero which is one of the indexes of the thermal recovery of a GCB was measured. With these kinds of measurement, we could estimate the performance of a GCB fundamentally. Futhermore these results were used to adjust the arc modeling with CFD(computational fluid dynamics) and we could increase the plausibility of the analytical method.