• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2012년도 춘계학술논문집 2부
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• pp.512-516
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• 2012

Recently the Korean government's green energy growth policy has been taken at the national level due to the sufficient supply of renewable energy. Some specific technique should be taken in consideration for the operation of the grid voltage and power quality management. In this case, there may have some chance of operational problems. Typical problems arise when grid-connected solar power produced by Pacific sunshine. The power flow in the reverse direction can create overvoltage on the distribution line and gives value of malfunction on the system. Line voltage and overvoltage adjustment practice can stop these symptoms occurred. Under these circumstances, this paper presents an interconnection test devices for photovoltaic(PV) systems composed of distribution system simulator, PV system simulator and control and monitoring systems using the LabVIEW S/W, and simulates the customer voltage characteristics considering the 3 parameters on the introduction capacity for PV systems, system configuration and Power factor. This paper also proposes a new calculation algorithm for voltage profile to make comparison between calculation values and test device values. The results show that the simulation results for the normal operation characteristics of PV systems which are very practical and effective.

• 한국환경과학회지
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• 제15권10호
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• pp.919-928
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• 2006

The present study applied an atmospheric flow field model in Gwangyang-Bay which can predict local sea/land breezes formed in a complex terrain lot the development of a model that can predict short term concentration of air pollution. Estimated values from the conduct of the atmospheric flow field were used to evaluate and compare with observation data of the meteorological stations in Yeosu and the Yeosu airport, and the effect of micrometeorology of surround region by the coastal area reclamation was predicted by using the estimated values, Simulation results, a nighttime is appeared plainly land breezes of the Gwangyang-bay direction according to a mountain wind that formed in the Mt. of Baekwooun, Mt. of Youngchui. Land winds is formed clockwise circulation in the north, clockwise reverse direction in the south with Gangyang-bay as the center. Compared with model and observation value, Temperature is tend to appeared some highly simulation value in the night, observation value in the daytime in two sites all, but it is veil accorded generally, the pattern of one period can know very the similarity. And also, wind speed and wind direction is some appeared the error of observation value and calculation results in crossing time of the land wind and sea land, it can see that reproducibility is generally good, is very appeared the change land wind in the nighttime, the change of sea wind in the daytime. And also, according to change of the utilization coefficient of soil before and after development with Gwangyang-Bay area as the center. Temperature after development was high $0.55\sim0.67^{\circ}C$ in the 14 hoots, also was tend to appear lowly $0.10\sim0.22^{\circ}C$ in the 02 hours, the change of u, v component is comparatively tend to reduced sea wind and land wind, it is affected ascending air current and frictional power of the earth surface according to inequality heating of the generation of earth surface.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.442-442
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• 2008

Hydrogen was produced by water plasma excited in very high frequency inductively coupled tube reactor. Mass spectrometry was used to monitor gas phase species at various process conditions. Water dissociation rate depend on the process parameters such as ICP power, flow-rate and pressure. Water dissociation percent in ICP reactor decrease with increase of chamber pressure and $H_2O$ flow rate, while increase with increase of ICP power. In our experimental range, maximum water dissociation rate was 65.5% at the process conditions of 265 mTorr, 68 sccm, and 400 Watt. The effect of $CH_4$ addition to a water plasma on the hydrogen production has been studied in a VHF ICP reactor. With the addition of $CH_4$ gas, $H_2$ production increases to 12% until the $CH_4$ flow rate increases up to 15 sccm. But, with the flow rate of $CH_4$ more than 20 sccm, chamber wall was deposited with carbon film because of deficiency of oxygen in gas phase, hydrogen production rate decreased. The main roles of $CH_4$ gas are to reacts with O forming CO, CHO and $CO_2$ and releasing additional $H_2$ and furthermore to prevent reverse reaction for forming $H_2O$ from $H_2$ and $O_2$. But, $CH_4$ addition has negative effects such as cost increase and $CO_x$ emission, therefore process optimization is required.

• 전기학회논문지
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• 제65권8호
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• pp.1340-1346
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• 2016

Utilization of Distributed Generations (DGs) using Renewable Energy Sources (RESs) has been constantly increasing as they provide a lot of environmental, economic merits. In spite of these merits, some problems with respect to voltage profile, protection and its coordination system due to reverse power flow could happen. In order to analyze and solve the problems, accurate modeling of DG systems should be preceded as a fundamental research task. In this paper, we present a PhotoVoltaic (PV) generation system which consists of practical PV cells with series and parallel resistor and an inverter for interconnection with a main distribution system. The inverter is based on controllable current source which is capable of controlling power factors, active and reactive powers within a certain limit related to amount of PV generation. To verify performance of the model, a distribution system based on actual data is modeled by using ElectroMagnetic Transient Program (EMTP) software. Computer simulations according to various conditions are also performed and it is shown from simulation results that the model presented is very effective to study DG-related researches.

• 한국전자통신학회논문지
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• 제16권6호
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• pp.1183-1194
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• 2021

전통적으로 전력시스템은 공급체계의 말단에 있는 소비자의 위치에서 보면 중앙집중화된 구조를 갖고 있다. 그러나 최근 수 십년간 지붕형 태양광, 영농형 태양광, 소형 풍력터빈, 배터리저장장치 및 스마트 가전품과 같은 분산에너지원의 등장을 보아왔다. 분산에너지원의 등장에 따라 배전계통 운전원의 역할도 확장된다. 확장된 분산전원의 진출은 배전망이나 송전망의 전통적인 계획과 운영에 영향을 주는 전력계통의 역조류와 예측성을 어렵게 할 수 있다. 이는 전형적인 계통계획, 정비 및 망관리, 정전할당 등 배전계통 운전원이 갖는 기능이 변경되어야 할 필요성을 증폭시킨다. 이 연구의 목적은 다중 분산전원을 갖는 미래 배전운전시스템을 설계하고 제안된 배전시스템 모델을 HILS로 구현 및 검증하는 것이다. 시험결과를 보면 제안된 배전시스템이 정상 영역에서 운전되고 배전선로 손실이 감소된다는 것을 보여준다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.946-949
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• 2001

This paper proposes a new zero-current switching (ZCS) pulse-width modulation (PWM) switch cell that has no additional conduction loss of the main switch. In this cell, the main switch and the auxiliary switch turn on and turn off under zero current condition. The diodes commutate softly and the reverse recovery problems are alleviated. The conduction loss and the current stress of the main switch are minimized, since the resonating current for the soft switching does not flow through the main switch. Based on the proposed ZCS PWM switch cell, a new family of dc to dc PWM converters is derived. The new family of ZCS PWM converters is suitable for the high power applications employing IGBTs. Among the new family of dc to dc PWM converters, a boost converter was taken as an example and has been analyzed. Design guidelines with a design example are described and verified by experimental results from the 2.5 kW prototype boost converter operating at 40kHz.

• Corrosion Science and Technology
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• 제17권3호
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• pp.116-122
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• 2018

The secondary coolant of a nuclear power plant has small amounts of various impurities (S, Pb, and Cl, etc.) introduced during the initial construction, maintenance, and normal operation. While the concentration of impurities in the feed water is very low, the flow of the cooling water is restricted, so impurities can accumulate on the Top of Tubesheet (TTS). This environment is chemically very complicated and has a very wide range of pH from acidic to alkaline. In this study, the characteristics of the oxide and the mechanism of stress corrosion cracking (SCC) are investigated for Alloy 690 TT in alkaline solution containing Pb, Cl, and S. Reverse U-bend (RUB) specimens were used to evaluate the SCC resistance. The test solution comprises 3m NaCl + 500ppm Pb + 0.31m $Na_2SO_4$ + 0.45m NaOH. Experimental results show that Alloy 690 TT of the crevice environment containing Pb, S, and Cl has significant cracks, indicating that Alloy 690 is vulnerable to stress corrosion cracking under this environment.

• 한국유체기계학회 논문집
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• 제8권4호
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• pp.20-26
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• 2005

When the pumps are started or stopped for the operation or tripped due to the power failure, the hydraulic transients occur as a result of the sudden change in velocity. The field tests on the waterhammer were carried out for Pangyo booster pumping station in which had six booster pumps and two in-line pumps with the motor of output 1,700 kW, respectively. The booster pumping station was equipped with the pump control valve as the main surge suppression device, and the surge relief valve as auxiliary one. But the pump control valve had not early controlled in the planned closing mode, the slamming occurred to the valve of which abruptly closed during the large reverse flow. Because the positive pressure wave caused by the pump failure was superposed on the slam surge, the upsurge increased so extremely that the pump control valve was damaged. After the air chambers were additionally installed in the booster pumping station, it was preyed that the water supply system acquire the safety and reliability on the pressure surge.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.208-216
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• 2004

The waterhammer occured when the pumps are started or stopped for the operation or tripped due to the power failure, the hydraulic transients occur as a result of the sudden change in velocity. The field tests of the waterhammer were carried out for PanGyo booster pumping station. The PanGyo pumuing station was installed booster pump of 6 sets and in-line pump of 2 sets. The main surge suppression device was equipped with the pump control valve and the surge relief valve as auxiliary. However, the pump control valve had not early controlled in the planned closing mode, and the slamming occurred to the valve of which abruptly closed during the large reverse flow. Because the pressure wave caused by the pump failure was superposed on the slam surge, the upsurge increased so extremely that the shaft of the valve was damaged. After the addition surge suppression device was equipped with air chamber. Further more in-line pump is needed surge suppression device that the pumping station acquired the safety and reliability for the pressure surge.

• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.1965-1977
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• 2018

This paper proposed a regenerative braking system (RBS) strategy for battery electric vehicles (BEVs) with a hybrid energy storage system (HESS) driven by a brushless DC (BLDC) motor. In the regenerative braking mode of BEV, the BLDC motor works as a generator. Consequently, the DC-link voltage is boosted and regenerative braking energy is transferred to a battery and/or ultracapacitor (UC) using a suitable switching pattern of the three-phase inverter. The energy stored in the HESS through reverse current flow can be exploited to improve acceleration and maintain the batteries from frequent deep discharging during high power mode. In addition, the artificial neural network (ANN)-based RBS control mechanism was utilized to optimize the switching scheme of the vehicular breaking force distribution. Furthermore, constant torque braking can be regulated using a PI controller. Different simulation and experiments were implemented and carried out to verify the performance of the proposed RBS strategy. The UC/battery RBS also contributed to improved vehicle acceleration and extended range BEVs.