• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.189-192
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• 2001

This paper proposed that an AC-DC converter system using multiple buck-chopper operates with four choppers connecting to a number of parallel circuits. To improve these, a large number of soft switching topologies included a resonant circuit have been proposed. And, some simulative results on computer are included to confirm the validity of the analytical results. The partial resonant circuit makes use of an inductor using step-down and a condenser of loss-less snubber. The result is that the switching loss is very low and the efficiency of system is high. And the snubber condenser used in a partial resonant circuit makes charging energy regenerated at input power source for resonant operation. The proposed conversion system is deemed the most suitable for high power applications where the power switching devices are used.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.673-676
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• 2001

The photovoltaic power generation system has a great future as clean energy instead of fossil fuel, which has many environmental problems such as exhausted gas or air pollution. In a utility interactive photovoltaic generation system, a three phase inverter is used for the connection between the photovoltaic array and the utility. This paper presents a three phase inverter for photovoltaic power system with current controller, voltage controller, PLL control system and the phase detector of interactive voltage by using dq transformation. The proposed inverter system provides a sinusoidal ac current for domestic loads and the utility line with unity power factor.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.117-122
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• 2005

This paper proposes an inverter for the grid-connected photovoltaic system based on the transformer-less inverter. This system consists of a high frequency converter bridge, high frequency transformer, diode bridge rectifiers, a DC filter, a low frequency inverter bridge, and an AC filter. The high frequency converter bridge switching at 20kHz is used to generate bipolar PWM pulse, and the high frequency transformer raise its voltage twice, which is subsequently rectified by diode bridge rectifiers to result in a full-wave rectified sine wave. Finally, it is unfolded by a low frequency inverter bridge to result in a 60Hz sine wave power output. Even though the high frequency link system needs more power semiconductors, a reduced size, light weight, and saved parts cost make this system more comparative than the other systems due to elimination of 60Hz transformer.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 제17회 워크샵 및 추계학술대회
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• pp.677-679
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• 2005

최근 나노입자를 이용하는 광전 화학전지(PEC, Photoelectrochemical)인 염료감응형 태양전지(DSC)의 효율이 증가함에 따라 DSC 태양광 발전 시스템의 성능 개선 또한 요구되어진다. 본 연구에서는 Fly-Back DC-DC 컨버터(변화비율1:10)를 이용하여 DSC셀의 전압을 DC 300V로 승압시켰다. 또한 풀브릿지 인버터를 사용하여 AC 220V, 60Hz의 출력전압을 얻었다. 연구에서 제안한 회로는 높은 효율의 동작특성과 간단한 제작, 낮은 제조비용, 그리고 안정성을 추구한다. 또 다른 주요점은 부하단에서 Feed back을 받아 동작을 컨트롤하는 것이다. 부하단의 출력 전압과 전류를 Feed back 받아서 DSP320LF2406을 A/D기능을 사용하여 실시간으로 부하의 변화에 대처하여 컨버터와 인버터의 동작을 제어한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1312-1313
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• 2011

IT 산업의 발전에 따른 디지털 부하 증가는 기존 교류 배전 방식에서 DC 전원 공급에 따른 전력 변환 손실을 야기시킨다. 또한, 향후 신재생에너지를 통한 발전원 및 전기자동차의 계통 유입 확대로 인해 AC/DC 전력 변환에 따른 손실은 더욱 증대될 것으로 예상된다. 이에 본 논문에서는 DC 전원 공급율에 따른 전력 공급량 산정 기법을 제안한다. 또한, 탄소배출 비용을 함께 고려하여 DC 전원 공급율에 따른 신재생에너지 계통 연계의 경제적 타당성을 분석한다.

• The Korean Journal of Ceramics
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• 제7권1호
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• pp.6-10
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• 2001

Ultrafine $(CeO_2)_{0.9}(Gd_2O_3)_{0.1}$ solid solution powders synthesized by the glycine-nitrate process, with specific surface areas of $19-23\;\textrm{m}^2$/g were sintered at $1500^{\circ}C$ for various sintering times and then their electrical characteristics were investigated using AC impedance and four-point probe measurements. The electrical resistivity of the sintered $(CeO_2)_{0.9}(Gd_2O_3)_{0.1}$ bodies showed the minimum value at the sintering time of 10 hrs. The minimum total resistivity of the $(CeO_2)_{0.9}(Gd_2O_3)_{0.1}$ bodies sintered at $1500^{\circ}C$ for 10 hrs seems to result from the lowest activation energy for the electrical resistivity by the combination between the activation energies for the resistivities at the grain interior and grain boundary.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.432-434
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• 1994

This paper describes a phase-shifter which can flexibly adjust the active and reactive power flow through an ac transmission line. The phase-shifter has two voltage-source converters sharing an energy storage capacitor. The magnitude of the injected voltage is controlled by the converter I connected in parallel with the sending terminal, while that of phase angle by the converter II in series with the line through the coupling transformer. In order to analyze the whole system operation, an equivalent circuit model was developed and verified by a computer simulation with EMTP code.

• 전기학회논문지
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• 제58권4호
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• pp.748-755
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• 2009

This paper proposes a 18-step back-to-back voltage source converter using four sets of 3-Level converter module with auxiliary circuit to increase the number of steps. The proposed back-to-back voltage source converter has an independent control capability of active power and reactive power at the interconnected ac system. The operational feasibility of proposed system was verified through computer simulations with PSCAD/EMTDC software. The feasibility of hardware implementation was verified through experimental results with a scaled hardware model. The proposed back-to-back converter can be widely applied for interconnecting the renewable energy source to the power grid.

• Journal of Electrical Engineering and Technology
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• 제7권5호
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• pp.672-680
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• 2012

This paper proposes the control strategy of the shunt Flexible AC Transmission System (FACTS) devices to improve transient stability in multimachine power system. The multimachine power system has high nonlinear response after severe disturbance. The concept of Lyapunov energy function is applied to derive nonlinear control strategy and it was found that the time derivative of line voltage is not only can apply to control the shunt FACTS devices in multimachine system but also is locally measurable signal. The fuzzy logic control is also applied to overcome the uncertainty of various disturbances in multimachine power system. This paper presents the method of investigating the effect of the shunt FACTS devices on transient stability improvement. The proposed control strategy and the method of simulation are tested on the new England power system. It was found that the shunt FACTS devices based on the proposed nonlinear control strategy can improve transient stability of multimachine power system.

• 조명전기설비학회논문지
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• 제28권9호
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• pp.20-27
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• 2014

The power consumption pattern of high-speed railway has rarely during night time. But, during service time, the power is consumed irregularly related to train operation. Especially certain unusual about 1-2 days of service time interval to indicate the power consumption is rapidly growing phenomenon, which causes the capacity of the power contract is the annual electricity bill to rise rapidly as the cause. Normally, amount of peak power consumption bill rate at railway substation is over 20% of total electrical bill. Therefore, high-speed railway substation is expected to be considerably larger savings by reducing the peak power of the default charge(demand power).