• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.303-311
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• 2014

This paper shows the test result of 2MVA BESS(Battery Energy Storage System) with wind-turbine in micro-grid of the Gapado. To implement of micro-grid with BESS, characteristics of generator and customer load in grid are considered. Also, to operate of 2-parallel PCU(Power Conversion Unit) in BESS, the droop control is adopted with operating mode of grid independent. Performances of BESS with wind-turbine were verified by analysis of power quality such as voltage harmonics, ratio of voltage and frequency regulation, and by measurement of waveform such as output voltage and current.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.7
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• pp.1176-1185
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• 2016

This paper proposes a new output voltage control scheme based on the SoC variation of the battery energy storage system (BESS) applicable for the stand-alone DC microgrid. The proposed control scheme provides relatively lower variation of the DC grid voltage than the conventional droop method. The performance of proposed control scheme was verified through computer simulations for a typical stand-alone DC microgrid which consists of BESS, photo-voltaic (PV) panel, engine generator (EG), and DC load. A scaled hardware prototype for the stand-alone DC microgrid with DSP controller was set up in the lab, and the proposed control algorithm was installed in the DSP controller. The test results were compared with the simulation results for performance verification and actual system implementation.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.1
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• pp.88-94
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• 1998

Installation design methods and results of an aircraft engine on the wing-mounted-nacelle type aircraft has been presented in this paper. The design process starts from design requirements and constraints and covers some major aspects of the engine installation design such as wing-nacelle interference drag, roll clearance, ground clearance, nose gear collapse margin, rotor burst and fuel tank capacity. The method was applied to 100-seat class airplane(K100). Results of the design suggest optimum nacelle location and nacelle installation angle(toe-in, incidence, droop angle) which satisfies in stalled engine performance and size/location of wing dry day.

• Journal of Power Electronics
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• v.19 no.2
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• pp.580-590
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• 2019

The concept of virtual synchronous generators (VSGs) is a valuable means for improving the frequency stability of microgrids (MGs). However, a great virtual inertia in a VSG's controller may cause power oscillation, thereby deteriorating system stability. In this study, a small-signal model of an MG with two paralleled VSGs is established, and a control strategy for maintaining a constant inertial time with an increasing active-frequency droop coefficient (m) is proposed on the basis of a root locus analysis. The power oscillation is suppressed by adjusting virtual synchronous reactance, damping coefficient, and load frequency coefficient under the same inertial time constant. In addition, the dynamic load distribution is sensitive to the controller parameters, especially under the parallel operation of VSGs with different capacities. Therefore, an active power increment method is introduced to improve the precision of active power sharing in dynamic response. Simulation and experimental is used to verify the theoretical analysis findings.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.172-173
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• 2012

Currently GaN based LED is known to show high internal or external efficiency at low current range. However, this LED operation occurs at high current range and in this range, a significant performance degradation known as 'efficiency droop' occurs. Auger process, carrier leakage process, field effect due to lattice mismatch and thermal effects have been discussed as the causes of loss of efficiency, and these phenomena are major hindrance in LED performance. In order to investigate the main effects of efficiency loss and overcome such effects, it is essential to obtain relative proportion of measurements of internal quantum efficiency (IQE) and various radiative and nonradiative recombination processes. Also, it is very important to obtain radiative and non-radiative recombination times in LEDs. In this research, we measured the IQE of InGaN/GaN multiple quantum wells (MQWs) LEDs with PSS and Planar substrate using modified ABC equation, and investigated the physical mechanism behind by analyzing the emission energy, full-width half maximum (FWHM) of the emission spectra, and carrier recombination dynamic by time-resolved electroluminescence (TREL) measurement using pulse current generator. The LED layer structures were grown on a c-plane sapphire substrate and the active region consists of five 30 ${\AA}$ thick In0.15Ga0.85N QWs. The dimension of the fabricated LED chip was $800um{\times}300um$. Fig. 1. is shown external quantum efficiency (EQE) of both samples. Peak efficiency of LED with PSS is 92% and peak efficiency of LED with planar substrate is 82%. We also confirm that droop of PSS sample is slightly larger than planar substrate sample. Fig. 2 is shown that analysis of relation between IQE and decay time with increasing current using TREL method.

• Electronics and Telecommunications Trends
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• v.24 no.6
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• pp.61-76
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• 2009

LED는 2000년대에 들어서면서 생활 전반에 사용되기 시작하여 최근에는 자동차용 부품과 TV의 back light unit에 이르기까지 모든 분야에서 다양한 용도로 사용되고 있다. 본 기고에서는 이러한 LED의 기판을 포함한 에피, 칩, 그리고 패키지 기술의 중요한 이슈와 기술의 동향에 대하여 간략히 정리하였다. 상용화되어 사용되는 사파이어나 SiC 기판 이외에 연구개발이 진행중인 GaN 기판 기술 등을 소개하고, 에피 기술에서는 활성층과 클래딩층 성장 기술의 이슈들을 제시하며, 칩의 종류와 특성을 중심으로 droop 현상과 광추출 기술 등을 살펴보고, 다양한 패키지의 종류 및 특징 등을 포함하는 LED 분야의 기술 동향에 대하여 설명한다.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.315-316
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• 2016

This paper proposes an enhanced distributed generation (DG) unit with an adaptive virtual impedance control approachin order to address the inaccurate reactive power sharing problems. The proposed method can adaptively regulate the DG unit thanks to the equivalent impedance, andthe effect of the mismatch in feeder impedance is compensatedto share the reactive power accurately.The proposed control strategy can be implemented directly without any requirement of pre-knowledge of the feeder impedances. Simulations are performed to validate the effectiveness of the proposed control approach.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.3 no.3
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• pp.60-67
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• 1989

본 논문에서는 열병합발전소로서 가스터빈을 이용하는 경우, 계통분리를 비롯한 각종고장에 따른 발전기 및 계통의 응답성을 검토하여 가스터빈의 운전방법 및 계통의 안전운전여부를 파악할수 있는 방법에 대하여 검토하였다. 특히 온도제어루프, 가속도제어루프를 비롯한 가스터빈의 제어루프와 Droop 및 등속도 운전과 같은 운전방법을 시뮬레이션에 포함하여 각종 사례연구를 통하여 열병합발전소의 적절한 운전방법을 연구하였다.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.542-543
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• 2012

본 논문에서는 저항성 수하제어 방식과 단일루프 강인 전압 제어기를 적용하여 단상 UPS 인버터의 비통신선 방식 5-병렬 운전 결과를 기술한다. 단일 루프 강인 전압 제어기를 이용해 단상 3kVA UPS 인버터 5대로 병렬운전 환경을 구축하였고, 저항성 주파수-전압 강하 방식의 수하 제어를 이용하여 저항 부하와 선형 부하에 대한 전력분담 특성을 PSIM 시뮬레이션을 통하여 확인하였다.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.184-185
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• 2016

본 논문에서는 직류 전기 선박의 발전시스템의 병렬 운전시 순환전류 저감 및 직류 전압유지에 효과적인 가변이득 드룹 제어 기법을 제시한다. PSIM을 이용한 시뮬레이션 결과를 보인다.