• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.319-320
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• 2015

A hybrid converter for the on-board charger consisting of a soft switching full bridge (SSFB) and a half bridge (HB) LLC resonant converter is proposed. The proposed topology adopts an additional switch and a diode at the secondary side of SSFB converter to guarantee the wide ZVS range of primary side switches and to eliminate the circulating current. The output voltage is regulated by controlling the duty cycle of secondary side switch. The effectiveness of the proposed converter was experimentally verified using a 10-kW prototype circuit. The experimental results show 96.8% peak efficiency.

• Journal of Power Electronics
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• 제19권6호
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• pp.1337-1350
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• 2019

This paper proposes a Phase-Shift Triple Full-Bridge (PSTB) Zero-Voltage Zero-Current-Switching (ZVZCS) converter with a high switching frequency and high efficiency. In the proposed converter, all three bridge legs are shared leading-legs, and all three transformers work in the Discontinuous Conduction Mode (DCM). Thus, all of the switches and diodes in the PSTB ZVZCS can be soft switched. Moreover, since all of the transformers can pass energy from the primary-side to the secondary-side when their primary-side currents are not zero, there is no circulating current. As a result, the PSTB ZVZCS converter can achieve a high efficiency at high operating frequencies. A theoretical analysis and the characteristics of the proposed converter are presented and verified on a 1MHz 200~300V/24V 1.2kW hardware prototype. The proposed converter can reach a peak efficiency of 96.6%.

• 한국전자파학회논문지
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• 제15권7호
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• pp.685-691
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• 2004

본 논문에서는 Multi-code CDMA(code division multiple access) 시스템에서 발생하는 높은 PAPR(Peak to average power ratio)을 저감하고, 신호가 HPA에서 비선형 왜곡을 감소시키기 위한 방법으로, SLM(Selected Mapping) 및 PTS(Partial Transmit Sequence) 기법과 함께 전치왜곡 기법의 혼합 기법을 제안한다. 제안된 기법에서 SLM 및 PTS 방법을 위해 사용된 위상 회전 정보는 별도의 채널을 통해 전송되고, 이러한 위상 회전 정보의 채널 통과에 따른 에러율은 시스템의 성능에 큰 영향을 미친다. 따라서 본 논문에서는 위상 회전 정보의 에러율을 고려한 이론적인 BER 수식을 제시하며, 이는 시뮬레이션을 통해 나타난 시스템의 BER 성능과 거의 같게 나타난다. 결국 PTS 및 SLM 방법을 전치왜곡기와 병행한 제안된 혼합 기법은 신호의 PAPR을 줄이고, HPA의 비선형 특성을 보상함으로써 시스템의 BER 성능을 향상시킨다.

• 정보처리학회논문지C
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• 제12C권4호
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• pp.511-518
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• 2005

왈시-하다마다 변환(Walsh-Hadamard Transform, WHT)을 적용한 OFDM(Orthogonal Frequency Division Multiplexing) 변조방법은 시스템의 PAPR(Peak-to-Average Power Ratio)을 줄여주고, 시스템의 BER(Bit Error Rate) 성능을 향상시키는 장점이 있다. 그러나 기존의 이러한 왈시-하다마다 변환에 기반한 OFDM 시스템은 여전히 비교적으로 높은 PAPR문제가 있다. 그러므로 본 논문에서는 DGT(Data Grouping Technique)이라고 부르는 기술을 제안하고, 이 기술과 왈시-하다마다 변환 기술을 적용하여 PAPR을 더욱 줄여주는 OFDM 시스템을 설계한다. 제안한 DGT기술은 WHT-OFDM뿐만 아니라 일반 OFDM에서 PAPR을 줄여주는 방법들 중에서 큰 단점이 되는 부가정보(side information)가 성능에 대해 독립성을 가진다는 특징이 있다. 컴퓨터 시뮬레이션을 통해 제안한 시스템의 유용성을 검사하고 성능을 검증하였다.

• 에너지공학
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• 제20권3호
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• pp.216-223
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• 2011

본 논문에서는 다양한 공장과 빌딩에서 조명제어시스템을 대상으로 계측 및 검증(M&V) 방법을 사용하여 효율적인 에너지 절약 방법을 제시한다. 에너지 가격을 줄이기 위해서는 전력피크시간에 제어가능한 다양한 수요자원을 고려하는 필요하지만, 일반적으로 빌딩에서 고려되는 수요자원은 피크전력이다. 본 논문에서는 M&V 방법을 사용하여 전력소비량을 줄일 수 있는 새로운 에너지절약방법을 제안하고 현장계측시스템을 구성하고 시뮬레이션 방법을 통해 제안된 방법이 효과적임을 확인한다.

• 한국해양공학회지
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• 제24권1호
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• pp.99-105
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• 2010

The concentration and size analysis of in-situ suspended particulate material were measured using an optical instrument, LISST-100, in the bottom layer at the three inlets of the Seomjin River Estuary, mouth of Gwangyang bay, and Gwangyang bay-side of the Namhae Bridge. In the Seomjin river estuary and mouth of Gwangyang bay-side of the Namhae Bridge, the in-situ mean grain size of the suspended material changed from a uni-modal distribution with a dominant peak at a coarse fraction to a bi-modal distribution with a secondary peak at the finer particles. Seomjin River. The interactions between suspended particulate concentration and beam attenuation coefficient of suspended particulate matters depended on the supply of finer and coarser particles in the mouth of Gwangyang Bay and Seomjin River. So, interactions reflected difference of the concentration, mean size and sorting of suspended particulate matters. The difference of interaction showed dynamic behaviors to the resuspension and deflocculation processes increased river discharge. This showed that it may be possible to use the interactions between the suspended particle concentration and beam attenuation coefficient to monitor the temporal and spatial distributions of in-situ particles.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 춘계학술대회
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• pp.310-312
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• 2011

복합 잡음 환경에서 원 신호의 음성이나 영상신호를 획득하거나, 전송 및 저장을 위해서 디지털필터가 사용되고 있다. 디지털필터는 크게 FIR 필터와 IIR 필터로 나눌 수 있다. FIR 필터 중에서 창함수는 선형위상의 특성을 가지고 있고 손쉽게 통과대역, 차단주파수 등을 설정할 수 있다. 본 논문에서는 기존의 창함수를 변형하여 설계한 후 필터 특성을 확인하기 위해 Peak side-lobe와 주파수 천이특성 등을 사용하여 기존의 방법들과 비교하였다.

• 조명전기설비학회논문지
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• 제25권11호
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• pp.39-49
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• 2011

Smart Grid has two main objectives on both supply and demand aspects which are to distribute the renewable energy sources on supply side and to develop realtime price responses on demand side. Renewable energy does not consume fossil fuels, therefore it improves the eco-friendliness and saves the cost of power system operation at the same time. Demand response increases the flexibility of the power system by mitigating the fluctuation from renewable energies, and reduces the capacity investment cost by shedding the peak load to off-peak periods. Currently Smart Grid technologies mainly focus on energy monitoring and display services but it has been proved that enabling technologies can induce the higher demand responses through many pilot projects in USA. On this context, this paper provides a price responsive algorithm for HEMS (home energy management system) on the real time pricing environment. This paper identifies the demand response as a core function of HEMS and classifies the demand into 3 categories of fixed, transferable, and realtime responsive loads which are coordinated and operated for the utility maximization or cost minimization with the optimal usage combination of three kinds of demand.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권1호
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• pp.69-84
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• 2018

In order to analyze the characteristics of propeller exciting force, the hybrid grid is adopted and the numerical prediction of KCS ship model is performed for hull-propeller-rudder system by Reynolds-Averaged Navier Stokes (RANS) method and volume of fluid (VOF) model. Firstly, the numerical simulation of hydrodynamics for bare hull at oblique state is carried out. The results show that with the increasing of the drift angle, the coefficients of resistance, side force and yaw moment are constantly increasing, and the bigger the drift angle, the worse the overall uniformity of propeller disk. Then, propeller bearing force for hull-propeller-rudder system in oblique flow is calculated. It is found that the propeller thrust and torque fluctuation coefficient peak in drift angle are greater than that in straight line navigation, and the negative drift angle is greater than the positive. The fluctuation peak variation law of coefficient of side force and bending moment are different due to various causes.

• E2M - 전기 전자와 첨단 소재
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• 제7권3호
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• pp.187-199
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• 1994

In order to find an effect of structural changes due to variation of addition ratio of anhydride hardener and postcuring herat-treatments upon electrical properties of epoxy composites, the dielectric properties over a frequency range from 30[Hz] to l[MHz] were investigated in the temperature range of 20-180[.deg. C]. From the dielectric properties, the a peaks related with glass-transition phenomena of epoxy network appeared near 130[.deg. C], the conduction loss in high temperature region above 150[.deg. C] due to thermal dissociation of hardener started off with the low frequency side and the .betha. peak concerned with contribution of movable unreacted terminal epoxy groups and curing agents in the glass states concurred with the high-frequency side below 20[.deg. C]. And an effect of an hydride hardener upon structural changes and of postcuring heat treatments upon structural stability in epoxy composites would be explained through the estimation of the distribution of relaxation times and the activation energy for a .alpha. peak according to the WLF equations.