• 전력전자학회논문지
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• 제14권4호
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• pp.261-267
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• 2009

최대전력점 추적기는 태양광 발전시스템의 대표적인 기능이다. 최대 전력점을 추종하기 위해서는 태양전지의 전압과 전류의 측정을 필요로 한다. 만약 측정 신호에 노이즈가 포함되어 있으면 발생되는 전력이 감소되어 태양광 발전의 효율이 감소하게 된다. 노이즈가 포함된 신호에 확장 칼만 필터 이론을 적용하여 최적의 추정된 신호를 얻어 낼 수 있다. 칼만 필터는 랜덤 노이즈가 포함된 신호에서 최적의 신호를 얻어내는데 사용된다. 또한 칼만 필터의 적용결과로 인덕터 전류와 같은 측정하지 않는 신호도 센서리스 추정이 가능하다. 본 논문에서는 시스템 모델링 방법과 확장 칼만 필터 설계 방법이 소개된다. 실험 결과로서 제안된 제어기의 성능을 확인하였다.

• 한국안광학회지
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• 제12권4호
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• pp.107-110
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• 2007

농촌지역 50대~80대 남녀 137명을 대상으로 자동 안굴절력계에 의한 원용 교정도수 측정, Trial frame와 Trial lens set을 사용한 근용 도수 측정, 최대조절력의 1/2과 2/3를 사용하였을 때의 유효조절력 산정 등을 통하여 조절력을 분석해 보았다. 그 결과 50대에서는 1.84~2.46D, 60대에서는 1.55~2.06D, 70대에서는 1.43~1.90D, 80대에서는 1.22~1.62D로 조사되어 기존에 알려진 나이에 따른 조절력에 비해 다소 높게 나타났다.

• Journal of Welding and Joining
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• 제29권2호
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• pp.56-63
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• 2011

his paper aimed to understand the residual stress in the dissimilar metal welds of nuclear power plant. Two kinds of residual stress were considered, which caused by welding and machining. Residual stress due to mechanical machining was measured by hole-drilling technique and x-ray diffraction method for the SA508 and F316L. Weld residual stress at dissimilar metal weld between SA508 and F316L was evaluated by FEA. Residual stress profiles were obtained for the inside surface and through thickness of welds. Machining effect was also analyzed by FEA. According to the residual stress measurement, it was observed that mechanical machining can generate tensile stress on the surface of the test material. However, FEA results showed that mechanical machining did not increase the tensile stress on the surface of weld region. Further study with more elaborate measurement and numerical analysis is required to identify the effect of machining on residual stress in the dissimilar metal weld region.

• 정보학연구
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• 제7권3호
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• pp.1-10
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• 2004

옥내${\cdot}$외의 전력선 환경에 대한 정확한 채널 모델링에 관한 노력이 최근에 이루어지고 있다. 알려진 일반표준, 제한과 발표된 모델들은 특별한 형태의 접근들이였다. 본 논문에서는 더 신속하고 효율적인 전력선 통신 실험을 위한 전력선 채널 모델링에 관한 연구이다. 용량성 부하 시뮬레이터는 전력선 옥내 망 모뎀 개발에 필수적인 장비이다. 총 244 경우의 용량성 부하 변화에 대한 주파수 응답 특성 측정으로 채널 모델링을 수행하였다. 본 측정 실험에서 PLC는 일반적으로 알고 있었던 특성 보다 더 확정적인 매체라는 것을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제7권3호
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• pp.304-311
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• 2012

So far, the importance for an accurate load model has been constantly raised and its necessity would be further more emphasized. Currently used load model for analysis of power system in Korea was developed 10 years ago, which is aggregated by applying the statistically estimated load compositions to load models based on individual appliances. As modern appliances have diversified and rapidly changed, the existing load model is no longer compatible with current loads in the Korean power system. Therefore, a measurement based load model is more suitable for modern power system analysis because it can accurately include the load characteristics by directly measuring target load. This paper proposes a ZIP model employing a Kalman-filter as the estimation algorithm for the model parameters. The Kamlan-filter based parameter identification offers an advantage of fast parameter determination by removing iterative calculation. To verify the proposed load model, the four-second-interval real data from the Korea Energy Management System (K-EMS) is used.

• Journal of Power Electronics
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• 제14권4호
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• pp.806-813
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• 2014

Planar electromagnetic interference (EMI) filters are widely used to restrain the conducted EMI of switching power supplies. Such filters are characterized by small size, low parasitic parameters, and better high-frequency performance than the passive discrete EMI filter. However, EMI filter performance cannot be exactly predicted by using existing methods. Therefore, this paper proposes a method to use scattering parameters (S-parameters) for the measurement of EMI filter performance. A planar EMI filter sample is established. From this sample, the relationship between S-parameters and insertion gain (IG) of EMI filter is derived. To determine the IG under different impedances, the EMI filter is theoretically calculated and practically measured. The differential structure of the near-field coupling model is also deduced, and the IG is calculated under standard impedance conditions. The calculated results and actual measurements are compared to verify the feasibility of the theory.

• 전력전자학회논문지
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• 제8권6호
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• pp.527-533
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• 2003

최근 민감한 전자부하의 사용증대에 기인하여 전직의 안정도와 신뢰도에 대한 관심이 증대되고 있다. 이에 전력풀질문제가 근래에 있어 일반적인 중요한 과제로 대두되었다. 이러한 전력품질문제를 진단하기 위하여 실효치나 FFT 등의 기법을 이용한 많은 알고리즘이 연구되어 왔으나 모든 전력품질문제를 진단하기에는 아직도 미진한 상황이다. 본 논문은 이산 웨이블릿을 응용한 전력품질문제의 진단 방법을 제안하고 웨이블릿의 이론에 대한 기본적인 설명과 함께 제안된 이론의 타당성을 입증하기 위하여 실제 전력품질문제 진단시스템을 설계하고 실험결과를 제시하였다.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1447-1453
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• 2014

This paper proposes the new method based on the availability of three points measurement and convexity of photovoltaic (PV) curve characteristic at the maximum power point (MPP). In general, the MPP tracking (MPPT) function is the important part of all PV systems due to their power-voltage (P-V) characteristics related with weather conditions. Then, the analog-to-digital converter (ADC) and low pass filter (LPF) are required to measure the voltage and current for MPPT by the digital controller, which is used to implement the PV power conditioning system (PCS). The measurement and quantization error due to rounding or truncation in ADC and the delay of LPF might degrade the reliability of MPPT. To overcome this limitation, the proposed method is proposed while improving the performances in both steady-state and dynamic responses based on the detailed investigation of its properties for availability and convexity. The performances of proposed method are evaluated with the several case studies by the PSCAD/EMTDC$^{(R)}$ simulation. Then, the experimental results are given to verify its feasibility in real-time.

• 조명전기설비학회논문지
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• 제29권2호
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• pp.69-74
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• 2015

Recently, there has been a surge in interest in equipment diagnosis and monitoring technology from the perspective of providing quality electricity in terms of reliability and safety. In order to meet the electrical demands of consumers, reliability of power supply needs to be maintained. For this purpose, a monitoring system for power cable is very important. Since real-time measuring equipment has many advantages, it is highly applicable. By measuring the load current and the surface temperature of power cables, we have monitored and identified the deterioration phenomena of power cables in operation. Since direct measurement of the cable conductor temperature is not easy, we have measured the surface temperature instead, and converted that temperature to obtain the conductor temperature of the cables. In addition, we have designed a system to detect the deterioration processes of the power cables in operation.

• International journal of advanced smart convergence
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• 제12권2호
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• pp.182-186
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• 2023

In this study, we measured the power and temperature of the floating horizontal solar cell in a coastal lagoon and compared with those of ground solar cell and water platform solar cell. Because the bottom surface of the floating horizontal solar cell was contacting the water, cooling effect was expected stronger than other cells. As a result of the measurement, the power of floating horizontal cell was 11.7% higher than that of the ground cell and 15% higher than that of the water platform cell. During the measurement, it was observed that water waves were continuously flowed on the top surface of floating horizontal cell by the wind, and it could be assumed that the cooling effect occurred not only on the bottom surface of the cell but also on the top surface. In order to analyze the cooling effect and power increasing of the horizontal cell in the wave situation, we measured power and temperature of the cell while generating artificial waves in a laboratory equipped with Zenon lamp as a solar simulator. At the height of thewater surface, the power of the cell with waves was 3.7% higherthan without waves and temperature was 4.6℃ lower. At 1 cm and 2 cm below the watersurface, power of the cell with waves was decreased by 14% and 11% than without waves while temperature was same . At 3 cm below the water surface, there was no effect of waves.