• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.95-96
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• 2016

본 논문은 독립 운전 모드에서 전압 고조파 보상을 위한 비례 다중 공진 제어 기반의 전압 제어에 대해 다루고 있다. 독립 운전 모드에서 인버터는 계통과의 연계 없이 전체 지역적 부하의 수요를 담당해야 하기 때문에 전압원으로서 정의된다. 그런데 이때 부하가 불평형 또는 비선형 부하인 경우 역상차, 영상차 또는 특정 고조파 전류가 발생하며 이로 인해 출력 전압이 왜곡된다. 본 논문에서는 앞서 언급한대로 전압 고조파 보상을 위해 흔히 사용되는 비례적분 제어기 대신 고조파 보상 제어의 단순화를 위해 비례 공진 제어기를 사용하였다. 하지만 이와 같은 비례 공진 제어를 실용적인 텀으로서 추가될 경우 전압 매그니튜드 추종 에러가 발생하게 되므로 본 논문에서는 추가적으로 실용적인 비례 공진 제어기가 갖는 단점을 극복하고자 비례 적분 기반의 간단한 전압 회복 기법에 대해 제안하며 제안된 제어 방식은 PSiM 시뮬레이션과 실험을 통해 입증되었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.9B
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• pp.1299-1307
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• 2001

고정된 패턴을 사용하는 기존의 고속 블록기반 움직임 추정법에서는 국소 최소해로 고립될 가능성이 있을 뿐만 아니라, 여러 움직임이 공존하는 움직임 경계에서 정확한 움직임의 추정이 어렵다는 문제점을 가지고 있다. 이러한 문제점을 극복하기 위하여 본 논문에서는 탐색점의 수를 줄이는 동시에 국소 최소해로의 고립을 피하기 위하여 탐색 후보영역을 적용한 다중 국소 탐색법(multiple local search method : MLSM)을 제안한다. 또한, 블록 내의 움직임 영역별 정합오차의 최소편차를 고려하는 새로운 정합함수를 제안함으로써 움직임 경계에서 움직임 벡터추정의 부정확성과 움직임 보상영상에서의 화질저하문제를 개선하고자 한다. 실험결과, 제안한 방법은 기존의 방법에 비해 움직임 경계에서의 추정에서 우수한 결과를 보였으며, PSNR에 대해서도 전역탐색법과 유사한 결과를 얻을 수 있었고, 움직임 보상결과, 움직임 경계부근에서의 향상된 화질을 얻을 수 있었다.

• Journal of Advanced Navigation Technology
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• v.17 no.1
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• pp.16-23
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• 2013

The effects of dispersion coefficient of dispersion compensating fiber (DCF) and residual dispersion per span (RDPS) on in the dispersion managed optical links for compensating the distorted 960 Gbps wavelength division multiplexd (WDM) signals due to group velocity dispersion (GVD) and optical nonlinear effects of single mode fiber (SMF) are investigated. It is confirmed that optimal net residual dispersion (NRD), which greatly affects compensating for optical signals, should be induced under the large launch power condition, irrelevant on the considered dispersion coefficient of DCF and RDPS. It is also confirmed that system performances are greatly improved by selecting the very small RDPS and very large dispersion coefficient of DCF.

• Journal of the Korean Professional Engineers Association
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• v.22 no.3
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• pp.14-20
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• 1989

전력수요의 급증에 따라 단위기의 용량 및 전력계통의 규모가 대형화되어 지속적인 안전운전이 계통운용의 최우선 과제가 되였으며, 신뢰도향상 및 계통간전력수급의 원활한 융통을 위하석 계통간의 연계는 물론 다계통간의 다중연계에 이어 국가간의 연계도 이루어지고 있다. 본고에서는 전력계통의 대형화 및 연계화 추세에 따라 계통 무효전력 조류의 신속한 조절과 속응전압조정의 필요성이 증대되어 그 응용이 확산되고 있는 Thyristor제어 정지형 무효전력 보상기(이하 SVC라 칭함)의 원리, 특성, 응용 및 계통에 미치는 효과에 대하여 고찰하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.541-544
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• 2001

The difference of transfer mode between TDMA and ATM causes cell delay variation(CDV) to be generated in the receiving station. I proposed a optimization method of timestamps for discrete-timestamps mechanism to compensate CDV and an application method in multiple timestamps mechanism.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.11
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• pp.2388-2400
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• 1997

In this paper, we analyzed the serial interference cancellation scheme and proposed the new serial interference cancellation scheme suppressing multiple access interference. Compensating for the near-far effect and the multiple access interference is critical for the stable performance of DS/CDMA system, and the serial multiple access interference cancellation has been proposed as one of the compensation methods. But this serial interference cancellation scheme has a linear variation in the number of cancellation operation each users. Becaure of this variation, it is difficult to show a stable performance. Hence, we suggested a new serial interference applying window technique to overcome this fault and made a performance estiamation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3C
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• pp.408-418
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• 2004

In this paper, we propose a novel scalable video coding algorithm based on adaptively weighted multiple reference frame method. To improve the coding efficiency in the enhancement layer, the enhancement frame is predicted by the sum of adaptively weighted double motion compensated frames in the enhancement layer and the current frame in the base layer, according to the input video characteristics. By employing adaptive reference selection scheme at the decoder, the proposed method reduce the drift problem significantly. From the experimental results, the proposed algorithm shows more than 1.0 ㏈ PSNR improvement, compared with the conventional scalable H.263+ for various packet loss rate channel conditions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.10
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• pp.994-1000
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• 2013

Conventional MIMO system is required to a number of RF chains as much as a number of antennas. If the number of antennas increased then the number of RF chains increased. Therefore, it is difficult to apply conventional MIMO system to mobile terminals with limited power. In this paper, we propose a TDM(time division multiplexing)-based single RF chain MIMO system. The outcome shows that performance of the proposed system is similar to conventional MIMO system using multiple RF chains when STO is corrected by phase angle estimation and the synchronizing signal of received signal. Therefore, it is possible to implement the MIMO-OFDM system of low power and complexity through a single RF chain.

• Journal of Advanced Navigation Technology
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• v.24 no.5
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• pp.408-414
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• 2020

The method of overcoming the limitation of optical phase conjugator applied into optical long-haul link for transmitting high capacity wavelength division multiplexed (WDM) channels was investigated. The configuration of optical link was based on dispersion-managed link, in which dispersion compensating fiber inserted into each fiber span with single mode fiber, and optical phase conjugator was added into suitable location of link. The maximum number of fiber spans as a function of the launch power of WDM channels in optical link with optical phase conjugator placed at the proposed location was induced and compared for analyzing the compensation performance of the distorted WDM channels. It was confirmed that the more optical phase conjugator depart from the midway of total transmission length, the less the distorted WDM channels was compensated, however, it was also confirmed that the degradation of compensation can be overcome by the suitable value of residual dispersion per span and by the reasonable choice of fiber span controlling total dispersion accumulated in overall transmission link.

• The Journal of the Korea Contents Association
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• v.10 no.4
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• pp.28-35
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• 2010

The variable block size motion estimation (ME) and compensation (MC) using multiple reference frames is adopted in H.264/AVC to improve coding efficiency. However, the computational complexity for ME/MC increases proportional to the number of reference frames and variable blocks. In this paper, we propose a new efficient reference frame selection algorithm to reduce the complexity while keeping the visual quality. First, a motion vector reference map is constructed by SAD of $4{\times}4$ block unit for multi reference frames. Next, the variable block size motion estimation and motion compensation is performed according to the motion vector reference map. The computer simulation results show that the average loss of BDPSNR is -0.01dB, the increment of BDBR is 0.27%, and the encoding time is reduced by 38% compared with the original method for H.264/AVC.