• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2153-2155
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• 2001

This thesis presents a development of intelligent digital governing system and it's application on Sumjingang Hydro-Power plant. The developed system consists of hardware, software and governing algorithm. The feature of hardware is triplex-modular fail safe redundant system for a safe turbine running. The software consists of operating system and application program. The operating system has real-time and multi-tasking features. And also, application algorithm is composed to run francis type hydro-turbine. The developed digital governing system is applied to Sumjingang hydro-power plant, Korea Hydro Nuclear Power Corporation.

• ETRI Journal
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• 제29권3호
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• pp.363-370
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• 2007

In this paper, we propose a flexible turbo decoding algorithm for a high order modulation scheme that uses a standard half-rate turbo decoder designed for binary quadrature phase-shift keying (B/QPSK) modulation. A transformation applied to the incoming I-channel and Q-channel symbols allows the use of an off-the-shelf B/QPSK turbo decoder without any modifications. Iterative codes such as turbo codes process the received symbols recursively to improve performance. As the number of iterations increases, the execution time and power consumption also increase. The proposed algorithm reduces the latency and power consumption by combination of the radix-4, dual-path processing, parallel decoding, and early-stop algorithms. We implement the proposed scheme on a field-programmable gate array and compare its decoding speed with that of a conventional decoder. The results show that the proposed flexible decoding algorithm is 6.4 times faster than the conventional scheme.

• 한국해양공학회지
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• 제34권6호
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• pp.475-480
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• 2020

Underwater operating platforms face difficulties regarding power supply and communications. To overcome these difficulties, this study proposes a hybrid surface and underwater vehicle (HSUV) and presents the development of the platform, control algorithms, and results of field tests. The HSUV is capable of supplying reliable power to the unmanned underwater vehicle (UUV) and obtaining data in real time by using a tether cable between the UUV and the unmanned surface vehicle (USV). The HSUV uses global positioning system (GPS) and ultra-short base line sensors to determine the relative location of the UUV. Way point (WP) and dynamic positioning (DP) algorithms were developed to enable the HSUV to perform unmanned exploration. After reaching the target point using the WP algorithm, the DP algorithm enables USV to maintain position while withstanding environmental disturbances. To ensure the navigation performance at sea, performance tests of GPS, attitude/heading reference system, and side scan sonar were conducted. Based on these results, manual operation, WP, and DP tests were conducted at sea. WP and DP test results and side scan sonar images during the sea trials are presented.

• Ocean Systems Engineering
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• 제10권4호
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• pp.359-371
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• 2020

The performance of a multi-level overtopping wave energy converter (OWEC) has been numerically and experimentally investigated in a two-dimensional wave tank in order to study the effects of opening width of additional reservoirs. The device is a fixed OWEC consisting of an inclined ramp together with several reservoirs at different levels. A particle-based numerical simulation utilizing the Lattice Boltzmann Method (LBM) is used to simulate the flow behavior around the OWEC. Additionally, an experimental model is also built and tested in a small wave flume in order to validate the numerical results. A comparison in energy captured performance between single-level and multi-level devices has been proposed using the hydraulic efficiency. The enhancement of power capture performance is accomplished by increasing an overtopping flow rate captured by the extra reservoirs. However, a noticeably large opening of the extra reservoirs can result in a reduction in the power efficiency. The overtopping flow behavior into the reservoirs is also presented and discussed. Moreover, the results of hydrodynamic performance are compared with a similar study, of which a similar tendency is achieved. Nevertheless, the LBM simulations consume less computational time in both pre-processing and calculating phases.

• Journal of Advanced Marine Engineering and Technology
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• 제31권5호
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• pp.583-591
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• 2007

This paper reports the performance of a 150W PV-wave hybrid system with battery storage in buoy. This system was originally designed to meet a new hybrid ower system for buoy in Korea. In the case or lighted buoys and lighthouses, a light failure alarm system of wireless radio is attached so that light failures are immediately notified to the office. At lighthouse offshore fixed lights and light buoys where commercial electricity is not available, the power source depends on solar system and batteries. This power system has a various problems. Therefore energy derived from the sunshine, wind and waves has been used as the energy source lot aids to navigation. Recently a hybrid system of combining the solar, wind and the wave generator is a favorable system lot the ocean facilities like lighthouse and buoy. The hybrid system in this paper is intended for variable DC load like light, communication system in the buoy and includes a PV-wane generation system and battery. This is composed a high efficiency charging algorithm, switching converter and controller. This paper includes discussion on system reliability, power quality, and effects of hybrid system in the buoy. Simulation and experimental results show excellent performance.

• 한국지능시스템학회논문지
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• 제19권1호
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• pp.145-151
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• 2009

유비쿼터스 네트워크의 실현을 위한 4세대 통신방식의 유력한 후보로 부상하는 OFDM (Orthogonal Frequency Division Multiplexing) 통신방식이 육상에서 주목받고 있으며, 고속 데이터 전송을 위한 Wireless LAN의 표준기술로 확정되어 있다. 해상통신의 경우에서도 OFDM 통신방식은 VHF 대역을 이용한 데이터 전송방식으로 제안되고 있으며 ITU (International Telecommunication Union)는 해상통신에서 32-point FFT (Fast Fourier Transform)를 사용하도록 권고하고 있다. 해상 통신에서는 해양사고 및 조난 시에도 통신이 이루어져야 하는 한계상황을 고려하면 OFDM 통신시스템의 중요 디바이스인 FFT는 저전력으로 동작되어야 한다. 따라서 본 논문에서는 OFDM 방식의 중요 디바이스인 32-point FFT를 저전력으로 동작시키기 위해 radix-2와 radix-4를 이용하여 저전력 32-point FFT 알고리즘을 제안한다. 최적화된 설계로 32-point FFT를 저전력 동작이 가능하도록 설계하였으며, 제안한 알고리즘은 VHDL (VHSIC hardware description language)로 구현하고 FPGA (field-programmable gate array) Spartan3 board에 장착하여 Matlab의 이론값과 비교, 검증하였다.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2017년도 공동학술발표회
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• pp.1-1
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• 2017

• 한국정보통신학회논문지
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• 제21권7호
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• pp.1455-1463
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• 2017

세계경기가 저성장, 저소비, 높은 실업률, 고위험, 짧은 호황 긴 불황 등을 기록하고 있다. 이에 따라 해운경기가 하락하여 선박 유지비용의 절감이 불가피해지고 있다. 이를 위해 그린 선박, 에코 선박, 스마트 선박과 같은 선박의 에너지를 절감하기 위한 연구가 활발히 진행 중에 있다. 친환경 선박에서 배터리를 사용하는 전력관리시스템은 중요한 연구분야 중 하나이다. 본 논문에서는 발전기만을 사용하는 일반적인 선박의 전력관리시스템의 중부하 제어를 분석하고 배터리 연계형 전력관리시스템에서 중부하를 제어하는 알고리즘을 연구하였다. 이를 위해 배터리 연계형 전력관리시스템의 구성을 제안하고 제안된 시스템을 기반으로 배터리 연계형 전력 시뮬레이터를 구성하였다. 구성된 시뮬레이터를 통해 배터리 연계형 전력관리시스템에서 중부하 제어에 따른 배터리의 동작을 정의하고 이를 확인하였다.

• 한국항해항만학회지
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• 제31권3호
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• pp.229-233
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• 2007

본 논문은 브이용 PV 시스템 성능과 최대전력점추적기의 알고리즘에 대하여 기술하고자 한다 현재 운영되고 있는 브이는 대부분 태양광을 활용한 독립형 전력 시스템을 이용하고 있다. 이러한 태양광 전력 시스템은 직류 출력 특성을 가지고 있으며 직류 버스와 연결된다. 태양광 전지판의 I-V 출력 특성은 일사량, 전지판의 온도에 따라 변화하며 태양광 전지 마다 그 특성이 각기 다르게 나타나기 때문에 태양광 전지는 최대전력추적방식의 알고리즘에 의해 운영되어야 한다. 이에 본 논문은 태양광 전지의 특성, 최대전력추적방식, 태양광 전지판의 최적경사각을 논의하고자 한다.

• Journal of Power Electronics
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• 제16권6호
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• pp.2192-2201
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• 2016

Wind energy is currently the fastest-growing electricity source worldwide. The cost efficiency of wind generators must be high because these generators have to compete with other energy sources. In this paper, a system that utilizes an open-winding permanent-magnet synchronous generator is studied for wind-energy generation. The proposed system controls generated power through an auxiliary voltage source inverter. The VA rating of the auxiliary inverter is only a fraction of the system-rated power. An adjusted control system, which consists of two main parts, is implemented to control the generator power and the grid-side converter. This paper introduces a study on the effect of unbalanced voltages for the wind-generation system. The proposed system is designed and simulated using MATLAB/Simulink software. Theoretical and experimental results verify the validity of the proposed system to achieve the power management requirements for balanced and unbalanced voltage conditions of the grid.