• 한국정보통신학회논문지
• /
• 제20권10호
• /
• pp.1949-1954
• /
• 2016

스마트 그리드(smart grid) 기술은 전력 공급자와 소비자 사이를 실시간으로 전력정보를 교환함으로써 전력의 효율성을 높이는 전력망 관리 기술이다. 최근에는 유지보수 및 설치가 용이한 태양광 발전시스템에 대한 적용이 늘고 있다. 그러나 태양광 발전 시스템은 고장진단이 어려우며, PV(PhotoVoltaics) 어레이 및 인버터(inverter) 등의 결함과 기타 잠재적인 출력저하 요소로 인하여 발전량이 감소하기도 한다. 이처럼 태양광 발전 시스템을 통하여 안정적인 에너지 포집과 관리 및 조속한 고장 검출이 필수 요구사항이라 할 수 있다. 본 논문에서는 태양광 발전 시스템을 대상으로 전력 생산량 및 이상 동작 현상을 모니터링하고 외부 환경을 계측하는 계측모듈을 개발하고, 계측된 정보 데이터를 전송할 수 있는 통신모듈을 통하여 원격지에서 태양광 발전 시스템의 동작 상태를 모니터링 하도록 설계하였다. 또한 스마트폰을 기반으로 구축된 태양광 발전 시스템을 실시간으로 관리하고 모니터링 할 수 있는 모바일 관리 시스템을 제시하고자 한다.

• 한국통신학회논문지
• /
• 제37권4B호
• /
• pp.227-235
• /
• 2012

무선센서네트워크에서 예기치 못한 지형과 자연현상 또는 노드 파손, 불균형적인 에너지 손실로 홀(hole)이 발생하는 것은 필수불가결하다. 이런 문제를 다루는 대부분의 현존 방식은 홀을 피하기 위해 정적인 우회 경로를 구성한다. 정적인 우회 경로는 홀 주변부에 있는 노드들의 과도한 에너지 손실을 유발한다. 그래서 데이터 패킷이 홀 주변 노드에 몰리고 노드들의 에너지는 급속하게 고갈되며 홀의 영역이 확대되는 효과가 나타난다. 이러한 문제점을 해결하기 위하여 가상 그리드 상에서 위치기반 라우팅 방식과 동적인 그리드 앵커포인터 설정을 통한 효율적인 홀 우회 방식을 제안한다. 제안된 홀 우회 방식은 홀이 있는 불규칙한 무선센서네트워크에서도 에너지 효율적이며 데이터 신뢰성을 제공하는 홀 우회 전송방식이다. 시뮬레이션 결과는 이러한 주장의 타당성을 제공한다.

• 한국군사과학기술학회지
• /
• 제17권6호
• /
• pp.800-809
• /
• 2014

The gridded environmental data is usually provided by the numerical simulation coupled with a data assimilation technique and various inter- or extrapolation algorithms, both of which are based on the observation spanning from simple equipments to satellites. But it is difficult to represent the natural phenomenon such as sea mount, internal-wave, warm eddy in modeling or observation because of increase in the complexity of model. This paper introduces the algorithm artificially representing the natural phenomenon and the techniques applying it to the gridded volume data and smoothing for natural effects. Moreover, the inserted results are analyzed by use of graphical tool. The results can be used for the battle simulation or acoustic model.

• Journal of Mechanical Science and Technology
• /
• 제18권12호
• /
• pp.2190-2203
• /
• 2004

A combined procedure for two-dimensional Delaunay mesh generation algorithm and an adaptive remeshing technique with higher-order compressible flow solver is presented. A pseudo-code procedure is described for the adaptive remeshing technique. The flux-difference splitting scheme with a modified multidimensional dissipation for high-speed compressible flow analysis on unstructured meshes is proposed. The scheme eliminates nonphysical flow solutions such as the spurious bump of the carbuncle phenomenon observed from the bow shock of the flow over a blunt body and the oscillation in the odd-even grid perturbation in a straight duct for the Quirk's odd-even decoupling test. The proposed scheme is further extended to achieve higher-order spatial and temporal solution accuracy. The performance of the combined procedure is evaluated on unstructured triangular meshes by solving several steady-state and transient high-speed compressible flow problems.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
• /
• pp.1159-1160
• /
• 2006

As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, this has raised potential problems of network protection on electrical power system. One of the numerous problems is an Island phenomenon. There has been an argument that because the probability of islanding is extremely low it may be a non-issue in practice. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an island can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficient to cause a trip, plus the time required to execute the trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. And, third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an island. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. So the verification of anti-islanding performance is strongly needed. In this paper, the authors propose the improved RPV method through considering power quality and anti-islanding capacity of grid-connected three-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"). And the simulation and experimental results are verified.

• 한국컴퓨터정보학회논문지
• /
• 제28권12호
• /
• pp.221-229
• /
• 2023

최근 전력 계통에 인공 관성, 감쇠, 블랙스타트 기능, 독립 운전 기능 등을 제공할 수 있어 많은 주목을 받고 있는 Grid-forming(GFM) 컨버터는 저전압 Microgrids(MG)에서 낮은 라인 임피던스의 X/R 비율과 작지 않은 전력각으로 인한 유효전력과 무효전력 간의 커플링 현상이 발생한다. 이러한 전력 커플링 현상은 GFM 컨버터의 안정성 및 성능 저하 문제, 부정확한 전력 공유 문제, 제어 파라미터 설계 문제를 유발하고 있다. 따라서 본 논문은 GFM 컨버터와 관련된 제어 방법뿐만 아니라 전력 디커플링 방법에 대한 검토 연구로서, 유망 제어 방법을 소개하고 전력 디커플링 방법에 대한 비판적 검토를 통하여 향후 연구 활동의 접근성을 높이고자 하였다. 이에 따라 전력디커플링 방법 연구를 위해 향후 연구자들이 쉽게 접근할 수 있어 분산 발전원 확대에 기여할 수 있을 것이다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 추계학술대회논문집
• /
• pp.848-854
• /
• 2006

In this study, a computational analysis system has been developed in order to investigate flow-induced vibration(FIV) phenomenon for general stator-rotor cascade configurations. Relative movement of the rotor with respect to stator is reflected by modeling independent two computational domains. Fluid domains are modeled using the unstructured grid system with dynamic moving and local deforming methods. Unsteady, Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation SST $k-\omega$ turbulence models are solved for unsteady flow problems. A fully implicit time marching scheme based on the Newmark direct integration method is used flow computing the coupled governing equations of the fluid-structure interaction problem. Detailed FIV responses for different flow conditions are presented with respect to time and vibration characteristics are also physically investigated in the time domain.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2009년도 춘계학술대회 논문집
• /
• pp.652-653
• /
• 2009

In this study, flow-induced vibration (FIV) analyses have been conducted for a 3D compressor blade model. Advanced computational analysis system based on computational fluid dynamics (CFD) and computational structural dynamics (CSD) has been developed in order to investigate detailed dynamic responses of designed compressor blades. Fluid domains are modeled using the computational grid system with local grid deforming and remeshing techniques. Reynolds-averaged Navier-Stokes equations with $\kappa-\varepsilon$ turbulence model are solved for unsteady flow problems of the rotating compressor model. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D compressor blade for fluid-structure interaction (FSI) problems. Detailed dynamic responses and instantaneous pressure contours on the blade surfaces considering flow-separation effects are presented to show the multi-physical phenomenon of the rotating compressor blade.

• 한국소음진동공학회논문집
• /
• 제16권9호
• /
• pp.937-948
• /
• 2006

In this study, a fluid/structure coupled analysis system for simulating complex flow-induced vibration (FIV) phenomenon of cascades has been developed. The flow is modeled using Euler and Wavier-Stokes equations with different turbulent models. The fluid domains are modeled using the unstructured grid system with dynamic deformations due to the motion of structural boundary. The Spalart-Allmaras (S-A) and the SST ${\kappa}-{\omega}$ turbulent models are used to predict the transonic turbulent flows. A fully implicit time marching scheme based on the Newmark direct integration method is used in order to solve the coupled governing equations for viscous flow-induced vibration phenomena. For the purpose of validation for the developed FIV analysis system, comparison results for computational analyses of steady and unsteady aerodynamics and flutter analyses are presented in the transonic flow region. In addition, flow-induced vibration analyses for the isolated cascade and multi-blades cascade models have been conducted to show the physical fluid-structure interaction effects in the time domain.

• 대한조선학회논문집
• /
• 제48권3호
• /
• pp.260-266
• /
• 2011

For long slender offshore structures, such as cables and pipe lines, their interaction with surrounding fluid flow becomes an important issue for global design of ocean systems. We employ a long circular cylinder as a representative case of slender offshore structure. A flexibly mounted cylinder in cross-flow generates complex vortex shedding and results in oscillation of the structure. In this paper, flow behind a circular cylinder at Re=100 is simulated. The vortex shedding pattern and flow induced motion are examined in the cross flow configuration as well as with various yaw-angled configurations. The "Lock-in" phenomenon is also observed when reduced velocity is approximately 4.0. The MAC Grid system, which is the typical grid system for Cartesian mesh and pressure correction methods, are used for solving the incompressible Navier-Stokes equations. Predictor/Corrector method is applied for obtaining a non-linear response of structure at the flexibly mounted. The existance and motion of the body is represented by the immersed boundary technique.