• Title/Summary/Keyword: Virtual Grid

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DC Injection Control for Grid-Connected Single-Phase Inverters Based on Virtual Capacitor

  • Wang, Wei;Wang, Ping;Bei, Taizhou;Cai, Mengmeng
    • Journal of Power Electronics
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    • v.15 no.5
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    • pp.1338-1347
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    • 2015
  • DC injection is a critical issue in transformerless grid-connected inverters. DC injection control based on virtual capacitor has the advantages of low cost, low loss, high accuracy and easy implementation. In this paper, the principle of DC injection control based on virtual capacitor was analyzed. In addition, the applicable conditions, working process, steady state error and advantages were also discussed in detail. The design of the control parameters based on virtual capacitor was proposed in a grid-connected inverter with LCL filter. The robustness of the control parameters was also discussed. Simulation and experimental results verify the validity of the analysis and demonstrate that this research has a certain value in engineering applications.

A Technic to Improve and Implement Virtual Environment Grid Information in War-game Model (워게임모델의 가상환경격자정보 개선과 구축 기법)

  • Choi, Beyoung-Moo;Yang, Hae-Sool
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.4
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    • pp.785-794
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    • 2009
  • We studied on a technic to improve and implement the virtual environment grid information in the war-game model. The virtual environment data are categorized into ground, sea, and air, and separatedly managed and operated. The data are implemented and managed in the geographical information and topography type information. The geographical information, including grid location coordinate and sea level, are managed in computer files as a grid type. We improved the representation of the sea level by mapping the sea level value of the grid information file into GCV and suggested the dynamic virtual environment implementation technic for the region with the large range of tide. In the experiments, we could know that it is possible to adopt the dynamic virtual environment to the war-game model.

Efficient Resource Management Framework on Grid Service (그리드 서비스 환경에서 효율적인 자원 관리 프레임워크)

  • Song, Eun-Ha;Jeong, Young-Sik
    • Journal of KIISE:Computer Systems and Theory
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    • v.35 no.5
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    • pp.187-198
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    • 2008
  • This paper develops a framework for efficient resource management within the grid service environment. Resource management is the core element of the grid service; therefore, GridRMF(Grid Resource Management Framework) is modeled and developed in order to respond to such variable characteristics of resources as accordingly as possible. GridRMF uses the participation level of grid resource as a basis of its hierarchical management. This hierarchical management divides managing domains into two parts: VMS(Virtual Organization Management System) for virtual organization management and RMS(Resource Management System) for metadata management. VMS mediates resources according to optimal virtual organization selection mechanism, and responds to malfunctions of the virtual organization by LRM(Local Resource Manager) automatic recovery mechanism. RMS, on the other hand, responds to load balance and fault by applying resource status monitoring information into adaptive performance-based task allocation algorithm.

Scalable Resource Sharing using Group Similarity Function in Grid System (그리드 시스템에서 그룹유사함수를 이용한 확장성 있는 자원공유)

  • Mateo, Romeo Mark A.;Lee, Jae-Wan;Lee, Mal-Rey
    • Journal of Internet Computing and Services
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    • v.11 no.4
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    • pp.73-83
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    • 2010
  • The scalability of a grid system should be efficiently designed to handle the increasing number of grid users. This paper presents a scalable resource sharing mechanism among virtual organizations (VO) in grid environment by the scalable virtual organizations (SVO). The proposed grid architecture is composed of standard services of a grid system to manage the SVO. We propose a group similarity function which is used to determine similarities among VOs to select the VOs to merge. We compared other similarity functions to the GSF and determined the throughput performance of the SVO using simulation for grid system.

A Virtual RLC Active Damping Method for LCL-Type Grid-Connected Inverters

  • Geng, Yiwen;Qi, Yawen;Zheng, Pengfei;Guo, Fei;Gao, Xiang
    • Journal of Power Electronics
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    • v.18 no.5
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    • pp.1555-1566
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    • 2018
  • Proportional capacitor-current-feedback active damping (AD) is a common damping method for the resonance of LCL-type grid-connected inverters. Proportional capacitor-current-feedback AD behaves as a virtual resistor in parallel with the capacitor. However, the existence of delay in the actual control system causes impedance in the virtual resistor. Impedance is manifested as negative resistance when the resonance frequency exceeds one-sixth of the sampling frequency ($f_s/6$). As a result, the damping effect disappears. To extend the system damping region, this study proposes a virtual resistor-inductor-capacitor (RLC) AD method. The method is implemented by feeding the filter capacitor current passing through a band-pass filter, which functions as a virtual RLC in parallel with the filter capacitor to achieve positive resistance in a wide resonance frequency range. A combination of Nyquist theory and system close-loop pole-zero diagrams is used for damping parameter design to obtain optimal damping parameters. An experiment is performed with a 10 kW grid-connected inverter. The effectiveness of the proposed AD method and the system's robustness against grid impedance variation are demonstrated.

Review of Virtual Power Plant Applications for Power System Management and Vehicle-to-Grid Market Development (전력시스템 관리 및 Vehicle to Grid 전력시장 개발을 위한 가상발전소의 활용방안)

  • Jin, Tae-Hwan;Park, Herie;Chung, Mo;Shin, Ki-Yeol;Foley, Aoife;Cipcigan, Liana
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.12
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    • pp.2251-2261
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    • 2016
  • The use of renewable energy sources and energy storage systems is increasing due to new policies in the energy industries. However, the increase in distributed generation hinders the reliability of power systems. In order to stabilize power systems, a virtual power plant has been proposed as a novel power grid management system. The virtual power plant plays includes different distributed energy resources and energy storage systems. We define a core virtual power plant technology related to demand response and ancillary service for the cases of Korea, America, and Europe. We also suggest applications of the proposed virtual power plant to the vehicle-to-grid market for restructuring national power industries in Korea.

Efficient Processing of Huge Airborne Laser Scanned Data Utilizing Parallel Computing and Virtual Grid (병렬처리와 가상격자를 이용한 대용량 항공 레이저 스캔 자료의 효율적인 처리)

  • Han, Soo-Hee;Heo, Joon;Lkhagva, Enkhbaatar
    • Journal of Korea Spatial Information System Society
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    • v.10 no.4
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    • pp.21-26
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    • 2008
  • A method for processing huge airborne laser scanned data using parallel computing and virtual grid is proposed and the method is tested by generating raster DSM(Digital Surface Model) with IDW(Inverse Distance Weighting). Parallelism is involved for fast interpolation of huge point data and virtual grid is adopted for enhancing searching efficiency of irregularly distributed point data. Processing time was checked for the method using cluster constituted of one master node and six slave nodes, resulting in efficiency near to 1 and load scalability property. Also large data which cannot be processed with a sole system was processed with cluster system.

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Development of a Virtual Frisch-Grid CZT Detector Based on the Array Structure

  • Kim, Younghak;Lee, Wonho
    • Journal of Radiation Protection and Research
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    • v.45 no.1
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    • pp.35-44
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    • 2020
  • Background: Cadmium zinc telluride (CZT) is a promising material because of a high detection efficiency, good energy resolution, and operability at room temperature. However, the cost of CZT dramatically increases as its size increases. In this study, to achieve a large effective volume with relatively low cost, an array structure comprised of individual virtual Frisch-grid CZT detectors was proposed. Materials and Methods: The prototype consisted of 2 × 2 CZTs, a holder, anode and cathode printed circuit boards (PCBs), and an application-specific integrated circuit (ASIC). CZTs were used and the non-contacting shielding electrode method was applied for virtual Frisch-grid effect. An ASIC was used, and the holder and the PCBs were fabricated. In the current system, because the CZTs formed a common cathode, a total of 5 channels were assigned for data processing. Results and Discussion: An experiment using 137Cs at room temperature was conducted for 10 minutes. Energy and timing information was acquired and the depth of interaction was calculated by the timing difference between the signals of both electrodes. Based on obtained three-dimensional position information, the energy correction was carried out, and as a result the energy spectra showed the improvements. In addition, a Compton image was reconstructed using the iterative method. Conclusion: The virtual Frisch-grid CZT detector based on the array structure was developed and the energy spectra and the Compton image were successfully acquired.

A Study on the Usefulness of VGR (Virtual Grid Role) Algorithm for Elevation of Image Quality in DR System (DR 시스템에서 화질 개선을 위한 VGR 알고리즘의 유용성에 관한 연구)

  • Yang, Hyun-Jin;Han, Dong-Kyoon
    • Journal of the Korean Society of Radiology
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    • v.14 no.6
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    • pp.763-772
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    • 2020
  • During X-ray examinations in the DR system, the scattered X-rays physically generated by the patient cause image blurring in poor quality. Although X-rays to increase the contrast of images, this increases the patient's exposure dose and is likely to result in grid induced artifacts. Therefore, the purpose of this study is obtain images similar to those of real-grid with non-grid level conditions using a VGR (Virtual Grid Role) algorithm that serves as a virtual grid. Comparing MTF, SNR and CNR of non-grid and VGR algorithm images obtained with 70% exposure conditions of real-grid images showed that the MTF0.5 differed from 0.265 to 0.350 and the MTF0.1 from 0.412 to 0.467 and the SNR, CNR were also different. In addition, comparing MTF, SNR and CNR of VGR algorithm and real-grid images showed that the MTF0.5 differed from 0.350 to 0.367 and the MTF0.1 from 0.467 to 0.483 and the SNR, CNR by little.

A Study of Automatically Authentication System for Virtual Resource Organization on Grid (그리드상의 가상 자원 조직에 대한 자동 인증 시스템 연구)

  • 최병선;이원구;이재광
    • Proceedings of the Korea Contents Association Conference
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    • 2004.05a
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    • pp.301-306
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    • 2004
  • The Grid VO(Virtual Organization) is temporary VO where gather indivisual, authority, or system resource, differ from previous VO concept that controled by internal principal and policy set. It have many problems in case of indivisuals, authorities, or system resources that became member\ulcorner of some Grid VO at same time and combination followed changing condition of system resource for building Grid VO. This paper propose lightweighted Grid VO authentication system based on XML security to solve the authentication of the problems occuring in building Grid VO. In this paper, Grid VO authentication system is including Grid VO authentication module that is intermediate management system in PH to previous authentication service structure and provide effective authentication service to Grid VO.

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