• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권10호
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• pp.4698-4716
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• 2017

Wireless signal transmission is influenced by environmental effects. These effects have also been challenging for Vehicular Ad hoc Network (VANET) in real-time communication. More specifically, in an urban environment, with high mobility among vehicles, a vehicle's status from the transmitter can instantly trigger from line of sight to non-line of sight, which may cause loss of real-time communication. In order to overcome this, a deterministic signal propagation model is required, which has less complexity and more feasibility of implementation. Hence, we propose a realistic path loss model which adopts ray tracing technique for VANET in a grid urban environment with less computational complexity. To evaluate the model, it is applied to a vehicular simulation scenario. The results obtained are compared with different path loss models in the same scenario based on path loss value and application layer performance analysis. The proposed path loss model provides higher loss value in dB compared to other models. Nevertheless, the performance of vehicle-vehicle communication, which is evaluated by the packet delivery ratio with different vehicle transmitter density verifies improvement in real-time vehicle-vehicle communication. In conclusion, we present a realistic path loss model that improves vehicle-vehicle wireless real-time communication in the grid urban environment.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.513-520
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• 2018

Since Paris Climate Change Conference in 2015, many policies to reduce the emission of greenhouse gas have been accelerating, which are mainly related to renewable energy resources and micro-grid. Presently, the technology development and demonstration projects are mostly focused on diversifying the power resources by adding wind turbine, photo-voltaic and battery storage system in the island-type small micro-grid. It is expected that the large-scaled micro-grid projects based on the regional district and town/complex city, e.g. the block type micro-grid project in Daegu national industrial complex will proceed in the near future. In this case, the economic cost or the carbon emission can be optimized by the efficient operation of energy mix and the appropriate construction of electric and heat supplying facilities such as cogeneration, renewable energy resources, BESS, thermal storage and the existing heat and electricity supplying networks. However, when planning a large residential town or city, the concrete plan of the energy infrastructure has not been established until the construction plan stage and provided by the individual energy suppliers of water, heat, electricity and gas. So, it is difficult to build the efficient energy portfolio considering the characteristics of town or city. This paper introduces an energy mix optimization(EMO) method to determine the optimal capacity of thermal and electric resources which can be applied in the design stage of the real large-scaled residential town or city, and examines the feasibility of the proposed method by applying the real heat and electricity demand data of large-scale residential towns with thousands of households and by comparing the result of HOMER simulation developed by National Renewable Energy Laboratory(NREL).

• 조명전기설비학회논문지
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• 제19권6호
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• pp.52-58
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• 2005

Micro-Grid의 개념은 CERTS(Consortium for Electric Reliability Technology Solutions)에 의해 제안된 새로운 분산 전원 망으로서 부하에 열과 수 $[KW]{\sim}1[MW]$ 사이의 전력을 함께 제공하는 Micro-Source에 의해 구성되어 있다. Micro-Source는 친환경적인 연료전지나 마이크로터빈 등을 에너지원으로 사용하며, 전력품질 제어를 위해 전압형 인버터를 채용하고 독립적인 유무효전력 제어가 가능한 새로운 개념의 분산전원이다. Micro-Source가 효율적으로 유효전력 및 무효전력을 전력시스템에 공급하기 위해서는 계통연계용 인덕터가 필요한데, 본 논문에서는 인덕터의 제어 범위와 각 변수의 한계를 함께 고려하고 전달 및 제어하고자 히는 유효 및 무효 전력의 범위에 의해 인덕터 용량을 결정하는 절차를 제안하였다.

• Journal of Information Processing Systems
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• 제7권2호
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• pp.299-320
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• 2011

The overhead of processing fine-grain tasks on a grid induces the need for batch processing or task group deployment in order to minimise overall application turnaround time. When deciding the granularity of a batch, the processing requirements of each task should be considered as well as the utilisation constraints of the interconnecting network and the designated resources. However, the dynamic nature of a grid requires the batch size to be adaptable to the latest grid status. In this paper, we describe the policies and the specific techniques involved in the batch resizing process. We explain the nuts and bolts of these techniques in order to maximise the resulting benefits of batch processing. We conduct experiments to determine the nature of the policies and techniques in response to a real grid environment. The techniques are further investigated to highlight the important parameters for obtaining the appropriate task granularity for a grid resource.

• 전력전자학회논문지
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• 제26권2호
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• pp.75-81
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• 2021

This study analyzes the resonance characteristics caused by the mutual interference between LCL filters and the grid impedance under the parallel operation of the grid-connected inverter using the LCL filter. These characteristics are verified through simulation and experiment. Two inverters are used to connect to the grid in parallel, and the system parameters, including the LCL filter, are set to the same conditions. In the case of inverters running in parallel at the point of common coupling, the presence of grid impedance causes mutual interference between the LCL filters of each inverter, and the deviation of the filter resonance frequency is analyzed to understand the parallel inverter. The correlation between the number of devices and the size of grid impedance is simulated by PSIM and verified by MATLAB. By connecting the real-time digital simulator Typhoon HILS to the DSP 28377 control board, the mutual interference characteristics are tested under the condition of two inverters running in parallel. The experimental and analysis results are the same, indicating the validity of the analysis.

• 품질경영학회지
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• 제49권2호
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• pp.201-211
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• 2021

Purpose: This paper proposes a density adaptive grid algorithm for the k-NN regression model to reduce the computation time for large datasets without significant prediction accuracy loss. Methods: The proposed method utilizes the concept of the grid with centroid to reduce the number of reference data points so that the required computation time is much reduced. Since the grid generation process in this paper is based on quantiles of original variables, the proposed method can fully reflect the density information of the original reference data set. Results: Using five real-life datasets, the proposed k-NN regression model is compared with the original k-NN regression model. The results show that the proposed density adaptive grid-based k-NN regression model is superior to the original k-NN regression in terms of data reduction ratio and time efficiency ratio, and provides a similar prediction error if the appropriate number of grids is selected. Conclusion: The proposed density adaptive grid algorithm for the k-NN regression model is a simple and effective model which can help avoid a large loss of prediction accuracy with faster execution speed and fewer memory requirements during the testing phase.

• Journal of Positioning, Navigation, and Timing
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• 제4권2호
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• pp.67-72
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• 2015

Power grid techniques are distributed over general power systems ranging from power stations to power transmission, power distribution, and users. To monitor and control the elements and performance of a power system in real time in the extensive area of power generation, power transmission, wide-area monitoring (WAM) and control techniques are required (Sattinger et al. 2007). Also, to efficiently operate a power grid, integrated techniques of information and communication technology are required for the application of communication network and relevant equipment, computing, and system control software. WAM should make a precise power grid measurement of more than once per cycle by time synchronization using GPS. By collecting the measurement values of a power grid from substations located at faraway regions through remote communication, the current status of the entire power grid system can be examined. However, for GPS that is used in general national industries, unexpected dangerous situations have occurred due to its deterioration and jamming. Currently, the power grid is based on a synchronization system using GPS. Thus, interruption of the time synchronization system of the power system due to the failure or abnormal condition of GPS would have enormous effects on each field such as economy, security, and the lives of the public due to the destruction of the synchronization system of the national power grid. Developed countries have an emergency substitute system in preparation for this abnormal situation of GPS. Therefore, in Korea, a system that is used to prepare for the interruption of GPS reception should also be established on a long-term basis; but prior to this, it is required that an evaluation technique for the time synchronization performance of a GPS receiver using an atomic clock within the power grid. In this study, a monitoring system of time synchronization based on GPS at a power grid was implemented, and the results were presented.

• 수산해양기술연구
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• 제51권3호
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• pp.312-320
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• 2015

The 1/5 scale-down model of the Bycatch Reduction Device (BRD) from an Argentinean demersal trawl was tested in a circulating water channel. The BRD is designed to help small Hake (merluza, merluccius hubbsi) to escape from a trawl. It is settled in front of a trawl codend, and is equipped with selection grids that help small fish to escape from the gear and guiding panels that help fish to meet with the grids. Bars of the grids are wires covered by the PVC and other parts of the BRD are made of net. When the velocity was less than 0.65 m/sec (2.81 Kont when translated to real towing speed) which is slow speed compared with real towing speed, position between an upper guiding panel and an upper selection grid were good to help small fish to escape. When the velocity was more than 0.8 m/sec (3.41 Knot when translated to real towing speed) which is similar to and faster than real towing speed, it was considered that small fish may have difficulties in escaping because the gap was not enough between an upper guiding panel and an upper selection grid. The lower selection grid was sat on the bottom of the tank without an angle due to the weight that it carries. Improvements were proposed to position the panels and the grids better.

• 한국음향학회지
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• 제39권3호
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• pp.179-190
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• 2020

본 논문에서는 일반 빔형성, 적응 빔형성, 압축센싱을 이용하여 도래각을 추정한다. 이때, 적응 빔형성으로 Minimum Variance Distortionless Response(MVDR)과 Multiple Signal Classification(MUSIC)을 사용하였고, 압축 빔형성(compressive sensing beamforming)을 위해 무격자 압축센싱(grid-free compressive sensing)을 적용하였다. 앞서 언급한 각 기법들의 이론적 배경 및 한계점을 소개하고 모의실험 및 실제 실험을 통해 각 기법의 성능을 비교하였다. 실제 실험은 반사 신호가 존재하는 환경에서 수행하였으며, 2대의 스피커를 통해 음원을 송신하고 8대의 마이크로폰을 사용한 선배열을 통해 데이터를 수신하였다. 모의실험 및 실제 실험 결과를 통해 상관신호가 존재하지 않을 때, 적응 빔형성과 무격자 압축 빔형성이 일반 빔형성보다 고해상도의 결과를 보임을 확인하였다. 반면, 반사 신호가 존재하는 환경에서 적응 빔형성의 성능이 저하되지만, 무격자 압축 빔형성의 경우 반사 신호의 영향을 받지 않고 일반 빔형성의 분해능이 개선됨을 확인하였다.

• 한국통신학회논문지
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• 제35권9B호
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• pp.1399-1406
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• 2010

기존 전력망에 ICT를 접목한 스마트 그리드 환경에서 고객니즈에 기반한 수용가 서비스를 도출하기 위하여 HV, FGD 및 정량설문조사를 통해 수용가의 전기사용 추구 가치와 Unmet 니즈를 분석하였다. 연구결과, 소비자들은 전기를 가전기기 이용을 더욱 '편리'하게 해주는 존재로 인식하고, 전자파 감전 감소의 '안전'을 추구하며, 이해가 쉽고 스트레스가 적은 전기 '절약'을 원하는 것으로 조사 되었다. 그리고 전기절약을 도와주는 간편한 '기능', 전기사용량이나 전자제품의 '정보', 전기절약 유도를 위한 '동기' 유발 등에 Unmet 니즈가 존재하는 것으로 분석 되었다. 본 연구에서는 고객이 추구하는 가치와 Unmet 니즈를 반영하여 전자기기에 대한 사용량 실시간 모니터링과 제어가 가능한 홈 네트워크와 결합된 서비스로서 에너지 사용량 알리미 서비스, 대기전력 차단 서비스, 댁내 가전기기 원격제어 서비스, 에너지 컨설팅 서비스 등 4종의 스마트 홈 서비스를 도출하였다. 미래 스마트 그리드 홈 서비스 고객은 4종 서비스 모두에 60%이상의 이용의향을 보였으며 특히 에너지 사용량 알리미 서비스와 대기전력 차단 서비스에 약 80%의 이용의향을 보였다.