• ETRI Journal
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• 제43권2호
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• pp.221-231
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• 2021

To resolve energy depletion issues in massive Internet of Things sensor networks, we developed a set of distributed energy beamforming methods with one-bit feedback and clustering for multi-node wireless energy transfer, where multiple singleantenna distributed energy transmitters (Txs) transfer their energy to multiple nodes wirelessly. Unlike previous works focusing on distributed information beamforming using a single energy receiver (Rx) node, we developed a distributed energy beamforming method for multiple Rx nodes. Additionally, we propose two clustering methods in which each Tx node chooses a suitable Rx node. Furthermore, we propose a fast distributed beamforming method based on Tx sub-clustering. Through computer simulations, we demonstrate that the proposed distributed beamforming method makes it possible to transfer wireless energy to massive numbers of sensors effectively and rapidly with small implementation complexity. We also analyze the energy harvesting outage probability of the proposed beamforming method, which provides insights into the design of wireless energy transfer networks with distributed beamforming.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권9호
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• pp.2134-2153
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• 2013

A network-coding-based scheme is proposed to improve the energy efficiency of distributed storage systems in WSNs (Wireless Sensor Networks). We mainly focus on two problems: firstly, consideration is given to effective distributed storage technology; secondly, we address how to effectively repair the data in failed storage nodes. For the first problem, we propose a method to obtain a sparse generator matrix to construct network codes, and this sparse generator matrix is proven to be the sparsest. Benefiting from this matrix, the energy consumption required to implement distributed storage is reduced. For the second problem, we designed a network-coding-based iterative repair method, which adequately utilizes the idea of re-encoding at intermediate nodes from network coding theory. Benefiting from the re-encoding, the energy consumption required by data repair is significantly reduced. Moreover, we provide an explicit lower bound of field size required by this scheme, which implies that it can work over a small field and the required computation overhead is very low. The simulation result verifies that the proposed scheme not only reduces the total energy consumption required to implement distributed storage system in WSNs, but also balances energy consumption of the networks.

• KEPCO Journal on Electric Power and Energy
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• 제5권4호
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• pp.295-309
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• 2019

본 논문은 신재생을 배전계통에 추가 수용하기 위해 배전계통의 접속허용기준을 상향하여 운전하는 방안을 검토하고 실증한 결과를 분석하는 내용을 다룬다. 대한민국의 배전계통의 경우, 일반적인 공용배전선로는 최대 10 MVA까지 신재생이 접속할 수 있도록 규정하고 있으며 신재생으로 인해 발생하는 역조류에 의해 계통전압이 전기사업법에서 지정한 범위를 초과하지 않아야 한다. 그러나 배전계통에 상시 존재하는 최소부하 및 발전원의 발전 특성에 따라 신재생을 추가 접속할 수 있는 여유용량이 존재할 수 있음을 고려해야 한다. 따라서 배전계통의 접속허용용량 기준 상향 검토를 위해, 신재생이 접속허용한도인 10 MVA만큼 최대한 접속된 상황에서 모든 신재생이 배전계통운영자에 의해 감시되고 있는 배전선로를 선정하여 단계적인 추가 접속을 시행하였다. 신재생으로 인한 배전계통의 전력조류와 전압 프로파일 영향을 분석함으로써 현재의 기준을 초과하여 신재생을 접속 시킬 때 발생 가능한 계통영향 분석과 더불어 향후 고려해야할 요인을 정의한다.

• Journal of Electrical Engineering and Technology
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• 제11권5호
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• pp.1100-1107
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• 2016

• Journal of Communications and Networks
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• 제18권4호
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• pp.649-657
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• 2016

In this paper, we investigate energy efficiency (EE) of the traditional co-located and the distributed massive multiple-input multiple-output (MIMO) systems. First, we derive an approximate EE expression for both the idealistic and the realistic power consumption models. Then an optimal energy-efficient remote access unit (RAU) selection algorithm based on the distance between the mobile stations (MSs) and the RAUs are developed to maximize the EE for the downlink distributed massive MIMO systems under the realistic power consumption model. Numerical results show that the EE of the distributed massive MIMO systems is larger than the co-located massive MIMO systems under both the idealistic and realistic power consumption models, and the optimal EE can be obtained by the developed energy-efficient RAU selection algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.3771-3788
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• 2015

This paper studies the distributed energy efficient resource management in the Internet of Things (IoT). Wireless communication networks support the IoT without limitation of distance and location, which significantly impels its development. We study the communication channel and energy management in the wireless communication network supported IoT to improve the ability of connection, communication, share and collaboration, by using the game theory and distributed learning algorithm. First, we formulate an energy efficient neighbor collaborative game model and prove that the proposed game is an exact potential game. Second, we design a distributed energy efficient channel selection learning algorithm to obtain the global optimum in a distributed manner. We prove that the proposed algorithm will asymptotically converge to the global optimum with geometric speed. Finally, we make the simulations to verify the theoretic analysis and the performance of proposed algorithm.

• 전기학회논문지
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• 제58권4호
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• pp.718-724
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• 2009

Recently, Increase of energy consumption is continued accordingly because economy is constant growth. so we need long term of energy supply stability and develop new energy source. The effort of environmental improvement is necessary and our country has to educe conservatory gas in these situation, our energy policy is summarized that minimizes energy consumption and uses kinds of energy source. This paper studied some effort of stability that distributed generation put in electric system through line fault, sudden load change. And then this paper calculated penetrated level of distributed generation in system transient stability.

• 인터넷정보학회논문지
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• 제8권3호
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• pp.57-63
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• 2007

분산 무선 네트워크에서 작업을 수행하기 위해서는 이동 단말기에 안정적인 전원의 공급이 필수적인 요소이다. 본 논문에서는 무선 네트워크에서 작업을 수행하기에 제한적인 조건인 전원문제의 해결을 위해서 모바일 단말기들의 이동성 관리를 통한 분산 작업을 효율적으로 수행하는 방안을 제시하였다. 에너지 사용량은 통계모델을 통하여 분석할 수 있으며, 또한 이동성 관리를 통해서 모바일 단말기 내에서 분산작업 수행시에 필요한 에너지 필요량을 예측할 수 있다. 그러므로 본 논문을 통하여 정규적인 이동성을 가지는 이동 단말기들을 통하여 안정적으로 분산 작업을 수행할 수 있는 알고리즘 및 그 유효성을 제시하였다.

• 플랜트 저널
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• 제17권3호
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• pp.34-36
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• 2021

기존의 중앙집중식 발전의 탈피와 에너지 전환 및 환경문제 인식에 의해 신재생에너지 기반의 분산발전시스템에 대한 관심이 증가하고 있다. 본 연구에서는 에너지저장장치로 납축전지를 사용하는 PV 및 WT 기반의 분산발전시스템을 모사하여 최적용량을 선정하였다. 기존 발전원으로 CHP를 채택하였으며 시스템의 최적용량은 기존발전원의 운전상황(전부하/부분부하)에 따라 MOGA를 통해 도출하였다. 또한 동일한 배터리 용량에서 배터리 충전방식이 달라지면 배터리의 수명이 달라지는 것을 확인하였다. 따라서 경제적이고 안정적인 전력수급을 위해서는 배터리 충전방식을 고려한 분산발전시스템의 용량선정이 수행되어야 한다.

• ETRI Journal
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• 제43권3호
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• pp.389-399
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• 2021

In this paper, we propose one-bit feedback-based distributed beamforming (DBF) techniques for simultaneous wireless information and power transfer in interference channels where the information transfer and power transfer networks coexist in the same frequency spectrum band. In a power transfer network, multiple distributed energy transmission nodes transmit their energy signals to a single energy receiving node capable of harvesting wireless radio frequency energy. Here, by considering the Internet-of-Things sensor network, the energy harvesting/information decoding receivers (ERx/IRx) can report their status (which may include the received signal strength, interference, and channel state information) through one-bit feedback channels. To maximize the amount of energy transferred to the ERx and simultaneously minimize the interference to the IRx, we developed a DBF technique based on one-bit feedback from the ERx/IRx without sharing the information among distributed transmit nodes. Finally, the proposed DBF algorithm in the interference channel is verified through the simulations and also implemented in real time by using GNU radio and universal software radio peripheral.