Fault-Tolerant Tasking and Guidance of an Airborne Location Sensor Network

N. Eva Wu,Yan Guo,Kun Huang,Matthew C. Ruschmann,Mark L. Fowler 대한전기학회 2008 International Journal of Control, Automation, and Vol.6 No.3

This paper is concerned with tasking and guidance of networked airborne sensors to achieve fault-tolerant sensing. The sensors are coordinated to locate hostile transmitters by intercepting and processing their signals. Faults occur when some sensor-carrying vehicles engaged in target location missions are lost. Faults effectively change the network architecture and therefore degrade the network performance. The first objective of the paper is to optimally allocate a finite number of sensors to targets to maximize the network life and availability. To that end allocation policies are solved from relevant Markov decision problems. The sensors allocated to a target must continue to adjust their trajectories until the estimate of the target location reaches a prescribed accuracy. The second objective of the paper is to establish a criterion for vehicle guidance for which fault-tolerant sensing is achieved by incorporating the knowledge of vehicle loss probability, and by allowing network reconfiguration in the event of loss of vehicles. Superior sensing performance in terms of location accuracy is demonstrated under the established criterion.

신재생 에너지 전원을 고려한 배전선로 고장구간 판단 기법

이한성(Han-Seong Lee),전철우(Cheol-Woo Jeon),김영국(Young-Kook Kim),임성일(Seong-Il Lim) 대한전기학회 2014 전기학회논문지 Vol.63 No.10

Faulted section identification is one of the most important function in distribution automation systems. Conventional over current detection based fault indicators frequently mal-operate due to the reverse fault current from the renewable energy resources. This paper present a new faulted section identification method based on the fuzzy decision making technique. In order to establish feasibility of the proposed method, case studies using Matlab Simulink has been performed.

QoS 멀티캐스트 라우팅을 위한 계획된 트리 재구성 방법

한승재(Seungjae Han),박선주(Sunju Park) 한국정보과학회 2007 정보과학회논문지 : 정보통신 Vol.34 No.2

전송-수신 쌍들을 연결하는 많은 수의 경로들로 이루어진 멀티캐스트 트리에서 네트워크 구성요소의 실패는 멀티캐스트 트리의 일부를 손상시킬 수 있다. 그러나 하나의 구성요소의 실패를 복구하기 위해 전체 멀티캐스트 트리를 다시 만드는 것은, 실패의 영향을 받지 않은 경로를 사용하는 그룹 멤버들까지도 서비스의 중단을 겪어야 하기 때문에 바람직하지 않다. 본 논문은 QoS 멀티캐스트 트리에서 재구성해야 할 영역을 줄이면서 재구성의 성공 가능성을 최대화하는 계획된 재구성(Pre-Planned Reconfiguration: PPR) 정책을 제안한다. PPR 방식은 멀티캐스트 트리의 전송-수신 쌍을 연결하는 각 경로에 재구성 경로를 미리 만들고, 이들 경로에 필요한 자원을 미리 예약해 둔다. 이를 위해 우리는 기존 멀티캐스트 트리의 변화를 최소화 하며 손상되지 않은 부분들의 서비스를 최대한 유지하는 재구성 경로의 라우팅 방법을 고안하였으며, 효율적 자원 공유 방법을 사용하여 재구성 경로들을 위해 예약된(실패가 일어나지 않을 경우 사용되지 않는) 자원의 양을 줄인다. PPR 방식은 실패 복구를 위해 여러 멀티캐스트 세션들이 동시에 엄청난 경쟁을 하는 것을 막을 수 있다. 시물레이션을 통해 최단경로 라우팅을 사용하는 전송자 중심 멀티캐스트 트리와 공유 멀티캐스트 트리에서 각각 성능을 평가한 결과, PPR 방식은 적당한 오버헤드내에서 모든 그룹 멤버들에게 성공적인 재구성을 제공한다. 또한 PPR 방식은 그룹 멤버쉽이 동적으로 변화할 때에도 잘 적응한다. A multicast tree includes several, possibly a large number of, paths connecting source-receiver pairs, and network failure may disable part of the multicast tree. Reconstruction of the entire multicast tree to recover from a component failure is highly undesirable, because some group members have to suffer service disruptions even though the communication paths to/from them are not affected by the failure. To limit reconfiguration region and to maximize the likelihood of successful reconfiguration, we propose and evaluate a pre-planned reconfiguration policy for QoS multicast sessions. Specifically, we equip a reconfiguration path (RP) with each end-to-end path that connects a source-receiver pair in the multicast tree, and reserve resources in advance along the RPs. Efficient resource-sharing techniques are applied to reduce the amount of resources reserved for RPs but not used in the absence of failures. This way, we prevent uncontrolled competition among different multicast sessions which may simultaneously try to recover from failures. We evaluate the performance of the proposed scheme using simulation on randomly-generated networks. We use the shortest-path routing for QoS multicast sessions, and simulate both source-based and shared multicast trees. The evaluation results indicates that successful pre-planned reconfiguration can be achieved for all group members with reasonable overhead. Our scheme is also shown to adapt well to dynamic changes of group membership.

커널 자원 관리 기법 설계 및 구현

김병진(Byung Jin Kim),백승재(Seung Jae Baek),김근은(Keun Eun Kim),최종무(Jong Moo Choi) 한국정보과학회 2009 정보과학회논문지 : 시스템 및 이론 Vol.36 No.3

모듈은 동적으로 커널에 적재 가능한 오브젝트 파일로써 적재된 이후에는 커널의 권한으로 모든 자원에 대해 완벽한 접근 권한을 가진다. 따라서 잘못 작성된 모듈이나 혹은 정상적으로 작성된 모듈이라 할지라도 운영체제의 상황에 따라 비정상 수행되는 경우 시스템 전체의 안정성과 신뢰성에 치명적인 영향을 끼친다. 따라서 본 논문에서는 모듈이 발생시킬 수 있는 다양한 자원관련 문제를 해결하기 위해 커널 자원 보호자를 설계하였다. 커널 자원 보호자는 메모리, 주 번호, 워크 큐 등 운영체제가 관리하는 다양한 자원에 대한 보호를 제공한다. 제안된 기법은 리눅스 2.6.18에 실제 구현되었으며, 실험을 통해 본 논문에서 제안한 커널 자원 관리가 커널 자원을 효율적으로 보호하고 있음을 보였다. Module is an object file that can be loaded into operating system dynamically and has complete privileged access to all resources in kernel. Therefore trivial misuses in a module may cause critical system halts or deadlock situations. In this paper, we propose Kernel Resource Protector(KRP) scheme to reduce the various problems caused by module. KRP provides protections of a variety of kernel resources such as memory, major number and work queue resource. We implement the scheme onto linux kernel 2.6.18, and experimental results show that our scheme can protect kernel resources effectively.

Providing survivability for virtual networks against substrate network failure

( Ying Wang ),( Qingyun Chen ),( Wenjing Li ),( Xuesong Qiu ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.9

Network virtualization has been regarded as a core attribute of the Future Internet. In a network virtualization environment (NVE), multiple heterogeneous virtual networks can coexist on a shared substrate network. Thus, a substrate network failure may affect multiple virtual networks. In this case, it is increasingly critical to provide survivability for the virtual networks against the substrate network failures. Previous research focused on mechanisms that ensure the resilience of the virtual network. However, the resource efficiency is still important to make the mapping scheme practical. In this paper, we study the survivable virtual network embedding mechanisms against substrate link and node failure from the perspective of improving the resource efficiency. For substrate link survivability, we propose a load-balancing and re-configuration strategy to improve the acceptance ratio and bandwidth utilization ratio. For substrate node survivability, we develop a minimum cost heuristic based on a divided network model and a backup resource cost model, which can both satisfy the location constraints of virtual node and increase the sharing degree of the backup resources. Simulations are conducted to evaluate the performance of the solutions. The proposed load balancing and re-configuration strategy for substrate link survivability outperforms other approaches in terms of acceptance ratio and bandwidth utilization ratio. And the proposed minimum cost heuristic for substrate node survivability gets a good performance in term of acceptance ratio.

하이브리드 클라우드 컴퓨팅에서 결함 포용을 위한 자원 선택 기법

위수연(SuYeon Wi),박지수(JiSu Park),이대원(DaeWon Lee),유헌창(HeonChang Yu) 한국정보기술학회 2011 Proceedings of KIIT Conference Vol.2011 No.5

하이브리드 클라우드 컴퓨팅은 유선 환경에서의 서버 기반 클라우드 컴퓨팅과 무선 환경에서의 모바일 기반 클라우드 컴퓨팅을 통합한 컴퓨팅 환경이다. 유선 환경의 클라우드에 비해 모바일 클라우드는 모바일 장치의 자유로운 이동으로 인한 네트워크 끊김으로 신뢰성이 낮아지기 때문에 모바일 클라우드 환경에서 신뢰적인자원 제공이 필요하다. 이에 본 논문에서는 모바일 장치의 정해진 이동 패턴을 분석하고 모바일 장치의 이동영역을 MAP이 관리하게 하여 이동성으로 인한 네트워크 끊김을 최소화한다. 그러나 모바일 장치가 MAP이 관리하는 영역을 벗어나게 되면 네트워크가 끊겨 결함이 발생하고, 작업을 수행할 수 없게 된다. 따라서 신뢰적인 작업 수행을 위해 신뢰도가 높은 자원을 선택하여 작업 이주를 하고, 지속적인 작업이 가능하게 한다. 또한 빠른 자원 선택을 위해 체크포인트된 작업 환경과 동일한 플랫폼을 가진 자원을 선택하여 작업이 가능하도록 한다. 이를 위해 동일한 플랫폼을 가진 자원끼리 그룹화하고 그룹 내에서 신뢰적인 자원을 선택하여 자원 제공을 한다. Hybrid Cloud Computing supports an environment that integrated wired based cloud computing with wireless based mobile cloud computing. Compared to the cloud computing of a wired environment, mobile cloud computing need to provide resource reliably due to the low trust which occurred by network disconnection on free movement of mobile device. In this paper, we analyze the mobility patterns of mobile devices and manage the movement of the mobile devices using MAP to minimize the network disconnection of mobility. However, the network fault occurs when the mobile device is out of the management area of MAP, and will not be able to perform jobs. Therefore, we select reliable resources and migrate of the jobs for the trustable usage to provide continuous operation. Also, we minimize the selection cost of the resources by checking which of the resource has the same platform of the checkpointed working environment. For this purpose, we group the resources by the platform, and provide the reliable resources using the group.

An interval type-2 fuzzy logic based strategy for microgrid protection

Bukhari, Syed Basit Ali,Haider, Raza,Saeed Uz Zaman, Muhammad,Oh, Yun-Sik,Cho, Gyu-Jung,Kim, Chul-Hwan IPC Science and Technology Press 2018 International journal of electrical power energy s Vol.98 No.-

<P><B>Abstract</B></P> <P>The concept of microgrids has been introduced to facilitate the integration of the distributed energy resources (DERs) into distribution networks in a more economical, reliable and environment-friendly manner. One of the critical challenges associated with microgrids is devising an appropriate protection strategy. This is because the fault current level continuously varies owing to the existence of DERs and to the fact that the microgrid can operate in grid-tied and islanded modes. This paper proposes a new protection strategy for microgrids using an interval type-2 fuzzy logic system. The proposed strategy considers various uncertainties associated with faults and employs two different fuzzy systems to detect, classify, and locate the faults in microgrids. The phase angle between superimposed modal voltage and modal current is used as an input to the fuzzy system designed to identify the fault direction. The significant feature of the proposed strategy is that it can protect the microgrid after a single-phase tripping event. To validate the effectiveness of the proposed strategy, we have performed extensive simulations using MATLAB/SIMULINK. The simulation results show that the proposed strategy can detect, classify, and isolate various faults in the microgrid. Moreover, the strategy also provides backup protection in case of failure of the primary protection.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Develop a new microgrid protection strategy based on interval type-2 fuzzy logic system. </LI> <LI> Considers various uncertainties associated with faults in microgrids. </LI> <LI> Identify fault direction using phase angle between superimposed modal voltage and modal current. </LI> <LI> Capable to protect the microgrid after a single-phase tripping event. </LI> </UL> </P>

대규모 해상풍력단지의 국내 전력계통 고장전류 영향성 분석

최남기,김범주,이병준,박보현,강숙현 한국풍력에너지학회 2021 풍력에너지저널 Vol.12 No.4

Offshore wind farms have been steadily expanding in power systems due to climate issues. Fault current from an offshore wind farm may be negligible since a small number of wind farms are connected to power systems. The short circuit current contributed by a wind farm is relatively smaller than the fault current contributed by a synchronous generator. However, for a large portion of offshore wind farms, the fault current is no longer negligible. It is required to carefully analyze the fault current of offshore wind farms since the fault property is different from conventional generators. To analyze the short circuit current from offshore wind farms, this paper carried out case studies by using planning data of power systems in Korea. The test results, based on the power systems operated by KEPCO, revealed that faulted buses with an exceeded circuit breaker capacity were found since the fault current contributed by the offshore wind farms has increased.

Fault Analysis Method for Power Distribution Grid with PCS-based Distributed Energy Resources

Kim, Dong-Eok,Cho, Namhun The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.2

In this study, we propose a fault analysis method for a power distribution grid with PCS-based DERs. We first explain the characteristics of a PCS-based DER. According to the characteristics, the DER is considered as a current-controlled voltage source, which produces varying voltages within a certain limit so that currents equal to given references flowing from the DER to the grid (currents controlled). So, we introduce the symmetrical equivalent models in the form of varying voltage source for fault analysis and then, construct a convex optimization problem to solve the fault problem associated with the equivalent models and grid conditions. Thus, the proposed method enables to perform a proper fault analysis considering the characteristics of the DER, which are currents controlled, voltage limited, and unity power factor achievement. To verify the validity of the proposed method, we perform computer simulations with the proposed method and with MATLAB Simulink, and the results are compared.

Static Equivalent Model of Inverter-based Distributed Energy Resource for Fault Analysis of Power Distribution Grid

Kim, Dong-Eok,Cho, Namhun,Yang, Seung-Kwon Korea Electric Power Corporation 2016 KEPCO Journal on electric power and energy Vol.2 No.4

In this paper, we propose a method to develop a static equivalent model of an inverter-based distributed energy resource (DER), where the model is used for a steady-state fault analysis of a power grid. First, we introduce the characteristics of an inverter-based DER as well as its general configuration. Then, we derive the equivalent model of the DER on the basis of the characteristics. Last, the performance of the proposed method is proven by the results of computer simulations.