• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1239-1248
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• 2018

This paper proposes a fault tolerant and high efficiency operation algorithm for a 4 LEG DC/DC converter for a battery energy storage system(BESS) forming a main power source in a standalone DC micro grid. The BESS for the main power supply in the stand-alone DC micro-grid is required to operate at high speed according to fault tolerant control and load by operating at all times. Fault-tolerance control changes the short-circuit fault to an open-circuit fault by using a fuse in case of leg fault in 4 legs, and operates stably through phase shift control. In addition, considering the loss of the power semiconductor, the number of LEG operation is adjusted to operate at high efficiency in the full load region. In this paper, fault tolerant control and high efficiency operation algorithm of DC/DC converter for BESS in standalone DC micro grid is presented and it is proved through simulation and experiment.

• Journal of Internet Computing and Services
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• v.3 no.5
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• pp.31-39
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• 2002

A rapid growth of internet and sudden increase of multimedia data demands for high-speed transfer media and if optimizec usage from the interface system. To achieve this level of network bandwidth, multiple NICs for support of high-speed network bandwidth have been developed and studied. Furthermore, the use of multiple NICs can provide high-speed LAN environment without large network environment modification, supports backward compatibility of current system and reduce overhead. However. if system failure is caused by SPOF(Single Point of Failure) fault of large-capacity multiple NICs, incredible loss will be met because it services large capacity of multimedia data, Therefore, to prevent loss coming from faults, we describe 'Fault tolerance of multiple NICs', which use the fault prevention mechanism. Considering inefficiency of availability and serviceability that is occurred with existing TMR, Primary-Standby approach and Watchdog time mechanism, we propose and design the efficient fault tolerance mechanism, which minimize down time as changing of detection period dynamically. Consequently, the fault tolerance mechanism proposed for reducing overhead time when the fault is occurred, should minimize system downtime overall.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.3_4
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• pp.204-212
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• 2004

Existing distributed systems have higher probability of failures occurrence than stand-alone system, so many fault tolerant techniques have been developed. Because of insufficient storage resulting from the increased fault tolerance information stored, the performance of system has been degraded. To avoid performance degradation, it needs delete useless fault tolerance information. In this paper, we propose a garbage collection algorithm for fault tolerance information. And we define and design the garbage collection agent for garbage collection of fault tolerance information, the information agent for management of fault tolerant data, and the facilitator agent for communication between agents. Also, we propose the garbage collection algorithm using the garbage collection agent. For rollback recovery, we use independent checkpointing protocol and sender based pessimistic message logging protocol. In our proposed garbage collection algorithm, the garbage collection, information, and facilitator agent is created with process, and the information agent constructs domain knowledge with its checkpoints and non-determistic events. And the garbage collection agent decides garbage collection time, and it deletes useless fault tolerance information in cooperation with the information and facilitator agent. For propriety of proposed garbage collection technique using agents, we compare domain knowledge of system that performs garbage collection after rollback recovery and domain knowledge of system that doesn't perform garbage collection.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2118-2126
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• 2017

The large-scale power system blackouts have indicated that conventional protection relays that based on local signals cannot fit for modern power grids with complicated setting or heavily loaded-flow transfer. In order to accurately detect various faulted lines and improve the fault-tolerance of wide-area protection, a novel multi-section weighed fault matching and detecting algorithm is proposed. The real protection vector (RPV) and expected section protection vectors (ESPVs) for five fault sections are constructed respectively. The function of multi-section weighed fault matching is established to calculate the section fault matching degrees between RPV and five ESPVs. Then the fault degree of protected line based on five section fault degrees can be obtained. Two fault detecting criterions are given to support the higher accuracy rate of detecting fault. With the enumerating method, the simulation tests illustrate the correctness and fault-tolerance of proposed algorithm. It can reach the target of 100% accuracy rate under 5 bits error of wide-area protections. The influence factors of fault-tolerance are analyzed, which include the choosing of wide-area protections, as well as the topological structures of power grid and fault threshold.

• Journal of Digital Contents Society
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• v.16 no.1
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• pp.123-126
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• 2015

This paper described fault tolerance system running on distributed multimedia. We implemented the error manager service so that the users participated in distribute multimedia collaborative work may refer synchronized error objects as the same view to others. distributed multimedia environment are based on IP-USN(Internet Protocol - Ubiquitous Sensor Network) and M2M(Machine to machine). This is a system that is suitable for detecting, sharing and recovering software error in distribute multimedia CSCW(Computer Supportes Cooperated Work) environment. With error synchronization system, a group cooperating users can synchronize error applications.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.661-663
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• 2004

본 논문에서는 SAN 기반 공유 파일 시스템인 SANfs의 fault-tolerance를 보장받기 위해 fault-tolerant server인 shadow server를 구현하였다 SANfs(1)는 SAN에서 Network-attached storage에 접근하는 여러 클라이언트가 서로의 데이터를 공유할 수 있도록 도와주는 파일시스템이다. SANfs에서 파일 관리를 위해 meta server를 두고 있으며, 이 서버에서 네트워크를 통해 접근하는 털러 클라이언트의 request를 관리한다. SAMfs에서는 meta server를 통해 중앙 집중식으로 파일시스템을 관리하고 있기에 meta server가 fault가 나게 되면 전체 시스템의 동작이 멈추게 되는 single point-of-failure의 문제가 생기게 된다. 본 논문에서는 meta server가 fault가 났을 경우에도 지속적으로 서비스를 할 수 있도록 shadow server를 두었으며. 이 서버가 meta server의 이상 시 그 기능을 대행하도록 하였다. 본 논문의 shadow server는 평상시에 meta server와 파일시스템의 metadata의 동기를 맞추고 있으며, 이 정보를 가지고 meta server로 그 기능을 전환하였을 때 서비스를 해 주도록 하고 있다. 상대 서버의 이상 유무의 판단은 heartbeat를 통해 이루어지고 있으며, meta server로의 failover는 heartbeat의 주기에 영향을 받음을 실험을 통해 알게 되었다.

• Nuclear Engineering and Technology
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• v.45 no.6
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• pp.795-802
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• 2013

For the improvement of APR1400 Diverse Protection System (DPS) design, the Advanced DPS (ADPS) has recently been developed to enhance the fault tolerance capability of the system. Major fault masking features of the ADPS compared with the APR1400 DPS are the changes to the channel configuration and reactor trip actuation equipment. To minimize the fault occurrences within the ADPS, and to mitigate the consequences of common-cause failures (CCF) within the safety I&C systems, several fault avoidance design features have been applied in the ADPS. The fault avoidance design features include the changes to the system software classification, communication methods, equipment platform, MMI equipment, etc. In addition, the fault detection, location, containment, and recovery processes have been incorporated in the ADPS design. Therefore, it is expected that the ADPS can provide an enhanced fault tolerance capability against the possible faults within the system and its input/output equipment, and the CCF of safety systems.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.10
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• pp.899-906
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• 2004

In this paper, fault tolerant algorithm is presented for a servo manipulator system. For fault tolerance of a servo manipulator system, reconfiguration algorithm accommodating a motor's failure has been presented. The algorithm considers a transport's degree of freedoms as redundant joints of a servo manipulator. The reconfiguration algorithm recovers the end effector's motion in spite of one motor's failure A modified pseudo inverse redistribution method has been proposed for the reconfiguration algorithm. Numerical examples and hardware tests have been presented to verify the proposed methods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.3
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• pp.470-476
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• 1997

The dynamic characteristics of industrial processes frequently cause an abnormal situation which is undesirable in terms of the productivity and the safety of workers. The goal of fault-tolerance is to continue performing certain activities even after the failure of some system cononents. A fault-tolerant intelligent monitoring and control system which is robust under disturbances is proposed in this paper. Specifically, the fault-tolerant monitoring scheme proposed consists of two process models and the inference module to preserve such a robustness. The results of turning experiments demonstrate the effectiveness of the fault-tolerant scheme in the presence of built-up edge.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.6
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• pp.762-770
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• 2015

Fault tolerance is a crucial design for a mission-critical computer such as engagement control computer that has to maintain its operation for long mission time. In recent years, software fault-tolerant design is becoming important in terms of cost-effectiveness and high-efficiency. In this paper, we propose MPCMCC which is a model-based software component to implement fault tolerance in mission-critical computers. MPCMCC is a fault tolerance design that synchronizes shared data between two computers by using the one-way message-passing scheme which is easy to use and more stable than the shared memory scheme. In addition, MPCMCC can be easily reused for future work by employing the model based development methodology. We verified the functions of the software component and analyzed its performance in the simulation environment by using two mission-critical computers. The results show that MPCMCC is a suitable software component for fault tolerance in mission-critical computers.