• 전기전자학회논문지
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• 제24권3호
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• pp.727-734
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• 2020

본 논문은 과도 고장을 가지는 비동기 순차 머신에 대한 내고장성 교정 제어를 다룬다. 본 논문에서 다루는 고장은 머신이 과도 상태 천이를 거칠 때 발현할 수 있으므로 비-기본 모드(non-fundamental mode)에서 원하지 않는 상태 천이를 일으킨다. 본 논문에서는 비동기 순차 머신의 비-기본 모드에서 발생하는 과도 고장을 탐지하고 극복할 수 있는 새로운 내고장성 제어 시스템을 제안한다. 교정 제어 이론의 틀 안에서 내고장성 제어기의 존재 조건과 설계 과정을 제시한다. 또한 제안된 제어 시스템의 효용성을 검증하기 위해 FPGA 실험을 실시한다.

• 전기학회논문지
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• 제62권6호
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• pp.731-736
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• 2013

Most of faults occurring in transmission lines are transient faults. For such faults, automatic reclosing is economic and effective method to improve the reliability and transient stability of power system. Many countries apply various reclosing schemes considering issues of their own systems such as transient stability, rate of success. Currently, different reclosing schemes are applied in Korean transmission systems according to a rated voltage. In this paper, we conduct an evaluation of reclosing schemes in Korean transmission systems considering transient stability. Computer simulations are performed by using ElectroMagnetic Transient Program (EMTP) and transmission system is modeled based on actual data of Korea.

• Journal of Electrical Engineering and Technology
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• 제1권1호
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• pp.8-15
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• 2006

Since the power swing depends on the operating time of the relay, the swing's magnitude can be reduced by an autoreclosure relaying system with an optimal reclosing algorithm. This paper proposes a method for stability improvement using optimal reclosure relaying. An optimal reclosure algorithm is applied to identify both temporary and permanent faults, and to predict system stability by applying WAM and high speed communication technology. It provides optimal control by predicting and determining the degree of stability, considering the real time transient stability using EEEAC. For temporary faults, the algorithm determines the system's stability and either recloses optimally for stable systems, or inserts series capacitance before optimal reclosure for unstable systems. It also applies an optimal reclosure algorithm to minimize shock and damage to the power system when reclosure fails due to permanent faults.

• 제어로봇시스템학회논문지
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• 제13권12호
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• pp.1147-1152
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• 2007

This paper deals with a scheme for fault-tolerance improvement of real-time embedded systems, which engages an equidistant checkpointing technique to tolerate transient errors. Transient errors are caused by transient faults which are the most significant type of fault in reliable computer systems. Transient faults are assumed to occur according to a Poisson process and to be detected in a non-concurrent manner (e.g., checked periodically). The probability of the successful real-time task completion in the presence of transient errors is derived with the consideration of the possible effects of the transient errors. Based on this, a condition under which inserting checkpoints improves the fault-tolerance of the system is introduced and an optimal equidistant checkpointing strategy that achieves the highest fault tolerance is presented.

• 제어로봇시스템학회논문지
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• 제14권4호
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• pp.376-380
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• 2008

This paper deals with a performance analysis of real-time control systems, which engages DMR(dual modular redundancy) to detect transient errors and checkpointing technique to tolerate transient errors. Transient errors are caused by transient faults and the most significant type of errors in reliable computer systems. Transient faults are assumed to occur according to a Poisson process and to be detected by a dual modular redundant structure. In addition, an equidistant checkpointing strategy is considered. The probability of the successful task completion in a real-time control system where periodic checkpointing operations are performed during the execution of a real-time control task is derived. Numerical examples show how checkpoiniting scheme influences the probability of task completion. In addition, the result of the analysis is compared with the simulation result.

• 한국멀티미디어학회논문지
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• 제10권7호
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• pp.882-892
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• 2007

본 논문에서는 임베디드 실시간 운영체제 수준에서 주기적 및 비주기적 태스크 스케줄링뿐만 아니라 태스크들의 일시적인 결함을 복구할 수 있는 결함허용이 가능한 임베디드 실시간 태스크 관리 메커니즘을 제안한다. 기존의 임베디드 운영체제들은 주기적 및 비주기적 태스크들을 동시에 고려한 스케줄링 메커니즘을 지원하지 않는다. 그리고 태스크 결함 복구 메커니즘의 미지원으로 인해 결함 태스크로 인한 시스템 고장을 야기할 수도 있다. 제안된 결함허용 실시간 태스크 관리 메커니즘은 운영체제 수준에서 주기적 태스크들의 마감시한과 비주기적 태스크의 실행완료를 보장할 뿐만 아니라 일시적인 결함이 발생한 태스크를 복구함으로써 태스크 결함으로 인한 시스템 고장을 방지할 수 있다.

• 한국전자통신학회논문지
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• 제17권3호
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• pp.399-408
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• 2022

본 논문에서는 기본 모드 원리를 침해하는 과도 고장이 존재하는 입력/출력 비동기 순차 회로의 내고장성 교정 제어 시스템을 제안한다. 비동기 순차 회로의 과도 천이 과정에서 발생하는 비-기본 모드 고장을 극복하기 위해서는 고장에 의한 상태 천이가 종료되는 시점을 알아야 하며, 회로를 고장 상태로부터 원래 도달해야 하는 상태와 출력 등가적인 상태로 보내기 위한 교정 동작을 구현해야 한다. 본 논문에서는 이러한 고장 탐지 및 극복을 구현할 수 있는 출력 피드백 교정 제어기의 존재 조건을 규명한다. FPGA 실험을 통해 제안된 제어 시스템의 설계 과정을 제시하고 응용 가능성을 검증한다.

• 제어로봇시스템학회논문지
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• 제10권8호
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• pp.748-754
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• 2004

In this paper, we propose the Triple Modular Redundancy (TMR) control system equipped with a checkpoint strategy. In this system, faults in a single processor are masked and faults in two or more processors are detected at each checkpoint time. When faults are detected, the rollback recovery is activated to recover from faults. The conventional TMR control system cannot overcome faults in two or more processors. The proposed system can effectively cope with correlated and independent faults in two or more processors. We develop a reliability model for this TMR control system under correlated and independent transient faults, and derive the reliability equation. Then we investigate the number of checkpoints that maximizes the reliability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.509-512
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• 1995

The relaying algorithm to calculate the fault distance from only transient signal at faults in T/L is presented. In this paper. At faults the oscillation frequency components exist in both voltage and current and these components minimize the input impedance shown in fault point. The equivalent source impedance shown in relaying point is needed to calculate the fault distance using these components. To source impedance, the reflection coefficient between forward wave and backward and the Prony's analysis is also employed to extract the oscillation frequency component from transient signals. The case study show that the new distance relaying algorithm satisfies the high operation speed and high accuracy even if the algorithm uses only transient signals.

• 전기학회논문지
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• 제62권1호
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• pp.120-126
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• 2013

This paper proposes a novel scheme of fault detection and self-recovery for space-borne dual ring counters subject to transient faults. The considered ring counter is equipped with hardware redundancy, but it has a limited output domain where direct access to the current state is unavailable. We employ the theory of corrective control to detect any transient fault occurring to the counter bits and to realize immediate self-recovery of the ring counter back to the normal state. The structure of the fault-tolerant controller is designed to be minimal regardless of the counter size. To validate the applicability, we implement the proposed system on a commercial FGPA board.