• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.152-154
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• 2005

This paper proposes new methods which are used for trouble detecting and tolerance of IED in IEC61850 based Substation Automation System. There are three point devices for construction of this system: Trouble Detection IED, Backup IED and Engineering Unit. Trouble Detection IED tests trouble of Bay IED and sends the result to Engineering Unit. And then Engineering Unit is able to control the system. When fault occurs in Bay IED, Backup IED will be substitute the troubled Bay IED. If this proposed scheme can be used in this system, the reliability of the Power System would be greatly improved.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.665-667
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• 1999

An adaptive algorithm is presented for diagnosis of actuator faults. The concept of unknown input decoupling is combined with an adaptive observer, leading to an adaptive diagnostic observer, which has the robustness property in the presence of an unmeasurable term such as uncertainties. The observation error equation for the adaptive diagnostic observer does not depend on the effect of uncertainties and used to construct an adaptive diagnostic algorithm that provides the estimates of the gains of actuators, which can be obtained directly via the use of the augmented error technique. The simulation results indicate that the proposed algorithm is more realistic in the sense that better robustness properties can be assured without knowledge about uncertainties and is potentially useful in the development of a fault tolerant control system.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2158-2160
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• 2004

본 논문에서는 불확실한 비선형 시스템에 대하여 새로운 고장진단 방법을 이용한 고장 허용 제어기를 설계한다. 잔류 신호는 비선형 관측기 구조를 이용하여 얻을 수 있다. 고장 성분은 neuro-fuzzy 근사기로 추정한다. 제안된 고장 허용 제어기는 강인 제어기와 고장 성분을 보상할 수 있는 보상제어기로 구성된다. 여기서 제안된 고장진단 방법은 고장으로 인해 발생되는 보상제어기의 크기로 고장을 진단함으로써 고장 전후의 강인 제어기의 특성을 계속유지 할 수 있게 설계하였다. 본 논문에서 제안한 고장 허용 제어기의 성능은 컴퓨터 모의실험을 통하여 증명하였다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.4
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• pp.168-176
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• 2001

In this paper, we develop a dual-duplex system which detects a fault by hardware comparator and switches to hot standby redundancy. This system is designed on the basis of MC68000 and can be used in VMEbus. To improve reliability, the dual-duplex system is designed in dual modular redundancy. The failure rate of electrical element is calculated in MILSPEC-217F, and the system RAMS(Reliability, Availiability, Maintainability and Safety) and MTTF(Mean Time to Failure) are evaluated by Markov modeling method. As the evaluation result shows improved reliability, it can be used as a component hardware for a highly reliable control system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.467-474
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• 1999

In this paper, Fault tolerant digital governor, using duplex I/O module and triplex CPU module and also 2 out of 3 voting algorithm and adding self diagnostic ability, is designed to realize ceaseless controlling and to improve the reliability of control system. The processor module of the system(SIDG-3000) is developed based on MC68EC040 32 Bit of Motorola, which guaranteed high quality of the module ,and SRAM for data also SRAM for command are separated. The process module also includes inter process communication function and power back up function (SRAM for back-up). System reliability is estimated by using the model of Markov process. The reliability of triplex system in mission time can be improved about 1.8 times in reliability 86%. 2.8 times in 95 %, 6 times in 99 % compared with a single control system. Designed digital governor system is applied after modelling of the steam turbine generator system of Buk-Cheju Thermal Power Plant. Simulation is carried out to prove the effectiveness of the designed digital governor system

• Journal of Power Electronics
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• v.14 no.1
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• pp.92-104
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• 2014

To insure stable operation and eliminate twice torque ripple, a topology for a six phase permanent magnet synchronous generator (SP-PMSG) with a neutral point connected together was analyzed in this paper. By adopting an extended transformation matrix, the mathematic model of the space vector control was established. The voltage and torque equations were deduced while considering the third harmonic flux and inductance. In addition, the suppression third harmonic method and the closed loop control strategy were proposed. A comparison analysis indicates that the cooper loss minimum method and the current magnitude minimum method can meet different application requirements. The voltage compensation amount for each of the methods was deduced which also takes into account the third harmonic effect. A simulation and experimental result comparison validates the consistency through theoretical derivation. It can be seen that all of the two control strategies can meet the requirements of post-fault.

• Journal of Power Electronics
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• v.17 no.1
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• pp.161-171
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• 2017

To enhance the reliability of two-motor drive systems, this paper proposes an improved direct torque control (DTC) scheme (P-DTC) for five-leg dual-PMSM drive systems. First, the topology of a five-leg dual-PMSM drive system is illustrated. To clarify the analysis of the P-DTC, the standard DTC scheme for three-phase drive systems is presented. The operation of a five-leg dual-PMSM drive system is classified into three situations according to the definitions of the switching-vector unions. Compared with the existing DTC scheme (R-DTC), the P-DTC can minimize the replacement of active switching-vectors to zero switching-vectors. When this replacement cannot be avoided, the P-DTC uses a proposed master-slave selection principle to minimize the system error. Comparing with the R-DTC, the P-DTC has lower torque ripples, a wider speed range and a faster torque increasing response. Experiments have been carried out in the coupling and independent modes, and the effectiveness of the P-DTC is verified by the obtained results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.5
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• pp.1829-1846
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• 2021

Transient faults occur in computation units of a processor, which can cause control flow errors (CFEs) and compromise system reliability. The software-based methods perform illegal control flow detection by inserting redundant instructions and monitoring signature. However, the existing methods not only have drawbacks in terms of performance overhead, but also lack of configurability. We propose a configurable approach CCFCA for detecting CFEs. The configurability of CCFCA is implemented by analyzing the criticality of each region and tuning the detecting granularity. For critical regions, program blocks are divided according to space-time overhead and reliability constraints, so that protection intensity can be configured flexibly. For other regions, signature detection algorithms are only used in the first basic block and last basic block. This helps to improve the fault-tolerant efficiency of the CCFCA. At the same time, CCFCA also has the function of solving confusion and instruction self-detection. Our experimental results show that CCFCA incurs only 10.61% performance overhead on average for several C benchmark program and the average undetected error rate is only 9.29%. CCFCA has high error coverage and low overhead compared with similar algorithms. This helps to meet different cost requirements and reliability requirements.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.3
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• pp.397-404
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• 2011

In this research, wish to suggest method to embody system that can accommodate defect of PLC and find actual propriety. Defect permission control system minimizes production damage because enables repair and checking without discontinuance and improve believability about whole system. Propose duplexing of system to embody this fault tolerant system. Therefore, composed control system that can permit defect or breakdown duplexings of various module proposing this system, and confirms to simulation and actuality kiln of defect permission control system through an application experiment, and compares for mean time between defect by estimate and defect special quality and system configuration of failure(failure) to improve believability of PLC control system together. In proposed system expression method and system mode and relation with operation mode, error discovery mode and switching tube of duplexing mode, and PLC's central processing unit of node study algorithm about master-standby conversion driving and continuous operation of 2 channels method that have 2 that is not one and deduced continuous operation method and result about defect permission in this algorithm and applies this result to actuality kiln control system and confirms continuous operation about PLC defect permission.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.1
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• pp.33-39
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• 2022

A multi-phase brushless direct current (BLDC) motor is widely used in large-capacity electric propulsion systems such as submarines and electric ships. In particular, in the field of military submarines, the polyphaser motor must suppress torque ripple in various failure situations to reduce noise and ensure stable operation for a long time. In this paper, we propose a polyphaser current control method that can improve efficiency and reduce torque ripple by minimizing the increase in stator winding loss at maximum output torque by controlling the phase angle and amplitude of the steady-state current during open circuit failure of the stator winding. The proposed control method controls the magnitude and phase angle of the healthy phase current, excluding the faulty phase, to compensate for the torque ripple that occurs in the case of a phase open failure of the motor. The magnitude and phase angle of the controlled steady-state current are calculated for each phase so that copper loss increase is minimized. The proposed control method was verified using hardware-in-the-loop simulation (HILS) of a 12-phase BLDC motor. HILS verification confirmed that the increase in the loss of the stator winding and the magnitude of the torque ripple decreased compared with the open phase fault of the motor.