• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.4
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• pp.34-41
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• 2003

A new technique for detecting parametric faults in mixed signal circuits is proposed Pseudo-random sequence from linear feedback shift register(LFSR) is fed to circuit-under-test (CUT) as stimulus and wavelets are used to compact the transient response under this stimulus into a small number of signature. Wavelet based scheme decomposes the transient response into a number of signal in different frequency bands. Each decomposed signal is compacted into a signature using digital integrator. The digital pulses from LFSR, owing to its pseudo-randomness property, are almost uniform in frequency domain, which generates multi-frequency response when passed through CUT. The effectiveness of this technique is demonstrated in our experimental results.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.1
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• pp.93-100
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• 2008

There are two ways of conventional thermal distortion analysis. One is the thermal elasto-plastic analysis and the other is the equivalent forces method based on inherent strain. The former needs exorbitant analysis time, while the latter cannot obtain results of stress field and it needs much time consumption with loads modeling on curved plates. Such faults in two methods have made difficulties in thermal distortion analysis of a large structure like ship hull. In order to solve them, new kind of thermal distortion analysis method was developed. We devised that the inherent strains was used as direct input factors in forms of boundary conditions. It was embodied by using thermal expansion coefficient in commercial code. We used the pre-calculated inherent strain as thermal expansion coefficient, and endowed nodes with imaginary temperatures. This method was already adopted at hull block welding distortion analysis which was considered as impossible, and gave productive results such as reduction of work time in the dry dock.

• 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.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.723-726
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• 2002

In this paper, a high efficiency leakage transformer for neon tube is developed to improve its power factor, to reduce its core loss and weight by using a technique of shape optimization and direction of grain-oriented silicon steel sheet. A protection circuit is designed for all types of neon transformer loaded with one or more neon lamps. Whenever the neon tube fails to be started up or comes to the life end, or encounters faults with open-circuits at the output terminals of the neon transformer, the protection circuit will be initiated to avoid more critical hazards. These neon transformers need a protection circuit to prevent from current stresses on circuit components by neon tube fail. The input of the transformer is automatically cut off when the abnormal condition occurs, preventing waste of no-load power. As the results of the study, the core weight is reduced by $11\%$, the power factor improved by $5\%$ and the efficiency increased by $6\%$ compared with the conventional type due to the employment of the grain-oriented steel sl)eel and the optimized core shape.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.203-207
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• 2008

Prestack depth migration is used to image for complex geological structure such as faults, folds, and subsalt. In this case, it is widely used the surface reflection data as a input data. However, the surface reflection data have intrinsic problems to image the subsalt and the salt flank due to the complex wavefields and multiples which come from overburden. For overcoming the structural defect of the surface reflection data in the imaging, I used the virtual sources in terms of seismic interferometry to image the subsurface and suppress the multiples using the velocity model of the lower part of the virtual sources. The results of the prestack depth migration using virtual source gathers and velocity model below receivers are similar geological interfaces to the results from shot gathers of the conventional ocean bottom seismic survey. And especially artificial interfaces by multiples were suppressed without applying any other data processing to eliminate multiples. This study results by numerical modeling can make a valuable imaging tool when it is applied to satisfied field data for specific condition.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.384-390
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• 2012

This paper proposes a fault diagnosis method of the line-to-line voltage sensors in 3-phase AC/DC pulse width modulation (PWM) converters. The line-to-line voltage sensors are an essential device to obtain the information of the grid voltages for controlling the 3-phase AC/DC PWM converters. If the line-to-line voltage sensors are mismeasured by various faults, the voltage sensors can obtain wrong information of the grid voltage. It has an adverse effect on the control of the converter. Therefore, the converter causes the unbalance input AC current and the DC-link voltage ripple in the 3-phase AC/DC PWM converter. Hence, fast fault detection and fault tolerant control are needed. In this paper, the fault diagnosis method is proposed and verified through simulations and experiments.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.3
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• pp.6-11
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• 2006

This paper describes the novel control techniques design of VSC(Voltage Sag Corrector) for the purpose of power line quality enhancement. A fast detecting technique of voltage sag is implemented through the detection of instantaneous value on synchronous rotating dq-reference frame. The first order digital filter is added in the detection algorithm to protect the insensitive characteristics against the noise. The relationship between the total detection time and cut-off frequency of the filter is described. The size of the capacitor bank used as the energy storage element is designed from the point of view of input/output energy with circuit analysis. Finally, the validity of the proposed scheme is proven through the simulated results.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.5
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• pp.385-393
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• 2020

This study introduces an analysis and control method for the variation of neutral point current in a grid-tied three-level neutral point clamped (NPC) converter under various grid imbalance operating conditions. Various fault cases with unbalanced amplitude and phase are systematically categorized and described using a unified metric called the imbalance factor. The fundamental component of neutral point current is generated under grid imbalance cases. The pattern and behavior of this fundamental component of neutral point current highly depend on the imbalance factor regardless of the particular type of grid fault cases. The control scheme for regulating the negative sequential component of AC input current effectively reduces the size of the fundamental component of neutral point current under a wide range of grid imbalance cases. The control scheme will enable a grid-tied three-level NPC converter to operate reliably and stably under various types of grid faults.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.3
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• pp.91-97
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• 2006

A major difficulty with the practical application of the multiple observer based IFDI schemes is the computational burden of the residual generation. In this paper, a new residual generator that employs function observers is proposed to reduce the computational burden, and the design methods of the IFDIS, equipped with the residual generator, are presented. The function observers employed in the residual generator can be considered as a dual of the unknown input (function) observer And it can be designed to estimate the measurement errors that are due to sensor faults. The error estimates are further processed to generate the residuals by which reliable fault detection/isolation result car be obtained. The proposed scheme is more useful, in real-time application, than any other multiple state observer based IFDISs. It can be effectively applied to fault tolerant control because the failure effects can be compensated by the use of the estimates of measurement errors. The proposed IFDI scheme is applied to an inverted pendulum control system for the IFDI of failed sensor and fault compensation.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.28B no.10
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• pp.807-821
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• 1991

A mulitpath MIN(Multistage Interconnection Network), CSMP(Chained Shuffle Multi-Path) network, is proposed, having fault-tolerance and dynamic reroutability. The number of stages and the number of links between adjacent stagges are the same as in single path MINs, so the overall hardware complexity is considerably reduced in comparison with other multipath MINs. The CSMP networks feature links between switches belonging to the same state, forming loops of switches. The network can tolerate multiple faults, up to (N/4)*(log$_2$N-1), having occured in any stages including the first and the last ones(N:NO. of input). To analyze reliability, terminal reliability (TR) and mean time to failure( MTTE) age given for the networks, and the TR figures are compared to those of other static and dynamic rerouting multipath MINs. Also the MTTE figures are compared. The performance of the proposed network with respect to its bandwidth (BW) and probability of acceptance(PA) is analyzed and is compared to that of other more complex multipath MINs. The cost efficiency analysis of reliability and performance shows that the network is more cost-effective than other previously proposed fault-tolerant multipath MINs.