• Journal of Power Electronics
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• 제8권1호
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• pp.10-22
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• 2008

The wind-driven doubly fed induction generator (DFIG) is currently under pressure to be more grid-compatible. The main concern is the fault ride-through (FRT) requirement to keep the generator connected to the grid during faults. In response to this, the paper introduces a novel model and new control scheme for the DFIG. The model provides a means of direct stator power control and considers the stator transients. On the basis of the derived model, a robust linear quadratic (LQ) controller is synthesized. The control law has proportional and integral actions and takes account of one sample delay in the input owing to the microprocessor's execution time. Further, the influence of the grid voltage imperfection is mitigated using frequency shaped cost functional method. Compensation of the rotor current pulsations is proposed to improve the FRT capability as well as the generator performance under grid voltage unbalance. As a consequence, the control system can achieve i) fast direct power control without instability risk, ii) alleviation of the problems associated with the DFIG operation under unbalanced grid voltage, and iii) high probability of successful grid FRT. The effectiveness of the proposed solution is confirmed through simulation studies on 2MW DFIG.

• 대한전자공학회논문지SD
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• 제38권4호
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• pp.292-301
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• 2001

IDDQ 테스트는 CMOS VLSI 회로에서 발생 가능한 여러 종류의 물리적 결함을 효율적으로 검출 할 수 있는 테스트 방식이다. 본 논문에서는 CMOS에서 발생 빈도가 가장 높은 합선고장을 효과적으로 검출할 수 있는 IDDQ 테스트 알고리즘을 이용하여 패턴 생성기를 개발하였다. 고려한 합선고장 모델은 회로의 레이아웃 정보에 의존하지 않으며, 내부노드 혹은 외부노드에 한정시킨 합선고장이 아닌 테스트 대상회로의 모든 노드에서 발생 가능한 단락이다. 구현된 테스트 패턴 생성기는 O(n2)의 복잡도를 갖는 합선고장과 전압 테스트 방식에 비해 상대적으로 느린 IDDQ 테스트를 위해서 새롭게 제안한 이웃 조사 알고리즘과 고장 collapsing 알고리즘을 이용하여, 빠른 고장 시뮬레이션 시간과 높은 고장 검출율을 유지하면서 적은 수의 테스트 패턴 생성이 가능하다. ISCAS 벤치마크 회로의 모의실험을 통하여 기존의 다른 방식보다 우수한 성능을 보였다.

• 한국지능시스템학회논문지
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• 제22권6호
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• pp.780-785
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• 2012

최근 풍력발전은 전 세계적으로 전기의 생산을 위해 사용되는 신재생 에너지원 중 가장 빨리 성장하고 있는 분야이다. 일반적으로 풍력발전 시스템은 설치 후 약 20년 동안 사용될 수 있도록 설계되며 따라서 장기간 운전할 경우, 풍력 발전기에서의 고장은 필연적으로 발생하게 된다. 특히 풍력발전 시스템의 너셀 내부에는 로터샤프트, 기어박스 및 발전기 등이 설치되며 이들 요소의 정상적인 동작을 보장하기 위한 각종 냉각 시스템이 설치된다. 만일 이들 냉각 시스템에 고장이 발생된다면 전체 풍력발전시스템의 정상적인 동작을 보장하는 것이 불가능하다. 이에 본 연구에서는 풍력발전 시스템 너셀 내부에 설치되는 각종 냉각장치의 고장을 미연에 방지할 수 있게 하는 IR 카메라 기반의 풍력발전용 고장검출 시스템을 제안하고 실제 시스템의 구현을 통해 제안된 기법의 유용성을 확인하고자 한다.

• 조명전기설비학회논문지
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• 제27권7호
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• pp.37-44
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• 2013

Phase to ground faults are possibly one of the maximum number of faults in power distribution system. During a ground fault the maximum fault current and neutral to ground voltage will appear at the pole nearest to the fault. Distribution lines are consisted of three phase conductors, an overhead ground wire and a multigrounded neutral line. In this paper phase to neutral faults were staged at the specified concrete pole along the distribution line and measured the ground fault current distribution in the ground fault current, three poles nearest to the fault point, overhead ground wire and neutral line. A simplified equivalent circuit model for the distribution system under case study calculated by using MATLAB gives results very close to the ground fault current distribution yielded by field tests.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.231-232
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• 2007

In this paper, a fault diagnosis and control integrated system (FDCIS) was developed to control the thermoelectric (TE) power in the SP-100 space reactor. The objectives of the proposed model predictive control were to minimize both the difference between the predicted TE power and the desired power, and the variation of control drum angle that adjusts the control reactivity. Also, the objectives were subject to maximum and minimum control drum angle and maximum drum angle variation speed. A genetic algorithm was used to optimize the model predictive controller. The model predictive controller was integrated with a fault detection and diagnostics algorithm so that the controller can work properly even under input and output measurement faults. With the presence of faults, the control law was reconfigured using online estimates of the measurements. Simulation results of the proposed controller showed that the TE generator power level controlled by the proposed controller could track the target power level effectively even under measurement faults, satisfying all control constraints.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.363-367
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• 1996

The robustness issues in fault detection and isolation(FDI) have received considerable attenuation in recent years, due to the increasing demand for safe and reliable operation of uncertain and complex dynamic systems. The aim of this paper is to present the FDI method by using proportional integral(PI) observer and unknown input observer(UIO) under the faults of actuators and sensors. Due to this simple residual generator, the PI observer can easily detect the both faults of actuator and sensor. A simulation results show the effectiveness of this methods.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권6호
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• pp.241-251
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• 2002

The effect of sensor faults in direct torque control(DTC) based induction motor drives is analyzed and a new Instrument fault detection isolation scheme(IFDIS) is proposed. The proposed IFDIS, which operated in real-time, detects and isolates the incipient fault(s) of speed sensor and current sensors that provide the feedback information. The scheme consists of an adaptive gain scheduling observer as a residual generator and a special sequential test logic unit. The observer provides not only the estimate of stator flux, a key variable in DTC system, but also the estimates of stator current and rotor speed that are useful for fault detection. With the test logic, the IFDIS has the functionality of fault isolation that only multiple estimator based IFDIS schemes can have. Simulation results for various type of sensor faults show the detection and isolation performance of the IFDIS and the applicability of this scheme to fault tolerant control system design.

• Journal of Power Electronics
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• 제16권1호
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• pp.57-65
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• 2016

Reverse matrix converters, which can step up voltages, are suitable for applications with source voltages that are lower than load voltages, such as generator systems. Reverse matrix converter topologies are advantageous because they do not require additional components to conventional matrix converters. In this paper, a detection method and a post-fault modulation strategy to operate a converter as close as possible to its desired normal operation under the open-switch fault condition in the rectifier stage are proposed. An open-switch fault in the rectifier stage of a reverse matrix converter causes current distortions and voltage ripples in the system. Therefore, fault-tolerant control for open-switch faults is required to improve the reliability of a system. The proposed strategy determines the appropriate switching stages from among the remaining healthy switches of the converter. This is done based on reference currents or voltages. The performance of the proposed strategy is experimentally verified.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.478-479
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• 2007

Many electrical fires are occurred by leakage currents and sparks generated by a short circuit. Earth leakage circuit breakers (ELCBs) should be tripped at the moment of the faults mentioned above. In this paper, we described the tripping characteristics of ELCBs against parallel arcing faults. A diesel engine generator with the capacity of 375 kVA source was adopted to provide enough large current when a parallel arcing occurred. The experimental results showed that most ELCBs we experimented were not tripped against short-duration pulse currents produced by parallel arcing because the ELCBs are designed to be tripped by a large current with long duration similar to power frequency.

• Journal of Electrical Engineering and Technology
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• 제7권4호
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• pp.486-492
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• 2012

This paper presents a novel objective function for distribution system reconfiguration for reliability enhancement. When islanding operations of distributed generators is prohibited, faults in the feeder interrupt the operation of distributed generators. For this reason, we include the customer interruption cost as well as the distributed generator interruption cost in the objective function in the network reconfiguration algorithm. The network reconfiguration in which genetic algorithms are used is implemented by MATLAB. The effect of the proposed objective function in the network reconfiguration is analyzed and compared with existing objective functions through case studies. The network reconfiguration considering the proposed objective function is suitable for a distribution system that has a high penetration of distributed generators.