• 항공우주기술
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• 제8권1호
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• pp.172-178
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• 2009

최근에 개발된 소형제트기는 조종사의 피로경감과 더불어 비행안전성 제고를 위하여 자동비행시스템이 필수적인 요소로 인식되고 있다. 또한, 소형항공기의 항공전자시스템은 집중화된 다중프로세서(centralized multi-processor)와 다중연산 계산구조(multi-process computing architectures)로서 B-777의 Integrated Modular Avionics와 유사한 시스템을 장착하는 추세이다. 이러한 소형항공기 시스템 변화는 고전적 비행방식인 조종사 중심의 비행방식에서 자동비행제어시스템(AFCS) 중심의 비행방식으로의 변화를 야기하였으며 자동 비행제어시스템의 비중은 보다 더 증가하고 있다. 이에 본 논문에서는 상용 소형항공기용 자동비행장치(Autopilot)에 대한 HILS를 구성하여 성능을 검증하였다. 또한, 현재 개발하고 있는 FBW용 FCC(Flight Control Computer)에 탑재될 자동비행 알고리듬에 대한 성능을 PILS를 통하여 확인하였고, 상용 Autopilot에 대한 HILS 결과와 같은 조건에서 비교하여 그 성능을 검증하였다.

• 전력전자학회논문지
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• 제20권3호
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• pp.290-295
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• 2015

Analysis and verification of reactive power compensator (RPC) for ITER pulsed power electric network (PPEN) are described in this paper. The RPC system is rated for a nominal power of 250 Mvar necessary to comply with the allowable reactive power limit value from the grid 200 Mvar. This system is currently under construction and is based on static var compensation technology with a thyristor-controlled reactor and a harmonic filter. The RPC minimizes reactive power from grid using prediction of reactive power consumption of AC-DC converters. The feasibility of the reactive power compensation was verified by assembling a real controller and implementing ITER PPEN in the real time digital simulator for the hardware-in-loop facility. When maximum reactive power is reached, grid voltage is stabilized and maximum reactive power decreased from 120 Mvar to 40 Mvar via the reactive power prediction method.

• Journal of Power Electronics
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• 제15권5호
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• pp.1274-1285
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• 2015

This paper deals with model reference adaptive system (MRAS) speed estimators based on a secondary flux for linear induction motors (LIMs). The operation of these estimators significantly depends on an adaptation mechanism. Fixed-gain PI controller is the most common adaptation mechanism that may fail to estimate the speed correctly in different conditions, such as variation in machine parameters and noisy environment. Two adaptation mechanisms are proposed to improve LIM drive system performance, particularly at very low speed. The first adaptation mechanism is based on fuzzy theory, and the second is obtained from an LIM mechanical model. Compared with a conventional PI controller, the proposed adaptation mechanisms have low sensitivity to both variations of machine parameters and noise. The optimum parameters of adaptation mechanisms are tuned using an offline method through chaotic optimization algorithm (COA) because no design criterion is given to provide these values. The efficiency of MRAS speed estimator is validated by both numerical simulation and real-time hardware-in-the-loop (HIL) implementations. Results indicate that the proposed adaptation mechanisms improve performance of MRAS speed estimator.

• 전력전자학회논문지
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• 제20권2호
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• pp.130-136
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• 2015

This study describes the structure and operation modes of vertical stabilization (VS) converter for international thermonuclear experimental reactor (ITER) and proposes a protection method. ITER VS converter supplies voltage (${\pm}1000V$)/current (${\pm}22.5kA$) to superconducting magnets for plasma current vertical stabilization. A four-quadrant operation must be achieved without zero-current discontinuous section. The operation mode of the VS converter is separated in 12-pulse mode, 6-pulse mode and circulation current mode according to the magnitude of the load current. Protection measures, such as bypass and discharge, are proposed for abnormal conditions, such as over current, over voltage, short circuit, and voltage sag. VS converter output voltage is controlled to satisfy voltage response time within 20 msec. Bypass operation is completed within 60 msec and discharge operation is performed successfully. The feasibility of the proposed control algorithm and protection measure is verified by assembling a real controller and implementing a power system including the VS converter in RTDS for a hardware-in-loop (HIL) facility.

• 전기학회논문지
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• 제61권12호
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• pp.1848-1856
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• 2012

This paper proposes a new grid-tied power conditioning system for battery energy storage, which is composed of a 2-stage DC-DC converter and a PWM inverter. The 2-stage DC-DC converter is composed of an LLC resonant converter connected in cascade with a 2-quadrant hybrid-switching chopper. The LLC resonant converter operates in constant duty ratio, while the 2-quadrant hybrid-switching chopper operates in variable duty ratio for voltage regulation. The operation of proposed system was verified through theoretical analysis and computer simulations. Based on computer simulations, a hardware prototype was built and tested to confirm the technical feasibility of proposed system. The proposed system could have relatively higher efficiency and smaller size than the existing system.

• Nuclear Engineering and Technology
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• 제50권5호
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• pp.690-697
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• 2018

Criticality alarm systems (CASs) are mandatory in nuclear plants for prompt alarm in the event of any criticality incident. False criticality alarms are not desirable as they create a panic environment for radiation workers. The present article describes the design enhancement of the CAS at each stage and provides maximum availability, preventing false criticality alarms. The failure mode and effect analysis are carried out on each element of a CAS. Based on the analysis, additional hardware circuits are developed for early fault detection. Two different methods are developed, one method for channel loop functionality test and another method for dose alarm test using electronic transient pulse. The design enhancement made for the external systems that are integrated with a CAS includes the power supply, criticality evacuation hooter circuit, radiation data acquisition system along with selection of different soft alarm set points, and centralized electronic test facility. The CAS incorporating all improvements are assembled, installed, tested, and validated along with rigorous surveillance procedures in a nuclear plant for a period of 18,000 h.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.297-299
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• 2016

본 논문에서는 MATLAB/SIMULINK 기반의 LNG 선박용 Power Generator 모델링을 수행하고 시뮬레이션 결과 모니터링이 가능한 인터페이스를 구현하였다. Power Generator의 주요 구성은 기계적 동력을 공급하는 엔진부(Diesel 엔진, Turbine 엔진)와 기계적 동력을 받아 전력을 생산 및 공급을 하는 동기발전기가 있다. 또한, 단일 용량을 초과하는 전체 부하를 공유하기 위해 병렬 연결된 Generator의 Load Sharing과 선박의 가상 부하에 따른 시뮬레이션을 수행하였다. 시뮬레이션 결과와 가상 부하에 따른 예상 결과의 비교를 통해 Power Generator 모델링의 신뢰성을 검증하였다.

• Journal of Power Electronics
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• 제15권3호
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• pp.610-620
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• 2015

An inherent zero-voltage and zero-current-switching phase-shifted full-bridge converter with reverse-blocking insulated-gate bipolar transistor (IGBT) or non-punch-through IGBT is proposed in this paper. This converter not only ensures that the switches in the lagging leg works at zero-current switching, but also minimizes circulating conduction loss without any additional auxiliary circuits. A 1.2 kW hardware prototype is designed, fabricated, and tested to verify the proposed topology. The control loop design procedures with small-signal models are also presented. A simple, low-cost, and robust democratic current-sharing circuit is also introduced and verified in this study. The proposed converter is a suitable alternative for compact, cost-effective applications with high-voltage input.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 추계학술대회
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• pp.279-282
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• 2012

본 논문에서는 3차원 영상처리용 TOF(Time-Of-Flight) 센서의 거리 측정을 위한 위상 연산기 하드웨어 구조를 제안한다. 설계된 위상 연산기는 CORDIC(COordinate Rotation Digital Computer) 알고리듬의 vectoring mode를 이용하여 arctangent 연산을 수행하며, 처리량을 증가시키기 위해 pipelined 구조를 적용하였다. 고정 소수점 MATLAB 모델링과 시뮬레이션을 통해 최적 비트 수와 반복 횟수를 결정하였다. 설계된 CORDIC 기반 위상 연산기는 Verilog HDL로 RTL 수준으로 모델링되었으며, MATLAB/Simulink와 FPGA 연동을 통해 가상의 3차원 데이터를 복원하였으며, 이를 통해 하드웨어 동작을 검증하였다.

• 한국해양공학회지
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• 제26권5호
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• pp.81-86
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• 2012

Unmanned underwater vehicles have many applications in scientific, military, and commercial areas because of their autonomy. In many cases, an underwater vehicle adopts a control algorithm based on a tactical inertial sensor for precise control. However, a control algorithm that uses a tactical inertial sensor is unsuitable for some underwater vehicle missions such as torpedo decoys. This paper proposes a control algorithm for an unmanned underwater vehicle that does not require precise control. The control algorithm proposed for an unmanned underwater vehicle adopts a low cost MEMS inertial sensor, and simulations using the specifications of the MEMS inertial sensor under development are performed to verify the control algorithm under a real environment. The results of these simulations are presented.