• Journal of Power Electronics
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• 제15권4호
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• pp.1006-1017
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• 2015

This paper presents a finite control set model predictive control (FCS-MPC) strategy for the AC/DC matrix converter used in grid-connected battery energy storage system (BESS). First, to control the grid current properly, the DC current is also included in the cost function because of input and output direct coupling. The DC current reference is generated based on the dynamic relationship of the two currents, so the grid current gains improved transient state performance. Furthermore, the steady state error is reduced by adding a closed-loop. Second, a Luenberger observer is adopted to detect the AC input voltage instead of sensors, so the cost is reduced and the reliability can be enhanced. Third, a switching state pre-selection method that only needs to evaluate half of the active switching states is presented, with the advantages of shorter calculation time, no high dv/dt at the DC terminal, and less switching loss. The robustness under grid voltage distortion and parameter sensibility are discussed as well. Simulation and experimental results confirm the good performance of the proposed scheme for battery charging and discharging control.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1593-1603
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• 2023

In deterministic and Monte Carlo transport codes, b-delayed emission is included using a group structure where all of the precursors are grouped together in 6 groups or families, but given the increase in computational power, nowadays there is no reason to keep this structure. Furthermore, there have been recent efforts to compile and evaluate all the available b-delayed neutron emission data and to measure new and improved data on individual precursors. In order to be able to perform a transient Monte Carlo simulation, data from individual precursors needs to be implemented in a transport code. This work is the first step towards the development of a tool to explore the effect of individual precursors in a fissile system. In concrete, individual precursor data is included by expanding the capabilities of the open source Monte Carlo code OpenMC. In the modified code - named Time Dependent OpenMC or OpenMC(TD)- time dependency related to β-delayed neutron emission was handled by using forced decay of precursors and combing of the particle population. The data for continuous energy neutron cross-sections was taken from JEFF-3.1.1 library. Regarding the data needed to include the individual precursors, cumulative yields were taken from JEFF-3.1.1 and delayed neutron emission probabilities and delayed neutron spectra were taken from ENDF-B/VIII.0. OpenMC(TD) was tested in a monoenergetic system, an energy dependent unmoderated system where the precursors were taken individually or in a group structure, and in a light-water moderated energy dependent system, using 6-groups, 50 and 40 individual precursors. Neutron flux as a function of time was obtained for each of the systems studied. These results show the potential of OpenMC(TD) as a tool to study the impact of individual precursor data on fissile systems, thus motivating further research to simulate more complex fissile systems.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.247-250
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• 2009

Sodium heat pipe for high-temperature solar thermal application was manufactured and tested for transient and steady-state operations. Total length of the heat pipe was 650 mm and the outer diameter was 12.7 mm. Thermal performance was compared experimentally for two different cooling methods of the forced and the natural convection cooling in the heat pipe condenser. During the experiment, the maximum temperature was about 1300K, and different cooling methods were applied to the condenser region to charge the operating temperature. The effective thermal conductivity and the thermal resistance were investigated as a function of heat flux, heat transport length, and operating temperature.

• 비파괴검사학회지
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• 제3권2호
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• pp.5-12
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• 1984

The purpose of this paper is to decide volume of crack by AE source wave analysis. The material studied in this paper was Titanium Alloy. Transient wave memory has 50 nano sampling time. The response function of specimens and transducer was obtained experimentally by use of specimens and transducer was obtained experimentally by use of breaking pencil lead as a reference simulated AE source, and the source waves were dertermined in terms of energy release-time functions explicitly through a time domain deconvolution. From experimental results, we can determine size of cracked volume.

• International Journal of Control, Automation, and Systems
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• 제3권spc2호
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• pp.262-269
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• 2005

In this paper, a nonlinear robust control approach is applied to design a controller for the Static Synchronous Compensator (STATCOM). A robust control dynamic model of STATCOM in a one-machine, infinite-bus system is established with consideration of the torque disturbance acting on the rotating shaft of the generator set and the disturbance to the output voltage of STATCOM. A novel recursive approach is utilized to construct the energy storage function of the system such that the solution to the disturbance attenuation control problem is acquired, which avoids the difficulty involved in solving the Hamilton-Jacobi-Issacs (HJI) inequality. Sequentially, the nonlinear disturbance attenuation control strategy of STATCOM is obtained. Simulation results demonstrate that STATCOM with the proposed controller can more effectively improve the voltage stability, damp the oscillation, and enhance the transient stability of power systems compared to the conventional PI+PSS controller.

• 한국정밀공학회지
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• 제14권10호
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• pp.141-150
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• 1997

분산은 확률모델을 표현하는 유용한 변수중 하나이다. 입력변수에 대한 함수로 표현되는 조건부 분산을 학습하는 신경회로망에 대한 많은 연구가 있어왔다. VALEAN이라는 신경회로망 역시 이러한 많은 연구중 하나인데 이것은 기본적으로 feedforward 다층 퍼셉트론 구조를 가지며 새롭게 제시된 에너지 함수를 사용하고 있다. 이 논문에서는 이 에너지 모델에 의해 결정되는 피드백에러(델타)가 신경망의 transient, steady state에서 미치는 영향을 다루었다. 과도 상태 분석에서는 델타와 수렴성, 안정성에 관한 내용을 다루고 모의 실험을 하였으며 정상 상태 분석에서는 신경회로망의 정상상태 에러의 크기와 델타의 크기사이의 상관관계에 대하여 다루었다. 학습 알고 리듬이 확률적이므로 정상상태 역시 확률적인 상태를 나타낸다. 따라서 델타의 크기에 따른 정상 상태 에러의 최대치는 확률적인 모델을 가지게 된다. 여기서는 이 확률 관계를 분석적으로 규명하고 이에 따라 원하는 신뢰도로 정상 상태 에러를 제어하기 위해 필요한 델타의 크기를 예측할 수 있는 이론적 배경을 마련하게 된다.

• 전기학회논문지
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• 제59권2호
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• pp.445-451
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• 2010

This paper presents a threshold adaptation based voice query transcription scheme for music information retrieval. The proposed scheme analyzes monophonic voice signal and generates its transcription for diverse music retrieval applications. For accurate transcription, we propose several advanced features including (i) Energetic Feature eXtractor (EFX) for onset, peak, and transient area detection; (ii) Modified Windowed Average Energy (MWAE) for defining multiple small but coherent windows with local threshold values as offset detector; and finally (iii) Circular Average Magnitude Difference Function (CAMDF) for accurate acquisition of fundamental frequency (F0) of each frame. In order to evaluate the performance of our proposed scheme, we implemented a prototype music transcription system called AMT2 (Automatic Music Transcriber version 2) and carried out various experiments. In the experiment, we used QBSH corpus [1], adapted in MIREX 2006 contest data set. Experimental result shows that our proposed scheme can improve the transcription performance.

• 대한화학회지
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• 제14권1호
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• pp.97-107
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• 1970

액체 구조의 천이상태 이론을 써서 고체 표면에 기체가 흡착된 계에 대한 상태합을 유도하였다. 이 상태합을 써서 아르곤, 질소, 벤젠 등이 여러 가지 흡착제에 흡착되었을 때의 흡착등온 곡선을 계산하였으며, 이 계산 값들은 측정치와의 좋은 일치를 보여 준다. 그리고 벤젠이 흑연 표면에 흡착되었을 때의 표면압, 물엔트로피, 물에너지, 몰흡착열 들을 계산하였다. 몰엔트로피는 표면이 단분자층으로 완전히 덮였을 때 최소값을 갖는다. 아울러 흡착에 관여된 여러 가지 물리적인 성질들의 계산 방법을 설명하였다.

• 수산해양기술연구
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• 제59권1호
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• pp.44-54
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• 2023

In this study, the second-order Nomoto's nonlinear expansion model was implemented as a Tagaki-Sugeno fuzzy model based on the heading angular velocity to design the automatic steering system of a ship considering nonlinear elements. A Tagaki-Sugeno fuzzy PID controller was designed using the applied fuzzy membership functions from the Tagaki-Sugeno fuzzy model. The linear models and fuzzy membership functions of each operating point of a given nonlinear expansion model were simultaneously tuned using a genetic algorithm. It was confirmed that the implemented Tagaki-Sugeno fuzzy model could accurately describe the given nonlinear expansion model through the Zig-Zag experiment. The optimal parameters of the sub-PID controller for each operating point of the Tagaki-Sugeno fuzzy model were searched using a genetic algorithm. The evaluation function for searching the optimal parameters considered the route extension due to course deviation and the resistance component of the ship by steering. By adding a penalty function to the evaluation function, the performance of the automatic steering system of the ship could be evaluated to track the set course without overshooting when changing the course. It was confirmed that the sub-PID controller for each operating point followed the set course to minimize the evaluation function without overshoot when changing the course. The outputs of the tuned sub-PID controllers were combined in a weighted average method using the membership functions of the Tagaki-Sugeno fuzzy model. The proposed Tagaki-Sugeno fuzzy PID controller was applied to the second-order Nomoto's nonlinear expansion model. As a result of examining the transient response characteristics for the set course change, it was confirmed that the set course tracking was satisfactorily performed.

• 한국안전학회지
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• 제8권4호
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• pp.207-212
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• 1993

상변화 에너지 저장장치는 변동하는 액체-고체 상접합면과 자연대류의 존재에 기인한 비선형성 때문에 해석적으로 분석하기가 어렵다. 핀(fin) 형태의 상변화 에너지 저장장치를 준선형화 시켜 열전달을 수치적으로 해석하여 실험 데이타와 비교 검증하였다. 대칭형 수평 핀에 대하여 준선형, 비정상의 얇은 2차원적 모델을 세우고 유한체적방법(FVM)에 의해 시간의 함수로 융해된 상변화물질의 비율과 액체-고체 상접합면의 형상을 예측하였다. 유한체적방법(FVM)에 의한 결과는 실험결과와 비교적 잘 일치하였다. 벽과 융해점 사이의 온도차가 클수록 융해된 상변화물질의 비율은 증가하였으며 대류항을 포함하는 경우가 없는 경우보다 실험결과에 더 가까운 해를 얻을 수 있었다.