• 자원ㆍ환경경제연구
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• 제33권2호
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• pp.113-133
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• 2024

태양광과 풍력을 중심으로 한 변동성 재생발전(VRE)은 탄소중립 달성의 주요수단이지만 높은 변동성과 불확실성으로 인해 전력공급의 안정성을 훼손시킨다. 에너지저장장치(ESS)는 수요이전을 통해 재생발전의 출력제한을 경감시킬 뿐만아니라 보조서비스 제공을 통해 안정적인 전력시스템 운영에 기여할 수 있다. 본 연구는 VRE로 인한 문제점이 점점 본격화되는 상황에서 ESS자원을 수요이전 기능과 예비력 제공기능 간에 어떻게 분배하는 것이 전력공급 효율성 최대화에 기여할 수 있는지 분석한다. 분석모형으로 재생발전의 변동성과 불확실성을 현실적으로 모의할 수 있는 확률적 전력시스템 최적화 모형을 적용하였다. 분석시점은 2023년과 2036년으로 설정하여 재생발전 보급수준별 ESS 최적자원분배 전략과 편익을 분석하였다. 분석결과는 크게 다음의 3가지로 요약가능하다. 첫째, ESS는 수요이전과 예비력 제공 모두에 탁월한 기능을 제공하며, 예비력 가격이 높게 설정될수록 수요이전 기능은 제한하고 예비력 제공에 집중함을 확인할 수 있었다. 둘째, 재생발전 출력제한은 필요예비력에 대한 대체재 역할을 하며, 예비력 가격 수준이 높아질수록 출력제한은 증가하고 필요예비력은 감소하는 것이 비용 합리적이다. 셋째, 기회비용이 반영된 합리적인 예비력 가격이 적용될 경우 ESS는 가까운 미래에 경제성을 확보할 수 있으며, ESS의 경제성은 재생발전 비중이 높을수록 더 커짐을 확인할 수 있었다. 본 연구는 전력공급 자원이 효율적으로 분배될 수 있는 가격기능이 바로 설때 비용 효율적인 전력부문 저탄소 전환이 가능함을 시사한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.395-397
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• 2002

Recently, electric heating using midnight power has brought a rapid increase. Therefore, the increase of midnight power use has much influenced on midnight load pattern and share more than 20% of total midnight electricity consumption. Hence, the distortion of load by using midnight power apparatus is severe and made the usage pattern ineffective electricity usage pattern. This paper analyze the load pattern of midnight power apparatus and policies that can effectively build midnight load. In addition, it provides policies on shifting midnight power apparatus load.

• 대한기계학회논문집A
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• 제28권12호
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• pp.1982-1989
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• 2004

In photoelasticity, the directions of principal stresses are given by isoclinic fringe patterns. In this study, photoelastic theory is represented by Jones calculus and the photoelastic 8-step phase shifting method is described. A feasibility study using computer simulation is done to get isoclinics from photoelastic fringes of a circular disk under diametral compression. Fringe patterns of the disk are generated from the stress-optic law. The magnitudes of isoclinics obtained from the fringe patterns of computer simulation and experiment are compared with those of theory. The results are close between them. Then, the 8-step phase shifting method is applied to get distributions of isoclinics along the specified lines of a cuved beam plate under tensile load. Experimental results obtained from the phase shifting method were compared with those of finite element analysis (ANSYS). It is confirmed that measurement of isoclinic distributions is possible by use of photoelasitc phase shifting method.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1294-1303
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• 2018

This study optimises the no-load voltage waveform of tubular hydro-generators by a simple design scheme. For different centerlines of the pole shoe and damper bar, the optimisation effects on the no-load voltage waveform are investigated in two tubular hydro-generators with different weighted powers (34 MW and 18 MW). The results are compared with those of the traditional stator-slots skewed design. The quality of the no-load voltage waveform was related to the shifting degree, and the different optimisation effects between the integer slot generator (q = 2) and the fractional slot generator (q = 11/2) were analysed. This research can improve the quality of the power output and no-load voltage waveform, and provide an effective reference for improving the industrial design and manufacture level of tubular hydro-generators.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1069-1078
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• 2018

Demand response (DR) programs give opportunity to consumers to manage their electricity bills. Besides, distribution system operator (DSO) is interested in using DR programs to obtain technical and economic benefits for distribution network. Since small consumers have difficulties to individually take part in the electricity market, an entity named demand response provider (DRP) has been recently defined to aggregate the DR of small consumers. However, implementing DR programs face challenges to fairly allocate benefits and payments between DRP and DSO. This paper presents a procedure for modeling the interaction between DRP and DSO based on a bilevel programming model. Both DSO and DRP behave from their own viewpoint with different objective functions. On the one hand, DRP bids the potential of DR programs, which are load shifting and load curtailment, to maximize its expected profit and on the other hand, DSO purchases electric power from either the electricity market or DRP to supply its consumers by minimizing its overall cost. In the proposed bilevel programming approach, the upper level problem represents the DRP decisions, while the lower level problem represents the DSO behavior. The obtained bilevel programming problem (BPP) is converted into a single level optimizing problem using its Karush-Kuhn-Tucker (KKT) optimality conditions. Furthermore, point estimate method (PEM) is employed to model the uncertainties of the power demands and the electricity market prices. The efficiency of the presented model is verified through the case studies and analysis of the obtained results.

• 한국통신학회논문지
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• 제24권10B호
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• pp.1971-1978
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• 1999

본 논문에서는‘shifting-level (SL) process’을 기초로 한 모델을 사용하여, VBR 부호화된 영상트래픽의 long-range dependence (LRD) 특성이 대기체계에 미치는 영향에 대해서 연구하였다. 연구 내용은 제1부와 제2부로 나누어 전개된다. 제 1부에서는 실제 영상트래픽의 자기상관함수가 exponential과 hyperbolic의 복합함수로 매우 정확히 표현될 수 있음을 보이고, 이러한 조건을 만족하는 SL process with compound correlations(SLCC)를 제안한다. 대표적인 SRD 모델인 DAR(1)모델과의 대기성능 비교를 통하여 hyperbolic한 상관도가 대기체계에 끼치는 영향을 분석한다. 분석결과 영상의 LRD 특성이 대기체계에 끼치는 영향의 중요도는 단순히‘Yes/No’로 답할 수 없으며, 트래픽 부하가 높아지면 그 영향이 강하게 나타나고, 반대로 트래픽 부하가 낮은 경우에는 무시할 수 있을 정도로 약하게 나타남을 알 수 있다. 여기에 사용하는 SL/D/1/K 대기체계의 해석방법을 제2부에서 다루게 된다.

• Journal of Mechanical Science and Technology
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• 제14권4호
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• pp.418-425
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• 2000

Recently, many passenger cars have adopted automatic transmissions for shifting gears, and thus the smooth and precise control of gear shifts of passenger car automatic transmissions has become more and more essential for the riding comfort of vehicles equipped with automatic transmissions. In this article, a neural network-based supervisor for an automotive shift controller considering the throttle opening, variations in throttle opening, and the driving load is presented. For using the driving load information, an observer-based driving load estimation algorithm is proposed. A proportional-integral-derivative controller along with an open loop controller is used as a low level controller for controlling the gear shifts, and a supervisory controller for properly adapting the shift control parameters of the low level shift controller is designed using ANFIS. To evaluate the control performance of the proposed supervisor-based shift controller, both simulation studies and experimental studies are performed for various shifting situations.

• 농업과학연구
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• 제48권3호
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• pp.597-606
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• 2021

Due to the characteristics of the farmland in Korea, forward and reverse shift is the most used. The fatigue of farmers is caused by forward and reverse shifting with a manual transmission. Therefore, it is necessary to improve the convenience of forward and backward shifting. This study was a basic study on the development of a current control system for forward and reverse shifting of agricultural tractors using proportional control valves and a controller. A test bench was fabricated to evaluate the current control accuracy of the control system, and the stability of the controller was evaluated through CPU (central processing unit) load measurements. A controller was selected to evaluate the stability of the proportional valve controller. The stability evaluation was performed by comparing and analyzing the command current of the controller and the actual current measured. The command current was measured using a CAN (controller area network) communication device and DAQ (data acquisition). The actual current was measured with a current probe and an oscilloscope. The control system and stability evaluation was performed by measuring the CPU load on the controller during control operations. The average load factor was 12.27%, and when 5 tasks were applied, it was shown to be 70.65%. This figure was lower than the CPU limit of 74.34%, when 5 tasks were applied and was judged to be a stable system.

• 전력전자학회논문지
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• 제22권5호
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• pp.423-430
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• 2017

This paper proposes a control methodology for a high efficiency operation of an inductive power transfer (IPT) converter by combining full bridge (FB) and half bridge (HB) controls. To apply the proposed control to the IPT converter, the characteristics of each control method are analyzed. By examining the output voltages of the IPT converter and a theoretical loss analysis, the control shifting points between FB and HB controls are evaluated in accordance with the coupling coefficients and the load. Based on the control shifting points, the FB-HB control algorithm is implemented. By applying FB-HB control, high efficiency operation at the light load condition can be achieved.

• 비파괴검사학회지
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• 제32권1호
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• pp.27-33
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• 2012

광탄성법은 실험역학에서 응력 또는 변형률을 해석하기 위한 여러 실험방법 중의 하나이며, 다양한 종류의 구조물의 응력 분포를 실험적으로 결정하는 기법이다. 광탄성법은 광탄성 영상의 등색 프린지와 등경 프린지로부터 광탄성 시편에 나타나는 전체의 응력장 분포를 정밀하게 측정할 수 있다. 본 논문에서는 여러 가지 광탄성 기법중 8단계 위상이동법(8-step phase-shifting method)에 관한 이론을 살펴보고, 경사균열이 있는 평판 시편에 인장을 가하여 나타난 광탄성 프린지로부터 경사균열 선단주위의 응력분포를 8단계 위상이동법으로 결정한 후, 이들 결과를 유한요소법(FEM)에 의한 결과와 비교하였다. 8단계 위상이동법을 이용한 실험에 의해 측정된 프린지 차수는 유한요소법에 의한 계산된 프린지 차수값에 근접하였다.