• 분석과학
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• 제7권3호
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• pp.253-260
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• 1994

Low power-low flow 유도결합 플라즈마 원자방출 분광법(ICP-AES)에서 분석적 특성에 대해 연구하였다. Low power ICP에서는 moderate power ICP보다 알짜세기는 감소하지만 바탕세기도 감소하여 알짜세기에 대한 바탕세기의 비는 오히려 증가하였다. Low power ICP에서도 작동조건에 따라 moderate power와 비슷한 검출한계를 얻을 수 있으며, 검량곡선도 $10^4{\sim}10^5$ 정도의 직선성을 가질 수 있었다. 알칼리 금속에 의한 이온화 방해영향은 시료운반기체의 사용량을 증가시킬수록 증가하지만, RF power의 변화에 대해서는 큰 차이가 없었다.

• Journal of Power Electronics
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• 제14권6호
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• pp.1166-1177
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• 2014

A new type of topology with medium-frequency-transformer (MFT) isolation for medium voltage wind power generation systems is proposed in this paper. This type of converter is a high density power conversion system, with high performance features suitable for next generation wind power systems in either on-shore or off-shore applications. The proposed topology employs single-phase cascaded multi-level AC-AC converters on the grid side and three phase matrix converters on the generator side, which are interfaced by medium frequency transformers. This avoids DC-Link electrolytic capacitors and/or resonant L-C components in the power flow path thereby improving the power density and system reliability. Several configurations are given to fit different applications. The modulation and control strategy has been detailed. As two important part of the whole system, a novel single phase AC-AC converter topology with its reliable six-step switching technique and a novel symmetrical 11-segment modulation strategy for two stage matrix converter (TSMC) is proposed at the special situation of medium frequency chopping. The validity of the proposed concept has been verified by simulation results and experiment waveforms from a scaled down laboratory prototype.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.837-841
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• 2001

Almost all power plant boiler has temperature distribution nonuniformity problem in heat transfer tube flow path. It can cause hot spot damage of superheated or reheated heat transfer section and reduce maintenance schedule when nonuniformity is severe. There are two solutions for improvement temperature nonuniformity. one is change of gas flow distribution of gas path and the other is contorl steam flow in tube bank. Of course, first method is very difficulty to apply but second method is'nt. In this paper, control steam flow is used to solve temperature nonuniformity of power plant boiler.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.329-332
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• 1991

This paper presents an algorithm to reduce the time to solve Power Equations using a Neural Net. The Neural Net is trained with samples obtained through the conventional AC Load Flow. With these samples, the Neural Net is constructed and has the function of a linear interpolation network. Given arbitrary load level, this Neural Net generates voltage magnitudes and angles which are linear interpolation of real and reactive powers. Obtained voltage magnitudes and angles are substituted to Power Equations, Real and reactive powers are found. Thus, a new sample is generated. This new experience modifies weight matrix. Continuing to modify the weight matrix, the correct solution is achieved. comparing this method with AC Load flow, this method is faster. If we consider parallel processing, this method is far faster than conventional ones.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.23-26
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• 2005

This paper describes the design, construction and implementation of matrix converter based on space vector modulation technique. The matrix converter provides sinusoidal input and output wave forms, bidirectional power flow, controllable input power factor and a compact design, compared to the VSI with diode rectification stage at the input. The implemented prototype of matrix converter is built using the exclusive IGBT module and has an input filter, overvoltage protection circuit and commutation means for overcoming practical issues. The good results tested using an induction motor are also presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.918-922
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• 1998

With the development of industry, the qualitical advancement of power is needed. Since it is placed in the end step of power system, the fault at the distribution system causes some users blackout directly. So if the fault occurs, quick restoration is very important subject and, for the reason, induction of the distribution automation system is now being progressed briskly. For the quick restoration of the faulted distribution system, the load shedding of the blackout-area must be followed, and the other problems like the shedded load, faulted voltage and the rest may cause other accident. Accordingly load shedding must be based on the precise calculation technique during the distribution system load flow(dist flow) calculation. In these days because of its superior convergence characteristic the Newton-Raphson method is most widely used. The number of buses in the distribution system amounts to thousands, and if the fault occurs at the distribution system, the speed for the dist flow calculation is to be improved to apply to the On-Line system. However, Newton-Raphson method takes much time relatively because it must calculate the Jacobian matrix and inverse matrix at every iteration, and in the case of huge load, the equation is hard to converge. In this thesis. matrix equation is used to make algebraical expression and then to solve load flow equation and to modify above defects. Then the complex matrix is divided into real part and imaginary part to keep sparcity. As a result time needed for calculation diminished. Application of mentioned algorithm to 302 bus, 700 bus, 1004 bus system led to almost identical result got by Newton-Raphson method and showed constant convergence characteristic. The effect of time reduction showed 88.2%, 86.4%, 85.1% at each case of 302 bus, 700 bus system 86.4%, and 1004 bus system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.646-647
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• 2007

The topology processor uses the status of circuit breakers as input. It operates on the bus section connectivity data, which is stored in the data base, to determine the bus/branch topology of the network. This output of the topology processor forms part of the input to the state estimation or dispatcher power flow. This paper describes the development of the topology processor using matrix structure.

• 전력전자학회논문지
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• 제10권6호
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• pp.550-559
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• 2005

매트릭스 컨버터는 VS떼 비하여 장수명, 입력역률 직접제어 및 에너지 회생 등의 장점을 갖고 있으나, 제어의 복잡성, ride-through 대책 및 낮은 전압이용률 등은 상용화를 위해 해결해야 할 난제이다. 본 논문에서는 SVM를 적용한 매트릭스 컨버터의 설계 및 구현방법을 제안한다. 입력 고조파를 저감시키기 위한 입력필터와 입출력의 과전압 방지와 free-wheeling을 위한 클램프 회로의 설계기법을 제시하고, 고속 DSP와 CPLD를 사용하여 공간벡터 제어 및 4 단계 전류(commutation) 제어를 구현하며, 매트릭스 컨버터의 양방향 스위치 구동을 위한 전용의 전원회로를 설계하여, 최적 구조의 전력회로를 제안한다. 그리고 구현된 매트릭스 컨버터를 유도전동기에 적용하여 성공적인 운전 결과를 얻을 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.311-315
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• 1998

Load Flow calculation methods can usually be divided into Gauss-Seidel method, Newton-Raphson method and decoupled method. Load flow calculation is a basic on-line or off-line process for power system planning, operation, control and state analysis. These days Newton-Raphson method is mainly used since it shows remarkable convergence characteristics. It, however, needs considerable calculation time in construction and calculation of inverse Jacobian matrix. In addition to that, Newton-Raphson method tends to fail to converge when system loading is heavy and system has a large R/X ratio. In this paper, matrix equation is used to make algebraic expression and then to solve load flow equation and to modify above defects. And it preserve certain part of Jacobian matrix to shorten the time of calculation. Application of mentioned algorithm to 14 bus, 39 bus, 118 bus systems led to identical result and the number of iteration got by Newton-Raphson method. The effect of time reduction showed about 28%, 30%, at each case of 39 bus, 118 bus system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.507-509
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• 2000

This study developed the window based power flow analysis software for distribution system. This system was developed by using Visual C++ 6.0 in Microsoft Windows 98 environment; therefore, it utilized many advantages of window based programming for providing user-friendly interface. The backward/forward sweep algorithm is implemented in this software for power flow analysis. Especially, this software includes the newly developed classes of complex function, matrix function, and power flow calculation procedure, so it has high flexibility for enhancement and modifications.