• 전력전자학회논문지
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• 제8권5호
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• pp.463-467
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• 2003

본 논문에서는 교류쵸퍼와 직렬보상변압기로 구성되는 교류전압제어장치에 대하여 연구한다. 먼저, 교류쵸퍼와 직렬보상변압기로 구성되는 기본적인 교류전압제어장치로 출력전압을 입력전압에서 10-20%정도 강압할 수 있는 형태의 강압형 교류전압 제어장치를 제안하고 기본동작원리 및 이의 안전한 운전을 위한 PWM 발생과 초기시퀀스로직을 제시하였다. 또한 이로부터 입력전압변동에 무관하게 일정 출력전압을 발생시키기 위한 자동전압제어장치(AVR: Automatic Voltage Regulator)로 사용가능한 두가지 형태의 직렬보상형 교류전압제어장치를 제안하고 동작원리를 기술하였다. 특히, 입력전압과 반대방향의 극성의 전압을 발생시킬 수 있는 새로운 형태의 양방향 교류쵸퍼를 제안하고, 이의 안전한 운전을 위한 PWM 발생을 위한 스위칭 패턴을 제시하였다. 제안된 교류전압제어회로의 경우 다양한 실험을 통하여 전력절감을 목적으로 하는 강압형 교류전압제어장치와 자동전압조절기의 용도로 효과적으로 적용될 수 있음을 확인하였다.

• 전기학회논문지
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• 제58권2호
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• pp.232-238
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• 2009

Flicker, also known as voltage fluctuation, is a newest problem of power quality issues, because it is caused by nonlinear loads such as electrical arc furnace and large-scale induction motor, which are country-widely used as the heavy industries of a country develop. An international standard, International Electrotechnical Commission (IEC) 61000-4-15, was published in 1997 and revised in 2003. With increasing concerns about flicker, its mitigation methods have been also studied. General countermeasures for flicker are divided into three categories: a) enhancing the capacity of supplying system, b) Series elements including series reactor and series capacitor and c) power electronic devices including static VAR compensator (SVC) and static synchronous compensator (STATCOM). This paper introduces how to mitigate the voltage flicker at the point of common coupling (PCC) and presents how to simulate and compare the flicker alleviating effects by each mitigation method, using IEC flickermeter based on the Matlab/Simulink program.

• Journal of Power Electronics
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• 제10권6호
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• pp.673-679
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• 2010

Input-series-output-parallel (ISOP) connected DC-DC converters enable low voltage rating switches to be used in high voltage input applications. In this paper, a DSP is adopted to generate digital phase-shifted PWM signals and to fulfill the closed-loop control function for ISOP connected two full-bridge DC-DC converters. Moreover, a stable output current sharing control strategy is proposed for the system, with which equal sharing of the input voltage and the load current can be achieved without any input voltage control loops. Based on small signal analysis with the state space average method, a loop gain design with the proposed scheme is made. Compared with the conventional IVS scheme, the proposed strategy leads to simplification of the output voltage regulator design and better static and dynamic responses. The effectiveness of the proposed control strategy is verified by the simulation and experimental results of an ISOP system made up of two full-bridge DC-DC converters.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.205-207
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• 2004

This paper proposes a new SSHG(Sag/swell and Harmonic Generator) injecting voltage by using series inverter. The proposed SSHG composes series inverter, DC capacitor as energy storage, rectifier and voltage clamp circuit. This SSHG is designed to generate typical power disturbances, such as voltage sag/swell, over/under voltage and voltage flicker. Also it is designed to generate unexpected voltage phase jumping waveform by controlling the series inverter. In this paper, three kinds of control methods for the proposed 2MVA SSHG are given. Typical voltage sag and swell waveforms are implemented by adopting simple control method. Also the voltage flicker is generated by changing the amplitude of the injected voltage in random. Owing to the limited bandwith of the proposed SSHG, high frequency transient waveforms can be obtained by using the open loop control. The simulation and experimental results are given to verify the operation of the proposed SSHG, Finally, conclusions are given.

• Structural Engineering and Mechanics
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• 제86권1호
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• pp.69-83
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• 2023

Analytical solutions to problems are crucial because they provide high-quality comparison data for assessing the accuracy of numerical solutions. Benchmark analytical solutions for the vibrations of cracked functionally graded material (FGM) plates are not available in the literature because of the high level of complexity of such solutions. On the basis of first-order shear deformation plate theory (FSDT), this study proposes analytical series solutions for the vibrations of FGM rectangular plates with side or internal cracks parallel to an edge of the plates by using Fourier cosine series and the domain decomposition technique. The distributions of FGM properties along the thickness direction are assumed to follow a simple power law. The proposed analytical series solutions are validated by performing comprehensive convergence studies on the vibration frequencies of cracked square plates with various crack lengths and under various boundary condition combinations and by performing comparisons with published results based on various plate theories and the theory of three-dimensional elasticity. The results reveal that the proposed solutions are in excellent agreement with literature results obtained using the Ritz method on the basis of FSDT. The paper also presents tabulations of the first six nondimensional frequencies of cracked rectangular Al/Al2O3 FGM plates with various aspect ratios, thickness-to-width ratios, crack lengths, and FGM power law indices under six boundary condition combinations, the tabulated frequencies can serve as benchmark data for assessing the accuracy of numerical approaches based on FSDT.

• 조명전기설비학회논문지
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• 제15권2호
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• pp.21-30
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• 2001

본 논문에서는 UPFC(Unified Power Flow Controller)설치 전력계통에서 어떤 선로의 전력조류를 원하는 값으로 직접 제어함과 동시에 계통 전체의 전력조류해석을 행하는 선로조류제약을 고려한 전력조류해석 알고리즘을 제시하고 이 알고리즘을 UPFC에 의한 과부하선로의 과부하해소제어에 적용하여 UPFC 제어 방법을 제시하고 사례연구를 통하여 UPFC의 제어효과의 효용성을 입증하였다. 또한 효과적인 조류해석을 위한 UPFC의 직·병렬 전압원의 초기치를 설정하는 공식을 유도하였다.

• 조명전기설비학회논문지
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• 제27권3호
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• pp.55-64
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• 2013

In this paper, a new topology which can add a small reactor in series to a condenser-bank type reactive power compensator to limit current is proposed. And also the proposed topology can add or remove a power condenser safely without any addition of inrush-current suppression resistance. The proposed method tests variable resistance of the drain source of a switching device which is controlled by gate voltage in a two-way switch with a diode rectifier and FET switch. In other words, the proposed method is a inrush-current suppression method with the structure of variable resistance. In particular, the proposed method creates smooth current without any resonance in inrush-current as well as is not limited by the time of switch on and off.

• 조명전기설비학회논문지
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• 제29권7호
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• pp.22-27
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• 2015

In this paper, the problem of voltage unbalancing in series-connected multiple electric double-layer capacitors(EDLCs) is studied. Good understanding of this problem is required in order to increase reliability and stability of an energy storage system comprising EDLCs. Existing methods to settle voltage unbalancing cannot mitigate the problem enough for each cell, since most method have been applied to each module. For equalizing between cells, Zener diode which is one of passive method have been well examined in literature. However, Zener have well not used in balancing due to heating problem. In addition, It is difficult to choose Zener diode fitted rating voltage of EDLC, because of its internal resistance. Thus, we proposed passive balancing using Zener diode by analyzing parasitic element of Zener and EDLC. To experimentally confirm the balancing effect, we compared in two occasions which are with and without passive. As a result, proposed passive balancing circuit mitigated unbalanced voltage gap between EDLCs.

• Journal of electromagnetic engineering and science
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• 제5권3호
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• pp.146-151
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• 2005

Electromagnetic penetration into an annular aperture in a thick conducting plane is investigated with the integral transform and eigen-function expansion method. The solution is analytic and is represented in rapidly-convergent series which is amenable to numerical analysis. Numerical computations shows that apertures with narrow annular gap have sharp transmit power peaks in frequency response.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.9-12
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• 1988

This paper shows a asymmetrically controlled method for the simultaneous control of real and reactive power generated by Superconducting Magnetic Energy Storage (SMES). Asymmetrically controled 12 pulse converter has been proposed in this paper for harmonic reduction of transformer primary current.