• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.208-211
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• 2004

Photovoltaic(PV) array, which is generally installed outside, has the possibility to be damaged by high voltage due to lightning. Because the electrical characteristics of PV array have not been fully identified by lightning yet, there is a very important issue whether PV array should be connected with ground or not. In this paper, a basic model of PV array is provided considering the PV cell's barrier capacitance and ground capacitance for analysis of electrical characteristics by lightning using PSCAD/EMTDC.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.323-325
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• 2008

Solar Array는 일사량 및 온도에 의해 얻을 수 있는 최대전력이 변화한다. 또한 Solar Array의 전압에 따라 출력 전력이 변화한다. 따라서 태양전지의 동작점을 최대 전력점에서 동작하게 하는 최대 전력점을 추적(MPPT:Maximum Power Point Tracking)하는 제어 시스템이 필요하다. 본 논문에서는 Solar Array의 전압과 전력의 상관관계를 이용하여 최대 전력점을 추종하는 제어 시스템을 제안한다. 이 방식은 빠르게 최대 동작점을 찾을 수 있고 높은 전력 변환 효율을 가지며 다른 방식에 비해 구성이 간단하다. 제안된 제어기법의 타당성을 검증하기 위하여 MPPT시뮬레이션과 실험을 수행하였다.

• 조명전기설비학회논문지
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• 제23권1호
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• pp.162-168
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• 2009

본 논문에서는 태양전지를 가지고 일정량의 태양광으로부터 최대 유효전력을 얻기 위해 고정식 태양광 발전시스템과 태양 위치추적기를 부착한 태양광 발전시스템에서 PV모듈의 각도 변화 및 어레이 간격에 따른 최적의 발전효율에 대한 연구 및 실험을 하였다. 먼저, PV 모듈의 다양한 각도를 가지고 실험한 결과 PV 모듈 경사각 30[$^{\circ}$]에서 측정한 결과 값이 경사각 20[$^{\circ}$] 및 40[$^{\circ}$]일 때보다 발전 효율이 $12{\sim}17$[%] 상승되었다. 그러므로 본 논문의 연구 결과에서는 태양광 발전시스템의 실용화 측면에서 PV 모듈의 경사각 30[$^{\circ}$] 설치를 하여 발전을 하는 것이 가장 좋은 변환 효율을 얻을 수 있었다. 하지만 태양전지를 지붕 및 옥상에 설치를 할 경우, 면적 활용이 좁고 겨울에 눈이 쌓이게 될 경우에는 경사각에 의해 빠르게 쓸려 내려갈 수 있도록 경사각을 35[$^{\circ}$]로 선정하는 것이 타당하다.

• 전력전자학회논문지
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• 제4권4호
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• pp.325-331
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• 1999

계통연계형 태양광발전시스템에서는 계통과 태양광시스템을 연계하기 위해 PWM 인버터가 이용된다. 인버터 시스템을 연속전류모드로 운전하면 맥동이 발생하게 되고, 직류전류의 맥동발생은 교류전류파형의 왜형을 가져온다. 본 연구에서는 직류입력전류의 맥동을 감소시키기 위하여 불연속모드 승강압초퍼로 인버터를 운전한다. 직류 전류에 포함된 고조파성분을 리플성분과 직류성분으로 분리하여 해석하고, 맥동이 없는 일정한 직류전류를 태양 전지로부터 인버터로 공급한다. 제안하는 인버터시스템은 단위 역률로 부하와 계통에 교류전류를 공급한다.

• Journal of Power Electronics
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• 제9권5호
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• pp.679-690
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• 2009

The paper presents a new photovoltaic inverter for stand-alone induction motor application. The proposed system is composed of two stages. First stage is for the photovoltaic dc power feeding and second stage is dedicated to the motor-inverter subsystem and control technique. A direct torque control (DTC) with a novel switching strategy for motor torque ripple minimization is introduced. The novel DTC strategy is based on selecting a suitable voltage vector group for motor torque ripple minimization. A three-level voltage source inverter (VSI) is used instead of a two level inverter because the first has more available vectors and lower ripples in the output current and flux than the second, thus it has lower torque ripples. The photovoltaic array and battery bank are sized and the configuration is indicated based on sun-hour methodology. Simulation results show a comparison between three systems; two level VSI with conventional DTC strategy, three level VSI with conventional DTC, and the proposed system that has a novel DTC switching strategy applied to three level VSI. The results show that the proposed system has lower ripples in the current, flux and torque of the motor.

• Journal of Electrical Engineering and Technology
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• 제7권4호
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• pp.524-529
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• 2012

This paper proposes a novel control strategy of a PV tracking system considering the shadow influence. If distance of between PV arrays is not enough, shadow can be occurred to PV module. In PV system, if shadow is occurred to PV modules then PV modules operates reverses bias, and will eventually cause hot-spot and loss. To reduce loss by shadow influence, this paper proposes shadow compensation algorithm using distance between arrays and shadow length of array. The distance between arrays is calculated by using azimuth of solar, and length of array shadow is calculated using by altitude of solar. The shadow compensation algorithm proposed in this paper compares distance between arrays and length of array shadow. When the shadow length is longer than the distance between arrays, the algorithm adjusts altitude of array to avoid the shadow effects. The control algorithm proposed in this paper proves validity through compared with conventional algorithm and proposes experiment result.

• 태양에너지
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• 제19권4호
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• pp.63-69
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• 1999

The conventional grid connected PV(Photovoltaic) system has a unstable output pattern due to its dependence on the weather condition, although solar-cell array averagely has a regular output characteristics to have a peak output nearly at noon. Therefore assuming the high density grid connection in the future, this unstable output pattern can be one of the main reasons to generate power disturbance such as voltage variation, frequency variation and harmonic voltage generation in low voltage distribution line. However general grid connected solar-cell system do not have functions to cope with these disturbances. Therefore this study proposed a advanced type grid connected PV system with functions to suppress output power fluctuation due to solar-cell array output variation and showed the levelling effect of fluctuation due to instantaneous array output variation.

• Journal of Power Electronics
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• 제14권1호
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• pp.156-164
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• 2014

The power-voltage (P-V) characteristic of a photovoltaic (PV) array is nonlinear and time varying with the change in atmospheric conditions. As a result, the maximum power point tracking (MPPT) technique must be applied in PV systems to maximize the generated energy. The incremental conductance (INC) algorithm, one of the MPPT strategies, is widely used for its high tracking accuracy, good adaptability to rapidly changing atmospheric conditions, and easy implementation. This paper presents a modified asymmetrical variable step size INC MPPT method that is based on the asymmetrical feature of the P-V curve. Compared with conventional fixed or variable step size method, the proposed method can effectively improve tracking accuracy and speed. The theoretical foundation and design principle of the proposed approach are validated by the simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.1945-1947
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• 1997

In this paper, a characteristics analysis of the grid-connected photovoltaic power generation system which uses the simulation method of PV array is reported. The control method of DC/AC power conversion were suggested to establish the basic application technology of photovoltaic systems. The results of the demonstration test of a 3kW grid-connected PV system show that the system utilization rate is 17.6% and the system efficiency is 8.9%.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2177-2180
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• 1997

The solar cell has an optimum operating point to be able to got maximum power. To obtain maximum power from Photovoltaic array, hotovoltaic power system usually requres maximum power point c tracking controller. The output characteristics of solar cell are nonlinear, and these characteristics vary with load solar insolation, solar cell temperature. Therefore the tracking control of maximum power point is the com-plicated problem. This paper presents power characteristics of residential Photovoltaic system applying a buck-boost conversion system.