• 한국산학기술학회논문지
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• 제17권7호
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• pp.704-712
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• 2016

최근, 전 세계적으로 신재생에너지에 대한 관심이 증가됨에 따라 친환경적이고 무한한 태양에너지를 이용하는 태양광전원의 설치가 급증하고 있다. 이러한 태양광전원은 주변 환경에 따라 출력이 크게 좌우되는데, 예를 들어 구름 또는 건물의 음영으로 인한 일부 모듈의 문제로 인해서 해당 스트링이 출력을 발생하지 못할 수 있다. 즉 기존의 제어방식에서는 모듈이 직렬로 연결된 스트링이 인버터에 연계되어 있으므로, 일부 모듈에 음영이 발생할 경우 스트링의 전압이 인버터의 동작전압 미만으로 되어 해당 스트링이 인버터에서 탈락되는 문제점이 발생할 수 있다. 따라서 본 논문에서는 각각의 스트링마다 전압을 제어하는 DC-DC 전압 레귤레이터를 이용하여, 스트링이 인버터에서 탈락되는 문제점을 개선하는 새로운 태양광전원 제어방식을 제안하였다. 또한, 회로해석 상용 프로그램인 PSIM S/W를 이용하여, 정전압 제어 및 MPPT(Maximum Power Point Tracking) 제어기능을 가지는 DC-DC 전압 레귤레이터와 위상동기루프(PLL, Phase-Locked Loop) 제어 기반의 3상 인버터의 모델링을 수행하였다. 이 모델링을 바탕으로 시뮬레이션을 수행한 결과, 부분적으로 음영이 발생하는 모듈을 가진 스트링이 인버터에서 탈락하는 현상을 개선함으로써 태양광전원의 운용효율이 향상됨을 확인하였다.

• 한국환경복원기술학회지
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• 제16권4호
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• pp.27-40
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• 2013

These day morden cities have serious climatic problems due to enviornmental load caused by excessive development of urbanization. As technological improvement to answer to various ecological disasters and climate changes are also called on the field of construction, inter-disciplinary studies linked to the estabilishment of sustainable energy generation systems and enviornmental control is needed in a consilient point of view. This study aims to analyse optimal site conditions for photovoltaic system and green roof planting through solar radiation simulation in a integrated perspective. In so doing, it seeks to proffer basic study for developing a sound use of roof area that is sustainable in environmental and resources aspects. A computer simulation showed that, in the case of total seasonal solar radiation, summer season resulted 312.5kWh in 35% of total annual solar radiation. This season indicated the lowest radiation rate of the year for direct sunlight in 45.8% of total seasonal solar radiation. Due to such solar radiation simulation, at the largest optimal planting area, Glechoma hederacea var. longituba secured $719.16m^2$ of gross roof area.

• 통합자연과학논문집
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• 제15권3호
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• pp.99-110
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• 2022

Solar photovoltaic (PV) system shows a non-linear current (I) -voltage (V) characteristics, which depends on the surrounding environment factors, such as irradiance, temperature, and the wind. Solar PV system, with current (I) - voltage (V) and power (P) - Voltage (V) characteristics, specifies a unique operating point at where the possible maximum power point (MPP) is delivered. At the MPP, the PV array operates at maximum power efficiency. In order to continuously harvest maximum power at any point of time from solar PV modules, a good MPPT algorithms need to be employed. Currently, due to its simplicity and easy implementation, Perturb and Observe (P&O) algorithms are the most commonly used MPPT control method in the PV systems but it has a drawback at suddenly varying environment situations, due to constant step size. In this paper, to overcome the difficulties of the fast changing environment and suddenly changing the power of PV array due to constant step size in the P&O algorithm, least mean Square (LMS) methods is proposed together with P&O MPPT algorithm which is superior to traditional P&O MPPT. PV output power is predicted using LMS method to improve the tracking speed and deduce the possibility of misjudgment of increasing and decreasing the PV output. Simulation results shows that the proposed MPPT technique can track the MPP accurately as well as its dynamic response is very fast in response to the change of environmental parameters in comparison with the conventional P&O MPPT algorithm, and improves system performance.

• Journal of Power Electronics
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• 제17권2호
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• pp.514-521
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• 2017

This paper proposes a shadowing compensation method for the solar modules of grid-connected photovoltaic generation systems. The shadowing compensator (SC) implemented by the proposed shadowing compensation method is used only for the solar modules that can be shaded by predictable sources of shading. The proposed SC can simplify both the power circuit and the control circuit as well as improve power efficiency and utilizes a voltage equalizer configured by a modified multi-winding fly-back converter. The proposed SC harvests energy from the entire solar cell array to compensate for the shaded sub-modules of the solar cell array, producing near-identical voltages of all shaded and un-shaded sub-modules in the solar cell array. This setup prevents the formation of multiple peaks in the P-V curve under shaded conditions. Hardware prototypes are developed for the SCs implemented by the conventional and modified multi-winding fly-back converters, and their performance is verified through testing. The experimental results show that both SCs can overcome the multiple peaks in the P-V curve. The proposed SC is superior to the SC implemented by the conventional multi-winding fly-back converter.

• Journal of Power Electronics
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• 제16권6호
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• pp.2129-2138
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• 2016

The full-bridge inverter, widely used for single-phase photovoltaic grid-connected applications, presents a leakage current issue. Therefore, an AC bypass branch is introduced to overcome this challenge. Nevertheless, existing modulation strategies entail drawbacks that should be addressed. One is the zero-crossing distortion (ZCD) of the AC current caused by neglecting the AC filter inductor voltage. Another is that the system cannot deliver reactive power because the AC bypass branch switches at the power frequency. To address these problems, this work proposes an optimized hybrid modulation strategy. To reduce ZCD, the phase angle of the inverter output voltage reference is shifted, thereby compensating for the neglected leading angle. To generate the reactive power, the interval of the negative power output is calculated using the power factor. In addition, the freewheeling switch is kept on when power is flowing into the grid and commutates at a high frequency when power is fed back to the DC side. In this manner, the dead-time insertion in the high-frequency switching area is minimized. Finally, the performances of the proposed modulation strategy and traditional strategies are compared on a universal prototype inverter. Experimental results validate the theoretical analysis.

• 전기전자학회논문지
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• 제23권1호
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• pp.173-180
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• 2019

재생에너지의 점유율 증가에 의하여 출력이 제한되는 사례가 발생하고 있다. 전형적으로 풍력발전의 발전량이 높고 부하가 낮은 새벽시간에 출력제한이 주로 발생하였으나, 태양광발전의 점유율이 증가하면서 낮 시간에 풍력발전의 출력이 제한되는 사례가 발생하고 있다. 현재의 전력계통 운영 상황에서는 태양광발전의 점유율이 증가할수록 풍력발전의 출력 제한이 더욱 증가시킬 것이며, 이는 풍력발전 운영자의 어려움을 가중시킬 것이다. 본 논문에서는 발전원 그리고 발전소별 출력 제한을 위하여 전력계통의 운영 어려움 유발하는 에너지원의 우선 제약을 기준으로 설정하여 기준에 따라 재생에너지의 출력 제한량을 분배하는 방안을 제시하였다.

• 신재생에너지
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• 제17권2호
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• pp.24-31
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• 2021

Renewable energy has become more popular with the increase in the use of solar power. Consequently, the disposal of defective and old solar panels is gradually increasing giving rise to a new problem. Furthermore, the efficiency and power output decreases with aging. Researchers worldwide are engaged in solving this problem by developing eco-module technologies that restore and reuse the solar panels according to the defect types rather than simple disposal. The eco-module technology not only solves the environmental problem, but also has economic advantages, such as extending the module life. Replacement of encapsulants contributes to a major portion of the module maintenance plan, as the degradation of encapsulants accounts for 60% of the problems found in modules over the past years. However, the current International Electrotechnical Commission (IEC) standard testing was designed for the commercialization of solar modules. As the problem caused by long-term use is not considered, this method is not suitable for the quality assurance evaluation of the eco-module. Therefore, to design a new accelerated test, this paper provides an overview of EVA degradation and comparison with the IEC and accelerated tests.

• Journal of Magnetics
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• 제19권3호
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• pp.295-299
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• 2014

Recently, module-integrated converter (MIC) research has shown interest in small-scale photovoltaic (PV) generation. The converter is capable of efficient power generation. In this system, the high frequency transformer should be made compact, and demonstrate high efficiency characteristics. This paper presents a core structure optimization procedure to improve the efficiency of a high frequency transformer of compact size. The converter circuit is considered in the finite element analysis (FEA) model, in order to obtain an accurate FEA result. The results are verified by the testing of prototypes.

• 조명전기설비학회논문지
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• 제24권12호
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• pp.84-90
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• 2010

In order to level electric power of the photovoltaic and wind-turbine system and ensure fast response of the fuel-cell and micro-turbine, the energy storage is required in the microgrid system. In this paper, a simplified simulation model of the battery energy storage for charging method with IUIa is developed using PSCAD/EMTDC. The model consists of e.m.f.(electromotive force), internal resistor and overvoltage capacitor. A method for deciding parameters of the model on a case-by-case basis is proposed. The developed model can be used in the simulation of a complicated system such as a microgrid system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 추계학술대회 논문집
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• pp.181-185
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• 2002

This paper discusses power balance control of photovoltaic/wind/diesel hybrid generation system for remote area power supplies. There are many control methods for hybrid power system. Among others, it must be adopted that the control method to guarantee a stable balance between supply and demand, regardless of the fluctuation of generator power by atmospheric changes. In this paper, it Is proposed that a hybrid generation system has a power-balanced controller to equilibrate generation power with a load demand, which is composed of DC bus-type power systems. To execute power balance control, it is assumed that all of power generators have a equivalent current-source characteristics. Through the results of simulation, the proposed scheme was verified.