• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.590-597
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• 2018

Recently, the installation of PV systems has been increasing due to the worldwide interest in eco-friendly and renewable solar energy. On the other hand, the output power of PV systems is influenced strongly by the surrounding weather conditions. In addition, the entire operation efficiency of PV systems may be decreased considerably even if only some of the PV modules are in the shade. In other words, the existing control method at which strings with modules in series are connected to an inverter may be not operated in the case that the string voltage in partial shade is lower than the operating range of the grid connected inverter. To overcome these problems, this paper proposes an operation efficiency improvement device of a PV system using a Li-ion battery, which can compensate for the voltage of each string in the PV system when it is partially shaded. In addition, this paper presents the modeling of the operation efficiency improvement device, including PV strings, Li-ion battery and a 3-Phase grid inverter based on the PSIM S/W. From the simulation results, it was confirmed that the proposed control method can improve the operating efficiency of PV systems by compensating for the string voltage with partial shade.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.22-33
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• 2021

In the case of open phase faults caused by the disconnection of distribution feeders interconnected to a PV system, many problems can occur depending on the core type and wiring method of the grid-connected transformers. Moreover, open phase faults are difficult to detect because the open phase voltage of the existing protection relay (Open Phase Relay (47)) can be maintained, even though a disconnection fault occurred, depending on the wiring method and the iron core type of the grid-connected transformer for a PV system. Therefore, this paper proposes a novel algorithm to detect open phase faults by comparing the currents and phases between the primary and secondary sides of a grid-connected transformer. In addition, this paper presents the modeling of a distribution system and protection devices for detecting open phase faults using PSCAD/EMTDC S/W, and implements a test protection device for detecting open phase faults based on the above-mentioned modeling. The simulation and test results confirmed that the proposed algorithm is useful for detecting open phase faults according to the wiring method and iron core type of grid-connected transformer for a PV system because operation slope and unbalance rate of the primary current exceed the setting value (30[%]) of the protection device.

• Journal of the Korean Solar Energy Society
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• v.32 no.2
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• pp.35-41
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• 2012

Knowledge of the solar radiation components and classified wavelength data are essential for modeling many solar photovoltaic systems. This is particularly the case for applications that concentrate the incident energy to attain high photo-dynamic efficiency achievable only at the higher intensities. In order to estimate the performance of concentrating PV systems, it is necessary to know the intensity of the beam radiation, as only this components can be concentrated, and The new PV cell can generate electricity from ultraviolet and infrared light as well as visible light. The Korea Institute of Energy Research(KIER) has began collecting solar radiation components data since January, 1988, and solar radiation classified wavelength data since November, 2008. KIER's solar radiation components and classified wavelength data will be extensively used by concentrating PV system users or designers as well as by research institutes. It is essential to utilize the solar radiation data as application and development of solar energy system increase. Consider able efforts have been made constructing a standard data base system from measure data.

• Journal of information and communication convergence engineering
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• v.6 no.4
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• pp.417-420
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• 2008

Solar electric systems have very little impact on environment, making them one of the cleanest power-generating technologies available. While they are operating, PV systems produce no air pollution, hazardous waste, or noise, and they require no transportable fuels. In PV system design, the selection and proper installation of appropriately-sized components directly affect system reliability, lifetime, and initial cost. In this research, we have studied the PWM(Pulse Width Modulation) signals. I proposed an efficient photovoltaic power interface circuit incorporated with a DC-DC converter and a sine-pwm control method full-bridge inverter. In grid-connected solar power systems, the DC-DC converter operates at high switching frequency to make the output current a sine wave, whereas the full-bridge inverter operates at low switching frequency which is determined by the ac frequency. Thus, it can reduce the switching losses incurred by the full-bridge inverter. Full-bridge converter is controlled by using microprocessor control method, and its operation is verified through computer aided simulations.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.2
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• pp.71-78
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• 2018

In this paper, we propose the performance enhancement of solar individual string power generation system using booster power control for voltage compensation. The proposed control method determines the variable voltage for the compensator using direct power control (DPC) modeling applied to motion factor estimation. This method also maintains excellent dynamic response to the characteristics of direct power control (DPC) by calculating the mismatch ratio of the arrestered PV modules. The validity of the proposed algorithm is verified through simulation and experiments.

• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.69-75
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• 2013

To increase the efficiency of the photovoltaic, almost photovoltaic appliances are controlled by Maximum Power Point Tracking(MPPT). Existing most of the PV MPPT techniques have used power which multiplies sensed output current and voltage of the solar cell. However, these algorithms are unnecessarily complicated and too expensive for small and compact system. The other hand, the proposed MPPT technique is only one sensing of the MPPT converter's output current, so there is no need to insert another sensors of battery side. Therefore, this algorithm is simpler compared to the traditional approach and is suitable for low power solar system. Further, the novel proper charge/discharge algorithm for the battery with PV MPPT is developed. In this algorithm, there is CC battery charge mode and load discharge mode of the PV cell & battery dual. Also we design current control to regulate allowable current during the battery charging. The proposed algorithm will be applicable to battery included solar cell applications like solar lantern and solar remote control car. Finally, the proposed method has been verified with computer simulation.

• Journal of the Korean Solar Energy Society
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• v.27 no.2
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• pp.53-59
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• 2007

Knowledge of the solar radiation components are essential for modeling many solar photovoltaic systems. This is particularly the case for applications that concentrate the incident energy to attain high photo-dynamic efficiency achievable only at the higher intensities. In order to estimate the performance of concentrating PV systems, it is necessary to know the intensity of the beam radiation, as only this component can be concentrated. The Korea Institute of Energy Research(KIER) has began collecting solar radiation component data since August, 1996. KIER's component data will be extensively used by concentrating PV system users or designers as well as by research institutes.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.471-478
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• 2011

This paper proposes a method of maximum power point tracking (MPPT) using fuzzy logic control for grid-connected photovoltaic systems (PV). First, for the purpose of comparison, because of its proven and good performances, the incremental conductance (IncCond) technique is briefly introduced. A double fuzzy logic controller (DFLC) based MPPT is then proposed which has shown better performances compared to the IncCond MPPT based approach. Modeling and Simulation in grid-connected PV system results are provided for both controllers under same atmospheric condition based PSCAD/EMTDC. The double fuzzy logic MPPT controller is then simulated and evaluated, which has shown better performances.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.326-328
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• 1996

The 10kW or 1MW model of a photovoltaic array written in PSPICE is presented in this paper. A problem with this large scale centralized photovoltaic system is the decrease of power due to the resistance of cable connecting individual subarray with inverter. In this paper, we analyzed the relationship between the resistance of cable and subarray output power of 1MW photovoltaic system by the PSPICE modeling. As a result of simulation, we can proved that photovoltaic array output power is limitted by the resistance of cable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.9-17
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• 2020

Recently, RES (renewable energy source) projects have been spreading all over the world as an alternative to solve the shortage of energy and environmental problems caused by fossil fuel consumption. The Korean government also supported the policy and demonstration project to increase the proportion of renewable energy to 63.8[GW] until 2030, which is 20[%] of the total power generation. On the other hand, output loss of a PV array can occur when the surrounding high-rise buildings and trees shade a PV array. Therefore, this paper proposes an algorithm to improve the output loss of a PV array, which electrically changes a circuit configuration of PV modules by wiring and switching devices. Furthermore, this study modeled a PV system based on PSIM S/W, which was composed of a PV array, a circuit configuration device, and a grid-connected inverter. From the simulations results with the modeling and test device, the existing method showed no output when 50% of the shade occurs in PV modules. In contrast, the proposed method could produce the output because the voltage in the PV module could be restored to 246[V], and the operation efficiency of the PV system could be improved by the operation algorithm of the circuit configuration device.