• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.3
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• pp.299-305
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• 2015

Global environmental concerns and the ever increasing need of energy, coupled with steady progress in renewable energy technologies, are opening up new opportunities for utilization of renewable energy resources. Distributed electricity generation is a suitable option for sustainable development thanks to the load management benefits and the opportunity to provide electricity to remote areas. Solar energy being easy to harness, non-polluting and never ending is one of the best renewable energy sources for electricity generation in present and future time. Due to the random and intermittent nature of solar source, PV plants require the adoption of an energy storage and management system to compensate fluctuations and to meet the energy demand during night hours. This paper presents an efficient, economic and technical model for the design of a MPPT based grid connected PV with battery storage and management system. This system satisfies the energy demand through the PV based battery energy storage system. The aim is to present PV-BES system design and management strategy to maximize the system performance and economic profitability. PV-BES (photovoltaic based battery energy storage) system is operated in different modes to verify the system feasibility. In case of excess energy (mode 1), Li-ion batteries are charged using CC-CV mechanism effectively controlled by fuzzy logic based PID control system whereas during the time of insufficient power from PV system (mode 2), batteries are used as backup to compensate the power shortage at load and likewise other modes for different scenarios. This operational mode change in PV-BES system is implemented by State flow chart technique based on SOC, DC bus voltages and solar Irradiance. Performance of the proposed PV-BES system is verified by some simulations study. Simulation results showed that proposed system can overcome the disturbance of external environmental changes, and controls the energy flow in efficient and economical way.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.59-63
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• 2005

The 800-kW PM (permanent magnet) synchronous generator is developed as a wind power generator. The matching converter is designed to control the torque and power depending on the wind speed regime. The generator starts to generate the power at the speed of 9 rpm and the rated output is generated at the speed of 25 rpm. The rated output power of an inverter is 750 kW when the PM synchronous generator is delivering 800 kW to the inverter. The inverter is specially designed to perform the maximum power point tracking (MPPT) at the low wind speed regime that is typical wind environment in Korea. The inverter test was done with a 2 MW M-G system at KERI (Korea Electric Research Institute). The M-G set has a 2 MW motor driver and a 38:1 gear to match the speed between the motor and the PM generator. The torque simulating the wind is applied to the PM generator by a DC motor. The test results show the inverter efficiency of $94.3\%$ at the rated power generating condition. The measured values show that the MPPT algorithm is working well. Overall reliability will be verified through the long-term site test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.8
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• pp.686-696
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• 2017

The major objective of this study is to develop and verify the KAUSAT-5 based on the modular 3U CubeSat standard platform. In the mechanical system design of a 3U standard platform, subsystem and micro equipment functions/performance should be integrated and miniaturized on micro-sized PCBs and electrical capability was maximized to accommodate multiple payloads. KAUSAT-5 is 3U-sized Cubesat which will be operated in Low Earth Orbit(LEO), which implements mainly two scientific missions; one is to observe the Earth through infrared camera and the other is to measure space radiation with a Geiger Muller tube. An additional mission is to verify the equipment(device) such as VSCMG and fuzzy logic-based MPPT internally developed. The results of ETB, qualification and acceptance level environmental tests were shown to verify standard platform and KAUSAT-5 Cubesat.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.190-193
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• 2001

In order to verify the efficiency or availability and stability of photovoltaic(PV) generation systems, huge system apparatuses are needed, in general, in which an actual size of solar panel, a type of converter system and some amount of load facilities should be installed in a particular location. It is also hardly possible to compare a Maximum Power Point Tracking (MPPT) control scheme with others under the same weather and load conditions in an actual PV generation system. The only and a possible way to bring above-mentioned problem to be solved is to realize a transient simulation scheme for PV generation systems using real weather conditions such as insolation and surface temperature of solar cell. The authors, in this paper, introduces a novel simulation method, which is based on a real-time digital simulator (RTDS), for PV generation systems under the real weather conditions. Firstly, VI characteristic equation of a solar cell is developed as an empirical formula and reconstructed in the RTDS system, then the real data of weather conditions are interfaced to the analogue inputs of the RTDS. The outcomes of the simulation demonstrate the effectiveness of the proposed simulation scheme in this paper. The results shows that the cost effective verifying for the efficiency or availability and stability of PV generation systems and the comparison research of various control schemes like MPPT under the same real weather conditions are possible.

• Journal of the Korean Solar Energy Society
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• v.34 no.4
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• pp.123-129
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• 2014

Photovoltaic and fuel cell systems can be used as power source in mobile robots. At this time the photovoltaic system generally generate power in daytime. The starting time of fuel cell is slower than the lithium battery. To compensate for these disadvantages, a battery charge-discharge system is used. Especially the bi-directional converter is used mainly in the charge-discharge method. The controller in a buck converter controls the input voltage of the converter to meet the maximum power point tracking(MPPT) performance. First of all, the simulations of hybrid system for battery charge-discharge system in each step simulated using solar and fuel cell modeling as input source in PSIM. Experiment of the buck and bi-directional converter system is conducted through using photovoltaic/fuel cel simulator(pCube) instead of solar and fuel cell. This hybrid system for battery charge discharge using photovoltaic/fuel cell generates emergency power for the communication system in mobile robot.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.735-737
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• 2017

An Off grid or remote solar electric systems are an energy supply to our home or to our companies without the utility of Grid at all. Off grid solar systems are very important for those who live in remote locations especially for developing countries where getting the electric grid is extremely expensive, inconvenient or for those who doesn't need to pay a monthly bill with the electric bill in general. The main critical components of any solar power system or renewable energy harvesting systems are the energy storage systems and its charge controller system. Energy storage systems are the essential integral part of a solar energy harvesting system and in general for all renewable energy harvesting systems. To provide an optimal solution of both high power density and high energy density at the same time we have to use hybrid energy storage systems (HESS), that combine two or more energy storage technologies with complementary characteristics. In this present work, design and simulation we use two storage systems supercapacitor for high power density and lithium based battery for high energy density. Here the system incorporates fast-response supercapacitors to provide power to manage solar smoothing and uses a battery for load shifting. On this paper discuss that the total energy throughout of the battery is much reduced and the typical thermal stresses caused by high discharge rate responses are mitigated by integrating supercapacitors with the battery storage system. In addition of the above discussion the off grid solar electric energy harvesting presented in this research paper includes battery and supercapacitor management system, MPPT (maximum power point tracking) system and back/boost convertors. On this present work the entire model of off grid electric energy harvesting system and all other functional blocks of that system is implemented in MATLAB Simulink.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.695-701
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• 2018

For a power grid that has a high wind penetration level, when wind speeds are continuously fluctuating, the maximum power point tracking (MPPT) operation of a variable-speed wind turbine (VSWT) causes the significant output power fluctuation of a VSWT, thereby significantly fluctuating the system frequency. In this paper, an improved power-smoothing scheme of a VSWT is presented that significantly mitigates the frequency fluctuation caused by varying wind speeds. The proposed scheme employs an additional control loop based on the frequency deviation that operates in combination with the MPPT control loop. To improve the power-smoothing capability of a VSWT in the over-frequency section (OFS), the control gain of the additional loop, which is set to be inversely proportional to the rotor speed, is proposed. In contrast, the control gain in the under-frequency section is set to be proportional to the rotor speed to improve the power-smoothing capability while avoiding over-deceleration of the rotor speed of a VSWT. The proposed scheme significantly improves the performance of the power-smoothing capability in the OFS, thereby smoothing the frequency fluctuation. The results clearly demonstrate that the proposed scheme significantly mitigates the frequency fluctuation by employing the different control gain for the OFS under various wind penetration scenarios.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.201-208
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• 2017

Recently, the installation of photovoltaic(PV) systems has been increasing due to the worldwide interest in eco-friendly and abundant solar energy. On the other hand, a PV system has approximately 25% power loss while the energy generated from solar cells is transformed to the power coupling point through a power conversion system (DC/AC). If the output voltage of a string in the PV system is lower than the operating range of the inverter when a part of module in the string has a shadow due to weather conditions, the string is not synchronized and the whole efficiency of output power in a PV system may be reduced significantly. Therefore, to overcome this problem, this paper proposes a novel control method to compensate for the lower voltage by introducing a DC/DC voltage regulator for each string in a PV system, which adopts a concept for MPPT (Maximum Power Point Tracking) control function using the P&O algorithm and adopts constant voltage control method used in an existing inverter. This paper also implements a 2kW DC/DC voltage regulator based on the proposed algorithm and performs a variety of scenario-based experiments. From the simulation result, it was confirmed that the operation efficiency in the proposed method is improved compared to the existing method.

• Journal of Navigation and Port Research
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• v.42 no.3
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• pp.167-176
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• 2018

A solar power generation system on single point moored offshore plant has independent power system In order to satisfy the maritime environment and account for the number of sunless days, it is important to supply stable electric power to the systems. For these reasons, solar panels are installed in multiple directions. However, a partial shading effect occurs because the amount of light incident on each panel is different. The generated power by the solar generation system installed on land is affected by the latitude, then it is installed at an angle of 30 to $45^{\circ}$. in the case of Korea. In the case of a solar power generation system installed in a mooring type of marine plant, there is a possibility that the maximum power point is outside of the controllable range due to the partial shading effect. Therefore, a power generation loss occurs. By reducing the light amount difference between both panels, the maximum power point can exist in a range where the MPPT algorithm can track the power. The purpose is so the power generation efficiency can be further increased. In this paper, simulation results show that the highest power generation efficiency is obtained at an installation angle of $20^{\circ}$.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.4
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• pp.297-304
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• 2013

This paper presents a improved control technique to overcome disadvantage when the inductor current of boost converter in PV system becomes DCM(Discontinuous Conduction Mode) due to the low insolation. MPPT(Maximum Power Point Tracking) output reference voltage could not be exactly followed by conventional dual-loop PI control method used typically because of the error between the actual current and measured current. Therefore, in this paper, Hybrid controller that changes the control method in DCM and CCM(Continuous Conduction Mode), and single state feedback controller are used to compensate that problem. The proposed control technique was verified by simulation using PSIM 9.0 and experiments.