• Journal of Power Electronics
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• v.10 no.5
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• pp.498-504
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• 2010

The output power fluctuations of renewable energy power plants such as wind turbine generators and photovoltaic systems result in frequency deviations and terminal voltage fluctuations. Furthermore, these power fluctuations also affect the turbine shaftings of diesel generators and gas-turbine generators which are the main power generation systems on isolated islands. Therefore, it is important to achieve torsional torque suppression. Since the measurement of torsional torque is technically difficult, and there is an uncertainty in the mechanical constants of the shaft torsional system. This paper presents an estimation system that estimates torsional torque by using a developed $H_{\infty}$ observer. In addition to the above functions, the proposed shaft torque observer incorporates a parameter identification system that aims to improve the estimation accuracy. The simulation results validate the effectiveness of the proposed $H_{\infty}$ observer and the parameter identification.

• Journal of the Korean Solar Energy Society
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• v.32 no.2
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• pp.11-18
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• 2012

Diesel fuel is expensive because transportation to remote areas adds extra cost, and it causes air pollution by engine exhaust. Providing a feasible economical and environmental solution to diesel generators is important. A hybrid system of renewable plants and diesel generators can benefit islands or other isolated communities and increase fuel savings. Renewable energy is, however, a natural source that produces a fluctuating power output. In this paper, hybrid power system of the marado lighthouse is proposed to supply stable power in the stand-alone hybrid power system. The proposed hybrid power system consists of the diesel generator, wind turbine, photovoltaic, fuel cell, and battery bank. To decrease the carbon emissions and find the optimization, the cost analysis of hybrid system is simulated using HOMER program and the optimized hybrid power system is designed.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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• pp.160-167
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• 2016

An energy storage system (ESS) is applied to increase the energy efficiency of large plants or buildings that consume much energy, to improve the power quality of power systems, and to stabilize renewable energy source such as photovoltaic or wind turbine. The ESS is composed of a power conditioning system (PCS) and an energy storage. The battery is used as the energy storage. The battery is needed to design and verify a hardware and control system of PCS. Usually, a battery simulator is used instead of a battery, which is costly and hard to manage. In this paper, the development of the battery simulator for performance verification of the MW-class PCS is described. The battery simulator simulates the charging and discharging characteristics of batteries to design and verify the hardware and control system of PCS.

• Proceedings of the Safety Management and Science Conference
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• 2002.11a
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• pp.279-284
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• 2002

All-vanadium redox flow battery(VRFB) has been studied actively as one of the most promising electrochemical energy storage systems for a wide range of applications such as electric vehicles, photovoltaic arrays, and excess power generated by electric power plants at night time. CPCS has been shown to have the characteristics as an excellent current collector for VRFB and electrochemical properties of specific resistivity 0.31 $\Omega$cm, which were composed of G-1028 80 wt%, PVC 10 wt%, DBP 5 wt% and FS 5 wt%. Energy efficiencies of VRFB with the CPCE and the existing electrode assembly were 84.14 % and 77.24 % respectively, in charge/discharge experiments at constant current of 200 mA, and the CPCE was confirmed to be suitable as the electrode of VRFB.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.2
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• pp.205-210
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• 2014

The micro grid considered in this paper consists of a diesel generator, a photovoltaic array, a wind turbine, a fuel cell, and a energy storage system. This paper explains and simulates the micro grid components in terms of accuracy and efficiency of having a system model based on the costs of fuel as well as operation and maintenance. For operational efficiency, the objective function in a diesel generator consists of the fuel cost function similar to the cost functions used for the conventional fossil-fuel generating plants. The wind turbine generator is modeled by the characteristics of variable output. The optimization is aimed at minimizing the cost function of the system while constraining it to meet the customer demand and safety of micro grid. The operating cost in fuel-cell system includes the fuel costs and the efficiency for fuel to generate electric power. To develop the overall system model gives a possibility to minimize of the total cost of micro grid. The application of optimal operation can save the interruption costs as well as the operating costs, and improve reliability index in micro grid.

• 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.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2450-2456
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• 2015

In this paper, we propose a real-time remote monitoring system for distributed solar power generation system. The proposed system consists of PVC, UTC, OTC and monitoring server. PVC collects the operational information from the PV's inverter via serial interface. The sensing data is transmitted to the server by wireless communications and stored in the DB server. The PV's status is monitored via UTC, and the operating of PVC and UTC are managed by OTC. In addition, by providing information about the power generated by PV system and failure diagnosis in real time, the proposed system shows the possibility of reducing the maintenance costs and improved failure recovery time.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.11
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• pp.699-704
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• 2017

The amount of electric power for photovoltaic power generation depends on the location of the power plant and the direction of solar cell. The solar cell controls the generation of solar power plants. Therefore, the structure of solar cell, manufacturing method, and optic technology were factors contributing to increased solar cell efficiency; however, the technical limit has been reached. Herein, we propose a new method to increase the solar cell efficiency using a wavelength conversion technology that converts ultraviolet and infrared rays, which are not effectively used in solar cells, into effective wavelength of solar cell. We used fluoride $Na(Ca)YF_4$ phosphor for wavelength conversion. Then, a wavelength-conversion fluorescent paste, prepared using an organic-silicon binder, was used to prepare a film that was applied to Si solar cells. It was confirmed that conversion efficiency improved by 5% or more.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.737-743
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• 2013

The small-scaled onsite generators such as photovoltaic power, wind power, biomass and fuel cell belong to decarbonization techniques. In general, these generators tend to be connected to utility systems, and they are called distributed generations (DGs) compared with conventional centralized power plants. However, DGs may impact on stabilization of utility systems, which gets utility into trouble. In order to reduce utility's burdens (e.g., investment for facilities reinforcement) and accelerate DG introduction, the advanced operation algorithms under the existing utility systems are urgently needed. This paper presents the advanced voltage regulation method in power systems since the sending voltage of voltage regulators has been played a decisive role restricting maximum installable DG capacity (MaxC_DG). For the proposed voltage regulation method, the difference from existing voltage regulation method is explained and the detailed concept is introduced in this paper. MaxC_DG estimation through case studies based on Korean model network verifies the superiority of the proposed method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.28-36
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• 2018

Islands are supplied with power from diesel generation or from photovoltaic power generation, and problems with offshore environmental impacts (age deterioration, salt pollution), environmental pollution (exhaust gas, noise, dust) and power generation costs (installation, maintenance) have increasingly emerged. In 2016, the cost recovery rate was only 27%, and deficits reached 73% on 65 islands managed by KEPCO. In terms of deficits, the costs incurred in the power generation sector accounted for 91%, with the ratio of fixed costs at about 60%. Analysis suggests that operating costs can be reduced with an optimal power supply system that improves power generation efficiency and makes operating systems more efficient. Therefore, it is possible to simplify fuel transportation and facility maintenance, because one island integrates the power plants of remote islands, and offshore cable is used to supply power to the other islands. From the economic evaluations in this paper, an algorithm deciding offshore cable layout validity for an integrated power supply between adjacent islands is presented. Simulation results based on the proposed algorithm confirmed that an integrated power supply is economical for existing stand-alone operations on islands having diesel generation, low peak power, and near distances.