• 신재생에너지
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• 제5권3호
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• pp.4-12
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• 2009

The effect of change in DFIG (doubly-fed wind power generator) rotating speed and active power on the grid was analyzed to understand the characteristics of wind power using the wind power simulator connected to the grid at Gochang Power Quality Test Center. Electric power quality improvement devices (DVR, STATCOM, SSTS) and electric power quality disturbance application devices for 22.9 kV grid are equipped at Gochang Power Quality Test Center. Induction motor and VVVF inverter were used to emulate the blade of a wind power generator, and a simulator for Cage wound induction generator and DFIG was developed. The trial line were assumed to be 20 km and 40 km in length, and variable wind speed pattern was set using wind speed data from Ducjeokdo to verify the power characteristics of the wind power generator according to rotating speed.

• International Journal of Precision Engineering and Manufacturing-Green Technology
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• 제5권5호
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• pp.623-630
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• 2018

The renewable energy systems have been in the spotlight as an alternative for environmental issues. Therefore, the governmental policies are being implemented to spread of promote power generation system using renewable energy in various countries around the world. In addition, Korea has also developed a policy called the power trading contract which can profit from electricity produced from renewable power generation system through Korea Electric Power Corporation (KEPCO) and Korea Power Exchange (KPX). As a result, the power trading contracts can trade power after self-consuming in-house by using small-scale renewable power system for residential customers as well as electricity retailers. The power trading contracts applicable as a small-scale power system have a 'Net metering (NM)' and a 'Power Purchase Agreement (PPA)', and these two types of power trading contracts trade surplus power, but payment method of each power trading is different. The microgrid proposed in this paper is based on grid connected microgrid using Photovoltaic (PV) system and Energy Storage System (ESS), that supplied power to residential demand, we evaluate the operation cost of microgrid by power demand in each power trading contracts and propose the appropriate power trading contracts according to electricity demand.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.270-279
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• 2018

This paper elucidates a hysteresis current controller for enhancing the performance of static synchronous compensator (STATCOM) using cascaded H-bridge multilevel inverter. Due to the rising power demand and growing conventional generation costs a new alternative in renewable energy source is gaining popularity and recognition. A five level single phase cascaded multilevel inverter with two separated dc sources, which is energized by photovoltaic - wind hybrid energy source. The voltages across the each dc source is balanced and standardized by the proposed hysteresis current controller. The performance of STATCOM is analyzed by connecting with grid connected system, under the steady state & dynamic state. To reduce the Total Harmonic Distortion (THD) and to improve the output voltage, closed loop hysteresis current control is achieved using PLL and PI controller. The performance of the proposed system is scrutinized through various simulation results using matlab/simulink and hardware results are also verified with simulation results.

• Journal of Electrical Engineering and Technology
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• 제8권2호
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• pp.238-243
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• 2013

In this paper, a novel approach for optimized installation and operations of battery energy storage system (BESS) and electric double layer capacitor (EDLC) modules for the renewable energy based intermittent generation is presented for them to be connected with an electric power grid. In order to make use of not merely the high energy density of battery but also the high power density of EDLC modules, it is very useful to devise the hybrid system which combines BESS and EDLC modules. The proposed method adopts the linear programming to calculate the optimized capacity as well as the quadratic programming to transmit the optimal operational signals to BESS and EDLC modules. The efficiency of this methodology will be demonstrated in the experimental study with the real data of wind speed in Texas.

• 전기학회논문지
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• 제60권6호
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• pp.1112-1121
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• 2011

A microgrid is an aggregation of multiple distributed generators (DGs) such as renewable energy sources, conventional generators, and energy storage systems that provide both electric power and thermal energy. Generally, a microgrid operates in parallel with the main grid. However, there are cases in which a microgrid operates in islanded mode, or in a disconnected state. Islanded microgrid can change its operational mode to grid-connected operation by reconnection to the grid, which is referred to as synchronization. Generally, a single machine simply synchronizes with the grid using a synchronizer. However, the synchronization of microgrid that operate with multiple DGs and loads cannot be controlled by a traditional synchronizer, but needs to control multiple generators and energy storage systems in a coordinated way. This is not a simple job, considering that a microgrid consists of various power electronics-based DGs as well as alternator-based generators that produce power together. This paper introduces the results of research examining an active synchronizing control system that consists of the network-based coordinated control of multiple DGs. Consequently, it provides the microgrid with a deterministic and reliable reconnection to the grid. The proposed method is verified by using the test cases with the experimental setup of a microgrid pilot plant.

• 한국태양에너지학회 논문집
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• 제28권6호
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• pp.87-92
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• 2008

Buildings are responsible for approximately 50% of current carbon dioxide emissions. Energy planning at a town and city scale needs a strategic approach, supported by strong planning policies. The purpose of this study was to investigate the urban scale grid-connected photovoltaic(PV) system for urban residential and commercial sector applications. The integration of PV technology into roof of houses is an approach that is being championed in Germany, Japan and United states etc. In the Korea, PV roofing systems already are given the large number of houses which are projected to be built by 2012. However unlike germany and Japan, urban scale grid-connected PV system is not yet installed. The solar city which is installed building-integrated photovoltaic system is available to use of renewable energy sources such as solar to meet demand, instead of fossil fuels, with the goal of realizing an ecologically oriented energy supply.

• 한국산학기술학회논문지
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• 제10권2호
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• pp.230-236
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• 2009

본 논문에서는 신재생 에너지 활용을 위한 그늘막 형태의 연계 계통형 태양광 발전 시스템을 제안한다. 제안하는 발전 시스템은 성하기에 해수욕장을 찾는 피서객들에게 상용전원과 연계 계통하여 최대 전력 수요를 충족시킬 뿐 만 아니라 그늘막으로서의 기능을 갖도록 설계하였다. 태양전지에서 생성된 전기를 낮 시간 동안 축전지에 충전하면 이를 야간에 전등이나 선풍기등에 이용할 수 있다. 축전지를 충전할 때 축전지의 성능을 유지하려면 충방전컨트롤러가 필요하다. 제안하는 축전지 충방전 컨트롤러는 고성능 마이크로프로세서를 사용하여 정확하고 안정된 동작을 하도록 설계하였고 사용자의 편의를 위해 디지털 표시기 및 축전지 교체시기 경보장치등을 갖추고 있다. 제안하는 발전 시스템을 영동 지역 해수욕장에 설치하고 실험을 통하여 전력 생산능력과 발전 성능을 확인하였다.

• 전력전자학회논문지
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• 제13권3호
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• pp.206-212
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• 2008

본 논문에서는 계통 연계형 태양광 발전 시스템의 새로운 FFT에 의한 위상추종 알고리즘을 제안한다. 신재생 에너지 분야에 적용되는 계통연계형 인버터에서는 계통과 동기를 위해서 반드시 계통의 위상 정보가 필요하다. 일반적으로 사용하는 3상 D-Q 변환에 의한 위상 추종과 달리 새롭게 제안하는 FFT를 사용하는 알고리즘은 게인튜닝 부분이 필요 없어 직접제어가 가능하며, FFT의 특성상 기본주파수 이외의 성분을 제외한 강력한 노이즈 제거효과로 인해 노이즈에 강한 특징을 가지고 있다. 시뮬레이션과 실험을 통하여 제안한 알고리즘의 성능이 만족함을 보였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.269-275
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• 2007

태양광 분야에서 일본은 기술 및 보급에 성공한 대표적인 사례로서 거론된다. 태양광의 에너지자원화를 목표로 30여 년간 지속적으로 국가차원의 기술개발 및 보급을 정책 사업화하여 진행시켰고 성공적인 선행 단계를 밟아 왔다. 현재까지의 성공을 기반으로 [태양광 비전 2030]을 수립하여 실현가능한 장기 목표를 구체화하는 단계에 있다. 이에 일본 태양광 산업 및 기술개발 방향에 대한 분석을 통해 오늘 우리에게 주는 시사점을 도출하여 차세대 성장 동력 산업이 될 국내 태양광분야의 발전을 위한 지표로 삼고자 한다.

• 한국지능시스템학회논문지
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• 제25권3호
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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.