• 디지털융복합연구
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• 제11권11호
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• pp.767-774
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• 2013

전기자동차 보급이 확대됨과 동시에 충전이 특정 시간대에 몰리거나 전력수요가 높은 시간대에 늘어나면 전력수급 균형이 불안해질 수 있다. 따라서 전기자동차 충전으로 인한 전력수요가 증가함과 동시에, 전기자동차의 전력수요를 분산시키고, 전기자동차 배터리의 여분의 전기를 활용할 수 있는 스마트그리드 구축이 중요해진다. 아직 국내에서 스마트그리드가 전기자동차의 전력망 영향 관리에 어느 정도 영향을 미치는지에 대해서는 정량적 연구가 미흡한 실정이다. 본 연구는 스마트그리드를 통한 전기자동차의 전력망 영향 관리 효과를 정량적으로 분석하고 정책적 시사점을 제시하였다. 결과적으로 스마트그리드는 전기자동차의 전력망 영향을 효과적으로 관리할 수 있었다. 전력시장 구조와 규제 프레임워크는 스마트그리드 기술의 실증과 상용화 촉진을 뒷받침할 수 있어야 할 것이다.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.549-558
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• 2017

DC distribution has several differences compared to AC distribution. DC distribution has a higher efficiency than AC distribution when distributing electricity at the same voltage level. Accordingly, power can be transferred further with low-voltage DC. In addition, power flow in a DC grid system is produced by only a voltage difference in magnitude. Owing to these differences, operation of a DC grid system significantly differs from that of an AC system. In this paper, the power flow problem in a bipolar-type DC grid with unbalanced load conditions is organized and solved. Control strategy of energy storage system on a slow time scale with power references obtained by solving an optimization problem regarding the DC grid is then proposed. The proposed strategy is verified with computer simulations.

• Journal of Power Electronics
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• 제16권2호
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• pp.748-759
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• 2016

The microgrid concept is a promising approach for injecting clean, renewable, and reliable electricity into power systems. It can operate in both the grid-connected and the islanding mode. This paper addresses the two main challenges associated with the operation of a microgrid i.e. control and protection. A control strategy for inverter based distributed generation (DG) and an energy storage system (ESS) are proposed to control both the voltage and frequency during islanding operation. The protection scheme is proposed to protect the lines, DG and ESS. Further, the control scheme and the protection scheme are coordinated to avoid nuisance tripping of the DG, ESS and loads. The feasibility of the proposed method is verified by simulation and experimental results.

• 전기학회논문지
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• 제64권8호
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• pp.1168-1179
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• 2015

This paper presents voltage and frequency control methods for a stand-alone Gasa Island Microgrid in South Korea that can be fully energized by renewable energy resources such as photovoltaic systems and wind turbines. To mitigate the variations of the output of renewable energy resources and supply more reliable electricity to customers, battery energy storage systems (BESSs) are employed in the stand-alone microgrid. The coordination between BESSs and pre-existing diesel generators is an important issue to manage the microgrid more securely. This paper presents voltage and frequency control schemes considering the coordination of BESSs and DGs. The effectiveness for the operating method is validated via simulation studies.

• 한국기계기술학회지
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• 제13권3호
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• pp.119-124
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• 2011

Electric night storage heater was introduced and disseminated for power grid balancing and efficient management of power generation facility. But fuel cost for heating has been increased rapidly while the cost of electricity increased slightly. This abnormal rate system caused peak load in winter at last. To solve this problem, application of an air source heat pump was suggested. In the study, the effect of replacing night heater by heat pump and the economics were analysed. In addition the expectation of prospect of heat pump penetration was simulated based on surveyed and investigated data. As a result, fund supporting as well as institutional backing was needed for effective propagation and return of investment.

• 대한화학회지
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• 제65권2호
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• pp.145-150
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• 2021

The present study describes a hands-on experiment to help students understand the concept of phase change or phase transition and its application in a phase change material (PCM). PCMs are substances that have the capability of storing and releasing large amounts of thermal energy. They act as energy storage materials that provide an effective way to save energy by reducing the electricity required for heating and cooling. Lauric acid (LA) was selected as an example of the PCM. Students investigated the temperature change of LA and the temperature (of air) inside the test tube. The differences in the temperatures of the systems helped students understand how PCMs work. A one-group pretest and posttest design was implemented with 34 grade-11 students in science and mathematics. Students' understanding was assessed using a multiple-choice test and a questionnaire. The findings revealed that the designed activity helped students understand the concept of phase change and its application to materials for thermal energy storage.

• 전기학회논문지
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• 제67권7호
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• pp.833-839
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• 2018

This paper presents an analysis and the methodology of optimal operation strategy of the ESS(Energy Storage System) for reduce electricity charges. Electricity charges consist of a basic charge based on the contract capacity and energy charge according to the power usage. In order to use electrical energy at minimal charge, these two factors are required to be reduced at the same time. QP(Quadratic Programming) is appropriate for minimization of the basic charge and LP(Linear Programmin) is adequate to minimize the energy charge. However, the integer variable have to be introduced for modelling of different charge and discharge efficiency of ESS PCS(Power Conversion System), where MILP(Mixed Integer Linear Programming) can be used. In this case, the extent to which the peak load savings is accomplished should be assumed before the energy charge is minimized. So, to minimize the electricity charge exactly, optimization is sequentially performed in this paper, so-called the Two Stage Hybird optimization, where the extent to which the peak load savings is firstly accomplished through optimization of basic charge and then the optimization of energy charge is performed with different charge and discharge efficiency of ESS PCS. Finally, the proposed method is analyzed quantitatively with other optimization methods.

• 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.

• 전기학회논문지
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• 제64권9호
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• pp.1391-1397
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• 2015

Recently, various researches are conducted in the application of regenerative energy produced during the operation of an electric locomotive. Regenerative energy is produced by a generator in the brake procedure. The generator is operated by kinetic energy of an electric railroad using an electric motor. The process of producing regenerative energy varies with the current type of a railroad and its running condition. The quality of electric power can be improved and electric energy can be utilized effectively, especially in the use of an energy storage system (ESS). Thus, it is necessary to apply ESS into AC section and high speed railway. This study analyses the composition of the regenerative ESS equipment installed in Yong-Jeong sectioning post, operational principle, charge and discharge algorithm and energy efficiency. The analysis shows that CO2 emissions can be reduced about 0.5 ton per a day. In addition, ESS helps saving the energy and the compensation of the voltage drop caused by the operation of high speed train when it is installed at the end of the feeder section. The number of high speed train will be increased continuously related to the electrification rate. Therefore, applying the ESS to high speed railway is expected to solve the instability of the feeder voltage and the equipment capacity problem caused by the high speed trains.

• 에너지공학
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• 제24권3호
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• pp.74-81
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• 2015

늘어나는 전력 수요와 탄소배출을 줄이기 위하여 정부는 신재생에너지 및 에너지저장장치 도입을 장려하고 있다. 정부 는 2020년까지 ESS 누적용량을 2GW로 확대할 예정이다. ESS 도입을 통하여 전력 피크를 줄일 수 있으며, 시간대별 차등요금제를 활용하여 남는 전력을 판매할 수 있다. 본 논문에서는 ESS 보급 확대에 따른 비용을 분석을 위한 모형을 제안하였으며, 2035년까지의 ESS 발전량과 발전단가를 분석하였다. 또한 ESS와 신재생에너지 연계에 따른 경제성 분석을 위하여 태양광발전 및 풍력발전 연계에 따른 사례연구를 진행하였고, ESS 보급 촉진을 위하여 정부의 추가적인 보급지원 정책이 필요함을 시사하고 있다.