• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.7
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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.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.2
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• pp.194-200
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• 2014

In DC micro-grid system energy storage systems (ESS) are responsible for storing energy and balancing power. Also, control target of the bidirectional DC-DC converter(BDC) for ESS should be changed depending on the operating mode. During the grid connected mode, the BDC controls the battery current or voltage. When a grid fault occurs, the BDC should change the control target to regulate the DC-bus. The BDC with conventional control method may experience large transient state during the mode change. This paper proposes a control method of BDC for ESS. The proposed control method is able to provide autonomous and seamless mode transfer by a variable current limiter. To validate the proposed concept, simulation results using PSIM and experimental results from a 2kW prototype are provided.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.2
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• pp.106-115
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• 2014

This paper proposes ESS DC-DC Converter using Redox Flow Battery (RFB) for stand-alone microgrid. Price, safety, expandability and dynamics are crucial in ESS. Reports show that Zinc-bromine (ZnBr) RFB is the best choice in ESS. Simple electrical ZnBr RFB model is obtained from charging test. DC-DC converter Inductor current-DClink Voltage model is proposed for the DC microgrid. For the controller design in z-domain, the K-factor method is by considering nature of the digital controller. The control performance has been verified with simulation and hardware experiments. Lastly 10kW DC microgrid using RFB test result is shown.

• Journal of the Korean Solar Energy Society
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• v.32 no.1
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• pp.25-31
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• 2012

This paper presents the characteristics of power generation output at Haeng-won wind farm and how to determine the optimized ESS capacity for power stabilizing. Depend on the fluctuation rate of wind power output variation, wind farm capacity and site, power stabilization will be impacted. Therefore, we need to determine proper ESS capacity. Using the actual data of Haeng-won wind farm from 2009. 3 to 2010.2., capacity of ESS was determined by moving average value. To verify the proposed algorithm, simulations are carried out with PSCAD/EMTDC program. As a result, optimal ESS capacity of Haeng-won wind farm in Jeju is estimated about 1.63 MWh.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.222-228
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• 2017

The aims of the demand response market are stabilization of the power supply and improving of the reliability of the power system. The various applications of the energy storage system (ESS) in the railway systems are studied and implemented to raise the energy efficiency. It is one of the most important how to determine the obligation reduction capacity (ORC) in participation to the demand response market because it has an influence on the profit extremely. In this paper, when participating to the demand response market with demands in the urban railway, we calculated the available ORC and economically evaluated ESS based on the real load data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.1
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• pp.61-67
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• 2018

High-power lithium batteries are suitable for equipment with high power output needs, such as for ESS's initial start-up. However, their management cost is increased by the installation of air-conditioning to minimize the risk of explosion due to internal temperature rise and also by a restriction on the number of charge/discharge cycles. High-capacity flow batteries, on the other hand, have many advantages. They can be used for over 20 years due to their low management costs, resulting from no risk of explosion and a high number of charge/discharge cycles. In this paper, we propose an ESS based on hybrid batteries that uses a lithium iron phosphate battery (LiFePO) at the initial startup and a vanadium redox flow battery (VRFB) from the end of the transient period, with a bi-directional PCS to operate two batteries with different DC voltage levels and using an efficient energy management control algorithm.

• Journal of the Korean Society of Safety
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• v.31 no.2
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• pp.10-17
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• 2016

The purpose of this paper is to deduct components that are in the group of highest risk(top 10%). the group is conducted for classification into groups by values according to risk priority through risk priority number(RPN) of FMEA(Failure modes and effects analysis) sheet. Top 10% of failure mode among total potential failure modes(72 failure modes) of ESS included 5 BMS(battery included) failure modes, 1 invert failure mode, and 1 cable connectors failure mode in which BMS was highest. This is because ESS is connected to module, try, and lack in the battery part as an assembly of electronic information communication and is managed. BMS is mainly composed of the battery module and communication module. There is a junction box and numerous connectors that connect these two in which failure occurs most in the connector part and module itself. Finally, this paper proposes RPN by each step from the starting step of ESS design to installation and operation. Blackouts and electrical disasters can be prevented beforehand by managing and removing the deducted risk factors in prior.

• The Magazine for Energy Service Companies
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• s.84
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• pp.8-11
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• 2013

지난 5월 28일 국무회의에서 박근혜 대통령은 "과학기술을 통한 에너지 효율성을 제고하거나 낭비를 막는 방법도 있고 스마트 그리드 같은 IT기술을 이용해서 실시간으로 자신이 얼마를 소모하는지 알려줌으로써 스스로 아껴 쓸 수 있는 방법이 있는데, 그런 방안도 적극 연구해 달라"고 당부했다. 실제로 우리 산업은 현재 ICT기술과 전력시장을 창조적으로 융합하여 새로운 시장을 형성하고, 이를 통해 신(新)성장동력, 신(新)서비스업을 육성해야 하는 시점에 직면해 있다. 전력공급에 소요되는 사회적 비용이 급증하여 빠른 속도로 증가하는 수요를 충족시키는데 많은 어려움이 있는 것도 사실이다. 늘어나는 수요에 따라 공급을 확대하는 공급중심 정책에서 합리적으로 수요를 줄인 후 공급을 확대하는 수요관리 중심의 정책으로 전환이 필요한 때이다. * 연평균 전력소비증가율('00~'10년, %) : 한국 5.3('10년 10.1), 일본 0.2, 미국 0.7, OECD 평균 1.0 최근 다각도로 전력 사용을 줄이기 위한 이벤트가 실시되고 있는데 실내온도 제한 등 일시적 절약에서 벗어나, 세계적 수준의 우리 ICT기술을 활용하여 근본적이고 시스템적인 수요관리 추진이 필요하다. 한편 전력수급 위기를 새로운 시장창출의 기회로 만드는 발상의 전환을 통해 창조경제시대의 신성장동력과 일자리를 창출하게 되는 기회가 될 수 있다. 이는 전통적인 에너지산업에 2차전지산업, 소프트웨어 산업을 융합하여 ESS, EMS, LED 등 ICT기반 에너지 신산업 시장 진출을 의미한다. 이번호에서는 ESS(Energy Storage System)라고 불리는 에너지저장장치에 대해 살펴보고자 한다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1174-1180
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• 2018

In December 2017, the government announced plans to increase the current proportion of renewable energy from 7% to 20% by 2030 through a plan called the Renewable Energy 3020 Implementation Plan. Therefore, the demand for installation of photovoltaic(PV), wind turbine(WT) and battery energy storage system(BESS) is expected to increase. In particular, the system combined with energy storage system(ESS) is expected to take up a large portion since PV and WT can receive high renewable energy certificates(REC) weights when combined with ESS. In this study, we calculate the optimal capacity of the power conditioning system(PCS) and the BESS by comparing the economical efficiency and maximize the efficiency of the PV-BESS system in which the PV and the BESS are connected. By analyzing the system marginal price(SMP) and REC, it maximize profits through application of REC weight 5.0 and optimal charge-discharge scheduling according to the SMP changes.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.603-604
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• 2015

본 논문은 UPS(Uninterrupted Power Supply)의 기능을 확장하여 ESS(Energy Storage System)로서 충방전 제어를 수행하는 hybrid UPS[1][2]인 UES(UPS+ESS)의 실제 구축사례를 기술한다. 기존 시스템의 변경을 최소화 하고 UPS 기능을 우선 동작하기 위해 UES는 UPS와 battery을 각각 제어하는 별도의 외부 제어장치를 이용하여 UES로서 시스템을 통합하며 각 부분 구성품의 호환성을 확보한다.