• 전기학회논문지
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• 제63권8호
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• pp.1033-1038
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• 2014

Electric vehicles should be connected to power system for charge and discharge of battery. Besides vehicle's battery is charged for a power source, it is also reversibly possible to provide power source from battery to power system. Researches on battery usage for regulation resources have been progressed and could cause cost increase excessively because they distribute regulation capacity equally without considering the battery wear cost of SOC, temperature, voltage and so on. This causes increase of grid maintenance cost and aggravate economical efficiency. In this paper it is studied that the cost could be minimized according to the battery condition and characteristic. The equation is developed in this paper to calculate the possible number of charge and discharge cycle, according to SOC level and weighting factors representing the relation between battery life and temperature as well as voltage. Thereafter, the correlation is inferred between the battery condition and wear cost reflecting the battery price, and the expense of compensation is decided according to the condition on battery wear-out of vehicle. In addition, using realtime error between load and load expectation, it is calculated how much regulation capacity should be provided.

• 전기학회논문지P
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• 제67권1호
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• pp.15-20
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• 2018

This paper presents the method of ESS energy capacity calculation for stand-alone renewable energy generation system consisting of photovoltaic energy. There is almost no power from photovoltaic system during sunless days. So this source is very weak in terms of the power supply reliability. To improve problem of power supply, battery is mainly used Energy Storage System(ESS). The number of sunless days and Depth of Discharge(DOD) is important factor to determine energy capacity of battery. However, a many study for economical design is required due to the high cost of ESS. In this paper, we propose the new method of ESS energy capacity calculation by applying different DOD for operation with and without sun. We determine the Battery capacity using higher DOD of operation during sunless day than the DOD of the normal operation. And we carried out an economic analysis of the calculation results.

• 플랜트 저널
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• 제17권3호
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• pp.34-36
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• 2021

기존의 중앙집중식 발전의 탈피와 에너지 전환 및 환경문제 인식에 의해 신재생에너지 기반의 분산발전시스템에 대한 관심이 증가하고 있다. 본 연구에서는 에너지저장장치로 납축전지를 사용하는 PV 및 WT 기반의 분산발전시스템을 모사하여 최적용량을 선정하였다. 기존 발전원으로 CHP를 채택하였으며 시스템의 최적용량은 기존발전원의 운전상황(전부하/부분부하)에 따라 MOGA를 통해 도출하였다. 또한 동일한 배터리 용량에서 배터리 충전방식이 달라지면 배터리의 수명이 달라지는 것을 확인하였다. 따라서 경제적이고 안정적인 전력수급을 위해서는 배터리 충전방식을 고려한 분산발전시스템의 용량선정이 수행되어야 한다.

• 전기전자학회논문지
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• 제23권2호
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• pp.580-585
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• 2019

배터리는 ESS, 전기자동차 및 무정전 전원 백업 시스템 등의 다양한 분야에서 사용이 증가하고 있다. 납산배터리는 에너지밀도가 낮지만, 신뢰성이 높고 저가격의 이점으로 대용량 전력백업 장비에 가장 많이 사용되는 배터리이다. 배터리의 사용에 따라 노화가 진행되면 충전 가능 용량(SoH)이 줄어들게 되어 상태를 추정하는 것이 매우 중요하며, 배터리의 내부저항으로 SoH를 추정하는 방법을 많이 사용한다. 본 논문에서는 대표적인 대용량 무정전 전원장치인 IDC를 위한 배터리 모니터링 시스템(BMS)을 제안하였다. 내부저항을 측정하는 간단한 알고리즘을 제안하고, BMS 시스템 구성을 위한 CPU 및 아날로그 회로 구성과 신호처리 알고리즘에 대한 연산 블록도를 보였다. 실제 IDC 현장에 적용한 측정결과 사례를 제시하여 제안한 방법의 유용함을 보였다.

• 전력전자학회논문지
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• 제24권3호
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• pp.139-146
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• 2019

As the number of electric vehicles (EVs) in Jejudo Island increases, the secondary use of EV batteries is becoming increasingly mandatory not only in reducing greenhouse gas emissions but also in promoting resource conservation. For the secondary use of EV batteries, their capacity and performance at the end of automotive service should be evaluated properly. In this study, the battery state information from the on-board diagnostics or OBD2 port was acquired in real time while driving three distinct routes in Jejudo Island, and then the battery operating characteristics were assessed with the driving routes. The route with higher altitude led to higher current output, i.e., higher C-rate, which would reportedly deteriorate state of health (SOH) faster. In addition, the SOH obtained from the battery management system (BMS) of a 2017 Kia Soul EV with a mileage of 55,000 km was 100.2%, which was unexpectedly high. This finding was confirmed by the SOH estimation based on the ratio of the current integral to the change in state of charge. The SOH larger than 100% can be attributed to the rated capacity that was lower than the nominal capacity in EV application. Therefore, considering the driving environment and understanding the SOH estimation process will be beneficial and necessary in evaluating the capacity and performance of retired batteries for post-vehicle applications.

• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.631-636
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• 2018

This paper proposed an optimal operation strategy for a hybrid energy storage system (HESS) with a lithium-ion battery and lead-acid battery for mild hybrid electric vehicles (mild HEVs). The proposed mild HEV system is targeted to mount the electric motor and the battery to a conventional internal combustion engine vehicle. Because the proposed mild HEV includes the motor and energy storage device of small capacity, the system focuses on low system cost and small size. To overcome these limitations, it is necessary to use a lead acid battery which is used for a vehicle. Thus, it is possible to use more energy using HESS with a lithium battery and a lead storage battery. The HESS, which combines the lithium-ion battery and the secondary battery in parallel, can achieve better performance by using the two types of energy storage systems with different characteristics. However, the system requires an operation strategy because accurate and selective control of the batteries for each situation is necessary. In this paper, an optimal operation strategy is proposed considering characteristics of each energy storage system, state-of-charge (SOC), bidirectional converters, the desired output power, and driving conditions in the mild HEV system. The performance of the proposed system is evaluated through several case studies with respect to energy capacity, SOC, battery characteristic, and system efficiency.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1992년도 추계학술대회 논문집
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• pp.136-140
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• 1992

The purpose of this research is to develop the lithium secondary battery. This paper describes the preparation, electrochemical properties of nontstoichiometric(NS)-$V_6O_{13}$ and characteristics of Li/$V_6O_{13}$ secondary battery. NS-$V_6O_{13}$ was prepared by thermal decomposition of $NH_4VO_3$ under Ar stream of 140ml/min~180ml/min flow rate. And then, this NS-$V_6O_{13}$ was used for cathode active material. Cathode sheet was prepared by compressing the composite of NS-$V_6O_{13}$, acetylene black(A.B) and teflon emulsion (T.E). Characteristics of the test cell are summarised as follows. Oxidation capacity of NS-$V_6O_{13}$ was about 20% less than its reduction capacity. A part of NS-$V_6O_{13}$ cathode active material showed irreversible reaction in early charge-discharge cycle. This phenomena seems to be caused by irreversible incoporation/discoporation of lithium cation to/from NS-$V_6O_{13}$ host. Discharge characteristics curve of Li/$V_6O_{13}$ cell showed 4 potential plateaus. Charge-discharge capacity was declined in the beginning of cycling and slowly increased in company with increasing of coulombic efficiency. Energy density per weight of $V_6O_{13}$ cathode material was as high as 522Wh/kg~765Wh/kg.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.378-379
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• 2006

The carbon thin film was developed by the CVD method using the carbon source of toluene with the stream of argon gas at $800{\sim}1100^{\circ}C$ for 1 hour. Developed carbon thin films have the material loading of 0.27 mg($800^{\circ}C$), 0.80 mg($900^{\circ}C$), 2.3 mg($1000^{\circ}C$), and 2.9 mg($1100^{\circ}C$) for the disk of 15 mm diameter on single side. The characteristics of carbon thin film as the anode of thin film battery were evaluated using Li|C coin cell. Li|C($1100^{\circ}C$) coin cell has the first specific discharge and charge capacity of 953 mAh/g and 374 mAh/g, respectively, resulting the first Ah efficiency of 39.3 %. Capacity retention of the 5th cycle was 93.2 % indicating good cycleability. The carbon thin film prepared by CVD shows good specific capacity and cycleability, but low Ah efficiency.

• 전력전자학회논문지
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• 제26권6호
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• pp.421-428
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• 2021

Lithium-ion secondary batteries exhibit advantageous characteristics such as high voltage, high energy density, and long life, allowing them to be widely used in both military and daily life. However, the lithium-ion secondary battery does have its limitation; for example, the output power and capacity are readily decreased due to the increased internal impedance during discharging at a lower temperature (-32℃, military requirement). Also, during charging at a lower temperature, lithium dendrite growth is accelerated at the anode, thereby decreasing the battery capacity and life as well. This paper describes a study that involves increasing the internal temperature of lithium-ion secondary battery by energy circulation operation in a low-temperature environment. The energy circulation operation allows the lithium-ion secondary battery to alternately charge and discharge, while the internal resistance of lithium-ion battery acts as a heating element to raise its own temperature. Therefore, the energy circulation operation method and device were newly designed based on the electrochemical impedance spectroscopy of the lithium-ion secondary battery to mediate the battery performance at a lower temperature. Through the energy circulation operation of lithium ion secondary battery, as a result of the heat generated from internal resistance in an extremely low-temperature environment, the temperature of the lithium-ion secondary battery increased by more than 20℃ within 10 minutes and showed a 75% discharging capacity compared with that at room temperature.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.98-105
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• 2014

As environmentally friendly energy takes center stage, interests for Electric Vehicles/Plug in Hybrid Electric Vehicles (EVs/PHEVs) are getting increase. With this trend, there is no doubt EVs will take large portion to penetrations of total cars. Therefore, accurate EV modeling is required. Battery is one of the main components with the power system view of aspect. Hence, in this paper, reviews and discussions of some types of batteries for EV are contained by considering energy density and weight of the batteries. In addition, simulations of Li-Ion battery are accomplished with various variables such as temperature, capacity fading and charge/discharge current. It is confirmed that temperature is the main factor of capacity fading. Validation of the modeled battery is also conducted by comparing it with commercialized battery.