• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.292-299
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• 2017

In this paper, multiple ESS(Energy Storage System) control strategy for microgrids is presented. Installation of ESS becomes mandatory when microgrids are used to supply high quality power to the loads. The one of main functions of the ESS is to maintain power balance. However ESS has limitation of its capacity and instantaneous injecting power. Power allocation method based on SOC(State Of Charge) of each ESS is proposed. P-Q control is employed as the basic control strategy for the distributed ESSs. By using the proposed method, the coefficients in the conventional P-Q control method are modified. The ESSs with higher SOC inject more active power, while those with lower SOC inject less, leading to more balanced SOC levels among the ESSs. The proposed method is demonstrated by simulation using PSCAD/EMTDC.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.11
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• pp.77-83
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• 2014

The Estimation of State of Charge(SOC) for batteries is an important aspect of a Battery Management System(BMS). A method for estimating the SOC is proposed in order to overcome the individual disadvantages of the current integral and Open Circuit Voltage(OCV) estimation methods by combining them using Extended Kalman filter(EKF). The non-linear characteristics of the Li-Ion RC battery model used in this study is also solved through EKF. The proposed method is simulated in a Matlab environment with a Li-Ion Kokam battery (3.7V, 1,500mAh). Results showed that there is an improvement in the estimation error when using the proposed model compared to the conventional current integral method.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.4
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• pp.324-331
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• 2007

This paper studies new estimation method for state of charge (SOC) of the hybrid electric vehicle lithium battery using sliding mode observer. A simple R-C Lithium battery modeling technique is established and the errors caused by simple modeling was compensated by the sliding mode observer. The structure of the sliding mode observer is simple, but it shows robust control property against modeling errors and uncertainties. The performance of the system has been verified by the UUDS test. The test results of the proposed observer system shows robust tracking performance under real driving environments.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.271-272
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• 2012

전류 적산법(Coulomb counting, ampere counting)을 이용한 배터리 SOC(State-of-Charge) 추정 방법은 상용화된 IC를 사용할 수 있기에 구현이 간단하고 SOC 정의를 통해 배터리 사용 가능한 시간을 쉽게 예측할 수도 있다. 하지만 초기 SOC 오류와 누적되는 전류 정보의 오차로 인해 추정이 실패하는 단점이 존재하기 때문에 이를 해결해주는 알고리즘이 필요하다. 본 논문에서는 전류 적산법 기반의 배터리 SOC 추정 회로에 확장 칼만 필터(EKF, Extended Kalman Filter)를 접목하여 전류 적산법을 이용하였을 때 나타날 수 있는 오차 누적을 줄이는 알고리즘을 제안한다. 또한 실험을 통해 제안된 배터리 SOC 추정 회로의 성능을 확인해본다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.15-23
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• 2017

This paper reports a SOC(State-of-Charge) estimation method using the extended Kalman filter(EKF) algorithm, which can allow real-time implementation and reduce the error of the model and be robust against noise, to accurately estimate and evaluate the charging/discharging state of the EV(Electric Vehicle) battery. The battery was modeled as the first order Thevenin model for the EKF algorithm and the parameters were derived through experiments. This paper proposes the changed method, which can have the SOC to 0% ~ 100% regardless of the aging of the battery by replacing the rated capacity specified in the battery with the maximum chargeable capacity. In addition, This paper proposes the EKF algorithm to estimate the non-linearity interval of the battery and simulation result based on Ah-counting shows that the proposed algorithm reduces the estimation error to less than 5% in all intervals of the SOC.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.182-186
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• 2007

This paper studied performance characteristics of hybrid automotive to replace existing fossil fuel vehicles. Specially, about power split type HEV that is T-HEV's drive system when a vehicle drives at steady speed, monitored both output of each engine, motor and generator and battery SOC (state of charge) and analyzed performance characteristic of power transmission system and electricity power parts. This study shows those that acquired and analyzed information from signals between HCU and each controller of actual T- vehicle. From this study, it is confirmed that each conditions of EV and HEV drive can be a improvement with respect to the fuel efficiency of vehicles.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.1072-1079
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• 2014

This paper introduces a coordinated droop control for the stand-alone DC micro-grid, which is composed of photo-voltaic generator, wind power generator, engine generator, and battery storage with SOC (state of charge) management system. The operation of stand-alone DC micro-grid with the coordinated droop control was analyzed with computer simulation. Based on simulation results, a hardware simulator was built and tested to analyze the performance of proposed system. The developed simulation model and hardware simulator can be utilized to design the actual stand-alone DC micro-grid and to analyze its performance. The coordinated droop control can improve the reliability and efficiency of the stand-alone DC micro-grid.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.87-88
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• 2010

주위온도, 사용연한 및 운전점 등에 의해서 동작특성이 변화되는 배터리의 SOC(State of Charge)를 정확하게 추정하는 것은 매우 어려운 과제이다. SOC를 추정하기 위해서는 배터리의 복잡한 비선형적인 특성을 고려한 등가 모델의 개발이 필요하다. 본 논문은 SOC 추정을 위해 최근까지 수행되었던 연구를 검토하고, SOC 추정을 위해 개발된 배터리 모델 및 추정기법을 비교 분석하고, PSIM 시뮬레이션 연구 결과를 제시한다.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.244-245
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• 2012

본 논문에서는 이산 웨이블릿 변환(DWT;discrete wavelet transform)의 다해상도 분석(MRA;multi-resolution analysis)을 통해 분해된 배터리의 저주파 전압 성분(approximation;$A_n$) 기반 SOC(State-of-charge) 추정방법을 소개한다. 급격한 전압 변화의 특성을 나타내는 고주파 전압 성분(detail;$D_n$)이 제거되고 저주파 전압 성분만이 SOC 추정을 위해 사용된다. 이 경우 기존 확장 칼만필터(EKF;extended Kalman filter)에서 SOC 추정에러를 개선하기 위해 사용되었던 노이즈 모델의 생략이 가능하여 알고리즘의 복잡성이 개선된다. 개선된 확장 칼만필터 기반 SOC 추정 결과를 통해 제안된 방법을 검증하였다.

• Journal of IKEEE
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• v.22 no.2
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• pp.455-459
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• 2018

In this paper, proposed a multi-channel charging control strategy for electric vehicle. This control strategy can adjust the charging power according to the calculated state-of-charge (SOC). Electric vehicle (EV) charging system using Particle Swarm Optimization (PSO) algorithm is proposed. A stochastic optimization algorithm technique such as PSO in the time-of-use (TOU) price used for the energy cost minimization. Simulation results show that the energy cost can be reduced using proposed method.