• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.108-116
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• 2003

This research presents the design and analysis of PCDU(Power Control & Distribution Unit) of communication satellite. The PCDU of a spacecraft must provide adequate power to each subsystem and payload during mission life, and it also needs high reliability and performance in space environment. A control circuit of the PCDU include bus sensing and filter circuits, error signal amplification circuit, error compensation circuit of SAS(Shunt Assembly Switch) and BPC(Battery Power Converter). The phase margin and DC gain for the designed circuits are analyzed through the frequency response characteristics of the compensated control circuit. And also the transfer function of the battery power converter circuit are discussed at the battery CCCM(Charge Continuous Conduction Mode) and battery C/DCCM(Continuous/Discontinuous Conduction Mode).

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.4
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• pp.372-377
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• 2016

The carbon felt used as the electrode of vanadium redox flow battery (VRFB) requires imprived electrochemical activity for better battery performance and efficiencies. Many efforts have been tried to improve electrochemical activity of the carbon felt as electrodes. In this study the alkali solution, KOH, is applied on surface treatment of the carbon felt electrode. The carbon felts were treated with KOH under room temperature and $80^{\circ}C$. The isopropyl alcohol was applied to improve wettability of the carbon felt during KOH treatment. The KOH treated carbon felt was analyzed by using the X-ray photoelectron spectroscopy (XPS). The XPS analysis of carbon felt electrode revealed on increase in the overall surface oxygen content of the carbon felts after KOH treatment. Also, cyclic voltametry tests showed electrochemical characteristics enhancement of the carbon felt.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.482-489
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• 2002

This paper studies the stand-alone photovoltaic system for the solar lighting lamp. The solar lighting lamp has PV modules, batteries, and charge & discharge system. The charge efficiency is improved for the control of each battery which is divided the charge from the discharge to change the structure of existing solar lighting lamp charge & discharge system. so, the charge and discharge times are reduced of 50% and the depth of discharge control can be controlled in the discharge cut off voltage. It can be effective of the battery use. If a battery is out of order, this system can be executed for a regular period. So we saved the repair cost and developed of system's stabilization. It Is possible to make economical effects to apply for solar lighting lamp used photovoltaic system.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.3
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• pp.133-139
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• 2002

In this paper, a prototype of an active auxiliary quasi-resonant DC link (QRDCL) snubber assisted voltage source bidirectional power converter (AC to DC and DC to AC) operating at zero voltage soft-switching (BVS) PWM nlode is presented for a Battery Energy Storage System (BESS). The operating principle of this QRDCL circuit and multifunctional control-based converter system, including PWM inverter mode in which energy flows from the battery bank to the three-phase utility-grid in addition to an active PWM converter mode in which energy flows from the utility-grid to the battery banks are described respectively by the control implementation on the basis of d-q coordinate plane transformation. The multifunctional operation characteristics of this three-phase ZVS PWM bi-directional converter with QRDCL is demonstrated fer a BESS under the power conditioning and processing schemes of energy supply mode and energy storage mode, and compared with a conventional three-phase hard switching PWM bi-directional converter for a BESS. The effectiveness of the three-phase ZVS PWM hi-directional converter with QRDCL is proven via the simulation analysis.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.130-136
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• 2009

A lumped parameter model of Li-ion battery in hybrid electric vehicle(HEV) is constructed and system parameters are identified by using recursive least square estimation for different C-rates, SOCs and temperatures. The system characteristics of pole and zero in frequency domain are analyzed with the parameters obtained from different conditions. The parameterized model of Li-ion battery indicates highly dependant of temperatures. The system pole and internal resistance changes 6.6 and 18 times at $-20^{\circ}C$, comparing with those at $25^{\circ}C$, respectively. These results will be utilized on constructing model-based state observer or an on-line identification and an adaptation of the model parameters in battery management systems for hybrid electric vehicle applications.

• 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.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1607-1610
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• 2009

The carbon-coated Si/Cu powder has been prepared by mechanical ball milling and hydrocarbon gas decomposition methods. The phase of Si/Cu powder was analyzed using X-ray diffraction (XRD), dispersive Raman spectroscopy, electron probe microanalysis (EPMA) and transmission electron microscope (TEM). The carbon-coated Si/Cu powders were used as anode active material for lithium-ion batteries. Their electrochemical properties were investigated by charge/discharge test using commercial LiCo$O_2$ cathode and lithium foil electrode, respectively. The surface phase of Si/Cu powders consisted of carbon phase like the carbon nanotubes (CNTs) with a spacing layer of 0.35 nm. The carbon-coated Si/Cu/graphite composite anode exhibited a higher capacity than commercial graphite anode. However, the cyclic efficiency and the capacity retention of the composite anode were lower compared with graphite anode as cycling proceeds. This effect may be attributed to some mass limitations in LiCo$O_2$ cathode materials during the cycling.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.6
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• pp.558-562
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• 2006

Although secondary batteries, called rechargeable batteries, are very important energy elements in modern society, their application is hindered by the typical nonlinear and irreversible characteristics. Precise monitoring of the state of health(SOH) for each battery cell on line is crucial for stable operation and proper management of them. This paper proposes diagnostic method of the SOH for a battery cell on line without interruption on its operation nor bad effect on its life. This paper practically diagnoses on 120 industrial batteries and provides some guide lines to decide whether to exchange or not.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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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.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.3
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• pp.183-191
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• 2021

A battery management system (BMS) provides some functions for ensuring safety and reliability that includes algorithms estimating battery states. Given the changes caused by various operating conditions, the state-of-health (SOH), which represents a figure of merit of the battery's ability to store and deliver energy, becomes challenging to estimate. Machine learning methods can be applied to perform accurate SOH estimation. In this study, we propose a Long-Term Recurrent Convolutional Network (LRCN) that combines the Convolutional Neural Network (CNN) and Long Short-term Memory (LSTM) to extract aging characteristics and learn temporal mechanisms. The dataset collected by the battery aging experiments of NASA PCoE is used to train models. The input dataset used part of the charging profile. The accuracy of the proposed model is compared with the CNN and LSTM models using the k-fold cross-validation technique. The proposed model achieves a low RMSE of 2.21%, which shows higher accuracy than others in SOH estimation.