• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1864-1873
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• 2018

Energy shifting is an innovative method used to obtain the highest profit from the operation of energy storage systems (ESS) by controlling the charge and discharge schedules according to the electricity prices in a given period. Therefore, in this study, we propose an optimal charge and discharge scheduling method that performs energy shift operations derived from an ESS efficiency model. The efficiency model reflects the construction of power conversion systems (PCSs) and lithium battery systems (LBSs) according to the rated discharge time of a MWh-scale ESS. The PCS model was based on measurement data from a real system, whereas for the LBS, we used a circuit model that is appropriate for the MWh scale. In addition, this paper presents the application of a genetic algorithm to obtain the optimal charge and discharge schedules. This development represents a novel evolutionary computation method and aims to find an optimal solution that does not modify the total energy volume for the scheduling process. This optimal charge and discharge scheduling method was verified by various case studies, while the model was used to realize a higher profit than that realized using other scheduling methods.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1369-1375
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• 2017

This paper presents an optimal operation scheduling algorithm for a smart home with energy storage system, electric vehicle and distributed generation. The proposed algorithm provides the optimal charge and discharge schedule of the EV and the ESS. In minimizing the electricity costs of the smart home, it considers not only the cost of energy purchase from the grid but also the life cost of batteries. The life costs of batteries are calculated based on the relation between the depth of discharge and life time of battery. As the life time of battery depends on the charge and discharge pattern, optimal charge and discharge schedule should consider the life cost of batteries especially when there is more than one battery with different technical characteristics. The proposed algorithm can also be used for optimal selection of size and type of battery for a smart home.

• Korean Journal of Materials Research
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• v.26 no.12
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• pp.696-703
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• 2016

In this study, we intensively investigated the effect of conductive additive amount on electrochemical performance of organic supercapacitors. For this purpose, we assembled coin-type organic supercapacitor cells with a variation of conductive additive(carbon black) amount; carbon aerogel and polyvinylidene fluoride were employed as active material and binder, respectively. Carbon aerogel, which is a highly mesoporous and ultralight material, was prepared via pyrolysis of resorcinol-formaldehyde gels synthesized from polycondensation of two starting materials using sodium carbonate as the base catalyst. Successful formation of carbon aerogel was well confirmed by Fourier-transform infrared spectroscopy and $N_2$ adsorption-desorption analysis. Electrochemical performances of the assembled organic supercapacitor cells were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements. Amount of conductive additive was found to strongly affect the charge transfer resistance of the supercapacitor electrodes, leading to a different optimal amount of conductive additive in organic supercapacitor electrodes depending on the applied charge-discharge rate. A high-rate charge-discharge process required a relatively high amount of conductive additive. Through this work, we came to conclude that determining the optimal amount of conductive additive in developing an efficient organic supercapacitor should include a significant consideration of supercapacitor end use, especially the rate employed for the charge-discharge process.

• 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 Electrical Engineers
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• v.63 no.1
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• pp.80-84
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• 2014

The discharge characteristics of Surface Dielectric Barrier Discharge (SDBD) reactor are investigated to find optimal driving condition with adjusting various parameter. When the high voltage with sine wave form is applied to SDBD source, successive pulsed current waveforms are observed owing to multiple ignitions through the long discharge channel and wall charge accumulation on the dielectric surface. The discharge voltage, total charge between dielectrics, mean energy and power are calculated from measured current and voltage according to electrode gap and dielectric thickness. Discharge mode transition from filamentary to diffusive glow is observed for narrow gap and high applied voltage case. However, when the diffusive discharge is occurred with high applied voltage, the actual firing voltage is always lower than that with low driving voltage. The $Si_3N_4$, $MgF_2$, $Al_2O_3$ and $TiO_2$ are considered for dielectric protection and high secondary electron emission coefficient. SDBD with $MgF_2$ shows the lowest breakdown voltage. $MgF_2$ thin film is proposed as a protection layer for low voltage atmospheric dielectric barrier discharge devices.

• Korean Chemical Engineering Research
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• v.45 no.3
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• pp.242-248
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• 2007

For an optimal design of automotive electric system, it is important to have a reliable modeling tool to predict the charge-discharge behaviors of the automotive battery. In this work, a two-dimensional modeling was carried out to predict the charge-discharge behaviors of a 12-V automotive lead-acid battery. The model accounted for electrochemical kinetics and ionic mass transfer in a battery cell. In order to validate the modeling, modeling results were compared with the experimental data of the charge-discharge behaviors of a lead-acid battery. The discharge behaviors were measured with three different discharge rates of C/5, C/10, and C/20 at operating temperature of $25^{\circ}C$. The batteries were charged with constant current of 30A until the charging voltage reached to a predetermined value of 14.24 V and then the charging voltage was kept constant. The discharge and charge curves from the measurements and modeling were in good agreement. Based on the modeling, the distributions of the electrical potentials of the solid and solution phases, the porosity of the electrodes, and the current density within the electrodes as well as the acid concentration can be predicted as a function of charge and discharge time.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.208-213
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• 2015

This study presents the estimation method for the optimal capacity of BESS(Battery Energy Storage System) in order to reduce the electric charges of common consumer. The daily optimal charge and discharge plan of BESS which satisfies the given constraints is established using linear programming through the change of rated output/rated capacity of the time that shows the electric charges in the highest reduced rate has been selected. There will be a problem to compare only reduced rate because the bigger the rated capacity, the more reduced rate is increased. Therefore, rated output/rated capacity of the time when the reduced amount of electric charges for a year is higher than the investment cost of BESS was selected.

• Proceedings of the Safety Management and Science Conference
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• 2003.11a
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• pp.343-350
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• 2003

The best Ppy weight ratio was 7 wt% and the optimal electrode composition ratio was 78 : 17 : 5 wt.% of (MSP-20 : BP-20 =1 : 1), (Super P : Ppy =10 : 7) and P(VdF-co-HFP). Implantation of Ppy as the conducting agents have led to superior electrochemical characteristics because of the low of internal resistance and faradaic capacitance. The result of unit cell with Ppy 7 wt% were as follows: 28.02 Fig of specific capacitance, 1.34 Ω of DC-ESR and 0.36 Ω of AC-ESR. Unit cell showed a good stability up to 200 charge-discharge cycles, retaining 82% of their original capacity at 200 cycles. From the analysis of impedance, the electrodes with Ppy 7 wt% showed low ESR, low charge transfer resistance and quick reaction rate. It was inferred that quick charge-discharge was possible. As compared with the specific capacitance (rectangular shape) of CV, it was also concluded that the specific capacitance originated from thecompound phenomena of the faradaic capacitance by oxidation and reduction of Ppy and the non-faradaic capacitance by adsorption-desorption of activated carbon.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.4 no.4
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• pp.258-263
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• 2011

In this paper, a high quality battery charge-discharge controller for new & renewal energy power generation system is designed. The proposed new controller has a function to manipulate the battery charging current precisely and it is suitable for various batteries including Lead-Acid battery generally used for solar power generation system. LCD display function is implemented to enhanced the user's convenience and minimization of standby power consumption is realized by optimal design using CAD tools.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.722-725
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• 2003

In AC plasma display, it is very important to quantify the wall voltage induced by the wall charge accumulated on the dielectric surface. If we know the quantities of the wall voltage in each period of every sequence; reset period, address period and sustain period, then it helps us to design the optimal driving waveform for high efficiency plasma display. We develop a new method to measure the wall voltage with VDS (Versatile Driving Simulator) system. From this method the wall voltage induced by a wall charge profiles just after the reset discharge of every cells in plasma display panel can be investigated and analyzed successfully. It is noted that the wall voltage profiles are influenced by the space charge and then they are stabilized as time goes by. It is also noted that both the remaining wall charge at the previous sequence and space charges contribute to wall voltage quantities just after the reset discharge. It is noted that the wall charges contribute dominantly after a few hundreds microseconds, while the space charges have been decayed within 100 ${\mu}s$ just after the reset discharge.