• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.1
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• pp.55-62
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• 2021

In order to improve fuel economy and reduce CO2, HEV adopts ISG system as a standard. This ISG system increased the electric load that the battery had to bear, and the number of starting increased rapidly. AGM Lead Acid batteries have been developed and used, but the charging time is about three times longer as the electrolyte amount control during formation must be maintained at a higher level compared to conventional lead-acid batteries. In this study, we tried to shorten the charging time by increasing the charging efficiency through the optimization of the formation pattern. In order to optimize the Formation Pattern, 10 charging steps and 6 discharging steps were applied to 16 multi steps, and the charging current for each step was controlled, and the test was conducted under 4 conditions (21 hr, 24 hr, 27 hr, 30 hr). As a result of simultaneous application of multi-step and discharge step, it was verified that minimizing the current loss and eliminating the sudden polarization during charging contributes to the improvement of charging efficiency. As a result, it showed excellent results in reducing the charging time by about 30 % with improved charging efficiency compared to the previous one.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1612-1614
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• 1994

Modulators Installed in PLS(Pohang Light Source) Linac are composed of a DC high voltage section, a charging section and a discharging section. PFN is charged by a resonant charging mechanism, and discharged by a switching device through the primary of the pulse transformer connected to a load. Charged PFN voltage must be well regulated to obtain stable output pulse voltage at the load. For this purpose, DCHV is controlled by a SCR controller with feedback signal, and PFN voltage is regulated by a De-Q'ing circuit. The full power operation test shows the pulse voltage regulation within ${\pm}0.13%$ with SCR feedback control alone, and within ${\pm}0.08%$ together with De-Q'ing. This paper describes the design concept and operational characteristics of the De-Q'ing circuit.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1763-1769
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• 2007

To improve the cycle-life and efficiency of an energy storage system for HEV, a dynamic control system consisted of a switch between a battery and an ultracapacitor module is proposed, which is appropriate for mild hybrid vehicle with 42V power net. The switch can be controlled based on the status of the battery and the ultracapacitor module, and a control algorithm that could largely decrease the number of high charging current peak is also implemented. Therefore the cycle life of the battery can be improved such that it is suitable for a mild hybrid vehicle with frequent engine start-stop and regenerative-braking. Also, by maximizing the use of the ultracapacitor, the system efficiency during high current charging and discharging operation is improved. Finally, this system has the effects that improves the efficiency of energy storage system and reduces the fuel consumption of a vehicle. To verify the validity of the proposed system, this paper presented cycles test results of different energy storage systems: a simple VRLA battery, hybrid energy Pack (HEP, a VRLA battery in Parallel with Ultracapacitor) and a HEP with a switch that controlled by energy management system (EMS). From the experimental result, it was proved the effectiveness of the algorithm.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.2
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• pp.158-163
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• 2022

The test method on the Type II high-pressure hydrogen storage tanks made of the metal wire hoop winding is a complex and high risk. Also closeup on the tank being test is difficult. In this study, we studied a mechanical test method for a high-pressure hydrogen tanks. This method must be simple, risk-free and possible to observe the change in microscopic behavior of a metal wire on a liner. As the results, it was possible to observe the microscopic behavior on the metal wire by the mechanical test method. Also, a simple and risk-free test was possible compared to the conventional test method for high pressure hydrogen tanks.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.357-360
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• 2005

Hyundai Motor Company developed the second generation of fuel cell hybrid electric vehicle based on Tucson SUV in 2004. This vehicle has cold start capability below -10C and its driving performances including maximum speed and accelerating time are almost similar to conventional Tucson SUV's performances without any sacrifice in terms of cabin space. Especially. the cold start capability was realized by utilizing only internal power sources such as fuel cell power and high voltage lithium ion polymer battery. In this paper, we will briefly introduce specifications of Tucson FCEV and its driving performances based on field test and simulations.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.143-149
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• 2022

As ESS safety issues increase recently, there is a need to more precisely monitor the temperature of the ESS. In this paper, DTS technology for temperature monitoring of ESS batteries is introduced and the temperature measurement principle is explained. The temperature of the battery module is measured using the DTS system, and the thermal deviation between battery cells inside the battery module is analyzed. In order to analyze how thermal imbalance affects the charging and discharging performance of the battery, an accelerated degradation test was conducted. Cycle life characteristics analysis, battery surface temperature change, and AC impedance characteristics were conducted to analyze how the performance of battery cells differs according to temperature conditions.

• Journal of Power Electronics
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• v.18 no.3
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• pp.879-891
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• 2018

A bidirectional dc-dc converter is used in battery energy storage systems owing to the growing requirements of a charging and discharging mode of battery. The magnetic coupling of output or input inductors in parallel-connected multi modules of a bidirectional dc-dc converter is often utilized to reduce the peak-to-peak ripple size of the inductor current. This study proposes a novel design guideline to achieve minimal ripple size of the inductor current under bidirectional power flow. The newly proposed design guideline of optimized coupling factor is applicable to the buck and boost operation modes of a bidirectional dc-dc converter. Therefore, the coupling factor value of the coupled inductor does not have to be optimized separately for buck and boost operation modes. This new observation is explained using the theoretical model of coupled inductor and confirmed through simulation and experimental test.

• Journal of the Korean Solar Energy Society
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• v.34 no.4
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• pp.1-7
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• 2014

The microgrid system is the combination of photovoltaic(PV) array, load, and battery energy storage system. The control strategies were defined as multi-modes of operation, including rest operation without use of battery, power charging, and power discharging, which enables grid connected mode or islanded mode. Photovoltaic power is a problem of the uniformity of power quality because the power generated from solar light is very sensitive to variation of insolation and duration of sunshine. As a solution to the above problem, energy storage system(ESS) is considered generally. There fore, in this study, we did basic research activities about optimization method of the amount of energy used, using a smart microgrid test-bed constructed in building. First, we analyzed the daily, monthly and period energy pattern amount of power energy used, and analyzed PV power generation level which is built on the roof. Utilizing building energy pattern analysis data, we was studied an efficient method of employing the ESS about building power consumption pattern and PV generation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.97-105
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• 2008

This paper presents simulated and experimental test results of optimal control algorithm for an encapsulated ice thermal storage system with full capacity chiller operation. The algorithm finds an optimal combination of a chiller and/or a storage tank operation for the minimum total operation cost through a cycle of charging and discharging. Dynamic programming is used to find the optimal control schedule. The conventional control strategy of chiller-priority is the baseline case for comparing with the optimal control strategy through simulation and experimental test. Simulation shows that operating cost for the optimal control with chiller on-off operation is not so different from that with chiller part load capacity control. As a result from the experimental test, the optimal control operation according to the simulated operation schedule showed about 14 % of cost saving compared with the chiller-priority control.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.3
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• pp.214-220
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• 2022

This paper proposes a test device designed for developing a high-voltage multilayer ceramic capacitor (MLCC). The proposed topology consists of an energy recovery circuit for charging/discharging capacitor, a flyback converter, and a boost converter for supplying power and a bias voltage application to the energy recovery circuit. The energy recovery circuit designed with a half-bridge converter has auxiliary switches operating before the main switches to prevent excessive current from flowing to the main switches. A prototype has been designed to verify the reliability of target capacitors following the voltage fluctuation with a frequency range below 65 kHz. To conduct high root mean square (RMS) current to the capacitor as a load, the MLCC test was conducted after the topology verification was completed through the film capacitor as a load. Through the agreement between the RMS current formula proposed in this paper and the MLCC test results, the possibility of its use was demonstrated for high-voltage MLCC development in the future.