• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.535-542
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• 2017

This paper proposes a simple 3-level interleaved charger-discharger for the uninterruptible power supply (UPS) with various combinations of battery cells. The proposed converter not only improves charging and discharging efficiency, but also reduces the physical volume and the cost. Furthermore, the converter also offers the capability of the neutral point voltage, so that more stable operation can be obtained. In addition, the proposed converter significantly reduces the ripple current of the battery inductor, thereby providing an expected life extension of the battery. Experimental results for a 300kVA UPS prototype verify the validity of the proposed converter. The proposed charger-discharger is suitable for UPSs and energy storage systems (ESSs) with wide input battery voltage ranges.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.473-475
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• 1993

Premium Service is the next service to be developed after the Freephone Service and Credit Call Service which has currently been developed and is being now tested. Premium Service is a service which provide information on a telephone line. The calls are charged with a special rate which includes service and call charge. Public telecommunication operator performs charging and accounting from the service user for the service provider and for every service provided subtracts the commission from the part of service revenue and gives the rest back to the service provider. This paper is about the study on the implementation of the Premium Service in the Service Switching Point.

• Journal of the Korean Society of Safety
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• v.20 no.3 s.71
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• pp.42-46
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• 2005

The static electricity by thinner flow and discharge energy is investigated experimentally for the purpose of preventing the electrostatic discharge and damage. Test system for evaluating streaming electrification consists of a teflon pipe, a reservoir tank a pump, flowmeters and an electrometer. When dielectric liquid flows through a pipe from one vessel to another, the potential difference generated in the collecting vessel is due to the accumulation of charges. These charges result from the convection of a part of the electrical double layer existing in the tube at the contact between the liquid and the inner wall. When the fluid velocity increases, the electric current increases proportionally. The charging current and accumulated charges by streaming electrification at the thinner velocity of 40cm/s are measured a range of 5 nA and $0.27{\mu}C$ respectively. This amount of static discharge energy generated by streaming electrification is enough to ignite flammable solvent. Therefore surface electric potential should decrease by using electrostatic shielding and ground.

• Journal of Power Electronics
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• v.15 no.4
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• pp.987-993
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• 2015

Wireless power transfer technologies typically include inductive coupling, magnetic resonance, and capacitive coupling methods. Among these methods, capacitive coupling wireless power transfer (CCWPT) has been studied to overcome the drawbacks of other approaches. CCWPT has many advantages such as having a simple structure, low standing power loss, reduced electromagnetic interference (EMI) and the ability to transfer power through metal barriers. In this paper, the CCWPT system with 6.78MHz class D inverter is proposed and analyzed. The proposed system consists of a 6.78MHz class D inverter with a LC low pass filter, capacitor between a transmitter and a receiver, and impedance transformers. The system is verified with a prototype for charging mobile devices.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.274-277
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• 1994

This paper describes a very fast rising high voltage pulse generation for studying surge phinomenon and prebreakdown of liquid dielectric by appling the traveling wave theory of the distributed circuit. This very fast rising high voltage pulse generator consists of a charging coaxial cable, a discharging switch, and a terminating resistance. As results, the rising time of pulses are about 31(nsec), which is very fast, and its duration is 950[nsec] when using 200[m] coaxial cable. The length of the coaxial cable and changing voltage can regulate the duration and the amplitude or the polarity of the pulse. When terminated the resistance, capacitor and inductor, the measured waveform corresponds with simulated waveform.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.996-998
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• 2005

전기철도나 지하철 분야에 사용되고 있는 고속 DC 차단기의 조작부는 solenoid actuator 방식이나 motor charging 방식을 주로 채택하고 있으나 구조가 복잡하고 부품수가 많아 부피가 크다는 단점이 있다. 이에 반해 magnetic actuator 방식은 동작시간과 제어가 용이하고 부품수가 감소하여 신뢰성과 반복성이 뛰어나다. 본 논문에서는 고속 DC 차단기 조작부를 영구자석 엑추에이터(PMA)방식으로 적용하고자 영구자석(PM)의 개략적 설계 및 이를 이용한 PMA 설계를 하였고, 유한요소 해석을 통해 이들의 동작특성을 해석하였다.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.206-207
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• 2016

The intermittent characteristics of wind power (WP) may have negative effect on grid stability, especially in weak grid. WP fluctuation rate can be reduced by using energy storage system (ESS) through charging and discharging. The operation of ESS will decide its losses and lifetime of batteries. From this point, this paper proposes WP smoothing control by using short-term average of WP. In this case, the ESS will only operate at high WP fluctuation rate. Then, the output power of ESS will be estimated by short-term average value. The effectiveness of proposed method will be verified by comparing with conventional method. The simulation results will be carried out by using Matlab program.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.6
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• pp.329-335
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• 2018

In an electric vehicle and Energy Storage System(ESS), a large number of batteries are connected in series or parallel to obtain high voltage and current. The battery management system(BMS) is needed because battery has a characteristic that explode in overcharging and overcurrent situations due to the nature of the battery material and the battery life is dramatically reduced when the battery is overdischarged below the specified voltage. In this paper, we proposed a system that can manage a large amount of batteries through the communication of master-slave type with multiple microcontroller. We confirmed the stable operation of the proposed system through the balancing-charging and storage mode experiments.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1069-1073
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• 2019

In this paper, an alternative non-isolated DC-DC converter with a high voltage boosting capability is proposed. Two inductors are used and one of them has its flux linkage increases during its charging period to achieve a high step-up voltage gain. Among the three integrated capacitors, one portrays the partial characteristic of the switched-capacitor technique, while the other two are connected in series across the load. With the two switches controlled using the same duty cycle, the proposed topology demonstrates the merits of a higher and wider range of step-up voltage gain when compared with recent topologies. In addition, a reduction in loss is induced and a higher efficiency is ensured with all the voltage stresses constrained within the output voltage. Operation of the proposed converter is analyzed and validated through experimental results obtained with a prototype.

• Journal of Auto-vehicle Safety Association
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• v.8 no.2
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• pp.30-36
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• 2016

According to revolutionary developments in automobile technologies, various electronically controlled components of vehicles are rapidly increasing. A variety of advanced vehicles (hybrid vehicle, hydrogen fuel-cell vehicle, electric vehicle, etc.) using electrical energy source are increasing, too. The electromagnetic compatibility is getting more important for development of a vehicle because those advanced vehicles are equipped with more new electronic systems. In general, electromagnetic compatibility tests consist of an electromagnetic interference (EMI) test and an electromagnetic susceptibility (EMS) test. In this paper, in order to investigate the electromagnetic interference in the cabin of vehicle by various electric and electronic components of vehicles, a series of narrowband electromagnetic emission tests are conducted. For comparison, the several digital home appliances (smartphone under charging, laptop compuer and digital camera), which are used a lot in daily lives, are tested.