Ji-Eun Baek

다중 직렬 연결된 대용량 EDLC 모듈에 적합한 전압 밸런싱 기법에 대한 연구

In this paper, the problem of voltage unbalancing in series-connected multiple electric double-layer capacitors(EDLCs) is studied. Good understanding of this problem is required in order to increase reliability and stability of an energy storage system comprising EDLCs. Existing methods to settle voltage unbalancing cannot mitigate the problem enough for each cell, since most method have been applied to each module. For equalizing between cells, Zener diode which is one of passive method have been well examined in literature. However, Zener have well not used in balancing due to heating problem. In addition, It is difficult to choose Zener diode fitted rating voltage of EDLC, because of its internal resistance. Thus, we proposed passive balancing using Zener diode by analyzing parasitic element of Zener and EDLC. To experimentally confirm the balancing effect, we compared in two occasions which are with and without passive. As a result, proposed passive balancing circuit mitigated unbalanced voltage gap between EDLCs.

Charging-balancing circuit design of series-connected electric double-layer capacitors in high power applications

The high power source which is included Electric-Double Layer Capacitors (EDLC) has been configured to generate power higher than limited power. Rated voltage of EDLC has low maximum value thats why it must need series-connection in high power applications. When EDLCs are series-connected, each cell has an unbalance voltage by each tolerance. Unbalance phenomenon is one of the facts reducing their life expectancy. Balancing or equalization is much studied in past years, but it is mostly not for high power applications. Hence, charging-balancing circuit of series-connected EDLCs is designed to equalize each cell and module voltages in this paper. It is not only discussion of circuit behavior but EDLC modeling of equivalent circuit which is considered parasitic elements causing voltage unbalance. Proposed balancing circuit mitigates voltage unbalance of EDLCs, as a result of charging-balancing circuit verified with simulation. Through the results, EDLC could be utilized in high power applications such as pulsed power, prime power source, hybrid electric vehicle.

In-line circuit modeling for damage analysis of RF front end system affected by high power electromagnetic pulse

Output of microwave have been increased with development of pulsed power system. The risk of RF front end system is dramatically increasing as the output of high power electromagnetic (HPEM) pulse increases. There are largely two ways of coupling HPEM pulse: (i) Front door coupling, which is through antennas and sensors to receive signals (ii) Back-door coupling, which is through unintended way such as punctures and slots. Compared to back-door coupling, front-door coupling is more risky and hazardous since it is coupled with intended parts. The simulation studies of this problem are conducted by numerical method. However it takes too many times in computation. In this paper, the in-line circuit modeling for damage analysis of the RF front end system affected by HPEM pulse is proposed. This integrated circuit modeling is simulated by the Electro Magnetic Transient Program (EMTP). It is simulated from the output of the HPEM system to the RF front end system. The target RF system of the study is the antenna. Passive circuit elements are used to model for antenna efficiency, propagation attenuation and etc.

Adjustable circuit model of vircator according to its characteristics

A virtual cathode oscillator (vircator) is one of the most important microwave generators, because it has advantages in simple structure, giga-watt level power and low impedance. Because of these advantages, it is widely used in high power electromagnetic (HPEM) pulse applications. The main disadvantage of the vircator is its low efficiency and it is complemented by simulation studies. Many of simulation studies are conducted by numerical method. Considering the connection to the pulse power part, a circuit modeling is needed. In this paper, the adjustable circuit model of the vircator according to its characteristics is proposed. Through the circuit model of the vircator, HPEM system can be handled as an integrated system, which contains a prime power part, a pulsed power part, a microwave source part, and others. This circuit analysis is simulated by the electromagnetic transient program (EMTP). Passive elements and switch are used to model for space-charge limitation, absorptions, oscillation and etc, which are derived from simulation condition (structure, input power). The vircator emission in the air is represented by the load. This study is helpful to efficiency researches because circuit elements are derived by the simulation conditions.

Damage Modeling of a Low-Noise Amplifier in an RF Front-End Induced by a High Power Electromagnetic Pulse

The RF front-end is a very vulnerable part of the coupling paths that are induced by a high power electromagnetic (HPEM) pulse. Existing studies found through experiment or simulation that low-noise amplifiers (LNAs) often break down or are damaged, which causes the malfunction of the RF front-end. To protect the RF front-end, the damage process of LNAs based on theory is required in detail. This paper summarizes the damage process, and a new library is developed describing the damage phenomenon of LNAs by using user-defined elements. The model can be combined with other circuit models, and can also offer variation of the internal parameters of LNAs by HPEM pulse. Existing physical protection methods have high costs and complexity, and it is difficult to provide perfect protection. Thus, the proposed model can contribute to protection studies utilizing a circuit model.

A 25-F Electric Double-Layer Capacitor Bank and DC Power Supply for Portable High-Current Applications

A portable dc power supply based on electric double-layer capacitor (EDLC) bank was established for high-power applications. EDLC bank needs a dc–dc converter to maintain a constant output voltage and current. Especially, a low-impedance load makes the voltage of capacitors discharge faster, and their discharging time is determined by RC time constant. The proposed system is designed as a fundamental concept, and deals with some issues occurring in a large-scale system. Also, this paper provides detailed information and consideration for a real establishment. Last, we performed a full-scale experiment using basic techniques.

Experimental analysis on hazardness of RF front-end system damaged by high power electromagnetic pulse

The high power electromagnetic(HPEM) is one of the major issue on military area in several years. Contrary to other direct weapons, it is nonlethal weapon that destroy or deceive electronic device but minimize the harm to human1. Commonly, there are two coupling path of electronic device damaged by HPEM pulse. One is the front-door coupling and the other is the back-door coupling2. Due to the front-door coupling is induced a lot more power than the back-door coupling, it is difficult to protect perfectly. Thus it needs to study the damage prediction and the protection method of RF front-end system affected by HPEM pulse.

Development of high step-up converter based on electric double-layer capacitors for DC plasma power supply

Summary form only given. A various power supplies for generating the plasma have been studied for decades. DC supply based on electric double-layer capacitor (EDLC) banks was studied and developed in this paper. EDLC has many advantages such as high power density, high speed charging/discharging characteristics1. Although EDLC is suitable for pulsed power applications as prime power, voltage rating of EDLC is so low that it has been rarely used. We proposed the high step-up converter to generate the high voltage DC-pulse from prime power using EDLCs. Supplying the stable voltage and current is an important part in DC plasma process. In previous pulsed power system, intermediate energy storage and pulse forming line are required for compression and shaping of the pulse2. Proposed converter is able to perform the compression and shaping without them. This idea needs two important abilities; one is that the converter should have a high voltage gain. Another is that the converter could cope with rapidly decreasing input voltage. In this paper, we proposed the idea and defined the system using high step-up converter. Also, the converter was verified with simulation. Proposed system and idea will promote the fusion works combining pulsed power and power electronics. Also, the developed power supplies are able to provide proper power to various plasma applications3.

Effects of electron beam focusing on virtual cathode formation in virtual cathode oscillator

As a high power microwave (HPM) source, virtual cathode oscillator has been studied due to its simplicity. A lot of experiments on virtual cathode oscillator has been conducted and reported to study the characteristics and to increase its efficiency. In order to increase its efficiency, ballistic focusing of an electron diode has been studied. And it is reported that the efficiency of virtual cathode oscillator is somewhat increased through the ballistic focusing.

Switching Losses Analysis of the Interleaved ZCT DC-DC Converter with Current Conduction Modes

In the issues of interleaved topology which have been in limelight as high power converter, various soft-switching methods are studied to reduce switching losses in high power application. The interleaved ZCT converter has an additional filter inductor to reduce losses of diodes during reverse recovery process. However, additional current conduction modes are occurred by the inductor, we need to analyze switching losses with inductor values on each mode. In this paper, current conduction modes and boundary conditions of interleaved ZCT converter are analyzed. In the conclusion, the minimum of switching losses in converter operation modes is analyzed by calculating switching losses.