• The Transactions of the Korean Institute of Power Electronics
• /
• v.13 no.6
• /
• pp.476-486
• /
• 2008

It is very important to design the input filter optimally in matrix converters. But, the input power factor is deteriorated in spite of the optimal filter design due to the existence of inductor and capacitor included in the filter, and it is hard to keep high power factor in the whole operating range which is one of the major advantages of the matrix converters because the power factor is changed according to the output frequency and the load current. In this paper, we introduce the new space vector modulation method which can preserve the input power factor almost unity even though the output load or the output frequency is varied. It is also presented how to implement the proposed method effectively.

• Journal of Power Electronics
• /
• v.4 no.2
• /
• pp.77-86
• /
• 2004

This paper presents a novel three-phase power module bridge type auxiliary resonant AC link snubber for the three-phase voltage-fed sinwave soft switching PWM inverter operating under specific instantaneous space voltage vector modulation. The operating principle of this resonant snubber is described for current source load model during one switching period, along with its design approach based on the simulation data. The performance evaluations of space vector modulation three-phase sinewave soft switching inverter with a new three-phase active auxiliary resonant AC link snubber are discussed as compared with those of three-phase voltage source-fed sinewave hard switching PWM inverter with a standard space voltage vector modulation strategy. The power loss analysis and conventional efficiency estimation of three-phase soft switching PWM inverter using ICBT modules are carried out including all the conduction power losses based upon the measured v-i characteristics of IGBT and its antiparallel diode as well as their switching losses.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.52 no.2
• /
• pp.107-111
• /
• 2003

In the power-line communication systems, there are many factors of noise and attenuation in the power-line channels, because they were designed for not the communication but the power transmission. Also the transfer function of the channels is highly changed with the topology and the load of the power-lines. To cope with these poor channel situation, channel modeling, one of the many studies in progress, is being studied hard. Channel modeling is essential to apply the active schemes to overcome the bad channel(e.g. modulation technique, channel coding, signal coupling & filtering, etc.) to the power-line communications. In this paper, we have realized the statistical model(this model is suggested as the channel modeling method for the power-line channels) that is combined the transfer function with the various noises. And we have compared and examined the results with the measured data. Also we have studied the plan which can effectively establish the channel data base for the channel information consisted of the parameters that are derived from this modeling, and we have studied the plan to utilize the data base.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.65 no.3
• /
• pp.158-164
• /
• 2016

In this paper, a high frequency flyback type zero voltage soft switching PWM DC-DC converter using IGBTs is proposed. Effective applications for this power converter can be found in auxiliary power supplies of rolling stock transportation and electric vehicles. This power converter is basically composed of active power switches and a flyback high frequency transformer. In addition to these, passive lossless snubbers with power regeneration loops for energy recovery, consisting of a three winding auxiliary high frequency transformer, auxiliary capacitors and diodes are introduced to achieve zero voltage soft switching from light to full load conditions. Furthermore, this power converter has some advantages such as low cost circuit configuration, simple control scheme and high efficiency. Its operating principle is described and to determine circuit parameters, some practical design considerations are discussed. The effectiveness of the proposed power converter is evaluated and compared with the hard switching PWM DC-DC converter from an experimental point of view and the comparative electromagnetic conduction and radiation noise characteristics of both DC-DC power converter circuits are also depicted.

• KEPCO Journal on Electric Power and Energy
• /
• v.7 no.1
• /
• pp.93-99
• /
• 2021

The government has proposed a mission to enhance intelligent power networks, decrease coal-fired generation, expand distributed energy resources, and promote energy prosumer into the distribution network in Korea. Installation cost of facility expansion to guaranteed interconnection with small distributed energy resources increases dramatically on KEPCO's distribution sector. And it is hard to withdraw in time. In addition, there are explicit research is required to meet the reliability on grid corresponding to the increase of distributed power. Infrastructure support for accommodating energy prosumer is also needed. Therefore, KEPCO is pushing transition to DSO by expanding distribution management scope and changing its roles. In addition, KEPCO is proactively preparing for integrated operation between distribution network and existing distributed power which is accommodated passively. KEPCO is also trying to accept multiple network users, e.g. building platforms, to manage a data and promote new markets. In the long term, transition to DSO will achieve saving investment costs for accommodating distributed sources and maintaining stable electrical quality. And it will be possible to create new business model using the platform to secure revenue.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.19 no.2
• /
• pp.75-80
• /
• 2013

The physicochemical properties of the hydroxypropylated mung bean, sweet potato and water chestnut starches were studied. The blue value and amylose content of mung bean starch were higher than those of sweet potato and water chestnut. Pasting temperature of hydroxypropylated starches were lower than those of native starch and decreased with increasing contents of propylene oxide. Peak viscosity increased with the increase of degree of hydroxypropylation. With increasing contents of propylene oxide, the clarity and swelling power of all starches were increased and those of mung bean were higher. Mung bean starch produced better hard capsules than sweet potato and water chestnut starch. Hydroxypropylated (>6% propylene oxide) water chestnut starch-based capsules completely dissolved, but hydroxypropylated (>12% propylene oxide) mung bean and sweet potato starch-based capsules were dissolved within 10 min. These results showed that hydroxypropylated starch-based capsules have potentials for pharmaceutical applications as a substitute for gelatin hard capsules.

• Journal of KIISE:Computer Systems and Theory
• /
• v.37 no.5
• /
• pp.285-291
• /
• 2010

Flash memory has many good features such as small size, shock-resistance, and low power consumption, but the cost of flash memory is still high to substitute for hard disk entirely. Recently, some mobile devices, such as laptops, attempt to use both flash memory and hard disk together for taking advantages of merits of them. However, existing OSs (Operating Systems) are not optimized to use the heterogeneous storage media. This paper presents a new buffer cache management scheme. First, we allocate buffer cache space according to access patterns of block references and the characteristics of storage media. Second, we prefetch data blocks selectively according to the location of them and access patterns of them. Third, we moves destaged data from buffer cache to hard disk or flash memory considering the access patterns of block references. Trace-driven simulation shows that the proposed schemes enhance the buffer cache hit ratio by up to 29.9% and reduce the total I/O elapsed time by up to 49.5%.

• Communications for Statistical Applications and Methods
• /
• v.15 no.2
• /
• pp.293-302
• /
• 2008

In this paper we propose a new feature, average power, for speech segments extraction with hidden Markov models, which is based on mel frequencies of speech signals. The average power is compared with the mel frequency cepstral coefficients, MFCC, and the power coefficient. To compare performances of three types of features, speech data are collected for words with explosives which are generally known hard to be detected. Experiments show that the average power is more accurate and efficient than MFCC and the power coefficient for speech segments extraction in environments with various levels of noise.

• Fashion & Textile Research Journal
• /
• v.13 no.5
• /
• pp.679-685
• /
• 2011

The purpose of this study is to analyze the formative characteristics and the aesthetic values of the Power suit in 1980s and the images of the Power suit styles shown in 08/09 F/W, 09 S/S, 09/10 F/W and 10 S/S collections. The results of this study are as follows: 1) The aesthetic values of the Power suit in 1980s are authority, sexuality and luxury to express the power, body and wealth. Authority is represented in wide and hard shoulders with pads and dark colors with stripe and no patterns. Sexuality is represented in tight waist jacket and tight skirt. Luxury is represented in luxurious fabrics and handicraft ornaments. 2) The Power suit styles shown in collections are expressed in classic, romantic, avant-garde and ethnic images: Classic images appeared in jacket which exaggerated shoulders with pads, mini skirt, tapered pants, dark colors with stripe and check patterns, rough materials and a waist belt. Romantic images are represented in the skirt with an asymmetric hem, pastel and splendid colors, lace and silk, romantic details made with gathers and flounces and fantastic accessories. Avant-garde images appeared in the deformed jacket, unperfected skirt, special materials and exaggerated accessories. Ethnic images are represented in big silhouette forms with wide shoulders jacket and wide pants, ethnic patterns, gold, orange and other vivid colors and ethnic accessories.

• Proceedings of the KIPE Conference
• /
• 1998.10a
• /
• pp.153-158
• /
• 1998

In this paper, a prototype of the auxiliary resonant commutated snubber circuit(ARCS) with a high frequency transformer power regeneration loop is described for voltage source type sinewave inverter system. This is a new soft switching topology developed for three phase voltage source soft-switching inverter, active power filter and reactive power compensator has significant advantage of current rating reduction for auxiliary active switching devices. In addition, this paper presents a novel prototype of voltage-source soft switching space vector-modulated inverter with ARCS mentioned above, which is more suitable and acceptable for high-power utility interactive power conditioning, along with a digital control scheme. The steady-state operating analysis of ARCS has the remarkable features and the practical design procedure of this resonant snubber are illustrated on the basis of computer simulation analysis. The operating performance evaluations in the steady-state of this three phase voltage source soft switching inverter are discussed and compared with the three phase voltage source hard switching inverter.