• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.129-131
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• 2006

This paper presents a new ZVS-PWM high frequency inverter. The ZVS operation is achieved in the whole load range by using a simple auxiliary reverse blocking switch in parallel with series resonant capacitor. The operating principle and the operating characteristics of the new high frequency circuit treated here are illustrated and evaluated on the basis of simulation results. It was examined that the complete soft switching operation can be achieved even for low power setting ranges by introducing the high frequency dual duty cycle control scheme. In the proposed high frequency inverter treated here, the dual mode pulse modulation control strategy of the asymmetrical PWM in the higher power setting ranges and the lower power setting ones, the output power of this high frequency inverter could introduce in order to extend soft switching operation ranges. Dual duty cycle is used to provide a wide range of output power regulation that is important in many high frequency inverter applications. It is more suitable for induction heating applications the operation and control principle of the proposed high frequency inverter are described and verified through simulated results.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.7
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• pp.297-305
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• 2006

This paper summarizes a development of visualization software for protective engineering in low-voltage power systems. The study is concentrated on the following aspects. First, a software engineering method is applied for designing the object-oriented program. The design and implementation of a Graphic User Interface(GUI) and its integration to a power system framework are developed using object-oriented programming(OOP) in Visual C++. Second, we develop the short circuit analysis module that oriented a low-voltage power system. It is possible to calculate a peak, symmetrical RMS, DC component and asymmetrical fault currents for each time. And it is the first software that can calculate the fault current for single branch of three-phase system. The calculation accuracy is compared with commercial software, and the libraries of low-voltage components are served for convenience use. Third, protective engineering functions are equipped. It is possible to automatically select the circuit breaker which based on the user input characteristics and the fault current calculation and examine the protective coordination. Through the case study, we verified that the developed software can be effectively used to examine the protective engineering in low-voltage power systems.

• Journal of Power Electronics
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• v.7 no.3
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• pp.246-256
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• 2007

In this paper, a novel type auxiliary active edge resonant snubber assisted zero current soft switching pulse modulation Single-Ended Push Pull (SEPP) series load resonant inverter using IGBT power modules is proposed for cost effective consumer high-frequency induction heating (IH) appliances. Its operating principle in steady state is described by using each switching mode's equivalent operating circuits. The new multi resonant high-frequency inverter with series load resonance and edge resonance can regulate its high frequency output power under a condition of a constant frequency zero current soft switching (ZCS) commutation principle on the basis of the asymmetrical pulse width modulation (PWM) control scheme. Brand-new consumer IH products using the proposed ZCS-PWM series load resonant SEPP high-frequency inverter using IGBTs is evaluated and discussed as compared with conventional high-frequency inverters on the basis of experimental results. In order to extend ZCS operation ranges under a low power setting PWM as well as to improve efficiency, the high frequency pulse density modulation (PDM) strategy is demonstrated for high frequency multi-resonant inverters. Its practical effectiveness is substantially proved from an application point of view.

• Journal of Power Electronics
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• v.14 no.3
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• pp.507-518
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• 2014

This paper presents a new cascaded asymmetrical single phase multilevel converter with a lower number of power semiconductor switches and isolated DC sources. Therefore, the number of power electronic devices, converter losses, size, and cost are reduced. The proposed multilevel converter topology consists of two H-bridges connected in cascaded configuration. One H-bridge operates at a high frequency (high frequency inverter) and is capable of developing a two level output while the other H-bridge operates at the fundamental frequency (low frequency inverter) and is capable of developing a multilevel output. The addition of each power electronic switch to the low frequency inverter increases the number of levels by four. This paper also introduces a hybrid switching algorithm which uses very simple arithmetic and logical operations. The simplified hybrid switching algorithm is generalized for any number of levels. The proposed simplified switching algorithm is developed using a TMS320F2812 DSP board. The operation and performance of the proposed multilevel converter are verified by simulations using MATLAB/SIMULINK and experimental results.

• Korea Trade Review
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• v.44 no.3
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• pp.105-121
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• 2019

This study applies diverse game theories to the US-China Trade War. The US-China Trade War can be analyzed as a game situation because the strategic decision-making process to maximize one's profit while considering the reaction of the other party is a game situation. However, related research suffered from some mistakes in applying the US-China Trade War as it is to classic game theory, because while the prisoners dilemma is based on the situation of No Communication, No Trust, No Cooperation, the US-China Trade War has a precondition different from that of prisoners dilemma, since it mutually communicates information and negotiation is repeated several times in a cooperative situation. The result of the trade negotiation will likely end as 'cooperate-cooperate'. Further, considering trade volume, trade interdependence, bargaining power based on economy, and the scale of damage caused by the Trade War, the US-China Trade War is progressing with the bargaining power of the US being higher than that of China. Since the current US-China Trade War is in an asymmetrical situation under the dominant bargaining power of the US, it is likely to reach 'US defect-China cooperative' in the long run.

• Journal of Communications and Networks
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• v.12 no.5
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• pp.442-448
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• 2010

Cooperative relaying methods have attracted a lot of interest in the past few years. A conventional cooperative relaying scheme has a source, a destination, and a single relay. This cooperative scheme can support one symbol transmission per time slot, and is caned full rate transmission. However, existing fun rate cooperative relay approaches provide asymmetrical gain for different transmitted symbols. In this paper, we propose a cooperative relaying scheme that is assisted with dual relays and provides full transmission rate with the same macro-diversity to each symbol. We also address equalization for the dual relay transmission system in addition to addressing the issues concerning the improvement of system performance in terms of optimal power allocations.

• Journal of Electrical Engineering and Technology
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• v.7 no.5
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• pp.778-783
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• 2012

The synthetic short-circuit making test to adequately stress the circuit breaker has been specified as the mandatory test duty in the IEC 62271-100. The purpose of this test is to give the maximum pre-arcing energy during making operation. And this requires the making operation with symmetrical short-circuit current that is established when the breakdown between contact gap occurs near the crest of the applied voltage. Also, if the interrupting chamber of circuit breakers is designed as the type of common enclosure or the operation is made by the gang operated mechanism that three-phase contacts are operated by one common mechanism, three-phase synthetic making test is basically required. Therefore, several testing laboratories have developed and proposed their own test circuits to properly evaluate the breaker performance. With these technical backgrounds, we have developed the new alternative three-phase making circuit.

• Journal of Power System Engineering
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• v.4 no.3
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• pp.48-54
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• 2000

This paper describes the effect of molding pressure, specimen geometries for Mixed Mode I/II interlaminar fracture toughness of carbon fiber reinforced plastic composites by using asymmetrical double cantilever beam(ADCB) specimen. The value of $G_{I/IIC}$ as a function of various molding pressure is almost same at 307, 431, 585 kPa. However it shows the highest value under 307 kPa molding pressure. The effect of $G_{I/IIC}$ due to the change of initial crack length of ADCB specimen was almost negligible in this study. It turns out that the condition for mix mode quasi-static crack growth in ADCB specimen is the ratio of the crack length to that of the specimen, i.e., ${\alpha}/L<0.4$.

• Communications for Statistical Applications and Methods
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• v.21 no.4
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• pp.309-316
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• 2014

Testing normality is very important because the most common assumption is normality in statistical analysis. We propose a new plot and test statistic to goodness-of-fit test for normality based on the generalized Lorenz curve. We compare the new plot with the Q-Q plot. We also compare the new test statistic with the Kolmogorov-Smirnov (KS), Cramer-von Mises (CVM), Anderson-Darling (AD), Shapiro-Francia (SF), and Shapiro-Wilks (W) test statistic in terms of the power of the test through by Monte Carlo method. As a result, new plot is clearly classified normality and non-normality than Q-Q plot; in addition, the new test statistic is more powerful than the other test statistics for asymmetrical distribution. We check the proposed test statistic and plot using Hodgkin's disease data.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.615-619
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• 2004

A new asymmetrical zero voltage switching (ZVS) active clamp forward converter is proposed. Since the ripple current of secondary inductor plays a key role in the ZVS operation of main power switch, the proposed converter shows an excellent ZVS performance. The synchronous rectification is employed to reduce the rectification loss. The operational principle and ZVS analysis are presented. Experimental results demonstrate that the proposed converter can achieve an excellent ZVS performance throughout all load conditions and the significant improvement in the efficiency for the 100W(5V,20A) prototype converter.