• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.459-466
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• 2022

Switching surges are a common type of phenomenon that occur on any sort of power system network. These are more pronounced on long transmission lines and in high voltage converter stations. At AC/DC hybrid transmission lines, the insulation coordination of such lines is mainly dictated by the peak level of switching surges, the most dangerous of which include three phase line energization and AC/DC converter station. The power system structure consist of AC/DC hybrid transmission lines which is combination of AC 765kV and ±500kV HVDC 1 bipole system for contingency analysis. The power system under study and its components are simulated using EMTDC software package, the effects of the various AC/DC mixing power lines are reviewed. The developed models of EMTDC conversion lines based on combination of AC/DC system are simulated and the characteristics of switching surge over-voltage from its results are discussed.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.6
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• pp.503-514
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• 2002

During the past two decades, primary pollutants in the ambient air have been substantially reduced in Korea by aggressive government efforts such as the switchover to clean fuels and equipment of automobiles with a three-way catalytic converter. However, visibility impairment in Seoul and major metropolitan areas has been a stubborn problem. It is apparent that both directly emitted fine particles mainly from vehicles and secondary fine particles from photochemical reactions could contribute to this visibility impairment. In addition, Korea is located downwind of the prevailing westerlies from China and is influenced by the emissions of air pollutants in China. In order to assess this complicated problem of visibility impairment, the visibility trends for the past 17 years observed at more than 60 stations throughout the country were analyzed. The results showed that visibilities were generally the lowest in the winter morning in comparison with those in the summer afternoon as well as the annual average values. It was believed that primary pollution was principally responsible for visibility impairment in most areas. The visibility in the summer afternoon was lower in clean coastal areas along with a high level of relative humidity due to the inflow of moist air accompanied by sea breeze. Although contributions of secondary particles from photochemical reactions and long-range transport of fine particles to the visibility impairment were probable, their certain evidences were not found.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.95-98
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• 2002

This paper presents a study on DSP(TMS320F240) controller design for multi-axes transportation system using BLDC servo motor. This BLDC servo motor controller was realized with DSP(Digital Signal Processor) and IPM (Intelligent Power Module). The multi-axes transportation system needs torque, speed, position control of servo motor for variable action. This paper implements those servo control with vector control and space vector modulation technique. As CPU of controller DSP(TMS320F240) is adopted because, it has PWM(Pulse Width Modulation) waveform generator, A/D(Analog to Digital) converter, SPI(Serial Peripheral Interface) port and input/output port etc. The controller of multi-axes transportation system consists of 3-level hierarchy structure that main host PC manages three sub DSP system which transfer downword command and are monitoring the states of end servo controllers. Each sub DSP system operates eight BLDC servo controllers which control BLDC servo motor using DSP and IPM Between host system and middle digital signal processor communicate with RS-422, between main processor and controller communicate with SPI port.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.323-324
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• 2013

This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multi-phase interleaved half-bridge topology. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is made up of three sub-interval operating modes; pre-charge mode, constant-current mode, and constant-voltage mode. The pre-charge mode employs the stair-case shaped current profile to accomplish shorter charging time while maintaining the reliable operation of the battery. The proposed system is specified to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 78A. Owing to the simple and compact power conversion scheme, the proposed solution has superior module-friendly mechanical structure which is absolutely required to realize flexible power expansion capability in a very high-current rapid charging system.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.429-430
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• 2017

본 논문은 Integrated Magnetics(IM)을 적용한 3-레벨 LLC 공진형 컨버터를 제안한다. 제안된 3-레벨 LLC 공진형 컨버터는 스위치 내압이 입력전압의 절반으로 보장되므로 스위칭 손실을 대폭 저감할 수 있어 고주파수 구동에 유리하다. 이에 따라 제안 회로는 리액티브 소자 저감에 유리하나, 회로 동작 상 2개의 공진 인덕터와 1개의 트랜스포머가 요구되는 단점이 있다. 이를 위해 본 논문에서는 자화 인덕터로 공진 인덕터를 대체하는 동시에 모든 자기 소자를 하나로 통합할 수 있는 새로운 IM을 제안하고 그 타당성 검증을 위해 인덕턴스 모델을 통한 이론적 분석과 350W-800kHz급 시작품 제작을 통한 실험결과를 제시한다.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.201-202
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• 2012

This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multi-phase interleaved half-bridge topology. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is made up of three sub-interval operating modes; pre-charging mode, constant-current mode, and constant-voltage mode. Each mode is operated according to battery states: voltage, current and State of Charging (SOC). The proposed system is able to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 67A. The optimal discharging algorithm for Vehicle to the Grid (V2G) operation has been adopted to maintain the discharging current of 1C. Owing to the simple and compact power conversion scheme, the proposed solution has superior module-friendly mechanical structure which is absolutely required to realize flexible power expansion capability in a very high-current rapid charging system. Experiment waveforms confirm the proposed functionality of the charging system.

• The KIPS Transactions:PartA
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• v.18A no.3
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• pp.109-114
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• 2011

We describe a technique for automatically proving compiler optimizations sound, meaning that their transformations are always semantics-preserving. As is well known, IR (Intermediate Representation) optimization is an important step in a compiler backend. But unfortunately, it is difficult to detect and debug the IR optimization errors for compiler developers. So, we introduce a C level error check system for detecting the correctness of these IR transformation techniques. In our system, we first create an IR-to-C converter to translate IR to C code before and after each compiler optimization phase, respectively, since our technique is based on the Memory Comparison-based Clone(MeCC) detector which is a tool of detecting semantic equivalency in C level. MeCC accepts only C codes as its input and it uses a path-sensitive semantic-based static analyzer to estimate the memory states at exit point of each procedure, and compares memory states to determine whether the procedures are equal or not. But MeCC cannot guarantee two semantic-equivalency codes always have 100% similarity or two codes with different semantics does not get the result of 100% similarity. To increase the reliability of the results, we describe a technique which comprises how to generate C codes in IR-to-C transformation phase and how to send the optimization information to MeCC to avoid the occurrence of these unexpected problems. Our methodology is illustrated by three familiar optimizations, dead code elimination, instruction scheduling and common sub-expression elimination and our experimental results show that the C level error check system is highly reliable.

• Korean Institute of Interior Design Journal
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• v.14 no.5 s.52
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• pp.254-261
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• 2005

This paper presents an attempt to develop a visual programming language-based 3D virtual reality authoring tool intended to compose virtual interior space. The rapid development of digital technology and the wide spread of the Intenet have expanded the different uses of virtual reality in a number of applications ranging from interior design to building maintenance. In particular, the construction of cyber spaces based on existing interior spaces is becoming increasingly important. Current research, however, remains at the level of converting 3D models into virtual reality models, despite practitioners' needs for structural space models. Moreover, commercial tools to build virtual reality space have the disadvantage of targeting people who have professional knowledge of computer programs and computer graphics. Accordingly, the 3D virtual reality authoring tool developed in this research - called the VESL system - enables virtual and structural space to be easily composed using intuitive and interactive visual interfaces, which are based on visual programming techniques. The VESL system also provides an XML based semantic description of interior space, to be used to describe interior space information. We anticipate that the virtual reality spaces composed by this system will be of considerable use in the fields of architecture and interior design. Further research issues identified at the end of the research include developing a converter/filter for transforming Internet virtual reality standard language, or VRML, and evaluating the application of the system for practical use.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.5
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• pp.1095-1101
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• 2012

This paper presents a design of a BLDC servo motor control system for the auto process of assembly and supply using DSP(Digital Signal Processor) controller and IGBT driver. The assembly and supply auto processing system needs torque, speed, position control of servo motor for variable action. This paper implements those servo control with vector control and space vector PWM(Pulse Width Modulation) technique. As CPU of controller, TMS320F240 DSP was adopted because it has PWM waveform generator, A/D converter, SPI(Serial Peripheral Interface) port and many input/output port etc. This control system consists of 3-level hierarchy structure that main host PC manages three sub DSP system which transfer downward command and are monitoring the states of end servo controllers. Each sub DSP system operates eight BLDC servo controllers which control BLDC motor using DSP and IPM. Between host system and sub DSP communicate with RS-422, between main processor and controller communicate with SPI port.

• Journal of Korea Soil Environment Society
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• v.3 no.2
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• pp.89-99
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• 1998

Sorption of the aqueous cyanide onto steel mill sludge and steel mill slag, both of which are the by-products from the converter furnace, was studied. In the study, the influence of temperature, activation energy, concentration and pH on sorption of cyanide was investigated. Three different temperature($25^{\circ}C$ > $37^{\circ}C$> $50^{\circ}C$) was chosen to represent that of landfill leachate. Initial concentration was 1 mg/$\ell$ 5 mg/$\ell$, 10 mg/$\ell$, and 20 mg/$\ell$. In addition, pH was set to three different level, that is, 3, 7, and 11 respectively. As the result of batch mode experiment for cyanide adsorption, the removal rate was found to be proportional to the initial concentration of cyanide. The order of removal rate was 20 mg/$\ell$> 10 mg/$\ell$> 5 mg/$\ell$> 1 mg/$\ell$. Similarly the influence of pH was proportional because of the change in solubility of cyanide. The order of removal rate was pH 11 > pH 7 > pH 3. As the temperature increased, so did the removal rate. The reaction was endothermic and the value of activation energy(Ea) was 127.93 J/mole and 59.44 J/mole respectively at 1 mg/ιand 20 mg/ιof initial concentration. From the experiment, it can be postulated that the capability of steel mill by-products to attenuate aqueous cyanide is enough to be used as substitute for clay liner of landfill site in the aspect of pollutant removal.