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Leg-Balancing Control of the DC-link Voltage for Modular Multilevel Converters
Sixing Du,Jinjun Liu,Jiliang Lin 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.5
This paper applies carrier phase shifted pulse-width modulation (CPS-PWM) to transformerless modular multilevel converters (MMC) to improve the output spectrum. Because the MMC topology is characterized by the double-star connection of six legs consisting of cascaded modular chopper cells with floating capacitors, the balance control of the DC-link capacitor voltage is essential for safe operation. This paper presents a leg-balancing control strategy to achieve DC-link voltage balance under all operating conditions. This strategy based on circulating current decoupling control focused on DC-link balancing between the upper and lower legs in each phase pair by considering the six legs as three independent phase-pairs. Experiments are implemented on a 100-V 3-kVA downscaled prototype. The experimental results show that the proposed leg-balancing control is both effective and practical.
Leg-Balancing Control of the DC-link Voltage for Modular Multilevel Converters
Du, Sixing,Liu, Jinjun,Lin, Jiliang The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.5
This paper applies carrier phase shifted pulse-width modulation (CPS-PWM) to transformerless modular multilevel converters (MMC) to improve the output spectrum. Because the MMC topology is characterized by the double-star connection of six legs consisting of cascaded modular chopper cells with floating capacitors, the balance control of the DC-link capacitor voltage is essential for safe operation. This paper presents a leg-balancing control strategy to achieve DC-link voltage balance under all operating conditions. This strategy based on circulating current decoupling control focused on DC-link balancing between the upper and lower legs in each phase pair by considering the six legs as three independent phase-pairs. Experiments are implemented on a 100-V 3-kVA downscaled prototype. The experimental results show that the proposed leg-balancing control is both effective and practical.
A PDPWM Based DC Capacitor Voltage Control Method for Modular Multilevel Converters
Sixing Du,Jinjun Liu,Teng Liu 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.3
This paper presents a control scheme with a focus on the combination of phase disposition pulse width modulation (PDPWM) and DC capacitor voltage control for a chopper-cell based modular multilevel converter (MMC) for the purpose of eliminating the time-consuming voltage sorting algorithm and complex voltage balancing regulators. In this paper, the convergence of the DC capacitor voltages within one arm is realized by charging the minimum voltage module and discharging the maximum voltage module during each switching cycle with the assistances of MAX/MIN capacitor voltage detection and PDPWM signals exchanging. The process of voltage balancing control introduces no extra switching commutation, which is helpful in reducing power loss and improving system efficiency. Additionally, the proposed control scheme also possess the merit of a simple executing procedure in application. Simulation and experimental results indicates that the MMC circuit together with the proposed method functions very well in balancing the DC capacitor voltage and improving system efficiency even under transient states.
A PDPWM Based DC Capacitor Voltage Control Method for Modular Multilevel Converters
Du, Sixing,Liu, Jinjun,Liu, Teng The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.3
This paper presents a control scheme with a focus on the combination of phase disposition pulse width modulation (PDPWM) and DC capacitor voltage control for a chopper-cell based modular multilevel converter (MMC) for the purpose of eliminating the time-consuming voltage sorting algorithm and complex voltage balancing regulators. In this paper, the convergence of the DC capacitor voltages within one arm is realized by charging the minimum voltage module and discharging the maximum voltage module during each switching cycle with the assistances of MAX/MIN capacitor voltage detection and PDPWM signals exchanging. The process of voltage balancing control introduces no extra switching commutation, which is helpful in reducing power loss and improving system efficiency. Additionally, the proposed control scheme also possess the merit of a simple executing procedure in application. Simulation and experimental results indicates that the MMC circuit together with the proposed method functions very well in balancing the DC capacitor voltage and improving system efficiency even under transient states.
U-러닝 환경에서 컴퓨터 교육을 위한 교과 교수·학습 모형 개발
정민식 ( Min-six Jung ),김혜민 ( Hye-min Kim ),이윤배 ( Yun-bae Lee ) 한국정보처리학회 2009 한국정보처리학회 학술대회논문집 Vol.16 No.1
정보 통신 기술의 발달은 전산화, 정보화, 지식 정보화 과정을 거쳐 현재 차세대 패더다임인 유비쿼터스화 단계에 이르렀다. 시간과 장소에 구애받지 않고 언제 어디서나 창의적이고 효율적인 학습자 중심의 교육환경을 제공할 수 있는 u-러닝 기술은 7차 교육과정 수행과 함께 필수적인 요소로 부각되고 있다. 최근 교육과정이 u-러닝 환경으로의 변화에 따라 교수․ 학습 체계역시 변화가 예상된다. 그리고 ICT를 활용한 교수·학습 모형과 교과별 콘텐츠에 대한 개발이 활발한 이유도 현재 u-러닝이 적극 추진되면서 교육환경에 대한 새로운 요구와 필요성이 증대되고 있기 때문이다. 따라서 교육환경인 u-러닝 시대에 맞추어 교과목에 대한 교수-학습 모형 연구가 이루어 져야 할 것이다. 본 연구에서는 선행 연구된 학습모형을 비교, 분석하여 유비쿼터스와 u-러닝에 대한 특성과 기능, 유비쿼터스 컴퓨팅 기술에 대해 고찰한다. 그리고 기존 컴퓨터 교과 분석을 통하여 컴퓨터교과의 중요성과 교육방법 영역, 컴퓨터교과 교수-학습 모형에 대한 연구를 통해 u-러닝 환경에서의 컴퓨터 교육을 위한 프로젝트 기반 교수-학습 모형을 설계하고 구현한다.
崔四行(Cui, Sixing) 한국중국어교육학회 2008 중국어교육과연구 Vol.0 No.8
The Korean students are used to making pronunciation mistakes when learning Chinese, This article is trying to analyze these mistakes from the historical points, and hopes to instruct the Chinese teaching.
崔四行(Cui, Sixing) 한국중국어교육학회 2008 중국어교육과연구 Vol.0 No.7
This paper aims to illustrate the similarities of the initials between modern Korean Chinese characters and medieval Chinese. Korean and Chinese are very different two languages, however, there is a systematic relation in the initials between modern Korean Chinese characters and medieval Chinese, and this paper will provide some evidences for this attractive phenomenon based on the research of medieval Chinese.