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RISS 인기검색어
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- 저자 : Jingwei Meng (검색결과 3 건)
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On Probability Distribution of Chloride Diffusion Coefficient for Recycled Aggregate Concrete
Jingwei Ying,Jianzhuang Xiao,Qiujiang Meng 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.1
In predicating the probability distribution of chloride diffusion coefficient of recycled aggregate concrete (DRAC), the morphological characteristics of three phases, i.e., the old attached mortar, the natural aggregate and the new mortar, should all be taken into account. The present paper attempts to develop a probability density evolution method (PDEM) to achieve this. After verifying the derived PDEM results with experimental results, the effects of old attached mortar to the DRAC are examined in a quantitative manner. It is found that (1) the variation of the attached mortar content is much sensitive to DRAC; (2) given the probability distribution of the content and chloride diffusion coefficient of old mortar, the probability distribution of DRAC can be analysed based on the PDEM; and (3) the critical chloride diffusion coefficient at a certain assurance rate can be obtained by the PDEM. The analysis results of this investigation will be valuable to the durability design for RAC.
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Analysis of submodule capacitor overvoltage during DC-side fault in hybrid MMC-based HVDC system
Yunbeom Gim,Zhengxuan Li,Jingwei Meng,Zexi Deng,Qiang Song 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
The hybrid modular multilevel converter (MMC) consisting of half-bridge submodules (HBSMs) and full-bridge submodules (FBSMs) is one of the promising converter topologies for HVDC system, due to its fault blocking capability without applying circuit breakers and relatively lower cost compared with FBSM-MMC. However, the energy stored in the lines will cause an overvoltage in the capacitor voltages of the FBSMs. This overvoltage is significant especially when the HVDC system contains long distance transmission lines. The capacitor overvoltage can threat the safe operation of the system and the lifetime of the components, and therefore shall be appropriately regulated. This work analyzes the DC fault current blocking process of a hybrid MMC based HVDC system, determines the major factors which influence the capacitor overvoltage, and proposes corresponding mitigation measures. The simulation results of a two-terminal HVDC system on PSCAD/EMTDC with various test conditions are presented to validate the proposed analysis.
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Jing Wei,Ruizhi Shu,Datong Qin,Teik C. Lim,Aiqiang Zhang,Fanming Meng 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.9
Multi-source driving transmission systems, in which the gear assembly is driven by multiple induction motors, are extensively used in new energy, aerospace, marine engineering, and in other fields. The multi-source driving system faces an even-load distribution problem, i.e., torque or speed synchronization issues. In this study, the synchronization characteristics of a multi-source driving transmission system under an impact load at different load change rates are studied. An accurate electromechanical coupling dynamic model of the system considering the flexible shafts, support bearing and meshing gear pair is established by applying virtual equivalent shaft elements. By considering the time-varying meshing and the coupling effects of the dynamic electric motor and the speed, torque and stator current synchronization characteristics are investigated using this model. Computational results show that the influence of the load change rate on the speed synchronization characteristics of the system is minor, but has a significant influence on the torque and stator current synchronization characteristics. The stator current root mean square value (RMS) can be chosen as a feedback signal to monitor the synchronization characteristics of the system. The proposed research provides the theoretical basis for the formulation of the synchronization control strategy for multi-source driving transmission systems.
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