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- 저자 : Zhangqi Liu (검색결과 2 건)
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Weiliang Wu,Xiping Liu,Jianwei Liang,Zhangqi Liu,Chaozhi Huang 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.3
Medium- and high-voltage motors are characterized by high power and large inertia, and are widely used in industrial frequency conversion. The cascaded H-bridge multilevel (CHB-ML) inverter adopts a modular design concept to realize high-voltage and high-power functions by cascading multiple identical low-voltage conversion units. Moreover, the harmonic content of the output current of the inverter is small. For this purpose, a multilevel inverter consisting of eight H-bridge inverter units cascaded in each phase is introduced to drive medium- and high-voltage asynchronous motors for starting and frequency regulation. The carrier phase-shifted sinusoidal pulse-width modulation technique, DC voltage equalization control of power unit, and speed sensorless vector control strategy based on a voltage–current hybrid chain observer are mainly introduced. The simulation and experimental results of the real-time digital simulation system (RTDS) of the asynchronous motor dragged by the inverter verify that the CHB-ML inverter with the proposed control strategy has good starting and frequency regulation performance. These findings provide a technical guarantee for the field of medium- and high-voltage high-power drives.
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Zhang, Qi,Zhu, Huan,Hu, Zhengyu,Liu, Guoxiang The Korean Society of Phycology 2016 ALGAE Vol.31 No.3
Freshwater red tides due to dinoflagellates have caused spectacular and regular “summer reddening” in recent years in Baishihai Lake, a temperate, meromictic, meso- or oligotrophic, high-altitude, landslide-dammed, deep lake located at the eastern edge of Tibetan Plateau in China. Based on morphological and molecular analyses, the causative organism has been identified as a new woloszynskioid dinoflagellate, Tovellia diexiensis Q. Zhang et G. X. Liu sp. nov. The vegetative cells are 20-32 μm long and 16-24 μm wide. They have a hemispherical episome and a broadly rounded hyposome with a short characteristic antapical spine. Usually cells are bright red due to the presence of numerous red-pigmented bodies, which often masked the yellowish green discoid chloroplasts. The amphiesma of motile cells comprise mainly quadrilateral, pentagonal or hexagonal thin plates, arranged in 4-5 latitudinal series on the episome, 1 in the cingulum and 4 on the hyposome. Molecular phylogenies based on small subunit ribosomal DNA and large subunit ribosomal DNA (LSU) indicate T. diexiensis from Baishihai Lake to belong to the family Tovelliaceae, which was monophyletic in our LSU phylogenies. During the bloom-forming period in 2005, cell density of T. diexiensis reached 9.15 × 10<sup>5</sup> cells L<sup>−1</sup>. Astaxanthin and its diester were found to be the major pigments in T. diexiensis, resulting in a characteristic blood-red color of the water in Baishihai Lake.
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