Modulation method of parallel interleaved three‑level inverter considering neutral point potential and phase current balance

Ying Zhong,Weichao Li,Liang Zhou,Chen Deng,Jinyang Han 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.2

The capacity and equivalent switching frequency of parallel interleaved inverters can be increased, but there are problems with neutral point potential balance and parallel bridge circulating current. This paper regards the parallel three-level inverter as a five-level inverter and five-level space vector integrated modulation is applied. On this basis, a neutral-point potential control strategy based on the mid-point charge to calculate the adjustment factor k is proposed. By further meticulously partitioning specific sector regions, the selection method of redundant vectors in the switching sequence is optimized without increasing the switching times, and the midpoint voltage ripple is reduced. Then, the redundant state allocation in the process of splitting the five-level into three-level is used as a new degree of freedom to suppress the circulating current of the parallel bridge, therefore realizing the control of voltage and current sharing. Finally, simulation and experiments verify the correctness and effectiveness of the method.

Hybrid varied virtual vector modulation method of parallel three‑level inverter considering neutral point potential and phase current balance

Ying Zhong,Weichao Li,Liang Zhou,Chen Deng,Ming Yan 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.7

The shift and low-frequency oscillations of neutral point potential are key issues in the neutral point clamped (NPC) inverter. The space vector pulse width modulation (SVPWM) algorithm has limited voltage balancing ability at high modulation levels and low power factors. The virtual SVPWM can achieve midpoint potential balance across the entire range, but it has the problem of multiple switching times and poor harmonic characteristics. Parallel three-level NPC inverters can increase the power rating and efficiency of systems, thus being suitable for high-power applications. However, their parallel topology also brings current sharing issues. This paper fi rst proposes several methods of combining varied virtual middle vectors based on fi ve-level vectors, which control the midpoint current by adjusting the action time of the basic vector. Second, different virtual vector combinations are used for voltage commands with different modulation indexes to reduce the switching frequency of the inverter and the synthesis vector error. The proposed hybrid method has fewer switching times, reduces the amplitude of midpoint voltage fl uctuation, and has good harmonic characteristics of output current. Finally, the feasibility and effectiveness of the hybrid method are verifi ed through simulation and experiments.

An approach to automatic boundary segmentation of solid models using virtual topology: toward reconstruction of design features

Yingzhong Zhang,Yufei Fu,Jia Jia,Xiaofang Luo 한국CDE학회 2020 Journal of computational design and engineering Vol.7 No.3

Boundary segmentation of solid models is the geometric foundation to reconstruct design features. In this paper, based on the shape evolution analysis for the feature-based modeling process, a novel approach to the automatic boundary segmentation of solid models for reconstructing design features is proposed. The presented approach simulates the designer’s decomposing thinking on how to decompose an existing boundary representation model into a set of design features. First, the modeling traces of design features are formally represented as a set of feature vertex adjacent graphs that use low-dimensional vertex entities and their connection relations. Then, a set of Boolean segmentation loops is searched and extracted from the constructed feature vertex adjacent graphs, which segment the boundary of a solid model into a set of regions with different design feature semantics. In the search process, virtual topology operations are employed to simulate the topological changes resulting from Boolean operations in feature modeling processes. In addition, to realize effective search, search strategies and search algorithms are presented. The segmentation experiments and case study show that the presented approach is feasible and effective for the boundary segmentation of medium-level complex part models. The presented approach lays the foundation for the later reconstruction of design features.

Synthesis, characterization and luminescence study of dimethyl[N-arylmethylenethiobenzahydrazonato]indium

Yingzhong Shen,Xiaoyan Wang,Sen Xu,Hulin Li 한국물리학회 2007 Current Applied Physics Vol.7 No.1

2InL [L= N-(4-methoxy)benzylidenethiobenzahydrazonato (1),N-(3,4-dimethoxy)benzyl-idenethiobenzahydrazonato (2),N-(4-N,N-dimethylamino)benzylidenethiobenzahydrazonato (3),N-(2-naphthyl)methylene thiobenza-hydrazonato (4) and N-(9-anthryl)methylenethiobenzahydrazonato (5)] have been synthesized by reaction of trimethylindium withappropriateN-arylmethylenethiobenzahydrozones. The complexes obtained have been characterized by elemental analysis,1H NMR,IR and mass spectroscopy. Compounds15 emit blue colors atkmax = 432479 nm when irradiated by UV light. The electroluminescent(EL) properties of15 were examined by fabricating EL devices using15 region (513578 nm).

Molecular Cloning of Hemoglobin Alpha-chain Gene from Pantholops hodgsonii, a Hypoxic Tolerance Species

Yingzhong, Yang,Droma, Yunden,Guoen, Jin,Zhenzhong, Bai,Lan, Ma,Haixia, Yun,Yue, Cao,Kubo, Keishi,Rili, Ge Korean Society for Biochemistry and Molecular Biol 2007 Journal of biochemistry and molecular biology Vol.40 No.3

To investigate the possible mechanisms of high-altitude native animals in adapting to high altitude, we cloned hemoglobin alpha-chain (alpha-chain Hb) gene from Pantholops hodgsonii, an animal species that indigenously lives at elevations of 3700-5500 m on the Qinghai-Tibetan plateau. Using reverse transcription polymerase chain reaction (RT-PCR) technique, the alpha-chain Hb gene was amplified from total RNA in the liver of the Pantholops hodgsonii. TA cloning technique was used and the PCR product was cloned into pGEM-T vector. The DNA sequence of the gene was highly homologous with sheep (99.1%), goat (98.6%), cattle (95.6%) and human (86.5%). The alpha-chain Hb gene encoded a 142-amino acid protein that could be identified with the homology of alpha-chain Hb protein in sheep (98%), goat (96%), cattle (91%) and human (87%). However, 18 alternations were detected when compared with the alpha-chain Hb gene in human, and 2 in sheep. Moreover, the alterations of a117 GluAsp and $\alpha$132 AsnSer in important regions were noted in human and sheep, respectively. Phylogenetic analysis suggested that the structure of alpha-chain Hb was highly similar to that in sheep. This study provided essential information for elucidating the possible roles of hemoglobin in adapting to extremely high altitude in Pantholops hodgsonii.

Influencing factor analysis of water invasion in condensate gas reservoir with bottom water based on fuzzy comprehensive evaluation and orthogonal experiment

Wende Yan,Zhilin Qi,Yingzhong Yuan,Xiaoliang Huang,Jiqiang Li 한국자원공학회 2019 Geosystem engineering Vol.22 No.6

Condensate oil and water invasion coexist in the condensate gas reservoir with bottom water. Because of influences of condensate oil pollution and water invasion, gas recovery obviously decreases. There are many factors influencing water invasion in a condensate gas reservoir with bottom water, including static petrophysical properties and dynamic operational conditions. Various factors play different roles in the process of water invasion, and the comprehensive effects of them on water invasion are difficult to be determined because these factors interfere with each other. With gas reservoir engineering method and numerical simulation technology, the factors including acuifer size, height of water avoidance, permeability, effective gas pay thickness, condensate oil saturation and gas well production rate on water invasion are researched. Water breakthrough time, stable production period and gas recovery are calculated for different cases under different parameter combinations through fuzzy comprehensive evaluation and orthogonal experiment design. Then sensitivities of these factors are analyzed and main factors influencing water invasion are selected and sequenced. The research supply theoretical basis for preventing and controlling water invasion thus improves development effect of condensate gas reservoir with bottom water.