Transformer balancing winding technology with effective shielding for suppressing common mode noise in flyback converters

Wenxiang He,Fannie Kong,Zhenmin Wang,Yanming Chen 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.8

The main methods for suppressing the common mode (CM) noise in flyback converters include adding a shielding layer and adding a balancing winding. To combine the advantages of both methods, a balancing winding with a shielding effect is proposed to suppress CM noise. First, the CM noise transmission path of a flyback converter is analyzed, and an equivalent model of CM noise is established. Then, combined with the CM noise characteristics of the flyback converter, the design criteria for the shielding-balancing winding are given. Finally, experiments are conducted on a flyback converter prototype. The CM noise spectra of four transformer structures (without a shielding layer, with a traditional copper foil shielding layer added, with a balancing winding and with the proposed shielding-balancing winding) are compared. The results show that the CM noise of the flyback converter can be effectively suppressed by adding the shielding-balancing winding proposed in this paper. In addition, the effectiveness of the proposed method is verified.

Low-Cost SVM-DTC Strategy of Induction Machine Drives Using Single DC-link Current Sensor

Wang, Wei,Cheng, Ming,Hua, Wei,Ding, Shichuan,Zhu, Ying,Zhao, Wenxiang Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.3

In conventional direct torque control (DTC) using space-vector modulation (SVM) of induction machine (IM) drives, at least three current sensors are needed. In this paper, a low-cost SVM-DTC strategy is proposed, in which only a single current sensor is used. The position of the voltage space vector is divided into two areas: effective and non-effective area. If it is located in the non-effective area, the voltage space vector will be shifted into the effective area with minimum distortion. Further, the switching frequency remains constant. The simulation is carried out on a MATLAB/Simulink platform and the simulated results verify the effectiveness of the proposed strategy.

Subsection Synchronous Current Harmonic Minimum Pulse Width Modulation for ANPC-5L Inverter

Jiuyi Feng,Wenxiang Song,Yuan Xu,Fei Wang 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

Medium voltage drive systems driven by high-power multi-level inverters operating at low switching frequency can reduce the switching losses of the power device and increase the output power. Employing subsection synchronous current harmonic minimum pulse width modulation (CHMPWM) technique can maintain the total harmonic distortion of current at a very low level. It can also reduce the losses of the system, improve the system control performance and increase the efficiency of DC-link voltage accordingly. This paper proposes a subsection synchronous CHMPWM approach of active neutral point clamped five-level (ANPC-5L) inverter under low switching frequency operation. The subsection synchronous scheme is obtained by theoretical calculation based on the allowed maximum switching frequency. The genetic algorithm (GA) is adopted to get the highprecision initial values. So the expected switching angles can be achieved with the help of sequential quadratic programming (SQP) algorithm. The selection principle of multiple sets of the switching angles is also presented. Finally, the validity of the theoretical analysis and the superiority of the CHMPWM are verified through both the simulation results and experimental results.

Synthesis and Properties of Self-healing Metallopolymers with 5-Vinyltetrazole Units and Zn(II)

Mifa Chen,Wenxiang Wang,Hou Chen,Liangjiu Bai,Zhongxin Xue,Donglei Wei,Huawei Yang,Yuzhong Niu 한국고분자학회 2019 Macromolecular Research Vol.27 No.1

The development of reversible and efficient self-healing materials symbolizes an emerging and challenging task in intelligent materials science. In this paper, a facile one-pot and two-step methodology was developed for the preparation of polyacrylonitrile-r-poly(butyl acrylate) (PAN-r-PnBA) and its subsequent modification. Zinc chloride (ZnCl2) was used as a catalyst to modify cyano groups and generate tetrazole groups of PAN-r-PnBA. Simultaneously, ZnCl2 effectively coordinates with the generated tetrazole group for highly self-healing performance. It was demonstrated that the metallopolymers (MPs) exhibited excellent self-healing properties at ambient temperature. The prepared tetrazole-based MPs can be used as a wide range of self-healing materials.

Model-free kinetics applied to an oxidation mechanism of a biomorphic carbon template derived from pine

Pengzhao Gao,Wenxiang Wang,Weiei Gong 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.4

A biomorphic carbon template (BCT) was developed by carbonizing pine under vacuum. Structural and oxidation properties of BCT were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). Experimental results show that BCT has a topologically uniform interconnected porous network microstructure, and is typical non-graphitizable carbon containing C =C bonds, C–O–C bonds and a C–H structure. The non-isothermal oxidation properties of BCT exhibit a partially self-accelerating characteristic; the oxidation process of BCT is firstly controlled by a chemical reaction, and then controlled by a chemical reaction and gas diffusion together, which is obtained from a Vyazovkin model-free method, and the corresponding activation energy (E a) is also calculated.

Adsorption Behaviors of As (III) from Aqueous Solutions on Ferric Hydroxide

Jincheng Li,Wenxiang Xia,Jie Li, Wei li,Xingchuan Xiao,Zhenxia Wang,Peng Li 한국도시환경학회 2010 한국도시환경학회지 Vol.10 No.2

Influence of temperature on the carbonization context, oxidation properties and mechanism of a porous biomorphic carbon template

Pengzhao Gao,Pengfei Hu,Wenxiang Wang,Weiwei Gong 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.3

A porous biomorphic carbon template (BCT) was prepared using a carbonized native aspen under an Ar atmosphere. Microstructural properties of the BCT were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Non-isothermal oxidation properties and the mechanism of the BCT formation were studied by thermogravimetric analysis (TGA). Experimental results show that microstructure of the BCT exhibits a honeycomb interconnected porous network and double-peaked distribution of pore diameters. The BCT phase belongs to amorphous carbon, with an increase of the carbonization temperature, the (002) peak of the XRD spectrum becomes stronger, the interplanar spacing decrease, and the structure of BCT slowly evolved towards that of ideal graphite. The non-isothermal oxidation process of BCT is controlled by a chemical reaction and gas diffusion together, and the two stages have different influences on the whole reaction rate with an increase of the conversion (a). The corresponding activation energy (E a) is also calculated.

Subsection Synchronous Current Harmonic Minimum Pulse Width Modulation for ANPC-5L Inverter

Feng, Jiuyi,Song, Wenxiang,Xu, Yuan,Wang, Fei The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.5

Medium voltage drive systems driven by high-power multi-level inverters operating at low switching frequency can reduce the switching losses of the power device and increase the output power. Employing subsection synchronous current harmonic minimum pulse width modulation (CHMPWM) technique can maintain the total harmonic distortion of current at a very low level. It can also reduce the losses of the system, improve the system control performance and increase the efficiency of DC-link voltage accordingly. This paper proposes a subsection synchronous CHMPWM approach of active neutral point clamped five-level (ANPC-5L) inverter under low switching frequency operation. The subsection synchronous scheme is obtained by theoretical calculation based on the allowed maximum switching frequency. The genetic algorithm (GA) is adopted to get the high-precision initial values. So the expected switching angles can be achieved with the help of sequential quadratic programming (SQP) algorithm. The selection principle of multiple sets of the switching angles is also presented. Finally, the validity of the theoretical analysis and the superiority of the CHMPWM are verified through both the simulation results and experimental results.

Investigation on a W Band Ridge-Loaded Folded Waveguide TWT

Jun He,Yanyu Wei,Yubin Gong,Wenxiang Wang,Gun-Sik Park IEEE 2011 IEEE transactions on plasma science Vol.39 No.8

<P>A W-band ridge-loaded folded waveguide traveling-wave tube (FWTWT) is modeled, and the nonlinear interaction between the electron beam and the electromagnetic field is investigated by utilizing a 3-D particle-in-cell (PIC) code, MAGIC. The process of beam-wave interaction for millimeter wave TWT is presented, including the longitudinal momentum of the electron, the averaged radiation power, and the influence of input power on output power. Compared with the conventional FWTWT at 95 GHz, the ridge-loaded FWTWT obtains a 29.3% higher output power and shortens 31.7% interaction distance. The radiation power and the gain of TWT are raised up in most of the working band covering from 85 to 97 GHz, indicating effectual enhancement of beam-wave interaction by loading ridge. Furthermore, the novel FWTWT works in 7-GHz bandwidth with output power varying only 1 dB throughout the band.</P>

Variations in bacterial and fungal communities through soil depth profiles in a Betula albosinensis forest

Can Du,Zengchao Geng,Qiang Wang,Tongtong Zhang,Wenxiang He,Lin Hou,Yueling Wang 한국미생물학회 2017 The journal of microbiology Vol.55 No.9

Microbial communities in subsurface soil are specialized for their environment, which is distinct from that of the surface communities. However, little is known about the microbial communities (bacteria and fungi) that exist in the deeper soil horizons. Vertical changes in microbial alpha-diversity (Chao1 and Shannon indices) and community composition were investigated at four soil depths (0–10, 10–20, 20–40, and 40–60 cm) in a natural secondary forest of Betula albosinensis by high-throughput sequencing of the 16S and internal transcribed spacer rDNA regions. The numbers of operational taxonomic units (OTUs), and the Chao1 and Shannon indices decreased in the deeper soil layers. Each soil layer contained both mutual and specific OTUs. In the 40–60 cm soil layer, 175 and 235 specific bacterial and fungal OTUs were identified, respectively. Acidobacteria was the most dominant bacterial group in all four soil layers, but reached its maximum at 40–60 cm (62.88%). In particular, the 40–60 cm soil layer typically showed the highest abundance of the fungal genus Inocybe (47.46%). The Chao1 and Shannon indices were significantly correlated with the soil organic carbon content. Redundancy analysis indicated that the bacterial communities were closely correlated with soil organic carbon content (P = 0.001). Collectively, these results indicate that soil nutrients alter the microbial diversity and relative abundance and affect the microbial composition.