Phase-Shift Triple Full-Bridge ZVZCS Converter with All Soft Switched Devices

Junjie Zhu,Qinsong Qian,Shengli Lu,Weifeng Sun 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.6

This paper proposes a Phase-Shift Triple Full-Bridge (PSTB) Zero-Voltage Zero-Current-Switching (ZVZCS) converter with a high switching frequency and high efficiency. In the proposed converter, all three bridge legs are shared leading-legs, and all three transformers work in the Discontinuous Conduction Mode (DCM). Thus, all of the switches and diodes in the PSTB ZVZCS can be soft switched. Moreover, since all of the transformers can pass energy from the primary-side to the secondary- side when their primary-side currents are not zero, there is no circulating current. As a result, the PSTB ZVZCS converter can achieve a high efficiency at high operating frequencies. A theoretical analysis and the characteristics of the proposed converter are presented and verified on a 1MHz 200~300V/24V 1.2kW hardware prototype. The proposed converter can reach a peak efficiency of 96.6%.

Influence of Device Parameters Spread on Current Distribution of Paralleled Silicon Carbide MOSFETs

Junji Ke,Zhibin Zhao,Peng Sun,Huazhen Huang,James Abuogo,Xiang Cui 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

This paper systematically investigates the influence of device parameters spread on the current distribution of paralleledsilicon carbide (SiC) MOSFETs. First, a variation coefficient is introduced and used as the evaluating norm for the parametersspread. Then a sample of 30 SiC MOSFET devices from the same batch of a well-known company is selected and tested underthe same conditions as those on datasheet. It is found that there is big difference among parameters spread. Furthermore,comprehensive theoretical and simulation analyses are carried out to study the sensitivity of the current imbalance to variationsof the device parameters. Based on the concept of the control variable method, the influence of each device parameter on thesteady-state and transient current distributions of paralleled SiC MOSFETs are verified separately by experiments. Finally, somescreening suggestions of devices or chips before parallel-connection are provided in terms of different applications and differentdriver configurations.

여자태권도 선수의 체지방 추정에 관한 연구

稻田俊治,강관희,선우진 한국스포츠리서치 2003 한국 스포츠 리서치 Vol.14 No.1

In order to product the equation for estimation body fat using the circumference and skinfold methods, twenty healthy female T.K.D. player university subjects were participated in this experiments. The results obtained in this study are summarized as followed. 1. Body density and %fat determined by underwater weighting method was 1.0493± 0.0089 and 16.4 ±3.7 respectively. 2. Body circumferences which presented the hightest correlation with the underwater weighting was abodominal (r=0.728, P<0.001) and hip (r=0.573, P<0.001) CIRCUMFERENCE. 3. Skinfold which presented the hightest correlation with the underwater weighting was abdominal (r=0.027, P<0.01), subscapular (r=0.547, P<0.01) and Pectoralis major (r=0.547, P<0.01) CIRCUMFERENCE.

Influence of Device Parameters Spread on Current Distribution of Paralleled Silicon Carbide MOSFETs

Ke, Junji,Zhao, Zhibin,Sun, Peng,Huang, Huazhen,Abuogo, James,Cui, Xiang The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

This paper systematically investigates the influence of device parameters spread on the current distribution of paralleled silicon carbide (SiC) MOSFETs. First, a variation coefficient is introduced and used as the evaluating norm for the parameters spread. Then a sample of 30 SiC MOSFET devices from the same batch of a well-known company is selected and tested under the same conditions as those on datasheet. It is found that there is big difference among parameters spread. Furthermore, comprehensive theoretical and simulation analyses are carried out to study the sensitivity of the current imbalance to variations of the device parameters. Based on the concept of the control variable method, the influence of each device parameter on the steady-state and transient current distributions of paralleled SiC MOSFETs are verified separately by experiments. Finally, some screening suggestions of devices or chips before parallel-connection are provided in terms of different applications and different driver configurations.

Phase-Shift Triple Full-Bridge ZVZCS Converter with All Soft Switched Devices

Zhu, Junjie,Qian, Qinsong,Lu, Shengli,Sun, Weifeng The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.6

This paper proposes a Phase-Shift Triple Full-Bridge (PSTB) Zero-Voltage Zero-Current-Switching (ZVZCS) converter with a high switching frequency and high efficiency. In the proposed converter, all three bridge legs are shared leading-legs, and all three transformers work in the Discontinuous Conduction Mode (DCM). Thus, all of the switches and diodes in the PSTB ZVZCS can be soft switched. Moreover, since all of the transformers can pass energy from the primary-side to the secondary-side when their primary-side currents are not zero, there is no circulating current. As a result, the PSTB ZVZCS converter can achieve a high efficiency at high operating frequencies. A theoretical analysis and the characteristics of the proposed converter are presented and verified on a 1MHz 200~300V/24V 1.2kW hardware prototype. The proposed converter can reach a peak efficiency of 96.6%.

Capacitor commutation type DC circuit breaker with fault character discrimination capability

Yao Sun,Yanfang Fan,Junjie Hou 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.6

Flexible direct current (DC) grids face a serious challenge in terms of rapidly isolating DC faults. A DC circuit breaker is an effective solution for DC fault isolation. To improve the fault-isolation and reclosing capability of fl exible DC systems, a new high voltage direct current (HVDC) circuit breaker topology with adaptive reclosing capability is proposed in this paper. The topology of the circuit breaker is a T-shaped structure, which has the ability to break the current in both directions and effectively reduce the cost of components. Meanwhile, after the fault is cleared, the circuit breaker is controlled to inject a voltage signal into the line. Based on this, to prevent the circuit breaker reclosing in the event of a permanent fault from having an impact on the system, a method for fault identification based on Euclidean distance that uses the voltage signal to identify the fault properties is proposed. Finally, the performance of the circuit breaker is simulated and verified by PSCAD/EMTDC simulation software, and compared with the typical existing circuit breakers to verify the effectiveness of the circuit breaker and reclosing scheme.

Functional Reconstitution of Cellulose Synthase in <i>Escherichia coli</i>

Imai, Tomoya,Sun, Shi-jing,Horikawa, Yoshiki,Wada, Masahisa,Sugiyama, Junji American Chemical Society 2014 Biomacromolecules Vol.15 No.11

<P>Cellulose is a high molecular weight polysaccharide of β1 → 4-<SMALL>d</SMALL>-glucan widely distributed in naturefrom plant cell walls to extracellular polysaccharide in bacteria. Cellulose synthase, together with other auxiliary subunit(s) in the cell membrane, facilitates the fibrillar assembly of cellulose polymer chains into a microfibril. The gene encoding the catalytic subunit of cellulose synthase is <I>cesA</I> and has been identified in many cellulose-producing organisms. Very few studies, however, have shown that recombinant CesA protein synthesizes cellulose polymer, but the mechanism by which CesA protein synthesizes cellulose microfibrils is not known. Here we show that cellulose-synthesizing activity is successfully reconstituted in <I>Escherichia coli</I> by expressing the bacterial cellulose synthase complex of <I>Gluconacetobacter xylinus</I>: CesA and CesB (formerly BcsA and BcsB, respectively). Cellulose synthase activity was, however, only detected when CesA and CesB were coexpressed with diguanyl cyclase (DGC), which synthesizes cyclic-di-GMP (c-di-GMP), which in turn activates cellulose-synthesizing activity in bacteria. Direct observation by electron microscopy revealed extremely thin fibrillar structures outside <I>E. coli</I> cells, which were removed by cellulase treatment. This fiber structure is not likely to be the native crystallographic form of cellulose I, given that it was converted to cellulose II by a chemical treatment milder than ever described. We thus putatively conclude that this fine fiber is an unprecedented structure of cellulose. Despite the inability of the recombinant enzyme to synthesize the native structure of cellulose, the system described in this study, named “CESEC (CEllulose-Synthesizing <I>E. Coli</I>)”, represents a useful tool for functional analyses of cellulose synthase and for seeding new nanomaterials.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bomaf6/2014/bomaf6.2014.15.issue-11/bm501217g/production/images/medium/bm-2014-01217g_0008.gif'></P>

Molecular dynamics simulation of tensile behavior of diffusion bonded Ni/Al nanowires

Zhenjiang Hu,Junjie Zhang,Yong Da Yan,Jiuchun Yan,Tao Sun,김동철,강성원 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.1

Interfaces play key roles in determining mechanical properties of materials. In current work we perform molecular dynamics simulations of diffusion bonding to evaluate the effect of temperature on the morphology of the Ni/Al interface and the strength of the diffusion bonded Ni/Al nanowires. The centro-symmetry parameter is adopted to identify defect atoms generated. Simulation results show that the thickness of the Ni/Al interface has strong dependence on the temperature of diffusion bonding. Following uniaxial tension tests indicate that the yield strength of Ni/Al nanowires is smaller than both the single crystalline Ni and Al nanowires, because of the Ni/Al interface acting as dislocation source and the mobilization of pre-existing dislocations at high temperature. It is shown that the mechanical properties of diffusion bonded Ni/Al nanowires strongly depend on the temperature.

Just-in-time Learning-aided Nonlinear Fault Detection for Traction Systems of High-speed Trains

Chao Cheng,Xiuyuan Sun,Junjie Shao,Hongtian Chen,Chao Shang 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.9

Traction systems in high-speed trains exhibit significant dynamic characteristics, which mainly arise from operation-point changes. Most existing fault detection methods provide static data models for global structures, especially for traditional multivariate statistical analysis methods constrained by constant operating points. The symptoms of incipient faults are slight and easily hidden. Despite the moderate effect of incipient faults, they will compromise the overall performance and remaining life of traction systems in the long run. Therefore, a just-in-time slow feature analysis method is proposed in this study. The salient advantages of the proposed method are: 1) It can be applied to dynamic non-linear systems; 2) It can detect incipient faults subject to environments containing noise and unknown disturbances; 3) It mitigates false alarms caused by parameter mutation during mode-switching. A series of experiments are carried out on a traction system platform to verify the effectiveness and superiority of the proposed method.

Determination of the number of ²³⁵U target nuclei in the irregular target using a fission time projection chamber

Jiajun Zhang,Jun Xiao,Junjie Sun,Mingzhi Zhang,Taiping Peng,Pu Zheng Korean Nuclear Society 2024 Nuclear Engineering and Technology Vol.56 No.2

Based on multiple measurements of ionization loss, the Time Projection Chamber (TPC) combines strong tracking ability with particle identification ability in a large momentum range, which is an important advantage of TPC detection technology over traditional ionization measurement technology. According to these two characteristics of TPC, applying it to the measurement of fission cross-section can greatly improve the measurement accuracy. During the measurement of the fission cross-section, the number of target nuclei is required to be accurately measured. So this paper introduces a method for measuring the number of ²³⁵U target nuclei using a fission TPC system. The measurement result agrees with the reference value, and relative error is around 1 %.