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- 저자 : Zhifeng Deng (검색결과 4 건)
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A novel medium voltage five-level converter with minimized volume
Deng, Zhifeng,Liu, Jinjun,Du, Sixing The Korean Institute of Power Electronics 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.10
In applications such as ship propulsion and of-shore wind power generation, it is important to minimize the volume of medium voltage power converters. To make this possible, a novel five-level converter topology is proposed in this paper. This converter is realized by connecting two half-bridge (HB) cells with a three-level neutral point clamped (3L-NPC) unit. In each HB cell, the switches are directly clamped to DC side capacitors where the larger volume high-voltage flying capacitors are avoided. By adopting the 3L-NPC unit, the volume of the proposed converter is further reduced. A comprehensive comparison result shows that the volume of the proposed converter is more than 7% less than existing five-level converters. The operation principle and modulation method of this converter are also introduced. Based on the phase-shift pulse width modulation (PS-PWM) method, the capacitor voltages of the proposed converter can be self-balanced. Simulation and experiment results are shown to verify the performance of this converter and the validity of the theoretical analysis.
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Pengfei Zhang,Kaichang Kou,Zhifeng Deng,Guanglei Wu 한국섬유공학회 2019 Fibers and polymers Vol.20 No.4
In this paper, the carbon-fiber double-layer spacer fabric (CFDSF) was firstly introduced into epoxy resin (EP) forfabrication of CFDSF/EP composite materials. It is indicated that the introduction of CFDSF can significantly improve themechanical properties of EP. Meanwhile, the influence of the content of modified carbon black (CB) on the mechanical andelectrical properties of CB/CFDSF/EP composite materials was investigated. The results showed that the flexural strengthand impact strength of the CB/CFDSF/EP composite materials were improved as the modified CB content increased to 3 %. The bending and impact strengths were found to be 123.8 MPa and 15.88 kJ/m2, respectively, owing to a fracture mechanismtransition induced via the addition of modified CB. As the modified CB content increased from 6 % to 15 %, the bending andimpact strengths exhibited a decreasing trend and typical brittle features were evident in the composite. Further, the volumeresistance of the CB/CFDSF/EP composite materials also presented a decreasing trend.
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Wang Yan,Wen Jun,Zheng Jiangyun,Deng Zhifeng,Zhou Yueyu,Jiang Guisheng,Xia Qiangsheng,He Enjie,Ning Lixin 한국물리학회 2021 Current Applied Physics Vol.26 No.-
Thermodynamic properties, electronic structures and spectroscopic properties of defects and Ce3+ in Y2O3 are studied by using the hybrid density functional theory associated with multi-reference configuration interaction ab-initio calculations. Thermodynamic transition energy levels of the easily generated oxygen vacancies in the host are analyzed according to HSE06-calculated formation energies, which may be conducive to interpretations of the persistent luminescence (PersL) of Y2O3-based phosphors. Besides, the locations of impurity states (caused by VO and Ce3+) in energy bands are obtained from derived density of states. Moreover, energies and oscillator strengths of 4f1 → 5d1 5 transitions of Ce3+ ions (at Y1 and Y2 sites) calculated from the CASSCF/CASPT2/ RASSI SO method agree reasonably well with experimental excitation spectra of Y2O3: Ce3+ phosphors, achieving the assignment of excitation spectra. The presented calculations can be applied to identify luminescent centers in Ce3+-doped phosphors and reveals possible native defects and their roles in the PersL of phosphors.
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Hui Chen,Jinjun Liu,Sixing Du,Cong Li,Zhifeng Deng 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
It is well-known issue that dc bias and oscillations will be introduced into phase current and dc current when the transmission power and control variables of three phase dual active bridge (3ph-DAB) converter have the abrupt changes. It will cause the magnetic saturation problem and degrade the dynamic response seriously. To solve this issue, this paper proposes a novel fast transient current control scheme with asymmetrical three phase (APS) control. By choosing suitable transient phase shift angles, the proposed method can greatly suppress the dc bias and overshoot of phase current and improve the transient performance significantly. It is presented to make 3ph-DAB transit from initial steady state to target steady state within one step through the proposed method and space-vector theory. The simulation results verify the effectiveness of proposed scheme.
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