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Annual Conference of the IEEE Industrial Electronics Society

作者： Cheng Wang Kai Zhang Liming Liu Wenxin Liu State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology ABB Inc. Electrical and Computer Engineering Lehigh University

ISBN: (纸本)9781479917631

Quasi-Z-source based modular cascaded multilevel converter featuring both the advantages of multilevel converter like modularity, scalability, distributed maximum power point tracking (MPPT) capability and the advantages of quasi-Z-source network (qZSN) like high efficiency, no consideration for annoying switching dead-zone, wide dc voltage boosting range etc. is a promising option for high power solar photovoltaic (PV) system. Nevertheless, inherent mismatch and varied operating conditions (both called module-mismatch) are still the issues to be disclosed. Asymmetrical active power harvesting among individual PV converter modules resulting from module-mismatch will fluctuate dc voltages and polarize the distribution of the alternating terminal voltage and may derivatively destroy the coordination between the QZS and the H-bridges (HB). In this paper, a novel modulation method for qZSN based cascaded modular multilevel converter with two modes which are low-loss mode for normal operation and extended mode for module-mismatch operation is proposed. With the former mode, the switching times are reduced greatly and then low the switching loss. When encountered by module-mismatch, extended mode is able to re-distribute power and then to balance dc-link voltages. Based on the modulation method, a reactive power compensation algorithm (RPCA) with larger operating range is applied in order to mitigate the polarization of ac voltage. Finally, a 3MW/12kV system with the proposed modulation and control strategy is developed in Matlab/Simulink platform. Simulation results are presented to demonstrate the effectiveness of the proposed technology.

关键词： Quasi-Z-source Cascaded PV Module-mismatch Modulation Reactive power compensation modulation mode reactive compensation multistage converter VOLTS DIRECT CURRENT cascades maximum power point trackers Polydnaviridae VOLTS ALTERNATING CURRENT Modularity

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Research of HTS Application on Tokamak Magnets

Research of HTS Application on Tokamak Magnets

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2015 International Conference on Power Electronics and Energy engineering（PEEE 2015）

作者： L.Ren X.Z.Deng Y.Xu H.Liu J.D.Li J.Shi Y.J.Tang State Key Laboratory of Advanced Electromagnetic Engineering and Technology R&D Center of Applied Superconductivity Huazhong University of Science and Technology

ISBN: (纸本)9781510807648

in this paper,the application feasibility of HTS tapes on tokamak magnets is discussed and the existing four kinds of HTS high current conductors are ***,an YBCO conductor structure suitable for a 10 GJ tokamak TF magnet is designed and the current carrying capacity is *** simulation result shows that the critical current of the YBCO conductor is about 75 kA@10 T,30 K.

关键词： HTS Application Tokamak Magnets YBCO conductor

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The role of photo-ionization and residual electrons in atmospheric pressure non-equilibrium plasma jets

The role of photo-ionization and residual electrons in atmos...

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IEEE International Conference on Plasma Science (ICOPS)

作者： S. Wu X. Lu State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan Hubei P R. China

Summary form only given. Atmospheric pressure non-equilibrium plasma jets (APNP-Js) generate plasmas in open space rather than in confined discharge gaps and are promising for applications in materials processing, nanotechnology, and plasma medicine. High-speed photographs have shown that the plasma plumes are in fact composed of bullet-like plasma volumes travelling at speeds of 10 4 -10 5 m/s. It is now generally agreed that the plasma bullets are similar to cathode-directed streamers 1 . For the propagation of cathode-directed streamers, free electrons ahead of the streamer front are needed; Photo-ionization is one of the key mechanisms to produce these free electrons. The existing theoretical models suggest possible critical roles of the local electric field induced by space charges, as well as photo-ionization and residual electron effects. However, we are not aware of experimental reports on the effect of photo-ionization on the plasma bullet *** critical factor that affects APNP-Js is the density of residual electrons left from previous repetitive discharges. The density of these electrons could be much higher compared to the seed electrons produced by natural radioactivity; this makes it even more difficult to quantify the contribution of photo-ionization. However, no investigations into the APNP-J ignition phase are presently available, especially to verify the common assumption that the residual electron density within the streamer propagation channel is high. In this work, complementary experiments and numerical modeling reveal the important role of photo-ionization in the propagation of plasma bullets. It is shown that the minimum electron concentration ~108 cm-3 is required for the regular, repeated propagation of the plasma bullets, while the streamers propagate in the stochastic mode below this threshold. The stochastic-to-regular mode transition is related to the higher background electron density in front of the propagating bullets.

关键词： Plasmas Discharges (electric) Nanotechnology Ionization electromagnetics Space exploration Materials processing

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Physical design of FEL injector based on the performance-enhanced EC-ITC RF gun

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Chinese Physics C 2014年第1期38卷 79-85页

作者：胡桐宁陈曲珊裴元吉李骥秦斌 State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology National Synchrotron Radiation Laboratory University of Science and Technology of China

To meet the requirements of high performance THz-FEL （Free Electron Laser）, a compact scheme of FEL injector was proposed. A thermionic cathode was chosen to emit electrons instead of a photo-cathode with its complex structure and high cost. The effective bunch charge was improved to ~200 pC by adopting an enhanced EC-ITC （External Cathode Independently Tunable Cells） RF gun to extract micro-bunches; back bombardment effects were almost eliminated as well. Constant gradient accelerator structures were designed to improve energy to ~14 MeV, while the focusing system was applied for emittance suppressing and bunch state maintenance. The physical design and beam dynamics of the key components for the FEL injector were analyzed. Furthermore, start- to-end simulations with multi-pulses were performed using homemade MATLAB and Parmela. The results show that continual high brightness electron bunches with a low energy spread and emittance could be obtained stably.

关键词： RF gun EC-ITC beam dynamics LINAC FEL injector

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Evolution characteristics of shock pressure wave on the copper debris irradiated by far-field high power annular laser beams

Evolution characteristics of shock pressure wave on the copp...

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第二届空间目标与碎片监测、清理技术及应用学术研讨会

作者：韩雪云 Yi Zhang Ning Wei Yufeng Peng College of Physics and Electronic Engineering Henan Normal University Henan Key Discipline Open Laboratory of Electromagnetic Wave Detecting Henan Engineering Laboratory of Optoelectronic Technology and Advanced Manufacturing

Based on a positive confocal unstable resonator(ab initio),the propagation characteristics of the laser field were investigated by means of fast Fourier transform(FFT).The output laser beam was focused on a copper target and generated a plasma plume expanding along the normal to the target *** the absorption of laser radiation on the copper debris as a target,the heating and melting of the material were described by a three-dimensional thermal conductivity *** spatial and temporal evolvements of the plasma shock wave(PSW)as functions of time after the pulse laser irradiating were *** results show that the maximum pressure of the plasma shock wave is8.18GPa at time t=0.8μs after the pulse laser is cut off,and then attenuates gradually with increasing of *** the time t=4.8ms,the maximum pressure decayed to 4.73GPa.

关键词： space debris high power pulsed laser plasma shock wave and laser ablation

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Characteristics of phase current and its application in fault section location in noneffectively grounded distribution systems

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Sensors and Transducers 2014年第2期165卷 176-181页

作者： Tang, Jinrui Yin, Xianggen Zhang, Zhe State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan 430074 China

Medium voltage distribution systems of some countries are mostly noneffectively grounded systems, and most of the distribution automation systems do not have the function of locating the fault section for single phase-to-ground fault. This paper presents a method of fault section location based on the characteristic of the phase current difference. It makes a deep analysis based on instantaneous symmetrical component method when single phase-to-ground fault happens. This method requires only a little data to be transferred and does not need voltage information, so it is easy to be popularized and applied in engineering practice. The effectiveness of the method has been verified by the PSCAD/EMTDC simulation results. © 2014 IFSA Publishing, S. L.

关键词： Location

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Traveling-wave-based fault-location method under low sampling rate

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Energy Education Science and technology Part A: Energy Science and Research 2014年第1期32卷 213-220页

作者： Tang, Jinrui Yin, Xianggen Zhang, Zhe State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology 430074 Wuhan China

This paper proposes a correction algorithm for traditional wave-front arrival time identification method based on wavelet transform maxima modulus under low sampling rate. It is disclosed that wave-front positioning accuracy under low sampling rate can be improved when the wavelet transform coefficients related to the two points which are nearest to the sampling point corresponding to the wavelet transform maxima modulus are used. The effectiveness and practicability of the extraction method of zero-mode velocity have been verified by PSCAD/EMTDC simulation results. © Sila Science. All rights reserved.

关键词： Wavelet transforms

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Minimum energy storage for power system with high wind power penetration using p-efficient point theory

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Science China(Information Sciences) 2014年第12期57卷 243-254页

作者： LI JingHua WEN JinYu CHENG ShiJie WEI Hua State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology School of Electrical Engineering Guangxi University

Minimum energy storage(ES)and spinning reserve(SR)for day-ahead power system scheduling with high wind power penetration is significant for system operations.A chance-constrained energy storage optimization model based on unit commitment and considering the stochastic nature of both the wind power and load demand is *** solve this proposed chance-constrained model,it is first converted into a deterministic-constrained model using p-efficient point theory.A single stochastic net load variable is developed to represent the stochastic characteristics of both the wind power and load demand for convenient use with the p-efficient point theory.A probability distribution function for netload forecast error is obtained via the Kernel estimation *** proposed model is applied to a wind-thermal-storage combined power system.A set of extreme scenarios is chosen to validate the effectiveness of the proposed model and *** results indicate that the scheduled energy storage can effectively compensate for the net load forecast error,and the increasing wind power penetration does not necessarily require a linear increase in energy storage.

关键词： energy storage spinning reserve wind power penetration chance constraints p-efficient theory kernel estimation

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electromagnetic interaction between local surface plasmon polaritons and an atmospheric surface wave plasma jet

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Chinese Physics B 2014年第3期23卷 404-411页

作者：陈兆权胡东刘明海夏广庆郑晓亮胡业林叶秋波陈明功祝龙记胡希伟 College of Electrical & Information Engineering Anhui University of Science and Technology State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology State Key Laboratory of Structure Analysis for Industrial Equipment Dalian University of Technology

We analyze the electromagnetic interaction between local surface plasmon polaritons （SPPs） and an atmospheric surface wave plasma jet （ASWPJ） in combination with our designed discharge device. Before discharge, the excitation of the SPPs and the spatial distribution of the enhanced electric field are analyzed. During discharge, the critical breakdown electric field of the gases at atmospheric gas pressure and the surface wave of the SPPs converted into electron plasma waves at resonant points are studied. After discharge, the ionization development process of the ASWPJ is simulated using a two- dimensional fluid model. Our results suggest that the local enhanced electric field of SPPs is merely the precondition of gas breakdown, and the key mechanism in maintaining the discharge development of a low-power ASWPJ is the wave-mode conversion of the local enhanced electric field at the resonant point.

关键词： surface wave plasma surface plasmon polaritons numerical simulation electromagnetic interac-tion

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Low-order harmonics analysis and suppression method for 400Hz single-phase VSI

Low-order harmonics analysis and suppression method for 400H...

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Annual IEEE Conference on Applied Power Electronics Conference and Exposition (APEC)

作者： Guoqing Yuan Siqin Luo Shiying Zhou Xudong Zou Kaifeng Zou State Key Laboratory of Advanced Electromagnetic Engineering and Technology HUST Wuhan Hubei China Qingdao Branch of Naval Aeronautical Engineering Institute Qingdao Shandong China

ISBN: (纸本)9781479967360

It is necessary to insert a dead-time in sinusoidal pulse width modulation (SPWM) voltage source inverter (VSI) to prevent a short circuit in the DC link. However, this will cause the dead-time effect, drop the fundamental voltage and introduce the 3 rd , 5 th and 7 th low-order harmonics into the output voltage. Conventional dead-time compensation methods either average voltage based or inductor current feedback compensation cannot be adopted in the case of high inductor ripple current. Moreover, even with high-precision detection of the inductor current polarity, the conventional methods are still not suitable when unipolar frequency doubling SPWM method is adopted. Dead-time effect is different when different SPWM methods are used. In this paper, dead-time effect of unipolar frequency doubling SPWM is analyzed and a new approach for eliminating low-order harmonics is proposed. Simulation and experiment on a 400-Hz prototype both show satisfactory results and verify the validity of the analysis and the effectiveness of the proposed control method.

关键词： Inductors Power harmonic filters Harmonic analysis Inverters Voltage control Resonant frequency Delays

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