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SSRN 2022年

作者： Dong, Chiheng Han, Meng Guo, Wenwen Zhang, Xianping Liu, Cong Huang, He Yao, Chao Wang, Dongliang Liu, Huajun Ma, Yanwei Key Laboratory of Applied Superconductivity Institute of Electrical Engineering Chinese Academy of Sciences Beijing100190 China University of Chinese Academy of Sciences Beijing100049 China Institute of Electrical Engineering and Advanced Electromagnetic Drive Technology Qilu Zhongke Jinan250013 China Institute of Plasma Physics Chinese Academy of Sciences Hefei China

Iron-based superconducting wires fabricated by the powder-in-tube method are promising candidates for practical applications due to their prominent high-field performance. The morphology, compactness and alignment of the superconducting grains, which are mainly determined by the deformation and post-sintering strategy, have a large significance for the current carrying ability. Herein, we apply a novel stainless steel/silver composite architecture combined with a scalable grooved rolling process to fabricate high-performance iron-based superconducting multifilamentary round wires. Highly dense superconducting filaments are obtained without hot-isostatic-pressing. A critical current density Jc=3.02×104 A/cm2 at 4.2 K and 10 T is achieved, which is the highest value ever reported in iron-based multifilament wires. Through detailed microscopic and theoretical analysis, we conclude the deformation mechanism of Ba0.6K0.4Fe2As2 grains and propose a supercurrent transport model for iron-based superconducting wires. We suggest that higher Jc can be achieved by introducing a better grain texture. Our method provides a simple and cost-effective way to densify practical superconducting wires and is very promising to be scaled up to long wire productions. © 2022, The Authors. All rights reserved.

关键词： Iron

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An Improved Design Method of Snubber Circuit for High-Voltage Diode Rectifier in Acceleration Grid Power Supply

An Improved Design Method of Snubber Circuit for High-Voltag...

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IEEE International Conference on Plasma Science (ICOPS)

作者： Shaoxiang Ma Shu Yang Dongyu Wang Ming Zhang Kexun Yu Yuan Pan State Key Laboratory of Advanced Electromagnetic Engineering and Technology WuhanHubeiChina430074

ISBN: (纸本)9781728153087

The acceleration grid power supply (AGPS) is a key component in negative ion based neutral beam injector (N-NBI) system to produce mega-volt DC voltage. Diode rectifier is utilized as the final converter in AGPS, and connecting diodes in series is an essential approach to generate such an ultra-high-voltage. To reduce overvoltage and balance the voltage across these diodes, a RC (resistance and capacitance) snubber circuit is usually connected parallel with each diode. But the number of serial diodes in the AGPS rectifier is so large, that the parasitic capacitance will have a significant impact on voltage distribution during the reverse recovery process. As for typical RC circuit design method, the unbalanced voltage sharing between the serial diodes is still serious.

关键词： Resistance Power supplies Snubbers Rectifiers Voltage Ions Plasmas

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Effect of Lanthanum on Microstructure Evolution and Mechanical Behavior of Mg-Al-Mn Alloy

SSRN

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SSRN 2023年

作者： Li, Xiaoqiang Xu, Qiyong Liu, Yangfan Zhang, Jiantao Liu, Dexue Le, Qichi Wang, Jinhui Zhu, Yunpeng Hu, Wenxin State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals Lanzhou University of Technology Lanzhou730050 China Key Laboratory of Electromagnetic Processing of Materials Ministry of Education Northeastern University Shenyang110819 China Qinghai Provincial Key Laboratory of New Light Alloys Qinghai Provincial Engineering Research Center of High Performance Light Metal Alloys and Forming Qinghai University Xining810016 China State Key Laboratory of Baiyunobo Rare Earth Resource Research and Comprehensive Utilization Baotou Research Institute of Rare Earths Baotou014030 China

Abstract: In this study, Mg-1.5Al-xwt%La-Mn (ALaM-x) (x = 0.5, 1, and 2) alloys were prepared by melting and casting followed by hot extrusion at 300 °C. The microstructure evolution and mechanical behavior of the alloys were studied. By observing the microstructure, it was found that the precipitated phases occurred the evolution of Al11La3 → Al2.12La0.88/Al2La → Mg12La with the decrease of Al/La, and the precipitated Al11La3 coarsened gradually with the increase of La amount. After extrusion, the fine rod-like Al11La3 was broken and refined, but the coarse Al11La3 was not completely broken, and aggregated and unevenly distributed in Mg matrix. Compared with the extruded pure Mg, the extruded ALaM-0.5 alloy presented finer microstructure with an average grain size of 1.83 μm and a refinement rate of 90%. The mechanical properties of the alloy exhibited a considerable improvement of TYS~262.5±3.0 MPa, UTS~275.0±2.4 MPa, an increase rate of 124.7% and 52.1%, respectively. Based on theoretical analysis, the high strength of the alloy was mainly attributed to refinement strengthening, dislocation strengthening, precipitation strengthening and texture strengthening, among them, refinement strengthening up to 42%. Furthermore, the inverse Hall-Petch relationship between (d-1/2) and strain hardening exponents (n) was found, and the precipitated phase could delay the weakening trend of strain hardening capacity with decreasing grain size. © 2023, The Authors. All rights reserved.

关键词： Magnesium alloys

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224-Gb/s 16QAM SV-DD Transmission Using Pilot-Assisted Polarization Recovery with Integrated Receiver

224-Gb/s 16QAM SV-DD Transmission Using Pilot-Assisted Polar...

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2021 Optical Fiber Communications Conference and Exhibition, OFC 2021

作者： Zhang, Sen Lu, Liwang Fan, Linsheng Chen, Bin Zhang, Tingting Zuo, Tianjian Liu, Lei Tang, Jin Zeng, Li Chen, Pengxin Huo, Jiahao Zhou, Xian Tao Lau, Alan Pak Lu, Chao Liu, Liu Guo, Changjian Network Technology Laboratory Huawei Technologies Co. Ltd. Shenzhen518129 China Guangdong Provincial Key Laboratory of Optical Information Materials and Technology South China Academy of Advanced Optoelectronics South China Normal University Guangzhou510006 China State Key Laboratory for Modern Optical Instrumentation College of Optical Science and Engineering Centre for Optical and Electromagnetic Research International Research Center for Advanced Photonics Zhejiang University Hangzhou310058 China BandP Laboratory Huawei Technologies Co. Ltd. Shenzhen518129 China School of Computer and Communication Engineering Beijing University of Science and Technology Beijing China Department of Electrical Engineering Hong Kong Polytechnic University Hong Kong Hong Kong Department of Electronic and Information Engineering Hong Kong Polytechnic University Hong Kong Hong Kong Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen518057 China

We propose and experimentally demonstrate a low-complexity pilot-assisted analytical method for polarization demultiplexing in SV-DD systems, achieving a 224-Gb/s 16QAM transmission over 40-km SSMF and can tolerate up... 详细信息

ISBN: (纸本)9781943580866

关键词： Quadrature amplitude modulation

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Efficiency-boosted semiconductor optical amplifiers via mode-division-multiplexing

arXiv

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arXiv 2023年

作者： Wang, Yi Wei, Yihui Dolores-Calzadilla, Victor Dai, Daoxin Williams, Kevin Smit, Meint Jiao, Yuqing Eindhoven University of Technology Eindhoven5600MB Netherlands Eindhoven University of Technology Eindhoven5600MB Netherlands State Key Laboratory for Modern Optical Instrumentation Center for Optical & Electromagnetic Research College of Optical Science and Engineering International Research Center for Advanced Photonics Zhejiang University Zijingang Campus Hangzhou310058 China Jiaxing Key Laboratory of Photonic Sensing & Intelligent Imaging Intelligent Optics & Photonics Research Center Jiaxing Research Institute Zhejiang University Jiaxing314000 China

Semiconductor optical amplifiers (SOA) are a fundamental building block for many photonic systems. However, their power inefficiency has been setting back operational cost reduction, and the resulting thermal losses constrain miniaturization, and the realization of more complex photonic functions such as large-scale switches and optical phased arrays. In this work, we demonstrate significant gain and efficiency enhancement using an extra degree of freedom of light - the mode space. This is done without changing the SOA's material design, and therefore high versatility and compatibility can be obtained. Light is multiplexed in different guided modes and is reinjected into the same gain section twice without introducing resonance, doubling the interaction length in a broadband manner. Up to 87% higher gain and 300% higher wall-plug efficiency are obtained in a double-pass SOA compared to a conventional single-pass SOA, at the same operating current, in the wavelength range of 1560-1580 nm. © 2023, CC BY.

关键词： Semiconductor optical amplifiers

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Study of Calculation Method of Current Induced by Closing-loop Operations Based on PMU in Distribution Networks with DG

Study of Calculation Method of Current Induced by Closing-lo...

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Power and Electrical engineering (ACPEE), 5th Asia Conference on

作者： Xiaotong Luo Shang Cao Chuye Hu Shaorong Wang Hongfa Ding State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China

ISBN: (数字)9781728152813

ISBN: (纸本)9781728152820

Closing-loop operations in distribution networks are regular operations that realize load transfer and operation adjustment without interrupting power supply. They improve power supply reliability, but they may also cause large loop current. In distribution networks with distributed generation and no-load transformers, loop current impacts induced by closing-loop operations may be more serious. So a method for calculating the closing-loop current of distribution network based on phasor measurement unit (PMU) that considers the effects of sympathetic inrush current and distributed generation (DG) is proposed. Firstly, obtain the loop circuit topology according to the depth-first search algorithm for directed graphs. Then consider the shunting effects of the branches, sympathetic inrush current generated by parallel no-load transformers and the transient characteristics of the distributed generation, and perform equivalent processing on the loop circuit. Finally, according to the equivalent circuit impedance parameters and the electrical quantity measured by PMU, calculate loop current. The closing-loop operation of the distribution network of Shanghai Lingang District is taken as a case to study. The results show that the method proposed in this paper is relatively accurate and practical.

关键词：

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Small-Signal Disturbance Compensation Control for LCL-Type Grid-Connected Converter in Weak Grid

Small-Signal Disturbance Compensation Control for LCL-Type G...

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作者： Zhu, Donghai Zhou, Shiying Zou, Xudong Kang, Yong Zou, Kaifeng School of Electrical and Electronic Engineering State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan430074 China Wuhan Second Ship Design and Research Institute Wuhan430205 China Naval Aeronautical University Qingdao266041 China

When the three-phase LCL-type converter is attached to a weak grid, its grid current control will interact with a phase-locked loop (PLL), via the point of common coupling voltage. And, the PLL dynamic has a negative influence on the current control, rendering an undesired performance to grid current control, even leading to the instability issue, if no effective measure is employed. To mitigate this problem, this article proposes a simple and visualized small-signal disturbance compensation control method for the LCL-type grid-connected converter. First, the effect mechanism of PLL dynamic on the current control is analyzed, and the root of the small-signal disturbance caused by PLL dynamic is identified subsequently. Based on this, an improved control method is proposed to compensate the aforesaid PLL-introduced small-signal disturbance terms in current loop, and then, the negative effect of PLL dynamic on the grid current control can be effectively reduced in the weak grid, without modifying the PLL parameters and structure. Moreover, the method is not influenced by the circuit parameters change, and it is robust to the variation of grid impedance. Finally, the proposed method is validated by the experiment. © 1972-2012 IEEE.

关键词： Phase locked loops

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The Impact of Primary Frequency Control of WTs on Ultra-Low Frequency Oscillation 5

The Impact of Primary Frequency Control of WTs on Ultra-Low ...

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2020 5th International Seminar on Computer technology, Mechanical and Electrical engineering, ISCME 2020

作者： Yang, Lei Zhang, Xiaojie Huang, Wei Wu, Chen Li, Shengnan Chen, Yixuan Kang, Hongkai Yunnan Electric Power Research Institute Kunming Yunnan650217 China State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan Hubei430074 China Power Dispatching Center of Yunnan Electric Power Group Co. Ltd Kunming Yunnan650217 China Power Planning Research Center of Yunnan Power Grid Co. Ltd Kunming Yunnan650217 China

Since entering the 21st century, as wind power develops rapidly, wind power plays an increasingly important role in the safe and stable operation of power systems. Since the wind turbines under traditional control don't provide frequency support, the frequency dynamics of the power grids after load disturbance will be deteriorated. Thus, wind farms are required to equip primary frequency control in many countries. Most existing researches on primary frequency control of wind turbines focus on control strategies and the impact on system frequency, but few studies pay attention to the impact of primary frequency control of wind power on ultra-low frequency oscillation. This paper first proposes an analysis framework for ultra-low frequency oscillations in power systems with wind power. On this basis, a motion equation model of wind turbines is established. Finally, an extended three-machine nine-node system is used as an example to analyze the impact mechanism of primary frequency control on ultra-low frequency oscillation. The impact mechanism provides reference for the design of primary frequency of wind turbines in some regional power grids with ultra-low frequency oscillation. © Published under licence by IOP Publishing Ltd.

关键词： Wind turbines

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COIL OPTIMIZATION DESIGN OF THE HORN SHAPE FOR UNDERWATER WIRELESS POWER TRANSFER

COIL OPTIMIZATION DESIGN OF THE HORN SHAPE FOR UNDERWATER WI...

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The 16th IET International Conference on AC and DC Power Transmission (ACDC 2020)

作者： Z. Yingqin R. Cancan L. Conghui L. Xiaobo L. Minghai State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China

In the application scenarios of underwater wireless power transfer (WPT), a horn shape coil is proposed in this paper. Aiming to obtain the uniform magnetic field in a specific area, the horn shape coil is optimized by reasonably setting the tilt angle and the spacing of the turns. Moreover, the horn coil with optimal tilt angle and the horn coil with uneven spacing are designed. Considering the eddy current loss in seawater, the model of WPT system in seawater is established using the 3D electromagnetic simulator. Through simulation and analysis of eddy current loss under different conditions, the influence of eddy current loss on efficiency is illustrated. Finally, the transfer efficiency and output power are obtained by simulation and calculation. Also, the performance of the designed system is evaluated. It is found that the proposed system can effectively enhance the stability and anti-offset capability of WPT system, and then obtain the stable and efficient output.

关键词： coils optimisation eddy current losses inductive power transmission seawater magnetic fields underwater equipment

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Robust Explicit Model Predictive Control based on State Feedback Linearization for Buck Converter

Robust Explicit Model Predictive Control based on State Feed...

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International Conference on Power Electronics and Motion Control (IPEMC)

作者： Jing Chen Yu Chen Lupeng Tong Li Peng The State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology (HUST) China

ISBN: (数字)9781728153018

ISBN: (纸本)9781728153025

Explicit model predictive control (EMPC) regards the linear time-invariant model as the prerequisite to deduce the offline control laws for online control. Thus, EMPC cannot be directly applied to Buck converters with variable load. A tradeoff method is to linearize Buck model under a specific load to obtain the time-invariant model to perform EMPC. However, since the obtained offline control laws is derived under the specific load, its performance will be degraded when the load varies. To fix this problem, this paper proposes to utilize State Feedback Linearization (SFL) technology to transfer the variable load term from model parameter matrix to state variables and control parameter. Based on such an equivalent model, EMPC can be directly performed and load-independent offline control laws are obtained. With such a methodology, only the load-dependent state variables and control parameter need to be updated online to adapt load variation, and the obtained control laws need not to be changed and can be discretized into a look-up table to reduce online computational burden, which suits the high switching frequency scenarios well. Details of the proposed methodology are given in this paper. Simulation and experimental results are also provided to demonstrate the effectiveness of the proposed control methodology.

关键词： Adaptation models State feedback Buck converters Predictive models Table lookup Load modeling Predictive control

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