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arXiv 2019年

作者： Han, Rui Zhu, Ping Banerjee, Debabrata Cheng, Shikui Yan, Xingting Zheng, Linjin CAS Key Laboratory of Geospace Environment Department of Engineering and Applied Physics University of Science and Technology of China Hefei230026 China International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan Hubei430074 China Department of Engineering Physics University of Wisconsin-Madison MadisonWI53706 United States Institute of Fusion Studies University of Texas at Austin AustinTX78712 United States

This article reports an evaluation on the linear ideal magnetohydrodynamic (MHD) stability of the China Fusion engineering Test Reactor (CFETR) baseline scenario for various first-wall locations. The initial-value code NIMROD and eigen-value code AEGIS are employed in this analysis. A good agreement is achieved between two codes in the growth rates of n = 1 − 10 ideal MHD modes for various locations of the perfect conducting first-wall. The higher-n modes are dominated by ballooning modes and localized in the pedestal region, while the lower-n modes have more prominent external kink components and broader mode profiles. The influences of plasma-vacuum profile and wall shape are also examined using NIMROD. In presence of resistive wall, the low-n ideal MHD instabilities are further studied using AEGIS. For the designed first-wall location, the n = 1 resistive wall mode (RWM) is found unstable, which could be fully stabilized by uniform toroidal rotation above 2.9% core Alfvén speed. Copyright © 2019, The Authors. All rights reserved.

关键词： Location

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Multi-Target Virtual Resistance Control Strategy in a 400 Hz Low Voltage Microgrid

Multi-Target Virtual Resistance Control Strategy in a 400 Hz...

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International Power Electronics Conference

作者： Yuze Li Xuejun Pei Zhi Chen Hanyu Wang Yong Kang State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Hubei China

This paper has proposed a multi-target virtual resistance strategy which can effectively realize targets of unbalanced voltage compensation and unbalanced current (power) sharing among inverters in 400 Hz low voltage microgrid. For unbalanced voltage compensation function, the strategy employs virtual resistance based on unbalanced voltage degree to compensate unbalanced voltage. For unbalanced current sharing function, the strategy uses current sharing degree and virtual resistance to share unbalanced current among inverters in parallel system. The experimental results of two inverters in parallel system are shown to prove the validity of proposed strategy. In addition, this strategy reduces large calculation and is easy to implement.

关键词： virtual resistance microgrid parallel system

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Hybrid Rectangular Bar Wave Windings to Minimize Winding Losses of Permanent Magnet Machines for EV/HEVs over a Driving Cycle.

Hybrid Rectangular Bar Wave Windings to Minimize Winding Los...

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International Conference on Magnetics (INTERMAG)

作者： X. Fan D. Li R. Qu C. Wang J. Li School of Electricity and Electronic Engineering Huazhong University of Science and Technology State Key Laboratory of Advanced Electromagnetic Engineering and Technology Wuhan China

The utility of thick rectangular wire wave windings in electrical machines for electrical vehicle/hybrid electrical vehicles (EV/ HEVs) have gained increasing interest due to its high slot filling factor, short end-winding, good manufacturability and excellent heat dissipation capability, etc. [1]. More EV makers tend to adopt this kind of windings in their new generation EV motors [2] [3]. However, significant eddy current losses may be induced in the thick bars especially at a high speed operation, thus reducing the machine efficiency and may cause winding local overheating. The conductor in a slot suffers from the circumferential flux caused by the armature (blue) and the radial flux caused by the magnet (red), as shown in Fig. 1 (a). The magnitude of radial flux density caused by the magnet and the circumferential flux density caused by the armature along the center line is shown in Fig. 1 (b). It can be seen that the flux density dramatically decreased as the distance to the stator bore increases. This means the conductors in the slot near the slot opening are exposed to a relatively large variable field by magnet and armature and significant AC losses may occur. Some methods have been reported to reduce the AC losses in the existing papers [4]-[6]. Reference [4] shows that the AC losses can be reduced by keeping the conductors away from the slot opening or using the magnetic wedge. Reference [5] and [6] reduce the AC losses by choosing an optimal winding layout and stranding the conductors, respectively. This paper proposes a novel hybrid rectangular bar wave winding consisting of copper bars and aluminum bars to reduce the winding losses. The aluminum bars are located close to the slot opening to suppress the induced AC losses for its high resistivity. It shows that the total winding losses can be reduced with the hybrid winding compared to with the conventional copper winding, especially at high speeds and light loads. Besides, the weight and cost can be als

关键词： Magnetics Conferences

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Control Design of Stand-Alone Brushless Doubly-Fed Induction Generator for Supplying Nonlinear Loads 21

Control Design of Stand-Alone Brushless Doubly-Fed Induction...

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21st International Conference on Electrical Machines and Systems, ICEMS 2018

作者： Elbabo Mohammed, Omer Mohammed Xu, Wei Liu, Yi Yu, Kailiang School of Electrical and Electronic Engineering Huazhong University of Science and Technology State Key Laboratory of Advanced Electromagnetic Engineering and Technology Wuhan China

ISBN: (纸本)9788986510201

This paper proposes a control method for standalone operation of the brushless doubly-fed induction generator (BDFIG) under nonlinear loads. The nonlinear loads could lead to distorted power winding (PW) voltage, which mainly contains fifth and seventh harmonics. The fifth and seventh harmonics can be eliminated by adding harmonics compensation loop to the machine side converter (MSC). And, the control winding current is regulated by proportional-integral-resonant (PIR) controllers. The effectiveness of the proposed control method is validated by both the simulation and experimental results. © 2018 KIEE EMECS (KIEE Electrical Machinery and Energy Conversion Systems).

关键词： Asynchronous generators

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Power Loss Analysis of a Novel Modular Multilevel Converter Based on Semi-full-bridge Sub-module with SiC-MOSFET Switched Capacitors

Power Loss Analysis of a Novel Modular Multilevel Converter ...

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Workshop on Wide Bandgap Power Devices and Applications in Asia (WiPDA Asia)

作者： Chen Xu Lei Lin Kai Hu State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan China

ISBN: (纸本)9781538643938

This paper presents a novel modular multilevel converter (MMC) whose sub-module (SM) is of semi-full bridge structure with SiC-MOSFET switched capacitors. Compared with conventional half-and full-bridge (H & FB) hybrid MMC, the proposed capacitor-switching semi-full-bridge (CS-SFB) MMC has the same DC fault ride through capability due to the unchanged positive and negative output voltage levels. The CS-SFB MMC not only possesses the sub-module consistency characteristic similarly as SFB SM, but also it has low power loss characteristic on account of CS technique. The currents of some Si-IGBTs and SiC-MOSFETs are half of the arm current, thus the conduction loss is reduced. Combined with the fast recovery characteristic of SiC-diodes, the switching loss can be reduced simultaneously. The calculation and simulation results based on the verification model show that CS-SFB MMC has better conduction and switching loss characteristic compared with CS-H & FB MMC, SFB MMC and H & FB MMC.

关键词： Switches Switching loss Valves Capacitors Voltage control Capacitance Bridge circuits

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Conformal Singularities and Topological Defects from Inverse Transformation Optics

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Physical Review Applied 2019年第3期11卷 034072-034072页

作者： Lin Xu Runqiu He Kan Yao Jing Ming Chen Chong Sheng Ying Chen Guoxiong Cai Shining Zhu Hui Liu Huanyang Chen Institute of Electromagnetics and Acoustics and Key Laboratory of Electromagnetic Wave Science and Detection Technology Xiamen University Xiamen 361005 China National Laboratory of Solid State Microstructures and School of Physics Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing Jiangsu 210093 China Institutes of Physical Science and Information Technology Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education Anhui University Hefei 230601 China Department of Mechanical Engineering and Texas Materials Institute the University of Texas at Austin Austin Texas 78712 USA

The conventional approach in transformation optics (TO) starts with a virtual space and determines a complicated material profile in physical space to achieve unconventional phenomena, such as invisibility cloaks. We demonstrate that complicated materials can be effectively fabricated by virtual space based on the reversed process of TO in two dimensions. We first show that a conformal singularity of a refractive-index profile, with either zero or infinity resulting from a power conformal mapping w=zα, is equivalent to a topological defect with positive charge or negative charge. The splitting effect and illusion effect are induced by the conformal singularities and related to the two-dimensional topological defects. Based on the equivalence, we fabricate a device of such a topological defect with a positive charge in experiments. Moreover, we observe its related light-bending functionality with laser beams. It has potential important applications in designing on-chip optical devices.

关键词： Cloaking Integrated optics Refraction Topological defects Topological effects in photonic systems Transformation optics Optical conformal mapping

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What is going on in magnesium alloys？

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Journal of Materials Science & technology 2018年第2期34卷 245-247页

作者： X.J. Wang D.K. Xu R.Z. Wu X.B. Chen Q.M. Peng L. Jin Y.C. Xin Z.Q. Zhang Y. Liu X.H. Chen G. Chen K.K. Deng H.Y. Wang School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Key Laboratory of Superlight Materials & Surface Technology (Ministry of Education) Harbin Engineering University Harbin 150001 China School of Engineering RMIT University City Campus Carlton VIC 3053 Australia State Key Laboratory of Metastable Materials Science and Technology Yanshan University Qinhuangdao 066004 China National Engineering Research Center of Light Alloy Net Forming Shanghai Jiao Tong University Shanghai 200240 China College of Materials Science and Engineering Chongqing University Chongqing 400030 China Key Lab of Electromagnetic Processing of Materials Ministry of Education Northeastern UniversityShnenyang 110819China Key Laboratory of Lightweight and High Strength Structural Materials of Jiangxi Province Nanchang University Nanchang 330031 China School of Chemical Engineering and Technology Tianjin University Tianjin 300350 China Shanxi Key Laboratory of Advanced Magnesium-Based Materials Taiyuan University of Technology Taiyuan 030024 China Key Laboratory of Automobile Materials of Ministry of Education & School of Materials Science and Engineering Jilin University Changchun 130025 China

China has been developed into one of the most active regions in terms of both fundamental and applied research on magnesium （Mg） and its alloys in the world from a solid base laid by its prominent metallurgist and materials scientists over the past decades. Nowadays, a large number of young-generation researchers have been inspired by their predecessors and become the key participants in the fields of Mg alloys, which consequently led to the establishment of China Youth Scholar Society for Magnesium Alloys Research in 2015. Since then, the first two China Youth Scholars Symposiums on Mg Alloys Research had been held at Harbin （2015） and Chongqing （2016） China, respectively. A number of crucial research inter- ests related to fundamental and applied Mg research were discussed at the conferences and summarized in this short perspective, aiming to boost far-reaching initiatives for development of new Mg-based materials to satisfy the requirements for a broad range of industrial employments. Herein, four main aspects are included as follows： i） Plastic deformation mechanism and strengthening strategy, ii） Design and development of new Mg-based materials, iii） Key service properties, and iv） New processing technologies.

关键词： Mg alloys Plastic deformation Strengthening Alloying design High performance Corrosion Fatigue behavior Creep Processing technologies Purification

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

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Journal of Physics: Conference Series 2021年第4期1748卷

作者： Lei Yang Xiaojie Zhang Wei Huang Chen Wu Shengnan Li Yixuan Chen Hongkai Kang Yunnan Electric Power Research Institute Kunming Yunnan 650217 China State Key Laboratory of Advanced Electromagnetic Engineering and Technology and School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan Hubei 430074 China Power Dispatching Center of Yunnan Electric Power Group Co. Ltd Kunming Yunnan 650217 China Power Planning Research Center of Yunnan Power Grid Co. Ltd Kunming Yunnan 650217 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.

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Study of Power System Oscillation with Wind Power Equipping Frequency Regulation

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Journal of Physics: Conference Series 2021年第5期1748卷

作者： Lei Yang Wei Huang Chen Wu Shengnan Li Yixuan Chen Hongkai Kang Yunnan Electric Power Research Institute Kunming Yunnan 650217 China Power Dispatching Center of Yunnan Electric Power Group Co. Ltd Kunming Yunnan 650217 China Power Planning Research Center of Yunnan Power Grid Co. Ltd Kunming Yunnan 650217 China State Key Laboratory of Advanced Electromagnetic Engineering and Technology and School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan Hubei 430074 China

As more and more countries and regions stipulate that wind farms need to have frequency regulation, especially in the power grid with high proportion of wind power. It's very clear that frequency regulation can improve the frequency dynamic of power system, but the influence of frequency regulation on power system oscillation is uncertain. This paper focuses on this influence and presents a linearized model to analyze the participation of the factors. In the end, a case system named four machine two area system is applied in the simulation to verify the validity of the model.

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Recent Advances in Research on Low Temperature Lithium Ion Batteries Power Source for Grid Equipments

Recent Advances in Research on Low Temperature Lithium Ion B...

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IEEE International Conference on Power and Power and Renewable Energy (ICPRE)

作者： Jian Wang Chen Bing Xiaojun Zhang Heming Deng Shouding Li Shun Tang State Grid Xinjiang Company Limited Electric Power Research Institute Urumqi P.R. China State Grid Electric Power Research Institute Wuhan P.R. China Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan P. R. China

ISBN: (数字)9781728145747

ISBN: (纸本)9781728145754

This paper summarized the recent developments in temperature-tolerance power supply for grid equipment, through the theoretical prediction, design synthesis and verification of key material systems, cell structure design, core mechanism and battery preparation engineering process, this report can develop batteries suitable for power source in grid equipments in low temperature regions to meet Xinjiang Power Grid. The demand for technology to achieve the leap-forward development of grid power quality services.

关键词： Electrodes Temperature Lithium Electrolytes Conductivity Lithium-ion batteries

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