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IEEE PES Asia-Pacific Power and Energy engineering Conference (APPEEC)

作者： Haiyan Tang Wei He Yongning Chi Xinshou Tian Yan Li Yukun Wang State Key Laboratory of Operation and Control of Renewable Energy & Storage Systems China Electric Power Research Institute Beijing China State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China

ISBN: (纸本)9781509054190

Along with the increasing of wind power penetration, the sub-synchronous oscillation phenomena may happen in wind power integrated system. This paper studies the sub-synchronous oscillation phenomena of doubly-fed induction generator (DFIG) based wind farm with series compensation, focuses on the dynamic characteristics of grid side converter control of DFIG and its optimal control. First, this paper analyzes the transfer characteristic of rotor-side and stator-side active power of DFIG, then combining with the analysis of DC capacitor voltage dynamic characteristics, the impacts of control strategy of grid side converter and its parameters on sub-synchronous oscillation behavior are studied. On this basis, a novel additional control strategy to suppress oscillation is proposed in grid side converter. The conclusions are verified by simulation cases of system integrated with DFIG based wind farm by series compensation.

关键词： Oscillators Voltage control Damping Stators Wind farms Rotors Wind power generation

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Dynamic phasor modelling and operating characteristic analysis of half-bridge MMC

Dynamic phasor modelling and operating characteristic analys...

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International Conference on Power Electronics and Motion Control (IPEMC)

作者： Xiaojun Lu Weixing Lin Jinyu Wen Wei Yao Ting An Yunfeng Li State Key Laboratory of Advanced Electromagnetic Engineering Huazhong University of Science and Technology Wuhan China Global Energy Interconnection Research Institute State Grid Corporation of China Beijing China

ISBN: (纸本)9781509012114

A unified dynamic phasor model for modular multilevel converter (MMC) under the rotating frame is developed. The model takes the AC voltage in the rotating frame and the DC voltage as electrical inputs, the fundamental frequency and second harmonic modulation indices as the control inputs. By separately modelling the controller, the electrical dynamics of MMC and the dynamics of external electrical system, the proposed dynamic phasor model is able to seamlessly interconnect with models of controllers and external electrical system. The dynamic phasor model of MMC is therefore normalized. By setting the derivative terms in the dynamic phasor model to be zero, static phasor model of MMC is achieved. By linearizing the dynamic phasor model around the steady-state operating point, small signal model of MMC is obtained. As a result, the proposed dynamic phasor model of MMC unifies the dynamic phasor model, static phasor model and small signal model of MMC. Based on the obtained static phasor model of MMC, an open loop circulating current suppressing control (CCSC) strategy and a method of analytically analyzing the operating characteristic of MMC are proposed. Simulations on PSCAD/EMTDC verified the accuracy of the dynamic phasor model, the efficacy of the open loop CCSC strategy and the different constraints on the PQ operation zone of a MMC.

关键词： Analytical models Voltage control Modulation Mathematical model Harmonic analysis Integrated circuit modeling Capacitors

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Formation and Characteristics of Negative Stepped Leaders in 4-10m Long Air Gap Discharges

Formation and Characteristics of Negative Stepped Leaders in...

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International Conference on Lightning Protection

作者： Shijun Xie Jianming Li Tao Luo Yu Zhang Junjia He Chuanqi Wu Yishi Yue Post-Doctoral Research Center State Grid Sichuan Electric Power Research Institute Chengdu China State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China

ISBN: (纸本)9781509048434

Natural lightning flashes are stochastic and uncontrollable, and thus it is difficult to observe the formation process of a downward negative stepped leader (NSL) directly and in detail. In this paper, the formation processes of NSLs in controllable laboratorial long-air-gap discharge experiments were studies. First, a series of negative long-air-gap discharge experiments with scales of 4~10 m were designed and carried out. According to the observation results of these experiments, two kinds of formation processes for NSLs with different scales were presented, and several of the characteristic parameters, including the scale, the propagation velocity and the dark period, were obtained. By comparing these characteristics with that in natural flashes, the similarity between the NSLs in the simulation experiments and those in natural flashes was proved, and the actual formation of NSLs in natural flashes was deduced.

关键词： stepped leader negative flash formation characteristics simulation experiment long air gap discharge

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A review on welding in make and break operation of electrical contacts 3

A review on welding in make and break operation of electrica...

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3rd International Conference on Electric Power Equipment - Switching technology, ICEPE-ST 2015

作者： Jiang, Huang Zhenbiao, Li State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan430074 China

ISBN: (纸本)9781467374149

Dynamic welding is an important phenomenon in electrical contact applications. A review is made in this paper to show the research progress in this field, which includes the welding phenomena in both making and breaking operation of contact, the relationship between the arcing duration and its contact welding occurrence, the difference of welding strength between short arc and long arc, the root cause of contact voltage pulse in separation, the possible mechanism of contact welding, etc. © 2015 IEEE.

关键词： Electric contacts

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Finite element analysis for the inhibition of electromagnetic acoustic testing (EMAT) Lamb waves multi-modes

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AIP Conference Proceedings 2017年第1期1806卷

作者： Suzhen Liu Yanwei Zhang Chuang Zhang Qingxin Yang 1Province-Ministry Joint Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability Hebei University of Technology Tianjin 300130 China 2Key Laboratory of Advanced Electrical Engineering and Energy Technology Tianjin Polytechnic University Tianjin 300387 China

Lamb waves are widely used in nondestructive testing (NDT) and structural health monitoring (SHM) for its obvious advantages, such as good directionality, longer-range propagation and lower loss etc. However, it is difficult to analysis and to interpret the echo signals because of its multi-modes and dispersion. In this paper, the properties of single-mode Lamb waves which were excited by double EMAT were studied based on the principles of multi-modes and the characteristics of wave structure. Simulation results show that the double transducer excitation structure can stimulate single-mode Lamb waves and eliminate the extra modes, which are produced by modal conversion at ends of the specimen. The single-mode excitation of Lamb waves is beneficial to reduce the difficulty of signal processing and provide reliable information to locate the defect. The researches in this paper can be used as a theoretical basis to design double transducer excitation system.

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Space-charge effect of the time-varying electron injection in a diode: classical and relativistic regimes

arXiv

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arXiv 2017年

作者： Liu, Yangjié Tang, Qi Wu, Biyi Faculty of Physics and Electronic Science Hubei University Hubei Collaboration Innovation Centre for Advanced Organic Chemical Materials Hubei Key Laboratory of Ferro & Piezoelectric Materials and Devices WuhanHubei Province430062 China Antennas Group School of Electrical Engineering and Computer Science Queen Mary University of London E1 4NS Mile End East London United Kingdom Department of Mathematical Sciences Rensselaer Polytechnic Institute United States Center for Electromagnetic Simulation Beijing Institute of Technology Haidian District Beijing China

Conventionally, space-charge (SC) limited current density is defined as the maximal current density allowed to traverse a diode under a DC voltage when a time-invariant flow is injected from the cathode. In this work, we study the SC limited current density under a time-varying injection for both classical and relativistic regimes and determine the maximal amount of limited current density under certain conditions. Our simulations show that it is unlikely that a time-varying injection emitted from cathode exceeds the known SC limits, in either classical or relativistic regime. Copyright © 2017, The Authors. All rights reserved.

关键词： Current density

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Integrated Intercalation-Based and Interfacial Sodium Storage in Graphene-Wrapped Porous Li4Ti5O12 Nanofibers Composite Aerogel

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advanced Energy Materials 2016年第13期6卷

作者： Chen, Chaoji Xu, Henghui Zhou, Tengfei Guo, Zaiping Chen, Lineng Yan, Mengyu Mai, Liqiang Hu, Pei Cheng, Shijie Huang, Yunhui Xie, Jia State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan430074 China State Key Laboratory of Materials Processing and Die and Mould Technology School of Materials Science and Engineering Huazhong University of Science and Technology Wuhan430074 China School of Mechanical Materials and Mechatronics Engineering University of Wollongong North WollongongNSW Australia State Key Laboratory of Advanced Technology for Materials Synthesis and Processing WUT-Harvard Joint Nano Key Laboratory Wuhan University of Technology Wuhan430070 China Collaborative Innovation Center of Intelligent New Energy Vehicle Tongji University Shanghai201804 China

Sodium storage in both solid–liquid and solid–solid interfaces is expected to extend the horizon of sodium-ion batteries, leading to a new strategy for developing high-performance energy-storage materials. Here, a novel composite aerogel with porous Li4Ti5O12 (PLTO) nanofibers confined in a highly conductive 3D-interconnected graphene framework (G-PLTO) is designed and fabricated for Na storage. A high capacity of 195 mA h g−1 at 0.2 C and super-long cycle life up to 12 000 cycles are attained. Electrochemical analysis shows that the intercalation-based and interfacial Na storage behaviors take effect simultaneously in the G-PLTO composite aerogel. An integrated Na storage mechanism is proposed. This study ascribes the excellent performance to the unique structure, which not only offers short pathways for Na+ diffusion and conductive networks for electron transport, but also guarantees plenty of PLTO–electrolyte and PLTO–graphene interfacial sites for Na+ adsorption. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

关键词： Storage (materials)

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Comparation of Magnetic Fields Between Cascade BDFM and Single-Frame BDFM

Comparation of Magnetic Fields Between Cascade BDFM and Sing...

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International Conference on Electrical Machines and Systems

作者： Zhenming Li Xuefan Wang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology China

ISBN: (纸本)9781467388634

Single-frame brushless doubly-fed machine (BDFM) is a new type of AC machine which is developed from the fundamentals of Cascade BDFM and can be used in many application fields. A magnetic field analytical model of Single-frame BDFM is established in this paper, which will demonstrate the difference of operating principles between single-frame BDFM and cascade BDFM by using finite element method (FEM). It is concluded that the operating principle of single-frame BDFM is similar to synchronous machine;while the operating principle of cascade BDFM shows some characteristics of a synchronized asynchronous machine.

关键词： FEM operating principle cascade

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A power decoupling method based on four-switch three-port DC/DC/AC converter in DC microgrid

A power decoupling method based on four-switch three-port DC...

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IEEE Transactions on Industry Applications

作者： Cai, Wen Jiang, Ling Liu, Bangyin Duan, Shanxu Zou, Changyue State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China

This paper presents a power decoupling method based on a four-switch three-port dc/dc/ac converter in dc microgrid. The proposed topology has three interfaces which can be connected with a dc source, a capacitor, and an ac port. With a corresponding power flow control method, this converter can decouple the low-frequency ripple power which is necessary for the ac port and undesirable for the dc source with small capacitor. The proposed topology is compact and cost-effective because, compared with the H-bridge inverter, no extra switches or devices are required. With the model of the proposed dc/dc/ac converter, a power control method with two inductors' current control is presented for power decoupling. In addition, the control parameters are designed as well. Experimental results on the laboratory prototype verified the feasibility of the proposed topology and the designed power control method. © 1972-2012 IEEE.

关键词： Power converters Capacitors Cost effectiveness Electric power distribution Power control Topology Dc micro grid Power decoupling Ripple control Single phase inverters Three port converters

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Stability analysis of instantaneous average current sharing control strategy for parallel operation of UPS modules 7

Stability analysis of instantaneous average current sharing ...

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7th Annual IEEE Energy Conversion Congress and Exposition, ECCE 2015

作者： Liu, Peng Chen, Changsong Cai, Jiuqing Duan, Shanxu State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan430077 China

ISBN: (纸本)9781467371506

This paper discusses and analyzes the parallel operation of uninterruptible power supplies (UPS) with instantaneous average current sharing control strategy. The analysis demonstrate that the control method introduces a virtual impedance between the inverters. If the impedance configured as resistive, it will simplify the control strategy, the paper analyzes the stability of the control system by changing the control diagram from voltage-source mode to current-source mode, precise stable condition has been obtained considering the varying line inductance. Simulation models and several experimental 220V/2kVA inverters are built and paralleled to verify the theoretical predictions. © 2015 IEEE.

关键词： Uninterruptible power systems

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