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International Conference on Electrical Machines and Systems

作者： Xiaoguang Wang Haitao Wang Hongqin Xie Dezhang Lou Kai Yang State Key Laboratory of Advanced Electromagnetic Engineering and Technology * Huazhong University of Science and Technology Wuhan 430074 R.P.China Hubei University of Technology School of Mechanical Engineering

ISBN: (纸本)9781467388634

This paper proposed an integrated hall magnetic encoder error correction method. In order to eliminate the steady-state error caused by installation errors and so on, this paper proposed three-phase zero and sine symmetric reconstruction. The sum of three-phase hall signal could be constant zero through zero reconstruction. In sine symmetric reconstruction method, transform threephase hall signal into two-phase orthogonal static coordinate to make sinusoidal orthogonal reconstruction. Then Symmetrical three-phase sinusoidal signal could be obtained using Clark transform. In order to solve dynamic error in temperature drift, this paper proposed a mapping projection method. This algorithm calculates real-time signal amplitude to get temperature drift coefficient. After standardize actual signal using this proportion factor, motor position angle can be received by querying standard table. The proposed solution can solve position angle constant and jump problem near the endpoint of angle section. Moreover, it has simple realization and high response speed. The simulation and experiments were carried out to prove the performance and validity.

关键词： reconstruction mapping projection looking-up table magnetic encoder

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Characteristics of Long Air Gap Discharge Current Subjected to Switching Impulse

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CSEE Journal of Power and Energy Systems 2015年第3期1卷 49-58页

作者： Yishi Yue Hengxin He Weijiang Chen Junjia He Chuanqi Wu Xiangen Zhao Feng Huo State Key Laboratory of Advanced Electromagnetic Engineering and Technology(Huazhong University of Science and Technology) Wuhan 430074China

Measuring the pre-breakdown current of long sparks in air is important for investigating the discharge *** the breakdown of long air gaps is conducted by a series of streamer-leader processes,the corresponding current signals cover a bandwidth of 0 to more than 20 *** accuracy of the current from the high voltage side is affected by the displacement current and impulse electromagnetic *** this paper,a coaxial current sensor with a DC bandwidth of 74.45 MHz is developed.A displacement current-restrained electrode structure is proposed to reduce the equivalent capacitance between the current sensor and the ground over 30 *** with the digital optical fiber synchronous acquisition unit,a current measurement system for long air gap discharge is *** the purpose of the UHV system’s external insulation optimization design,the discharge current waveform of a 6 m rod-plane air gap under positive switching impulse voltage with 250µs and 1000µs time to crest is *** images and stressed voltage are combined to analyze the continuous feature of a current waveform under critical time to crest impulse and discontinuous feature under long front duration *** the purposes of a lightning protection study,the current waveform of a 10 m rod-plane air gap is subjected to negative switching ***,the pulse characteristics of the current corresponding to the single channel and branching stepped negative leader are discussed.

关键词： Charge density fluctuation coefficient leader discharge long air gap discharge transient current measurement

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Rotor dynamics of DFIG wind turbines under grid faults

Rotor dynamics of DFIG wind turbines under grid faults

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International Conference on Renewable Power Generation, RPG 2015

作者： Ye, Chao Ying, Jie Hu, Jiabing Wang, Yajing Wang, Ningbo State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan430074 China Wind Power Technology Center Gansu Electric Power Corporation Lanzhou730050 China

ISBN: (纸本)9781785610400

With the increasing wind power penetration, the electromechanical transient stability of wind turbines is more and more significant. Deep research of rotor dynamics of wind turbines is fundamental to the stability analysis during grid faults. This paper concentrates on the rotor motion of doubly-fed induction generator (DFIG) wind turbines (WTs) during a symmetrical grid fault. Various factors having influence on input or/and output powers are considered under the existing transient power control strategy. The objective of this paper is to provide an insight into the rotor dynamic behaviour of DFIG WTs during grid faults.

关键词： Wind turbines

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Coordinated strategy between positive- and negative-sequence currents of wind farms for transient stability enhancement of synchronous generators under asymmetrical grid faults

Coordinated strategy between positive- and negative-sequence...

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International Conference on Renewable Power Generation, RPG 2015

作者： Wang, Longfei He, Wei Hu, Jiabing Wang, Ningbo State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan430074 China Wind Power Technology Center Gansu Electric Power Corporation Lanzhou730050 China

ISBN: (纸本)9781785610400

As the penetration of wind power is growing, it is demanded that wind farms should contribute to maintaining power system stability, for particularly under various grid fault conditions. Highly-penetrated wind farms are able to influence synchronous generators' (SGs') behaviour for transient stability enhancing by injecting the designed positive- and negative-sequence currents, especially when the electric distance between wind farms and SGs is short. In this paper, SG's transient stability during asymmetrical grid faults is the centre of interest. The relationships between SG's rotor swing function and wind turbines injecting currents are analysed based on the mathematical models of unbalanced power system. Coordinated requirements for positive- and negative-currents injection of wind turbines, for the purposes of to enhance transient stability, are proposed during asymmetrical faults. Time domain simulation validates the result.

关键词： Wind farm

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General Diagnosis of Transformer Winding Axial Displacement Faults Based on FEM Simulation and On-site Experiments

General Diagnosis of Transformer Winding Axial Displacement ...

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IEEE Electrical Insulation Conference

作者： Fei Lu Lei Jin Siwei Liu Yi Liu Hua Li Fuchang Lin State Grid Key Laboratory of On-site Test Technology on High Voltage Power Apparatus State Grid Hubei Electric Power Research Institute State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science & Technology

ISBN: (纸本)9781467387071

Structural faults detection of power transformers are quite significant, and general diagnosis based on different test and simulation methods is commonly used to detect mechanical and/or electrical faults in power transformers. In this paper, the diagnosis of the transformer winding axial displacement faults based on FEM simulation and on-site experiment is carried out and presented. Based on the FEM simulation, it is necessary to analyze the effect of the axial displacement faults on the change of the electrical parameters. The whole winding's or the single disk's axial displacement are under consideration, and different fault levels are taken into consideration in the simulation analysis to investigate the influence of axial displacement on the electrical parameters. Using the calculated parameters, a distributed model of the power transformer based on ATP/EMTP is present to study the performance of frequency response curve on the axial displacement with different fault levels. The operating states of several 110 kV power transformers are tracked, and a typical transformer after the short-circuit impact is tested. The FRA test results are obtained before and after the short-circuit impact. The simulation results and the on-site test results are compared, and they show a better consistency. It can be concluded that under the typical impact of the axial displacement, the frequency response curve starts an obvious variation from 150 kHz, and the resonances and anti-resonances are shifted to the high frequency direction. The overall fault detection results show that the proposed method can discriminate the winding axial displacement fault with the high hit ratio.

关键词： Power transformer Frequency response analysis Axial displacement Winding deformation Finite element method

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Fuzzy comprehensive evaluation for transmission grid planning based on combination weight

Fuzzy comprehensive evaluation for transmission grid plannin...

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International Conference on Power and Energy, CPE 2014

作者： Li, Z.H. Lin, Y. Chen, W.H. You, D.H. Wang, G. Dong, M.L. Chen, Q.R. Zou, Y. Hu, J. Guangdong Power Grid Development Research Institute Co. Ltd GuangzhouGuangdong China State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology WuhanHubei China

ISBN: (纸本)9781138027824

In order to remedy the defect that the determination of weight in fuzzy comprehensive evaluation is impacted by subjectivity, the combination weight is introduced. In this paper, the optimization Model combines the subjective weight and objective weight, which is solved by PSO, is built. At the same time, In order to give full consideration to the uncertain and fuzzy factors which involved in the grid planning, this paper combines the combination weight and fuzzy comprehensive evaluation to assess the grid-planning scheme. The calculation results of IEEE Garver-6 show that the proposed fuzzy comprehensive evaluation system is clear in theory and convenient to calculate, the combination weight is objective and reasonable as well as its results are scientific and intuitive. © 2015 Taylor and Francis Group.

关键词： Particle swarm optimization (PSO)

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Assistant decision-making method for distribution network planning based on Topsis and combination weight

Assistant decision-making method for distribution network pl...

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International Conference on Power and Energy, CPE 2014

作者： Li, Z.H. Lin, Y. Xu, L. Yang, X.Y. Wu, J.S. Chen, W.H. Zhang, K.M. Zhang, B.H. Guangdong Power Grid Development Research Institution Co. Ltd GuangzhouGuangdong China State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology WuhanHubei China

ISBN: (纸本)9781138027824

In order to solve the widespread problems of integrated decisions in grid planning, a comprehensive evaluation method of decision-making is proposed based on composition of TOPSIS method and combination weights. Used in network planning actual case, and describe the method of calculation process step by step. By constructing the optimization model, the subjective weights and objective weights are combined and particle swarm optimization is applied to strike the index weight, and improvement of TOPSIS method is completed. The actual results of the assessment plan cases confirmed the rationality and effectiveness of this method. © 2015 Taylor and Francis Group.

关键词： Particle swarm optimization (PSO)

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Modularized small signal modelling method for DC grid

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical engineering 2016年第11期36卷 2880-2889页

作者： Lu, Xiaojun Lin, Weixing Wen, Jinyu Li, Yunfeng Wu, Yanan An, Ting State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology WuhanHubei Province430074 China Global Energy Interconnection Research Institute Changping District Beijing102211 China

A modularized small signal modelling method for DC grid was proposed. A DC grid is divided into AC network subsystems, converter subsystems and the DC network subsystem, where each converter subsystem is further divided into AC electrical module, DC electrical module, controller module, signal filtering module and phase lock loop module. Models of each subsystem and each module are interlinked through linking matrixes to form the overall small signal model of a DC grid. Small signal model of each module and the linking matrixes between different modules were derived. A generic control model based on control flag was proposed to model different typical VSC controllers using a same modelling structure. Linking matrixes between DC network and the converter systems were derived, an overall modelling matrix for DC grid was then presented. Accuracy of the proposed modelling method was verified on a 3-terminal HVDC system. Results show that for small disturbance, the small signal model is able to output almost identical simulation results as detailed electromagnetic model and nonlinear state-space model. The proposed modular modelling method and generic controller modelling method is able to significantly reduce the complexity of small signal modelling of DC grids. © 2016 Chin. Soc. for Elec. Eng.

关键词： Controllers

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Discontinuous Precipitation Reaction Front of Cellular Recrystallization for a Single-Crystal Superalloy Studied by Electron Microscopy

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Chinese Physics Letters 2015年第7期32卷 106-109页

作者：卓龙超梁淑华王锋刘玉峰熊继春 School of Materials Science and Engineering Xi'an University of Technology Xi'an 710048 National Center for Electron Microscopy in Beijing School of Materials Science and Engineering State Key Laboratory of New Ceramics and Fine Processing Laboratory of Advanced Materials Tsinghua University Beijing 100084 State Key Lab of Power Systems Department of Thermal Engineering Tsinghua University Beijing 100084 Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials Beijing 100095

Combining analytical transmission electron microscopy systematic tilting, scanning transmission electron microscopy mapping and nano-beam electron diffraction operations, we obtain direct experimental proofs on the boundary type, elemental distribution and structure of the cellular reerystallization reaction front for a single- crystal superalloy. It is demonstrated that the cellular recrystallization reaction front usually corresponds to coincidence site lattice boundaries, and a thin layer of γ-forming elements such as Re, Cr, Mo and Co invariably exists in the direct reaction front. Furthermore, the thin layer with γ-forming elements is proved to be γ phase, with the same orientation as the neighboring original matrix.

关键词： CR OM Discontinuous Precipitation Reaction Front of Cellular Recrystallization for a Single-Crystal Superalloy Studied by Electron Microscopy

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A unified dynamic phasor modeling and operating characteristic analysis of electrical system of MMC

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical engineering 2016年第20期36卷 5479-5491页

作者： Lu, Xiaojun Lin, Weixing An, Ting Li, Yunfeng Wen, Jinyu Yao, Wei State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology WuhanHubei Province430074 China Global Energy Interconnection Research Institute Changping District Beijing122000 China

A unified dynamic phasor model (DPM) for electrical system of modular multilevel converter (MMC) under the rotating frame was proposed. The model considers the AC voltage components in the rotating frame and the DC voltage as electrical inputs, takes the fundamental frequency and second harmonic components of modulation indices as the control inputs. By individually modeling the controller, the internal dynamics of MMC and the dynamics of external electrical system, the proposed dynamic phasor model is capable of conveniently interconnecting models of MMC electrical dynamics, controllers and external electrical system. The dynamic phasor model of MMC was therefore normalized. By setting the derivative terms in the DPM to zero, static phasor model for the electrical system of MMC was achieved. By linearizing the DPM around the steady-state operating point, small signal model for the electrical system of MMC was obtained. As a result, the proposed DPM unified the dynamic phasor model, static phasor model and small signal model of MMC. Based on the obtained static phasor model of the MMC, an open loop circulating current suppressing control (CCSC) strategy and a method of analytically analyzing the operating characteristic of MMC considering various constraints were 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. © 2016 Chin. Soc. for Elec. Eng.

关键词： Controllers

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