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power Tech Conference

作者： Gengyin Li Ming Zhou Biao Zhang Jin Yang Key Laboratory of Power System Protection Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China School of Electrical and Electronic Engineering China Electric Power University Baoding Hebei China

Voltage sag, one of the modern power quality problems, may cause tremendous economic loss, which needs scientific method to evaluate. This paper proposes an approach using quality loss function and signal-to-noise ratio (SNR) in quality engineering theory to make economic assessment to voltage sag. The inverted normal probability loss function is used to describe losses of single-type sags, where SNR method is applied to integrate different types together. The index of sag-caused loss is proposed, which is an important parameter for PQ evaluation. A five-node 35 kV distribution system is used to verify the proposed approach. The result shows that the proposed method could effectively assess financial losses caused by sags and be a reasonable instruction for PQ evaluation, improvement and pricing.

关键词： power quality Voltage fluctuations power generation economics power engineering and energy IEEE members power markets Pricing Signal to noise ratio power system economics Electric variables measurement

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Study of UHV DC corona performance in a mini corona cage

Study of UHV DC corona performance in a mini corona cage

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Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference

作者： Wei Wang Chengrong Li Jianbin Fan Chen Gu Yitao Jiang Guohua Cui Beijing Key Laboratory ofHigh Voltage & EMC Key Laboratory ofPower System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing China China EPRI Beijing China

To research the effect of high altitude on corona performance of UHV DC transmission line, the corona inception voltage gradient of a copper line at different air pressure level from 101 kPa to 61 kPa was measured in a mini corona cage. The results have been compared with calculated results of Peek law and the corona inception voltage gradient correction factor of air pressure was presented.

关键词： Corona Voltage Humidity system testing Laboratories Copper Pressure measurement Oscilloscopes power transmission lines Acoustic measurements

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WAMS Implementation in China and the Challenges for Bulk power system protection

WAMS Implementation in China and the Challenges for Bulk Pow...

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IEEE General Meeting power& Energy Society

作者： Qixun Yang Tianshu Bi Jingtao Wu Beijing Sifang Automation Company Limited North China Electric Power University China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under MOE North China Electric Power University Beijing China Beijing Sifang Automation Company Limited Beijing China

Synchronized phasor measurement technology has been gaining increasingly interests in China due to its wide area time synchronization capability and fast transmission speed. Over 10 years of implementation of wide area measurement system (WAMS) in Chinese power grid have shown its great value in power system dynamic monitoring and potential applications in system modeling and validation, feedback control and system wide protection. This paper reviews the overall implementation of WAMS in China and analyzes the corresponding characteristics of WAMS. Moreover the challenges for bulk power system protection with synchronized phasor measurement technology are presented also.

关键词： power system protection Wide area measurements Area measurement Gain measurement Velocity measurement Time measurement power grids power system dynamics monitoring Modeling

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Research on Identifiability of Equivalent Motor in Composite Load Model

Research on Identifiability of Equivalent Motor in Composite...

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power Tech Conference

作者： Ma Jin Han Dong He Renmu Dong Zhaoyang David J. Hill Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control of Ministry of Education North China Electric Power University Beijing China School of Information Technology and the Electrical Engineering University of Queensland Saint Lucia QLD Australia Department of Information Engineering Australian National University Australia

Load modeling is very important for power system dynamic analysis and control. The composite load model widely applied recently in the power system operation centre consists of the static load and the equivalent motor. Current practices in measurement-based load modeling identify all the parameters in this composite load model. However, it is not clear whether all these parameters could be identified from the measurements. This paper investigates the identifiability of the equivalent motor parameters in the composite load model. Trajectory sensitivity approach is applied first to find the motor parameters that have great effects on the measured active as well as reactive load dynamics. The analysis results show that the motor outputs have various sensitivities with respect to the parameters. Since the voltage disturbance, the active load and the reactive load dynamics are applied to identify the motor parameters, those parameters affecting the measurements to a great extent are observable, thus identifiable from the measurements; while those that have little effects on the motor outputs are unobservable from the measurements and consequently unidentifiable. The case studies verify the identifiability of the motor parameters.

关键词： Load modeling power system modeling power system dynamics power system simulation power system stability power system analysis computing power system measurements Voltage power system control power systems

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Research on the Model and control Strategy of One Multi-Module-Converter Based VSC-HVDC

Research on the Model and Control Strategy of One Multi-Modu...

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2007 IEEE International Symposium on Industrial Electronics (ISIE 2007), vol.2

作者： Guoliang Zhou Xinchun Shi Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding China

This paper presents a model and control strategy for one multi-module-converter based VSC-HVDC system. Each converter operates with a fairly low switching frequency, and thus it is applicable to select high-power low-switching-frequency and low-conduction-loss electronic devices such as IGCT or GTO in high-power applications. A mathematical model is developed for the overall multi-module-converter based VSC-HVDC system. A controller is also designed systematically for the HVDC system based on the developed system model. Performance of the overall HVDC system and effectiveness of the designed controller are evaluated based on digital time-domain simulations in the MATLAB software environment.

关键词： power conversion Switching frequency Mathematical model Switching converters HVDC transmission Topology Voltage Sampling methods power system modeling Reactive power control

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The Effect of DVR on Distribution system with Distributed Generation

The Effect of DVR on Distribution System with Distributed Ge...

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International Conference on Electrical Machines and systems 2007(ICEMS2007)(第十届国际电机与系统会议)

作者： Xuanxuan Liu Peng Li Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China

Recent years, some DG (distributed generation) have been introduced in distribution systems, and the voltage violation problem has been at stake for the distribution system. The impact of DG integration on distribution system is studied in this paper, and the transient stability mechanism of DG is analyzed theoretically. This paper investigates the dynamic analysis of a DVR when applied to correct the voltage distortion in distribution system. Then the model of DG is built by Matlab/Simulink. And it is used to study the impact of DG integration on the distribution system. Then the voltage regulation-dynamic voltage restorer (DVR) is introduced to distribution network with distributed generation. A calculation method for DVR in distribution system with distributed generation is proposed, which is based on a semi-period algorithm to extract fundamental component from fault signal then extract the fundamental positive sequence voltage by the decomposition instantaneous link, and then the quantity of voltage compensation can be solved by direct detection algorithm. Simulation results show that the introduction of DVR (dynamic voltage restorer) to the distribution system with distributed generation is good for voltage regulation and making a good guarantee of the voltage quality of sensitive loads; and the algorithm for DVR is simple and effective.

关键词： Distributed control Voltage control power system stability power quality control systems Signal restoration Detection algorithms Photovoltaic systems Wind turbines power systems

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Measurement-based Load Modeling using Genetic Algorithms

Measurement-based Load Modeling using Genetic Algorithms

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Congress on Evolutionary Computation

作者： Jin Ma Ren-mu He Zhao-yang Dong David J. Hill Key Laboratory of Power System Protection and Dynamic Secutitu Monitoring and Control of Ministy of Education North China Electric Power University Beijing China The School of Information Technology and Electrical Engineering University of Queensland QLD Australia The Department of Infotmation Engineering Australian National University Australia

Load modeling is very important to power system operation and control. Measurement-based load modeling has been widely practiced in recent years. Mathematically, measurement-based load modeling problem are closely related to the parameter identification area. Consequently, an efficient optimization method is needed to derive the load model parameters based on the feedback of estimation errors between the measurements and model outputs. This paper reports our work on applying genetic algorithms on measurement-based load modeling research. Due to its robustness to the initial guesses on the load model parameters, genetic algorithms are very suitable for load model parameter identification. Two cases including both the real measurement in a power station and the digital simulation are studied in the paper. For comparison purpose, the classical nonlinear least square estimation method is also applied to find the load model parameters. The simulated outputs from the load model confirm the efficiency of genetic algorithms in measurement-based load modeling analysis. Future work will focus on fastening the converging speed of the genetic algorithms, and/or utilizing more efficient evolutionary computation methods.

关键词： Load modeling Genetic algorithms power system modeling Parameter estimation power system measurements power system control power systems control system synthesis Area measurement Optimization methods

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The Propagation Characteristics of Electromagnetic Wave Generated from Partial Discharges in power Transformer by FDTD Simulation

The Propagation Characteristics of Electromagnetic Wave Gene...

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2007 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, vol.1

作者： Zhiguo Tang Chengrong Li Wei Wang Hui Wang Li Wang Yansheng Ding Beijing Key Laboratory of High Voltage & EMC North China Electric Power University China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University China State Grid Corporation of China Beijing China

The radiation and propagation of electromagnetic (EM) waves generated from PD caused by the obstruction of main transformer components are studied by FDTD simulation in order to get more information for PD location and diagnosis. Current filament, perfect conductive cylinder and perfect conductive spiral coil models are used to simulate the radiation and the influences of iron-core and transformer coil to the propagation of EM waves. The results demonstrate dynamic propagation process of EM waves in time order, and prove the correctness of the shortest optical path principle. But the attenuation and distortion of EM waves-especially the first peak amplitude-caused by the obstruction of large solid conductive obstacle like iron-core are quite intensive that it may cause great difficulties to identify exact arriving time position of incident waves coming along the shortest optical path. While the influences of the coil to the propagation of EM waves are so little that HF EM waves can penetrate it in almost linear path.

关键词： Electromagnetic propagation Electromagnetic scattering Character generation power generation Partial discharges power transformers Finite difference methods Time domain analysis Electromagnetic radiation Coils

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Numerical prediction of EMI on the secondary DC cable in cable tunnel due to a direct lightning strike in substation

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IEEE TRANSACTIONS ON MAGNETICS 2006年第4期42卷 863-866页

作者： Lei, Q Xiang, C Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education School of Electrical Engineering North China Electric Power University Hebei 071003 China

Electromagnetic interference (EMI) on secondary de cable in cable tunnel due to a direct lightning strike in substation threatens the safe operation of electronic equipment and system connected to the cable. In order to reduce EMI, the cable shield is generally connected to the grounding grid at both ends. Ground potential difference between two grounding points of the cable shield can be high due to high impedance of the grounding grid at high frequencies. In this paper, we present a hybrid method to analyze this complex system. As a result, both the current flowing in the cable shield and the transverse voltage between the cable core and shield are calculated. Compared with the measured results, the proposed method is demonstrated to be correct and effective.

关键词： electromagnetic interference (EMI) grounding grid in substation lightning secondary cable

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Analysis of power line tower lightning surge impedance using the time domain electromagnetic method

Analysis of power line tower lightning surge impedance using...

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4th Asia-Pacific Conference on Environmental Electromagnetics, CEEM'2006

作者： Mingxia, Zhang Xiang, Cui Lin, Li Changzheng, Gao Zhibin, Zhao Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding China

ISBN: (纸本)1424401836

A time domain electromagnetic field approach is proposed to investigate the lightning surge impedance of the full scale UHV tower with grounding system. The model, which is validated by comparing the result to those of other method, can be used to analyze the lightning surge performance of a power line more accurately. Finally, this method is applied to analyze the surge impedance and potential of a real UHV tower.

关键词： Electric lines

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