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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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Study on the SVPWM algorithm of N-level inverter in the context of non-orthogonal coordinates

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Frontiers of Electrical and Electronic Engineering in China 2006年第2期1卷 199-204页

作者： XIAO Xiang-ning JIANG Xu LIU Hao LIU Hui-wei KONG Sheng-li Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power UniversityBeijing 102206China Electric Power of Henan Zhengzhou 450000China

In this paper,the authors propose a new space vector pulse width modulation(SVPWM)algorithm based on non-orthogonal coordinates for N-level ***,it is pointed out that classicalαβcoordinates-based SVPWM has many shortcomings because of improper coordinate ***,a non-orthogonal coordinates-based SVPWM is proposed to solve these *** proposed algorithm can easily identify which sector the reference space vector falls in and conduct simple operations to find the duty cycle of each ***,it is verified that the proposed SVPWM is actually a pulse−width modulation(PWM)technology based on line voltages.

关键词： power electronics N-Level SVPWM KL coordinates

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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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The structure and realization of voltage sags monitoring system based on GPRS and web

The structure and realization of voltage sags monitoring sys...

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2006 China International Conference on Electricity Distribution, CICED 2006

作者： Chen, Pengliang Xiao, Xiangning Tao, Shun Ye, Zhifeng Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University 102206 China

ISBN: (纸本)0863416381

In this paper, the status of the study on the voltage sags monitoring at home and abroad is summarized. Based on the GPRS wireless communication and Web technology, the dynamic monitoring and data analysis system has designed for monitoring the voltage sags uninterrupted in a local network. The voltage sags in the receiving end network region are recorded, analyzed and counted by this system, at the same time, the information of these sags is transmitted to a remote computer using GPRS. This system can provide the policy-making support for alleviating the voltage quality questions. Based on Web, clients can login the service to scan periodical and non-periodical statistics reports of sag events.

关键词： Monitoring

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Study of TCPS-PWM based high-voltage cascade multilevel H-bridge active power filter

Study of TCPS-PWM based high-voltage cascade multilevel H-br...

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2006 China International Conference on Electricity Distribution, CICED 2006

作者： Zhou, Guoliang Shi, Xinchun Guo, Xiuhong Fu, Chao Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding 071003 China

ISBN: (纸本)0863416381

A novel control strategy for 11-level cascade H-bridge APF based on TCPS-PWM is proposed in this paper. When the cascade inverter is applied to active power filter for distribution system, it is expected that the switching frequency and the EMI will be dramatically reduced below that of the traditional one. By the strategy, each power unit operates with relatively low frequency. At the same time, the equivalent switching frequency is still high so as to meet the high tracing ability for better compensation performance. This paper also focuses on the transposing modulation method to solve the problem of the balance of each DC voltage. PSIM is adopted for simulation of 11-level cascade H-bridge high-voltage active power filter which is to compensate the 10kV distribution system. Analytical and simulated results show the feasibility and superiority of the proposed strategy.

关键词： Pulse width modulation

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A new 10kV dynamic reactive power compensation and harmonics suppression equipment

A new 10kV dynamic reactive power compensation and harmonics...

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2006 China International Conference on Electricity Distribution, CICED 2006

作者： Yin, Zhongdong Xiao, Xiangning Zhang, Jianhua Shu, Qing Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Ministry of Education Beijing 102206 China

ISBN: (纸本)0863416381

In this paper, an integrating schme to suppress the harmonics and compensate the reactive power based on the topology of thyristor controlled reactors (TCR) is presented. A new 10kV/500kvar dynamic reactive power compensation and harmonics suppression prototype made by placing a series of individual low voltage TCR reactive power modules in parallel and connecting them to the system through a multi-coil transformer has been developed. Experimental results have proven that the new euipment not only has all the advantages of the TCR but also very low level harmonics, which eliminates the need for suppression euipments. Furthermore, the cost is decreased and the reliability of the system is increased by avoiding euipments connected in series. A low voltage modular structure is adopted to increase the system capacitance and ease in augmenting the design. This equipment can solve the problems of large scale of load fluctuation and the serious excess of harmonic level.

关键词： Reactive power

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Transient plane wave coupling to overhead line above a multi-layer soil

Transient plane wave coupling to overhead line above a multi...

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2006 IEEE International Symposium on Electromagnetic Compatibility, EMC 2006

作者： Qi, Lei Cui, Xiang Li, Lin IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding Hebei China

ISBN: (纸本)142440293X

Considering the displacement current in the multi-layer soil, the formulas of the ground return impedance and the Fresnel reflection coefficients are derived in frequency domain. These expressions are valid for discretional soil conductivities and the whole range of frequencies. For the convenience of transient analysis, the vector fitting method is adopted to expand the time-domain forms of the ground return impedance and the Fresnel reflection coefficients into the sum of finite exponential functions which are easy to be treated. Based on the recursive algorithm for the time-domain convolution, the finite difference time-domain (FDTD) method improved by the authors is used for the transient analysis of the external excited overhead line. Compared with the existing method applicable for homogeneous soil, the proposed method is demonstrated to be correct. © 2006 IEEE.

关键词： Overhead lines

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