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17th International Zurich Symposium on Electromagnetic Compatibility, 2006

作者： Gao, Changzheng Li, N. Li, Bing Zhao, Zhibin Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Under Ministry of Education North China Electric Power University Baoding Hebei 071003 China

ISBN: (纸本)3952299049

The power line tower lightning surge impedance is computed using an electromagnetic field approach. After comparing the results computed by our method and those tested with both a vertical conductor and reduced scale 4-poles model of tower, the method we used is proved to be right and more practical as the soil and the grounding system of the tower can be considered in the method. Using this method, the lightning surge impedance of the full scale UHV tower with grounding system is analyzed and the results show that the lightning surge impedance of a tower on the perfect ground has a little difference with those of an actual tower considering both its grounding system and soil resistivity, and when the soil resistivity is changed, the surge impedance changes slightly. Furthermore, a circuit model of the tower is obtained by Vector Fitting method based on the results we computed. Using the circuit model, the lightning surge performance of a power transmission line can be analyzed more accurately by EMTP or other methods.

关键词： Lightning protection

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Subcell FDTD modeling of electrically thin dispersive layers using Z transforms

Subcell FDTD modeling of electrically thin dispersive layers...

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17th International Zurich Symposium on Electromagnetic Compatibility, 2006

作者： Jiao, Chaoqun Cui, Xiang Li, N. IEEE Key Laboratory of Power System Protection Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding 071003 Hehei Province China

ISBN: (纸本)3952299049

A novel technique for treating electrically thin dispersive layers with the finite-difference time-domain (FDTD) method based on Z transforms is introduced. The proposed model is based on the subcell technique, where the constitutive relations are locally averaged in the FDTD grid. The most significant feature of the proposed model is its ability to model rather complicated dispersive layers having multiple pole pairs. The model is validated with several numerical examples making comparison with the exact results.

关键词： Electromagnetic dispersion

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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 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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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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Numerical calculation of grounding current through Capacitive Voltage Transformer due to substation switching operation

Numerical calculation of grounding current through Capacitiv...

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2006 IEEE International Symposium on Electromagnetic Compatibility, EMC 2006

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

ISBN: (纸本)142440293X

The constituent of Capacitive Voltage Transformer (CVT) are almost capacitances in primary side, and they act essentially as a short circuit to the transient current produced by a switching operation, which will generate high grounding current. Because capacitance is lumped parameter, so this paper use Finite-Difference Time Domain method (FDTD) to build calculation formula of Multi-Conductor Transmission Lines (MTL) whose branch points has lumped parameter network. Based on the formula, the grounding current through CVT produced by substation switching operation has been calculated. The calculation results of this paper are anastomotic with the simulation based on EMTP. It has certain consult meaning for the research of substation electromagnetic interference (EMI) on primary and secondary equipments. © 2006 IEEE.

关键词： Electric grounding

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Overvoltage analysis of long AC transmission line connected with VSC in power system restoration

Overvoltage analysis of long AC transmission line connected ...

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7th IET International Conference on Advances in power system control, Operation and Management, APSCOM 2006

作者： Li, Guangkai Li, Gengyin Liang, Haifeng Zhao, Chengyong Yin, Ming Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding 071003 Hebei China

ISBN: (纸本)0863412467

Overvoltage in power system restoration must be verified. The basic principle of VSC-HVDC (voltage source converter based high voltage direct current transmission) is briefly introduced. VSC-HVDC has such characteristics as flexible operation and control modes, independent control of active and reactive power, and operation on four quadrants. The overvoltage of the overvoltage between AC transmission line and the line connected with VSC-HVDC are calculated by theory analysis and simulation on PSCAD/EMTDC. The comparison of those overvoltage shows that the overvoltage of long AC transmission line connected with VSC-HVDC is lower than that of pure AC transmission lines. So the application of VSC-HVDC can enhance the speed of power grid restoration.

关键词： Restoration

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