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2007 IEEE power Engineering Society General Meeting, PES

作者： Wang, Zengping Ma, Jing IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding 071003 Hebei Province China

ISBN: (纸本)1424412986

This paper presents a novel scheme based on grille fractal for distinguishing between inrush currents and internal fault currents in transformers, which is derived from the singularity detection in the waveforms. First, differential currents are analyzed on the basis of grille fractal (GF). Noises are then filtered by use of the adaptive generalized morphological filter (AGMF). In a total of 158 experimental cases, the inrush current is characterized by the drastic variation, but the faulty current is kept almost constant. The experimental results indicate that the proposed technique is stable and reliable during discrimination between internal faults and magnetizing inrush currents, and saturation of current transformers (CTs). © 2007 IEEE.

关键词： Electric fault currents

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A novel algorithm for discrimination between inrush currents and internal faults based on equivalent instantaneous leakage inductance

A novel algorithm for discrimination between inrush currents...

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2007 IEEE power Engineering Society General Meeting, PES

作者： Ma, Jing Wang, Zengping IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding 071003 Hebei Province China

ISBN: (纸本)1424412986

A novel scheme based on equivalent instantaneous leakage inductance (EILI) to distinguish inrush currents from internal fault currents in power transformers is proposed, which is derived from the circuit differential equation. First, the EILI that represents different characteristics between the inrush current and an internal fault is defined, and its calculation methods and the criteria of two-winding and three-winding transformers are derived. This method does not require B-H curve data and the parameters of leakage inductances obtained from the transformer manufacturer. A total of 147 experimental cases verify that the EILI calculated in real time is able to clear internal fault even light fault rapidly and correctly. © 2007 IEEE.

关键词： Fault tolerance

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Parameters optimization of VSC-HVDC control system based on simplex algorithm

Parameters optimization of VSC-HVDC control system based on ...

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2007 IEEE power Engineering Society General Meeting, PES

作者： Chengyong, Zhao Xiangdong, Lu Guangkai, Li IEEE Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Baoding 071003 Hebei Provinece China

ISBN: (纸本)1424412986

The performance of VSC-HVDC system depends on the parameters of control system, and usually PI controllers have been used to adjust system to fulfill desired objectives. However, the optimization methods for PI controllers' parameters of VSC-HVDC system are very few up to now. A control strategy based on direct analytic expression for VSC-HVDC is presented and the corresponding control system is designed. Simplex algorithm and system objective function are adopted to optimize the PI parameters for single- and multi-objective VSC-HVDC system on the basis of the control strategy. Simulation results in PSCAD/EMTDC software testify the performance of VSC-HVDC control system with optimized PI parameters and show that the controllers with the optimized PI parameters can effectively control VSC-HVDC system. Advantages of the control system with optimized parameters, such as precise control, quickly responding time and strong robustness have been testified by step response. © 2007 IEEE.

关键词： HVDC power transmission

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Imitation of the characteristics of the wind turbine based on DC motor

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Frontiers of Electrical and Electronic Engineering in China 2007年第3期2卷 361-367页

作者： LIU Qihui HE Yikang ZHAO Rende Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North Electric Power UniversityBeijing 102206China College of Electrical Engineering Zhejiang UniversityHangzhou 310027China

This paper analyzed the operating principles and power and torque characteristics of the wind turbine and the direct current motor (DC motor), and investigated the operating characteristics of the wind turbine compared to that of the DC motor. The torque imitation scheme, which has good performance and high feasibility, together with the whole wind turbine imitation system, was provided. The wind turbine imitation system includes not only a hardware platform composed of PC, data-collection board and thyristor-based velocity-regulator, but also monitor software of wind turbine imitation. The experimental results of different occasions verify the correctness and feasibility of the wind turbine imitation scheme proposed in this paper, which provided a valid idea for wind turbine imitation and investigation of wind power generation techniques in the laboratory.

关键词： wind turbine DC motor imitation character-istics wind power generation

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New criterion for transformer differential protection to rapidly identify transferring faults

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Dianli Xitong Zidonghua/Automation of Electric power Systems 2007年第20期31卷 61-64+107页

作者： Yang, Qing Zheng, Tao Xiao, Shiwu Huang, Shaofeng Liu, Wanshun Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

Current transformer saturation has always been one of the major problems of degraded reliability of the transformer differential protection. The ratio restraining differential characteristic can enable the transformer protection to be immune to the mal-operation in the external fault to some extent. But how to unblock the differential protection rapidly for the transferring fault form an external one to an internal one has become a new problem. This paper presents a new method of unblocking the differential protection for the transferring fault. In the method proposed, current comparison is made between he maximal value of the integrated negative phase sequence component of the current on the two sides of a transformer and the integrated negative phase sequence component of the differential current. Based on the current comparison results, the method proposed can not only accurately identify the internal fault and the external one, but also the transferring fault developed from the external fault to the internal one. Simulation results of ATP validate the effectiveness of the method proposed.

关键词： Transformer protection

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New algorithm based on time differential method to identify sympathetic inrush of transformers connected in wye-delta mode

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第13期27卷 6-11页

作者： Gu, Jun Zheng, Tao Xiao, Shi-Wu Liu, Wan-Shun Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

In recent years, several cases of mal-operation of transformer differential protection due to sympathetic inrush appeared, but the problem how to distinguish the sympathetic inrush has not been resolved yet. Based on the synchronization measurement of the change of line current and differential current, an algorithm of distinguishing the sympathetic inrush and blocking the differential protection was put forward, which is applicable to two paralleled wye-delta connected transformers. Under the condition that the current transformer saturated, a method based on the mathematical morphology to identify the synchronization of the change of line current and differential current was proposed. Adopting the abrupt change of line current in the other side as auxiliary criterion, this algorithm could distinguish the sympathetic inrush, and internal, external fault during sympathetic inrush occurring. Simulation results validate its feasibility and reliability.

关键词： Transformer protection

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Improved multilevel SVPWM and its generalized algorithm

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第4期27卷 90-95页

作者： Jiang, Xu Xiao, Xiang-Ning Zhao, Yang Ren, Ai-Ping Wang, Quan-Tao Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

The modulation is the key technique for multilevel inverter, an improved line voltage modulation strategy is proposed, which is based on the nonorthogonal AX coordinates SVPWM and makes some further comprehensive analysis on the original conclusions. The advantage of the strategy is that it has clearer physical meaning and more simple form. One improved three phases balance modulation algorithm for the single phase is got by the proper arrangement of output vectors taking advantage of the basic circuit theory;and then the generalized modulation strategy is deduced, which is suitable for three phases unbalance situation by the consideration of pulse area equal principle. This proposed modulation algorithm has simple format and clear physical concept, in addition, it's easy for the digital implementation. The digital simulations and experiments are presented to verify the conclusions.

关键词： Pulse width modulation

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Novel principle of transformer protection based on equivalent instantaneous leakage inductance and loop equation

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第19期27卷 39-44页

作者： Wang, Zeng-Ping Ma, Jing Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Baoding 071003 China

On basis of transformer loop equation, a novel principle of transformer protection using equivalent instantaneous leakage inductance is presented. The principle is independent of short-circuit reactance and leakage inductance of each side can be effectively monitored in real time. Therefore, sensitivity and reliability of transformer protection can both be improved by calculating equivalent instantaneous leakage inductance. The principle is also applicable for three-winding transformer. dynamic testing results verify this scheme that has been stable during inrush current and is able to reliably and quickly clear internal fault even fault is light.

关键词： Transformer protection

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Synthetic evaluation of power quality based on extenics

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Dianli Zidonghua Shebei / Electric power Automation Equipment 2007年第12期27卷 44-47+52页

作者： Ding, Li Jia, Xiu-Fang Zhao, Cheng-Yong Li, Geng-Yin Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Baoding 071003 China

A power quality evaluation method combining extenics and AHP(Analytic Hierarchy Process) is presented. Three matter-element models are set based on power quality analysis using matter -element theory of extenics, and quantified to form relationship matrix using relation-function theory of extenics. The target weights are figured out using AHP. The final quantitative grade of the power quality is calculated based on relation-matrix and target weights. The power quality level of synthetic evaluation is obtained by combining the relationship matrix and the target weights. As an example, the power quality of PCC(the Point of Common Coupling) is evaluated, which shows that, the proposed method can evaluate power quality quantitatively and qualitatively and distinguishes different power quality levels effectively.

关键词： power quality

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Study on wide area measurement system based control strategy to prevent cascading trips

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第19期27卷 32-38页

作者： Xu, Hui-Ming Bi, Tian-Shu Huang, Shao-Feng Yang, Qi-Xun Ma, Rui Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

Cascading trips caused by flow transferring are the crucial reason of a lot of well-known blackouts. It threatens the security and reliability of power systems severely. A wide area measurement system (WAMS) based control strategy to prevent cascading trips caused by flow transferring is presented. By analysis of the relationship of node injection current and branch current of network, the principle of control nodes selection of load shedding and generator tripping and the calculation method of control quantity are proposed. The corresponding of the control strategy is also given. The calculation method of branch current before the control action during power system dynamic process is given. The simulation results of 10-generator 39-bus New England System show that the control strategy can prevent cascading trips effectively.

关键词： Electric power systems

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