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New algorithm to distinguish the transferring fault of transformer protection based on morphological gradient

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2008年第22期28卷 75-80页

作者： Zheng, Tao Gu, Jun Huang, Shao-Feng Wang, Zeng-Ping Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

Distinguishing the transferring fault is one of difficulties for transformer differential protection. According to CT (current transformer) saturation characteristic, a new algorithm of distinguishing the transferring fault is put forward. As the primary current of CT crosses zero, a small linear transmission part of CT would appear, no matter how CT saturated. Based on this characteristic, the waveform of the differential current would expose discontinuous parts when an external fault occurred;in contrast, this phenomenon would not appear for an internal fault. The morphological gradient is adopted to deal with the waveform between two adjacent extremal points of the differential current. By dividing the gradient waveform into three parts and calculating each part's area, the discontinuous in the differential current could be detected according to the relative size of three above areas. By judging whether the discontinuous parts are existed in the differential current, the transferring faults could be easily distinguished. Simulation results show that this algorithm can distinguish the internal fault, external fault and the fault transferred from the external to the internal under the condition of CT saturation.

关键词： Electric instrument transformers

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A power price forecasting method based on nonparametric GARCH model

A power price forecasting method based on nonparametric GARC...

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3rd International Conference on Deregulation and Restructuring and power Technologies, DRPT 2008

作者： Hong, Li Hao, Xiong Weiguo, Li Yi, Sun Guoyi, Xu IEEE North China Electric Power University Wuhan University Beijing Institute North China Electrical Power University Electrical Engineering School North China Electric Power University Beijing China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control

ISBN: (纸本)9787900714138

Based on nonparametric conditional heteroscedasticity estimation theory, an improved power price forecasting method is proposed in this paper. In this method, according to the practical power price curve, conditional variance function is built and the model is determined by nonparametric estimation method. Besides, in the nonparametric estimation process, the iterative estimation algorithm is introduced to deal with the problem where conditional standard deviation is unpredictable. And the estimation credence of conditional variance function is improved by continually modifying the estimation value of conditional standard deviation as input variance. On the research of day-ahead time series fluctuation characteristics of power price in California in 2000, the time series of Humb node is modeled and forecasted. And the test results show that the model proposed in this paper can better reflect time series volatility clustering characteristics of power price, and it can improve forecasting effect of peak power price by using nonparametric estimation theory. © 2008 DRPT.

关键词： Time series

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Immune genetic algorithm based on regulating new definition of antibody density for power system reactive power optimization

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Diangong Jishu Xuebao/Transactions of China Electrotechnical Society 2008年第2期23卷 115-119页

作者： Li, Yulong Zong, Wei Lu, Xianyan He, Qiuyu Yuan, Qihong Wang, Qian Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

By integrating an immune genetic algorithm, a regulating strategy based on a new definition of antibody density for reactive power optimization in power system is proposed. Firstly, the penalty coefficient adjusted dynamically was applied to the objective function. Then artificial immunity mechanism is introduced into the genetic operation. It is similar to consider to be each antibody on encoding. And then based on similar vector distance choice tactics were proposed, which keep the population diversity. At the same time, it can guarantee algorithms faster convergence. Thus simple genetic algorithm was correspondingly improved. Finally, the proposed method is applied to IEEE30 buses test systems. The result of calculation illustrates that the proposed hybrid strategy is effective. It shows that compared with SGA in the same condition, this approach can reduce remarkably iterative times and improve rate of convergence of the algorithm for reactive power optimization.

关键词： Genetic algorithms

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Multi-target controller of three-level NPC based VSC-HVDC transmission system and Its RTDS simulation

Multi-target controller of three-level NPC based VSC-HVDC tr...

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IEEE International Conference on Sustainable Energy Technologies, ICSET

作者： Jianhua Zhang Sheng Li Jingfu Shang Weiwei Zhao Chunye Li Department of Electrical Engineering the School of Electrical and Electronic Engineering North China Electric Power University Beijing China Key laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education Beijing China College of Electrical and Power Engineering Taiyuan University of Technology Taiyuan China

This paper builds the dynamic mathematic model of the three-level Neutral Point Diode Clamped (NPC) converter, discusses the fundamental principles of the active and reactive power control for three-level Voltage Source Converter based HVDC (VSC-HVDC) system. To fully utilize the controllability of VSC-HVDC, multi-target controller is developed to control AC and DC system respectively. Improved sine wave PWM (ISPWM) technique is designed to raise the DC voltage utility rate. Real time digital simulation (RTDS) is done to verify the validity of the proposed control strategy and controllers and demonstrate the good performance of VSC-HVDC.

关键词： Converters power conversion control systems Pulse width modulation Mathematics Mathematical model power system modeling Diodes Reactive power control HVDC transmission

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Study on assessment method of load’s disturbance property

Study on assessment method of load’s disturbance property

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International Conference on Electric Utility Deregulation and Restructuring and power Technologies (DRPT)

作者： Xiufang Jia Zhang bo Liu Fazhan Sun Minghao Key Laboratory of Power System Protection andDynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Baoding Hebei China Zhengzhou Power Supply Company Zhengzhou Henan China

Assessment of load's disturbing property needs to be studied for confirming power quality responsibility and making a power price by its quality. In this paper, load's disturbing property is assessed by means of the analytic hierarchy process (AHP) and the grey relational analysis (GRA). First, the weight of index such as power factor, current total harmonic distortion, unbalance factor and reactive power fluctuation, which can characterize load's property, is obtained by AHP method. In order to assess the degree of load disturbance, a standard load in power system is defined. Then, based on the GRA, can get relativity degree between each disturbing load and standard load. Relativity degree can describe the gap between each disturbing load and standard load. The degree that disturbing loads creates influence to the electrical network is known by means of relativity degree. Finally, calculating examples are brought forth to validate feasibility of the method.

关键词： power quality Voltage power supplies Reactive power Sun Total harmonic distortion power system economics power generation economics Environmental economics Circuit simulation

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A new solution to generators start-up sequence during power system restoration

A new solution to generators start-up sequence during power ...

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International Conference on Electric Utility Deregulation and Restructuring and power Technologies (DRPT)

作者： Qiang Liu Libao Shi Ming Zhou Gengyin Li Yixin Ni Key Laboratory of Power System Protection and Dynamic Security Monitoring and Contro under Ministry of Education North China Electric Power University Baoding China National Key Laboratory of Power Systems Shenzhen Tsinghua University Shenzhen China Department of Electrical and Electronic Engineering University of Hong Kong Hong Kong China

Optimal generators start-up strategy in the restorative control of a power system following a blackout is a complex, multi-stage decision optimization problem. A novel solution strategy involving the corresponding model and approach to this problem is presented in this paper. The aim of the method is to maximize the total MWh load served over a restoration period whilst considering the corresponding constraints. The proposed model is first discretized as a series of knapsack problems with respect to each time step. The classic backtracking search method is employed to solve those knapsack problems. Moreover, the optimal generators start-up solution procedure is illustrated as well. The proposed method, to some extent, can make the trade off between the simulation precision and the computing efforts better. Case studies based on a modified 15-generator test system as benchmark are carried out to demonstrate the effectiveness and validity of the proposed model and method.

关键词： power generation power system restoration power system control power system modeling Optimal control control systems power systems Search methods Computational modeling system testing

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Eigenvector Selection in Load Classification and Model Generalization

Eigenvector Selection in Load Classification and Model Gener...

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3rd International Conference on Electric Utility Deregulation and Restructuring and power Technologies (DRPT 2008), vol.1

作者： Xiao-yu Zheng Jin Ma Ren-mu He Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control of Ministry of Education North China Electric Power University Beijing China

It has been well recognized that the load model has great effects on the power system analysis and control. However, it is also widely known that the load modeling is a quite difficult problem due to its special properties such as time-variant characteristics of the load. In this paper, the measurement-based load modeling approach and multi-curve identification technique are applied in Hushitai power station in Northeast China. In order to build practical load models that can describe the actual load characteristics without changing the model parameters too often, cluster analysis is used to classify the loads. Two main kinds of eigenvectors used in cluster analysis are also compared. Finally, based on the load classification, a new aggregation method is proposed to build load models with good generalization capability. Case studies show the efficiency of the proposed method.

关键词： Cluster analysis Measurement-based load modeling Load classification Model generalization

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Novel HV circuit breaker reliability testing measure based on image processing

Novel HV circuit breaker reliability testing measure based o...

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2008 Joint International Conference on power system Technology powerCON and IEEE power India Conference, powerCON 2008

作者： Guiyan, Cui Shutao, Zhao Chenguang, Zhao Baoshu, Li Department of Electric and Electronic Engineering School of North China Electric Power University Baoding 071003 Hebei Province China 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 North China Electric University China

ISBN: (纸本)9781424417629

Aimed at the difficulty of sensors installation in high-voltage (HV) circuit test experiment, a novel image processing based measure is put forward to detect the mechanical parameters. Through the on-off action images were captured by digital camera with the HV circuit breaker switching, the moving contact travel parameter can be calculated from image analyzing. At the meantime, the necessary timing or interval parameter can be calculated by the electrical signal processing. So most of other key mechanical characteristic parameters, include moving contactor trip, average velocity, bounce frequency, switching time-consuming and over-travel etc., can be also derived associated with the moving travel parameter and time-signal set. It is a non-contact measurement method, which can instead of grating sensor installed on the HV circuit breaker. Experiments result that this new method can obtain the HV circuit breaker mechanical parameter accurately, and it can increase the testing automatic level greatly. © 2008 IEEE.

关键词： Travel time

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United planning of urban distribution network substation based on differential variance bacterial colony chemotaxis algorithm

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2008年第SUPPL.期28卷 58-64页

作者： Wang, Zhi-Qiang Liu, Wen-Xia Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Min. of Edu. North China Electric Power University Changping District Beijing 102206 China

An improved differential variance bacterial colony chemotaxis (DVBCC) algorithm was presented for the urban power network substation planning. Bacterial colony chemotaxis (BCC) algorithm improves the speed of convergence compared with bacterial chemotaxis (BC) algorithm through the introduction of perception in bacterial colony, and also increases the possibility of a local optimum. DVBCC adopts adaptive control perception scope according to colony' distribution condition, at the same time adds differential variance operator in order to increase the variety of bacterial colony and improves its robust and global optima searching capability. In this paper completed economy of substation optimization planning of 110 kV and 220 kV voltage grade in urban power network was taken as objective function, and factors of geographical effect was considered. The results indicated that DVBCC algorithm outperforms BCC and particle swarm optimization (PSO) algorithms in solving substation planning problem and the proposed model has good economy and practicability.

关键词： Biochemistry

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Novel principle of transformer protection based on generalized instantaneous power

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2008年第13期28卷 78-83页

作者： Ma, Jing Wang, Zeng-Ping Wu, Jie Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China Zhejiang Electric Power Design Institute Hangzhou 310014 China

On the basis of power differential method, a novel principle of transformer protection using generalized instantaneous power is presented. By eliminating the mutual flux leakage in the transformer loop equation, a two-terminal network only containing the winding resistance and the leakage inductance is generated. According to the direct current component of the generalized instantaneous power flowing into the two-terminal network, magnetizing inrush and internal fault can be distinguished. The principle is independent of inrush and iron loss and has less calculation burden. Simulation and dynamic testing results verify that this scheme has stability during inrush current and is able to clear internal fault even light fault reliably and quickly.

关键词： Transformer protection

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