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Xu C.,University of Sichuan | Liu N.,University of Sichuan | Zhao H.,University of Sichuan | Zhu G.-P.,Tsinghua University | And 2 more authors.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

Because of the characteristic of small capacity and low inertia of the inverter based micro-generation, the load changing in islanded micro-grid has large impact on frequency and voltage. A novel frequency control strategy of micro-grid based on the secondary frequency regulation of power system is proposed. Traditional droop control strategy of micro-grid is not a no-error adjustment. It can't guarantee the frequency of micro-grid operate at rated state when the load changes. Besides the P-f droop control strategy, the proposed frequency control strategy introduces the proportional-integral (PI) control into control flow. The process is a no-error adjustment, which is similar to the secondary frequency regulation of power system. In order to overcome the disadvantage of low inertia of micro-grid, a first-order inertia link which imitates the motion equation of rotor of synchronous generator is added to the proposed frequency control strategy. So the stability of frequency in micro-grid is greatly improved. The typical operation states of micro-grid such as loads change, loads shock, the random loads fluctuation in islanded mode, and the operation states transform are simulated based on MATLAB/Simulink. Simulation results verify the correctness and validity of the proposed frequency control strategy. Source


Chen L.-P.,University of Sichuan | Xiao X.-Y.,Smart Grid Key Laboratory of Sichuan Province | Zhang Z.,Yibin Electrical Power Bureau | Wang Y.,University of Sichuan
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

In order to depict the duration of voltage sags more precisely, the time characteristic of protection system is taken into consideration, which influences the duration of voltage sags obviously. Based on the traditional model for voltage sags frequency assessment, the mapping relationship between voltage sags duration and frequency is established using the method of fault positions, which can reflect the actual process of the protection operation. The proposed method is applied to the IEEE 30-bus test system, and the simulation results show that the time characteristic of protection system has an obvious effect on voltage sags frequency assessment, and neglect of the time characteristic of protection system would result in large error. The proposed method is simple, adaptive and practical, and it is of academic value and practical foreground. Source


Zhang L.Y.,Sichuan University | Xiao X.Y.,Smart Grid Key Laboratory of Sichuan Province
Applied Mechanics and Materials | Year: 2013

The necessity of research on the vegetation-related failure and its inherent hidden timescale in the cascading failures is attached importance based on the facts of recent blackouts internationally. The dynamic behavior of line sag and the vegetation growth are modeled. The time of vegetation related failure after step increase of the line current due to other disconnect events is calculated considering specified physical circumstances, and it can help operators be aware of the necessary urgency of system crisis. Case studies are made on WSCC-9 and IEEE-24 test system respectively, and the results show the method proposed is able to identify collapse sequences due to vegetation-related failures and corresponding timescales, and make great contribution to the prediction and prevention of cascading failures. © (2013) Trans Tech Publications, Switzerland. Source


Huang Y.,University of Sichuan | Huang Y.,Smart Grid Key Laboratory of Sichuan Province | Liu J.,University of Sichuan | Liu J.,Smart Grid Key Laboratory of Sichuan Province | And 4 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

A battery model is developed. The scale effect of electric vehicle centralization is analyzed and a framework of centralized electric vehicles taking part in vehicle to grid is described. By developing the load frequency control model for electric vehicles participation, the role and effect of the control model is studied. The simulation results show that, as a type of mobile battery energy storage facility, electric vehicles can provide faster system reserve by effective controlling. © 2012 State Grid Electric Power Research Institute Press. Source


Zhao H.,University of Sichuan | Xiao X.,University of Sichuan | Xiao X.,Smart Grid Key Laboratory of Sichuan Province | Li Z.,Chengdu Electric Power Bureau | And 2 more authors.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2011

According to the transition process of equipment fault status, all kinds of status excluding normal and complete fault status are considered as incomplete fault status and the possibility of equipment failure due to voltage sag is evaluated. The voltage tolerance level of sensitive equipment is characterized by the interval data and, combined with the randomness of voltage sag, the interval possibility of incomplete fault status is determined. To more comprehensively take the complexity and uncertainty into account, the hybrid entropy is used to measure the randomness and fuzziness of practical voltage sag and the model of maximum interval hybrid entropy is developed to estimate the equipment sensitivity under certain conditions and to obtain the point probability of equipment failure rate. Comparison with the measured data of personal computer failure rate due to voltage sag shows that, the results in small samples are quite accurate. The simulation for IEEE 33-bus system proves the effectiveness of the introduced method. Source

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