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Li H.,Nanjing Southeast University | Li H.,Xuzhou Normal University | Wan Q.,Nanjing Southeast University | Xiang C.,Jiangsu Fangtian Power Technology Co.
Dianli Zidonghua Shebei/Electric Power Automation Equipment

Based on the analysis of the relationship between the output power of wind farm and the input wind speed, a method of wind farm equivalence considering wind speed is proposed, which, considering the wind power utilization coefficient of wind generator varies along with the wind speed, describes piecewise the wind power utilization coefficient as the function of wind speed and takes it as the weight of equivalent wind speed. The proposed equivalence method is compared with the traditional equivalence method by simulation and result shows that the error of equivalence considering different wind power utilization coefficients is smaller. Source

Li C.,Jiangsu Fangtian Power Technology Co. | Yuan Y.,Jiangsu Electric Power Research Institute | Lu Y.,Jiangsu Fangtian Power Technology Co. | Ning Y.,Jiangsu Fangtian Power Technology Co.
Dianwang Jishu/Power System Technology

The transfer method of sampled data in process-level network of smart substation is one of key technical problems in smart substation. At present, there are two sampled data transferring methods, namely the point-to-point transferring and networking transferring. The system structure can be simplified when networking transferring is used, however its operation depends on global synchronization system, so the failure in global synchronization system leads to the whole system out of service, so the networking transferring of sampled data should not depend on global clock. A new local synchronization scheme, in which the margin unit is used as local master clock and the protection, measuring and control devices as slave clocks, is proposed, and there are many slave clocks in a single measuring and control device, which are locally synchronized with local master clock in margin unit. By means of optimizing the clock selection and tracking mechanisms of IEEE1588, and utilizing interpolation the synchronous data sampling is implemented, and the dependence on global synchronization system is effectively avoided. Main advantage of the proposed scheme is that the networking transferring of sampled data is implemented without global synchronization system. Results of applying the proposed scheme to engineering practice show that the proposed scheme is more reliable and practicable than traditional networking scheme. Source

Xiang C.,Jiangsu Fangtian Power Technology Co. | Fan L.,Jiangsu Fangtian Power Technology Co. | Jiang Y.,Jiangsu Fangtian Power Technology Co. | Gu T.,Nanjing Southeast University | Gu W.,Nanjing Southeast University
Dianli Zidonghua Shebei/Electric Power Automation Equipment

With the tested LVRT(Low Voltage Ride Through) data and relative parameters of wind farms in Jiangsu, a model is built in DIgSILENT for a large-scale wind farm based on doubly-fed induction generators, which describes in detail the dynamic LVRT characteristics of different wind turbines within the farm. The responses of different wind turbines to different voltage sags are compared and analyzed to evaluate the LVRT capability of the farm. The principle conclusions are summarized. The cascading trip-off sequence during a serious incident is obtained by simulation and the mechanism of interaction between turbines is analyzed to illustrate the cascading trip-off process. For enhancing the LVRT capability of wind farm, measures are proposed: properly increase the setting value of crowbar protection, flexibly operate the grid-side converter and apply SVC. Source

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