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Zhang X.,Nanjing University of Science and Technology | Li Q.,Jiangsu Electric Power Research Institute | Yin M.,Nanjing University of Science and Technology | Ye X.,Nanjing University of Science and Technology | Zou Y.,Nanjing University of Science and Technology
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering

To avoid oscillations of rotor speed at maximum power points (MPP) and to overcome wrong searching directions for MPPs due to the turbulence of wind speed, an improved hill-climbing searching (HCS) method for maximum power point tracking (MPPT) was proposed. It not only inherits the advantage of the variable-step HCS method so that MPP can be rapidly reached, but also introduces the mechanisms of detection and halt at MPP. Thus, the mechanical damage to wind turbines around MPP, resulted from rotor speed oscillations can be effectively reduced. Moreover, following the halt of HCS, the disturbance to determinations of searching directions caused by wind speed variations was resolved and as a result more wind energy was captured. Based on a simplified model of the wind energy conversion system, simulation studies were presented to verify the effectiveness and advantage of the improved method. © 2012 Chinese Society for Electrical Engineering. Source

Nan Y.,Jiangsu Electric Power Research Institute
Sensors and Transducers

This article designed and had completed a digital image gathering system by the means of the ARMS3C44B0X processor and CMOS image sensing component. Considering the superiority of the ARM technology and the CMOS image sensing technology, the system combined the image gathering with the imagery processing recognition function in a module and had the advantages of rich function, strong handling ability, nimble connection and convenient expansion. The characteristic system was that it constructed the image gathering hardware platform on the base of S3C44B0X, studied and transplanted the Bootloder vectoring procedure and the uClinux operating system and can realize the real-time and multi-duty processing, thus enhanced the manageable capacity of the system largely. © 2013 IFSA. 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

Lei G.,Nanjing Southeast University | Gu W.,Nanjing Southeast University | Yuan X.,Jiangsu Electric Power Research Institute
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society

Because of the impact on users caused by voltage sags and the need of making the price by quality in the electric power market, this paper proves the necessity of evaluating voltage sags. On this basis, a voltage sag quantitative evaluation method is presented. In this method, ITIC and SEMI F47 curves are taken as the reference with system and equipment taking into account. The invariable weights and relational coefficients are respectively acquired by means of the analytic hierarchy process (AHP) and the grey relational analysis (GRA). With the combination of relational coefficients and invariable weights, the variable weights are obtained and in the last the relational grades can be calculated. Less the relational coefficients are, more serious the voltage sags are. It shows that the proposed method can reflect the real disturbance levels of voltage sags after comparing with traditional energy indices. Source

Xu H.,Jiangsu Electric Power Research Institute
Dongli Gongcheng Xuebao/Journal of Chinese Society of Power Engineering

Three sects of domestic 1 000 MW ultra-supercritical pressure once-through boilers were introduced. The causes for failure of water-wall with vertical tube panels of ultra-supercritical pressure once-through boilers were analyzed. Results show that the direct cause for failure of water-wall with vertical tube panels is that the throttles located at entrance of water-wall have been blocked by deposits of magnetite pollutants. While the fundamental cause is the high content of forenoon at the inlet of economizer caused by poor all volatile feedwater treatment. Efficient anti-explosion strategies are put forward. Once overheating phenomenon of water-wall occurs, which indicates that serious blocking of throttles might exist, tube cutting inspection should be taken as soon as possible. Local cleaning should be carried out for the throttles by a special chemical cleaning procedure. And the feedwater should adopt oxygenated treatment. Source

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