Characteristics of ultracapacitor and classic model have been introduced in this paper. Due to its superior performance, ultracapacitor is used for hybrid energy storage system with lead-acid battery. The performance and potential application of hybrid energy storage system have been elaborated, which make some contribution to the promotion and application of energy storage technology.
This paper analyzes the calculation method of unbalanced electromagnetic force by rotor winding inter-turn short-circuit fault, analytical calculating method neglects saturation, cogging and other factors, so the calculation accuracy is not high, in order to accurately calculate the magnetic field and the unbalanced electromagnetic force, this paper propose to analyze generator magnetic field by a finite element software Ansys, the obtained magnetic field data are further used to analyze the distributed electromagnetic force and the total force that generator rotor suffered, electromagnetic force distribution law of different slots, different levels of inter-turn short-circuit are got, which provide a basis for further studying the full force on generator rotor.
When generator operates normally, armature reaction magnetic fie]d synchronous]y rotates with rotor, and rotor winding won't induce additional harmonic current, When stator winding hnd r6tor wlnding inter-turn short circuit fault has happened, armature reaction magnetic fie]d non-synchronous]y rQtates with rotor. so additional harmonic current is induced in rotor winding. Through analyzing electromagnetism charactcristic on stator and rotor winding fault respectively, it is known that the additional excitation current harmonic on stator winding fau]t mainly is twice electrica] frequency, and that on rotor winding fault is the function ofair-gap excitation magnetic field harmonic frequency, po]es' pairs ofgenerator and rotor mechanica] revolution.Finally, the excitation current of MJF-30-6 synchronous non-salicnt pole generator is acquired on stator and rotor winding jnter-turn short circuit fault respectively, the results of verification show that the theory analysis is right,
In load forecasting of a bulk power system, the geographical scope of forecasting region is large, the main electrical load effecting factors in sub districts are different greatly. So it is very significance to establish different load forecasting model according to self-feature of each sub district of a large area, by which the forecasting load is closer to the fact load than establishing one model in whole to forecast electrical load. This paper presents a grid model in terms of geographical division for short-term load forecasting in a bulk power system. The subset model in each geographical grid, considering its own historical loads and meteorological conditions, is more effective and could lead to more accurate results. Therefore, every subnet model is established based on the mining default rules on rough sets (MDRBR) algorithm. First, the MDRBR algorithm is discussed, and the constructing process of the multi-layered rule-network of daily load forecasting is then analyzed in detail. Furthermore, the whole process of load forecasting based on the MDRBR algorithm is presented. Finally, an example using actual historical data shows that the grid forecasting model can yield high accurate results, reduce noises effectively, and is efficient in computation and rule searching.
Based on the microwave radiometry, the brightness temperature of insulator contamination is introduced to the contamination detection with an 8mm microwave radiometer. And the relation between the brightness temperature and Equivalent Salt Deposit Density(ESDD) together with Nonsoluble Salt Deposit Density(NSDD) was analyzed by fitting the data from artificial contamination tests under dry and wet conditions, respectively, which obeys the law of power function. The exponent characterizing the influence of ESDD on the brightness temperature is independent of NSDD. And the influence of ESDD on the brightness temperature of contamination is smaller than that of NSDD. Based on the tests and analysis, a model of monitoring system is introduced with radiometer detection.
The WRF V2 model was examined and evaluated in the precipitation forecast of Jintan from May to September in 2008 using daily precipitation forecast of product information. through test and analysis to the forecast of single point precipitation. The results show that: (1) the precipitation forecast accuracy rate of each month of the single point (55%-75%) is about 10% lower than the regional (65% -85%). (2) the WRF V2 model has a moderate precipitation forecast accuracy rate (75%) for the rain or shine, moderate rain and less precipitation. However, when forecasting heavy rain and more precipitation, the model’s capability is weak. (3) the model has a higher probability of empty forecast (above 60%), and a lower probability of omission forecast. With the increase of the precipitation level, the empty rate reduced while the omission rate increased. (4) The stage precipitation forecast effect of 24h is better than 12h, namely, the forecast period is the longer, the smaller the error of the actual situations in precipitation, and the better effect of the simulation of the model.
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