Statistics Modeling, Analysis Of Electrified Traction Loads Harmonic Currents

With the development of modern industrial technology, the nonlinear loads of power system increases constantly, while the power electronic device is widely used, the voltage and current in the power networks is distorted. There are a great deal of higher harmonic in the power networks, the quality of electric energy in the power networks is serious deteriorated; On the other hand, because of the level of industrial automation is improved, such as microprocessors and PLC large number of intelligent devices being used in industrial process control, the need of the power quality is increasing more and more . In recent years, powerful the power electronic commutated device is widely used in the electrified railway , the electrified railway is one of the main sources of harmonics in the power network. Because the random fluctuations of Electric Railway load, therefore using statistical methods to description harmonic is more accurate.Probability density histograms of h-order harmonic currents are acquired under the situation that had already measured harmonic data, and probability of each scatter point have already been known. Therefore, fitting the curve of probability density capitalize amounts to best squared approximation of scatter data.Firstly, creation reasons, harms of harmonic currents, the present research of electrified railway harmonic currents in my country, the dynamic state of research on random of electrified railway harmonic currents are introduced. Secondly, it is mainly discussed that two phases harmonic model of the traction power supply system is interchanged to three phases harmonic model. Harmonic transformed matrix in the difference mode of connection and characteristics of the unbalance harmonic currents of the injecting system are discussed too. Thirdly, three kinds of analytical methods of the electrified railway harmonic currents to statistics are introduced in brief: measure method, superposition method, probabilistic vectors of summation. Lastly, distribution characteristics of statistics are analysised by making use of measured harmonic currents data, to analysis the which traction load, thus the scatters of traction load and histogram of probability density are obtained, the curves of probability density are obtained with best squared approximation of scatter data, thereby the distribution characteristics of traction load harmonic current are obtained.