Research On Probability Distribution Model Of Electrified Railway Traction Load Disturbance Current

Electrified railway traction load is an important single phase load in power system,and it is also one of the main harmonic sources.With the developement of power quality monitoring system,it is important to study probability distribution model of electrified railway traction load based on measured data.The probability distribution of the traction load is obtained by curve fitting method based on the probability distribution histogram of measured data.The method proposed in this paper can be used to calculate the probability distribution of different measured data,such as voltage,current and so on.In consideration of the problem that the fitting effect is poor due to the maximum entropy method trapped in local optimum,an improved maximum entropy method based on the distribution characteristics of measured data is proposed which can make the probability distribution more content with the actual distribution.In view of the problem that the cloud transform method may not converge,a cloud transform method considering fitting in negative number interval is proposed,which lowers the requirement of parameters and improves the convergence of the method.According to high accuracy of the cloud transform method and the simpleness of the maximum entropy method,the cloud entropy method is proposed,which ensures high accuracy and simpleness of cloud entropy method.Fitting effect is evalued by fitting error parameters and different measured data are used to prove the correctness of the above method.It is proposed that using the probability density function of cloud entropy method to set up measured database to solve the problem of large storage space and inconvenient in use of the original measured data.It is proposed that harmonic of traction substation that is newly-built or not being mornitoreds is forecasted based on the information of traction load,such as train operation timetable.The cloud entropy probability distribution of harmonic is a supplement to the measured database.ETAP simulation model of regional power grid is built.According to the measured database established by cloud entropy method,the simulation parameter of traction load is calculated by the probability distribution.The simulation analyzes the influence of traction load on power quality of regional power grid and points out the possible power quality problem and the corresponding control suggestions.