Dynamic Simulation Method For Traction Power Supply Of Electrified Railway In Weak Power Supply Area

With the rapid development of China ’ s electrified railway,the rapid growth of traction load has a negative impact on the power quality of the power grid,especially in the areas with weak power supply,the power supply capacity of the power system is small,and the random fluctuation of the traction load causes great fluctuation of the grid voltage,which will not only aggravate the three-phase voltage imbalance,thus affecting the normal power consumption of other users at the public connection point,but also affect the traction power supply of the electrified railway,resulting in the decrease of the terminal voltage of the traction network and endanger the safe operation of the train.Due to the randomness and uncertainty of traction load itself,it is difficult to describe the dynamic model of traction load with traditional models,which poses a great challenge to the dynamic simulation of traction power supply.In this paper,starting from the key influencing factors of traction load dynamic simulation,combined with the characteristics of traction power supply load in weak power supply area,aiming at the two decisive factors of train operation characteristics and train tracking interval affecting the level characteristics of traction load,the probability distribution characteristics of each are studied,and then the composite probability model is constructed by random variables.The case analysis shows that the model can well describe the dynamic uncertainty,timing and probability distribution characteristics of traction load of electrified railway.Finally,the development of dynamic simulation software is completed.Firstly,the influence of electrified railway traction load on power grid is analyzed,and the characteristics of modern electrified railway and the challenges faced by establishing traction load dynamic model in weak areas of power grid are introduced.The modeling and simulation calculation methods of traction power supply system are introduced,and the applicability of the two commonly used methods is discussed by using simulation cases.Finally,the main factors affecting the level of traction power supply load are analyzed,and the technical route for in-depth study of the two uncertainties of train tracking interval and train load characteristics is determined.Due to the randomness of train tracking interval,the reliability of traditional dynamic simulation results based on train diagram is poor,which cannot reflect the influence of tracking interval on dynamic simulation of traction load in actual train operation.By fitting the probability distribution of the number of trains in the measured power supply interval,the mathematical model of train tracking interval is derived based on statistical probability theory,and then the probability model of traction power supply dynamic simulation is constructed.The application of train dynamic tracking interval in dynamic simulation is realized based on Monte Carlo simulation.When the train runs under cruise conditions,the basic resistance suffered by the train remains unchanged.The traction of the train is mainly affected by the additional resistance of the ramp,and the ramp is the main factor affecting the random fluctuation of the train load characteristics.Therefore,the probability distribution of the length of the ramp is fitted based on the measured data,and then the time series composite probability model of the traction load is constructed.Finally,the development of electrified railway traction power supply dynamic simulation software is completed.The software includes the basic functions of system equipment parameter management,traction power supply system model construction,power flow calculation and so on.At the same time,the dynamic simulation functions of traction load composite probability model and traction load probability model are embedded.