Research On Protection Method Based On The Distribution Parameters Of Reflux System In DC Traction Power Supply System

It is an important restricting factor of traffic congestion for the urban development.Developing urban rail transit has become the most effective way to solve urban traffic congestion.The safety of DC traction power supply system is related to the normal operation of the urban track.Therefore,it is of great significance to study the operating characteristics,fault analysis and protection analysis of DC traction power supply system.In this paper,the working principle of the DC traction power supply system is analyzed in detail.The DC traction power supply system is modeled and the fault characteristics of it are analyzed.Besides,the main protection and backup protection of the DC traction power supply system are studied.For the limitation of main protection,two new protection methods are proposed.The main contents are as follows:Firstly,the principles of rectification of urban rail transit power supply system and rectifier unit are introduced.Based on Matlab,a 24-pulse rectifier unit model is built.The 12-pulse and 24-pulse rectified voltage waveforms are simulated and compared.Based on the distribution parameters of the reflow system,a model is built on matlab.Then,the distribution parameters of reflux system were studied.The short circuit model of dc traction power supply system is set up.The short-circuit characteristics of the DC traction power supply system under the condition of unilateral power supply,bilateral power supply and large bilateral power supply are analyzed in detail.The main protection of current dc traction power supply system is analyzed.The current rising rate and the current increment(DDL)protection is studied.The DDL protection is used to monitor the current rise rate in the DC feeder.If the setting value is reached,the incremental protection is activated.If the current is increased,the current increment reaches the setting value,the increment of the current protection will activate.Second,the models of the single locomotive start,the dual locomotive at the same time start and the double locomotives have started are built.The limitations of the main protection DDL protection of the DC feeder are simulated and analyzed.A new protection method based on current integration value,current mean value and maximum value ratio is proposed,and the feasibility of the method is verified by simulation.Finally,the protection method of power balance is proposed based on the distribution parameters of the reflow system.The main factors influencing the protection method are analyzed and the equivalent power loss power under the condition of bilateral power supply,the large bilateral power supply are studied.The feasibility of this method is verified.This method is compared with the previous method based on current integration value,current mean value and maximum value ratio,This method solves the shortcomings of current integration value,current mean value and maximum value ratio method which is lack of speed.