Identification Modeling And Optimization Design Of Electric Locomotive Control Power Source Converter

With the rapid development of China's railway industry,the transformation of railway electrification has been deepening.High energy utilization have gradually turned into the backbone among various railway delivery vehicles.In the coming years,railway transport,especially passengers' transport,will become faster and more efficient.In the process of railway processing in China,the switching power converter has been regarded as an indispensable electrical equipment in the locomotive control system.Because of its wide use in trains,the maintenance and replacement of switching power converters on locomotives have been particularly important,which contributes to the safety of trains.As a new type of power supply device,the switching power supply converter provides the necessary electrical energy for different electrical equipment on the trains.The switching power supply converter is a time-varying hybrid nonlinear system.To establish a precise mathematical model of the switching power supply converter can simulate,analyze,and predict the failure of the converter in advance.Due to the complicated structure of the converter design circuit,it is necessary to simplify the auxiliary circuit into a simple one that can be researched.Each item in the main circuit has an influence on its working characteristics,thus it is necessary to analyze the working characteristics of the converter,as well as the influence of the main circuit element on its working characteristics.In a nutshell,the primary theoretical basis for maintaining and replacing the switching power supply converter has mainly involved in setting up the converter system experimental platform,collecting data,establishing a mathematical model,and identifying the accuracy of the value of each component of the circuit in the model.Based on the converter errors,this paper selects a DC/DC buck converter as the research object.On the basis of the physical design circuit,the complex circuit is simplified into a feasible one,and the working characteristics of the buck converter are analyzed and simulated.This paper also analyses the effects of each component on the output voltage and inductor current of the converter in the main circuit.In particular,the influence of the change in the equivalent resistance of the capacitor on the waveform of the inductor current and the output voltage is researched.Besides,the change in the equivalent resistance of the capacitor has caused a change in the proportion between the inductor's current and the output voltage,and the changed proportion has been quantified based on a mathematical relationship.The proportion also determines the time required for the converter to transition from transient to steady state in the beginning of operation.Secondly,On the basis of the simulation results of the working characteristics and the different circuit configurations of the buck converter under different working conditions,the circuit equations are established based on Kirchhoff's law and current law.What's more,the state space method is used to linearize the nonlinear converter system.Then a mathematical model of the buck converter is established,and the input-output state equation and the control-output state equation of the model will be obtained and the model is verified by simulation.At the same time,the output voltage,output current,capacitor voltage,inductor current,and input voltage of the converter are selected as experimental data acquisition targets for analyzing the working characteristics of the converter,and an experimental platform is built to collect data.Based on experimental data and the differential evolution identification algorithm,the values of each component in the mathematical model has been selected to be identified and compared by using the input-output state equation of the model.All of these aim to evaluate the accuracy of the converter model and the accuracy of the various components of the circuit,as well as the inefficiency of circuit components.The PID controller compensation network of the converter has been simply designed,and the controlling effect has also been verified and analyzed on the basis of the model control-output state equation.The research results indicate that ideal results have been gained on the selection of the model and the algorithm after the buck converter is established and the components are identified.Besides,the identification results of the model components are also in line with the requirements of industrial field,which provides a favorable theoretical basis of the maintenance and the replacement of converter.