Design Of DC-DC Auxiliary Power Supply For Locomotive Based On Sliding Mode Control

With the continuous upgrading and development of modern railway transportation in my country,especially after entering the 21 st century,my country’s rail transit has proposed the construction goal of "eight verticals and eight horizontals" on the basis of completing the construction of "four verticals and four horizontals",plus the "Belt and Road".The need for the development of international regional economic cooperation has provided development opportunities for the rail transit equipment manufacturing industry,making the application of locomotives more extensive.Locomotives are developing in the direction of electrification,automation,and intelligence.The auxiliary electrical equipment of locomotives is more complex and requires higher performance,and higher requirements are placed on the supporting power supply to ensure the safe and reliable operation of the equipment.For this reason,this dissertation puts forward the research and design of the power supply for the power supply demand of the auxiliary electrical equipment of the locomotive,which has practical significance for the manufacturing of the railway locomotive equipment in our country.Through in-depth analysis and research of a large number of domestic and foreign power conversion technology references and applications in rail transit rolling stock,this dissertation has a deep understanding of the power conversion principles and applications of several main circuit forms in DC-DC converters.The sliding mode variable structure theory is applied to the DC-DC converter,and a set of locomotive DC-DC auxiliary power supply based on sliding mode control is designed.The main work of the thesis includes:(1)Demonstrate the design scheme of the locomotive auxiliary power supply according to the performance requirements of the product,determine the design scheme of the power supply as "double transistor forward power circuit + FPGA digital control",analyze the working process of the circuit,and establish a mathematical model,the transfer function of the double transistor forward circuit is derived;then the advantages and disadvantages of several linear and nonlinear control strategies are analyzed,and the sliding mode variable structure control strategy is determined in this dissertation.(2)The principle of sliding mode control is analyzed,and the design steps of sliding mode variable structure are described.The sliding mode control theory is applied to the double transistor forward converter,and a fixed frequency PWM sliding mode control method is designed.(3)Design the specific hardware circuit of the locomotive auxiliary power supply,and calculate the parameters of the transformer,switch tube,diode,output filter inductance,capacitor and other main components of the auxiliary power supply of the locomotive according to the performance indicators of the power supply;the digital control circuit chooses FPGA as the control platform;the sampling circuit adopts a 12-bit high-speed parallel sampling chip,and the corresponding detection circuit,sampling circuit and driving circuit are designed.(4)Perform MATLAB software simulation on the system first,compare the control effects of PI and sliding mode variable structure control algorithms;then use the Verilog language to program the control system under the Quartus Ⅱ platform,and use ModelSim software for simulation,and finally tested the sample to verify its performance.The experimental results show that the sliding mode variable structure control method based on fixed frequency PWM technology used in this dissertation has stable output voltage,small ripple,and is insensitive and robust when interference occurs outside the system,and other characteristics,basically meet the requirements of locomotive auxiliary power supply.