| In recent years,urban rail transit in China has developed rapidly,and ride safety has been paid more and more attention.Subway vehicles operate in underground space.When the vehicle power supply system is paralyzed,it is necessary to ensure smooth air circulation in the vehicle and ensure the comfort and safety of passengers.Therefore,it is particularly important to configure reliable emergency ventilation power supply in the subway carriage.The traditional emergency ventilation power supply adopts the circuit topology of boost converter and three-phase two-level combination.The Boost circuit has simple structure and easy control,but the input and output are not electrically isolated,and the high-power IGBT switching device works in the hard switching state,so it is difficult to improve the switching frequency,efficiency and power density.In view of this,combined with the application scenario of emergency ventilation power supply,this thesis studies the main circuit topology,adopts appropriate control strategy and optimizes its design,so as to realize the electrical isolation of input and output and improve work efficiency and power density.Firstly,combined with the input and output characteristics of emergency ventilation power supply,the advantages and disadvantages of three main circuit topology schemes are compared and analyzed,and the combination scheme of highfrequency isolated DC/DC converter and three-phase two-level inverter is selected for research.In order to reduce the switching loss under high frequency operation,phase shifted full bridge ZVS converter is introduced into the front isolated DC/DC circuit.According to the technical parameters of emergency ventilation power supply,the overall structure design of power supply is completed.The working characteristics of the phase shifted full bridge ZVS converter,the basic unit of the main circuit,are analyzed from the aspects of working principle,realization conditions of soft switch,loss of duty cycle and oscillation of rectifier diode;The working principle and modulation mode of three-phase two-level inverter are analyzed,and SVPWM modulation is selected to improve the utilization of bus voltage.Secondly,according to the technical parameters of emergency ventilation power supply,the power supply hardware is designed.The hardware circuit is divided into DC/DC phase-shifting full bridge boost circuit,DC/AC three-phase inverter circuit,control circuit and auxiliary power supply circuit.Calculate and select the magnetic components,filter circuits and power devices of the main circuit;Complete the control circuit design with TMS320F28035 as the main control core,including driving circuit,sampling circuit and protection circuit;A flyback auxiliary power supply based on UC3843 control is designed to realize multi-channel isolated output and supply power to the control circuit.Then,the small signal modeling of the front stage phase shifted full bridge ZVS converter is carried out,the transfer functions of duty cycle output voltage and inductance current are deduced,the voltage closed-loop control strategy is selected,and the closed-loop PI controller is designed.The latter inverter circuit selects the constant voltage frequency ratio control strategy widely used in the field of variable frequency speed regulation to realize output voltage and frequency regulation.The software program is designed based on CCS software,including the design of main program and interrupt program to realize the digital control of voltage closed-loop PI control,constant voltage frequency ratio control,SVPWM modulation and power protection.Finally,the principle of constant voltage frequency ratio control of phase-shifting full bridge ZVS converter and inverter circuit is simulated and analyzed by using PSIM and MATLAB software to verify the feasibility of the system scheme.Make a prototype of emergency ventilation power supply,build an experimental platform,debug the software and hardware of the power supply,and verify the function,efficiency and power density improvement effect of the power supply.There are 76 figures,13 tables and 57 references in this thesis. |
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