Emergency Starting Power Supply Of Urban Rail Transit

At present,the control system voltage of urban rail transit vehicles in China is divided into two types: DC24 V and DC110 V.In the normal driving process of the vehicle,the vehicle auxiliary inverter system charges the battery,and then the battery supplies power for the control system.If the battery fails,the vehicle control system will be powered off.Therefore,it is necessary to set up an emergency power supply.In order to make the urban rail transit vehicles start and charge the battery through the control system in the case of battery power loss.The thesis uses DC-DC converter to reduce the contact line voltage to the power supply voltage of the control system.This DC-DC converter is used as the emergency power supply of the control system.According to the voltage characteristics of urban rail contact line and the power consumption of vehicle control system,the thesis determines the technical indexes of high voltage wide range input and low voltage low power output emergency power supply.According to the technical index,common DC-DC converter topologies are analyzed.And the double switch flyback DC-DC converter is selected as the main circuit topology of emergency power supply.And the working principle of this topology is analyzed.According to the technical index of 500V-900 V input and rated 24V/280 W output,the hardware of emergency power supply is designed.Including: input and output filter circuit design,circuit switching device selection,MOSFET drive circuit design,and high frequency transformer design.The switch control strategy of the main circuit is determined to be the peak current PWM strategy.According to the strategy,UC3844 is selected as the circuit control chip.According to the working principle of UC3844 and the input and output parameters of the main circuit,the isolated output voltage feedback compensation circuit based on TL431 and PC817,the primary side current sampling circuit,the clock oscillation circuit,the input overvoltage and undervoltage protection circuit,the output overcurrent protection circuit and other peripheral circuits of the control system are designed.In order to reduce the component voltage stress of rated 1500 V input power supply,combined with the 750 V voltage level emergency power supply design experience,the thesis designs two groups of 500V-1000 V input,rated 110V/140 W output power modules to form the ISOP power supply system.Based on the peak current control strategy of a single module,the input voltage sharing of the ISOP system is realized through three loop control.Then the two modules can supply the same power.Finally,through PSIM software,the 750 V and 1500 V voltage level emergency power supplies are simulated and verified.In the laboratory,two power supply prototypes are built respectively for experimental verification.The simulation results and experimental results are consistent with the theoretical analysis.It proves the correctness of the theoretical analysis and the feasibility of the scheme design.