Simulation Study On Propulsion Power Supply For Magnetically Suspended Test Train

High-speed maglev rail transit has the advantages of high speed,strong climbing ability,safety and comfort,and has become a hot spot of competition in the field of rail transportation in all countries.At present,the research and development of1000km/h maglev test train has entered a critical stage.The traditional inverter power supply cannot provide the energy for the test train to accelerate to 1000km/h within3s～5s.Therefore,the experimental power supply for the test train is studied.The power source uses multi-level inverter technology and super-capacitor combined with bidirectional DC/DC circuit as energy source.This project takes the propulsion power device as the research object and carries out study on its control system.The main research work is as follows:1.The topology of the test train inverter power supply is studied,the working principle is analyzed,and the mathematical model of six-phase cascade H-bridge inverter in d-q coordinate system is established.The modulation strategy of the inverter is analyzed,and a hybrid modulation strategy with better performance is determined,which integrates the advantages of high frequency pulse width modulation(PWM)strategy and Nearest Level approximation Modulation(NLM)strategy.2.In order to meet the experimental requirements,a three-stage(constant current-constant power-constant voltage)charging scheme is designed.The bidirectional DC/DC circuit is studied,which responses for super-capacitor charging and energy output.The Buck and Boost operation modes are analyzed separately.On this basis,the frequency domain model of the DC/DC circuit is established.The pre-charging scheme is analyzed and calculated,and the estimated charging time is given.The calculation is in good agreement with the charging experiment.In order to maintain the voltage stability of the supporting capacitance of the bidirectional DC/DC circuit,a dual PI controller is designed,and a simulation model is built to verify it.The current decoupling control,total voltage balance control and in-phase voltage control are adopted to maintain the voltage balance inter-phases and the capacitive voltage balance supported by the in-phase unit module,and the simulation experiments are carried out to verify the control strategy.3.For the problem of the end effect of linear induction motor,the mathematical model of six-phase linear induction motor in d-q coordinate system is established by introducing dimensionless factor Q.in order to verify the output characteristics and the driving ability of the inverter,the V/F control model combining the inverter with the linear induction motor is constructed.The speed and current double loop PI controller is designed,and verified by simulation.