Research Of CRH2 Bullet Trains Power Transmission System

The motive power core of bullet trains used in high-speed rail and EMU is power transmission system.In this paper,power transmission system of CRH2 bullet trains is resrarched as the object,including rectifier,inverter traction motor and its control system.,and the harmonic characteristics are obtained.In rectifier,single-phase three level topology and SPWM modulation algorithm are adopted.In order to reduce the fluctuation of DC voltage,a transient current control strategy with high response speed and high control precision is adopted.In inverter,three-phase three level topology and SVPWM modulation algorithm are adopted.The calculation of region judgment and the vector action time are deduced.By coordinate transformation,the stator currents of motor are decomposed into into flux component and torque component.Based on the matrix equations of the motor in d-q coordinate system,the mathematic model of vector control is deduced.The indirect rotor magnetic field oriented control is adopted,by which motor speed can track the speed command quickly and motor stator current is controlled within the permissible range.Aiming at the problem of neutral point potential balance,according to effect analysis of the the switch state on neutral point potential in rectifier and inverter,SVPWM inverter vector time correction coefficient is introduced,and neutral point potential is controlled nearby balance point.Aiming at the problem of over-voltage of IGBT in converter,the reason of the over voltage is analyzed.In order to achieve better buffering effect,the topology and parameters of snubber circuit are improved.Considering the change of resistance,motor mechanical inertia and damping,IGBT over-voltage problem in converter,the model of power transmission system of CRH2 bullet trains is built in ATP-EMTP.The simulation results show that the harmonic characteristics of CRH2 are same with actual measured results,which prove the accuracy of the model.in start,traction,braking and uniform condition,the running speed of the motor can quickly track the command change.