The Influence Of Pantograph-Catenary Disconnection And Passing Neutral Section On Power Electronic Traction Transformer

With the vigorous development of the high-speed railway business,the lightweight and high-efficiency train traction drive system has become a research focus.Compared with traction drive systems based on power frequency transformers,power electronic traction transformers have advantages in weight,volume,and controllability,which is the trend of traction transformers in the future.The train will encounter many working conditions when running.Pantograph-catenary disconnection and passing neutral section are two of common working conditions.State overvoltage or overcurrent threatens the safe and reliable operation of trains.This article will research on the influence of these two working conditions on the power electronic traction transformer and the suppression strategy.Firstly,the topology structure and its control strategy suitable for power electronic traction transformer are studied,and the corresponding mathematical model is established.The topological structure consists of a cascaded PWM rectifier and a dual active bridge converter,which are respectively a rectifier stage and an isolation stage.The typical catenary parameters are selected to calculate the simulation parameters of the equivalent circuit,and the simulation model is built in the MATLAB\Simulink to obtain the simulation results under steady-state operating conditions,acceleration and deceleration conditions,and verify the model’s performance effectiveness.Secondly,based on the classic arc model,an arc mathematical model suitable for pantograph-catenary disconnection is established,and its corresponding simulation model is built.For the operating conditions of single arcing and secondary arcing,simulations under middle off-line and large off-line time are carried out,and the simulation results are analyzed,and the input overvoltage and the input overvoltage generated by different off-line operating conditions on the power electronic traction transformer are obtained.Input overcurrent,increased harmonic and DC side voltage fluctuations,and proposed suppression measures based on constant current charging strategy and virtual direct power control.Simulations verify the effectiveness of the suppression measures under different offline times.Finally,the time sequence of passing neutral section based on train and electronic switch are analyzed,and the simulation model is built and simulated in two conditions.In the former condition,the pre-power off and delayed power-on operations make the state of power electronic traction transformer more stable,but the main impact is that the power failure time is longer and the train speed loss is greater.In the later condition,short-term loss of power causes the input voltage,current overshoot and DC side voltage fluctuation of the power electronic traction transformer,and the above influence will be exacerbated due to the sudden change of the phase difference before and after the phase divided.Based on the suppression strategy under the off-line operating conditions of the pantograph-catenary,an optimized phase-locking strategy is proposed,and the simulation is carried out under the different phase,which verifies the effectiveness of the measures.