Research On Suppression Method Of Operating Overvoltage And Inrush Current Of Emu Based On Phase Selection Control

With the continuous development of China’s electrified railways,the safety problems of EMUs are gradually exposed.At present,most of the traction power supply systems in China adopt a segmented power supply structure,and the EMU needs to close and open the on-board vacuum circuit breaker(VCB)when entering and exiting the phase-separated area.Therefore,the EMU will generate operating overvoltage and inrush current when it passes through the phase-separated area.It will cause insulation shock to the EMU equipment,and in severe cases,it will affect the safe and stable operation of the EMU.In this thesis,the phenomenon of overvoltage and excitation inrush current caused by the opening and closing operation of the vacuum circuit breaker during the phase transition process of the EMU is studied.And based on the phase selection control technology,a phase selection control scheme that comprehensively considers the operating overvoltage and the inrush current is proposed.First of all,based on the phase transition process of the EMU,this thesis analyzes the transient process of the opening and closing operation of the VCB,and it is concluded that the transformer is in no-load state when the VCB is opened and closed.Based on this,an equivalent model of opening and closing of the VCB of the EMU is established.The mechanism of overvoltage and inrush current caused by opening and closing operation of VCB is analyzed,and it is concluded that the opening and closing phase is the key factor affecting the operating overvoltage,and the closing phase and transformer remanence are the key factors affecting the inrush current.Secondly,based on field experiments and theoretical analysis,the key electrical parameters that affect the transient process of the VCB of the EMU are obtained,and established the traction power supply system model of "train-catenary-traction substation".The simulation results are compared with the operating overvoltage and inrush current results in the actual test process to verify the accuracy and reliability of the model.Then,based on the simulation model,the influencing factors of operating overvoltage and inrush current are analyzed,and the effective regular of opening and closing phase on the amplitude of operating overvoltage and the effective regular of closing phase and transformer remanence on the amplitude of inrush current are obtained.Finally,in order to ensure the reliability of the phase selection control technology and reduce the influence of harmonics and noise on the extraction of the reference electrical signal of the phase selection control,a design idea of FIR filter suitable for reference signal detection is proposed.Based on the data of the opening voltage of the VCB in the actual test,the relationship curve between the opening phase and the transformer remanence is fitted,and the opening phase is connected with the transformer inrush current.A multi-objective optimization scheme that comprehensively considers the opening overvoltage,closing overvoltage and closing inrush current is constructed.And through the particle swarm optimization algorithm,the optimal opening phase and closing phase are obtained,which provides a new idea for the phase selection control technology of EMUs.