Research On Voltage Oscillation Suppression Of Vehicle-network System Based On Vehicle Rectifier Control

With the widespread operation of high-power,high-speed,and high-density nonlinear AC-DC-AC EMUs and electric locomotives are put into the operation,the issues of power quality in traction supply system have become increasingly prominent,which leads the appearance of various accidents frequently appeared.There are multi-band oscillations including low-frequency oscillation and high-frequency harmonic occurred in railway field,which endangers the safety of the railway operation.Aiming at these issues,AT(Auto-transformer)traction network and CRH3(China Railway High-speed 3)EMU models are established,the EMUs-network coupling system is deduced.The mechanism of two kinds of oscillations is construed.Considering the vehicle side of the coupling system,the corresponding suppression measures of oscillation based on vehicle rectifier are proposed.The main research contents are as follows:(1)Combined with actual parameters,all parallel double line AT traction network and CRH3 EMUs models are established,and vehicle-network electrical coupling model are integrated.(2)The vehicle-network coupling cascade system model is deduced,Nyquist criterion is used to analyze the system,the critical conditions for the low-frequency oscillation of the system are obtained,and the low-frequency oscillation phenomenon is simulated and reproduced.The causes of harmonic produced is studied,and the mechanism of high-frequency resonance is analyzed,the resonance frequency of the system is obtained,and the factors affecting high-frequency resonance are studied.(3)The sliding mode and passive compound control strategy for the rectifier of CRH3 EMU is designed by utilizing use of the advantages of sliding mode control and passive control,which shows that there is better performance in the rectifier based on the proposed control,and the low-frequency oscillation are suppressed effectively.(4)The SHEPWM(Specific Harmonic Elimination Pulse Width Modulation)and FCS-MPC(Finite Control Set-Model Predictive Control)are introduced into the EMU rectifier modulation to suppress the harmonics near the resonance frequency of the EMU,and verified on the simulation model,which shows that there is better dynamic and steady-state performance of the hybrid modulation method,and there is good effect on the suppression of the high-frequency resonance of the vehicle-network system.