Study On Control Strategy Of Three-level Current Converter For Traction Drive System Of High Speed EMU

The high-speed railway has been in existence for decades since its birth.In recent years,the rapid development of domestic high-speed railway has brought great convenience to people’s production and life.At the same time,high-speed railway development will face many problems and guarantee.The long-term stable and safe operation of high-speed railway EMUs has become more and more important.AC locomotive rectifiers,as a key component of traction drive systems,attract the attention and research of scholars at home and abroad.This paper takes CRH2 series EMU three-level rectifiers as research objects.Taking the static and dynamic characteristics of the traction rectifier as the main research target,the two control strategies of the rectifier are compared under different working conditions.Firstly,the working principle and different operating states of the three-level rectifier are analyzed.For the traditional PI double closed-loop control mode,the problem of large uncertainties and nonlinear factors in the high-speed railway traction system cannot be solved,and the high-order sliding mode is combined.Control theory,a second-order sliding mode rectifier control method based on super-twisting algorithm is proposed.The super-twisting controller is used in the current inner loop,and the first-order sliding mode controller is used in the voltage outer loop to effectively suppress the shake in the sliding mode control.The vibration problem is to improve the dynamic and static response speed and anti-interference of the system,and reduce the pollution of the grid generated by the harmonics generated by the rectifier device.In order to verify the superiority of the super-twisting sliding mode control proposed in this paper,the simulation analysis of the three-level traction system circuit model established in this paper is carried out.According to the actual operating conditions of CRH2 series EMUs,the rectifiers work changes under the three conditions of starting EMU,constant speed operation and braking,and the rectifier circuit parameters in accordance with the traction system are designed and compared with the traditional PI control.The results show that The super-twisting sliding mode control method proposed in this paper is superior to the former in maintaining the DC side voltage steady state,AC current harmonic content and high power factor operation,which embodies the simple design of the sliding mode controller based on the super-twisting algorithm.Good robustness and fast response.Simulation results show the feasibility and effectiveness of this algorithm.