Research On The Control Strategies And Experiments Of Single-phase Three-level Rectifier For Traction System

High-speed railway plays an important role in transportation system.In recent years,the development of the railway has received increasing attention.As an important constituent part in the high-speed railway traction system,the single-phase three-level rectifier deserves further study,which is of great research significance.Single-phase three-level rectifier is the research object of this paper.The state space expression of single-phase three-level rectifier was worked out after the study of its working principles and the mathematical model.Based on this,study is carried out on the control strategy and the modulation strategy.In the aspect of the control strategy,a detailed analysis is made on the double closed-loop control,the proportional resonance(PR)control and the predictive current control.It proves that there isn't a grid current state-error occurs in the proportional resonance control,which proved the superiority of proportional resonance control.In the aspect of the modulation strategy,space vector pulse width modulation(SVPWM)and selective harmonic elimination pulse width modulation(SHEPWM)are analyzed in detail.In addition,a careful study is made on the vector space division in space vector pulse width modulation,the establishment of multiple levels topology harmonic elimination equations in selective harmonic elimination pulse width modulation and the selection of parameters.Aimed at the problem of neutral point balance in multiple levels topology,a solution has been proposed for the two modulations above.On the basis of theoretical research,PSIM was used to simulate the "PR+SHEPWM" and compared with the results of proportional integral control and space vector modulation.The simulation results show that the designed control strategy can achieve higher power factor,stable and adjustable DC-link voltage,eliminate specific harmonics and reduce the total harmonic distortion of the grid current.Based on theoretical and simulation studies,an scale-down experimental platform was built and a high-efficiency,high-precision controller is designed based on FPGA.A series of experimental tests have been conducted to demonstrate the effectiveness of proposed method.