Harmonic Analysis And Suppression Strategy Of Single Phase PWM Rectifier

As the grid side converter of high-speed train electric traction system,single-phase pulse rectifier is coupled with power supply network through traction transformer.Under the influence of various elements,there is a certain degree of harmonic distortion in the network side current of single-phase pulse rectifier,which leads to the harmonic pollution of traction power supply network and the decline of power supply quality.In order to increase the power density of traction converter system,LC second ripple resonant filter circuit at DC side of rectifier is usually cancelled,but it will bring difficulties to harmonic suppression of rectifier.Based on this,the following work has been doneFirstly,the topology and mathematical model of single-phase PWM rectifier are introduced.Based on the analysis of the relationship between DC voltage fluctuation and grid side current distortion,the generation mechanism of grid side current harmonics of single-phase PWM rectifier is further studied,and the harmonic suppression technology based on internal model principle is briefly introduced.Secondly,compared with the double closed-loop control of transient current control,the double closed-loop control strategy based on proportional resonance(PR)control is analyzed.By using the advantage of no steady-state error tracking for the specified frequency AC signal,the suppression performance of grid side current harmonic and the ability of anti grid voltage harmonic distortion interference are improved,and then the optimized double closed-loop control model is constructed,The simulation results show that the PR control is effective.Thirdly,in order to reduce the adverse effect of DC side ripple voltage on grid side current harmonics through feedback link and improve the control ability of grid side converter on rectifier,a specified sub notch filter is added in the outer voltage loop,and the simulation results are compared with the previous ones.Finally,a compound control method of single-phase PWM rectifier based on repetitive control and PR control in parallel in the inner current loop and notch filter in the outer voltage loop is proposed,which not only has the advantages of PR control,no static error tracking and very good dynamic response to current tracking,but also has the advantages of repetitive control,which can improve the steady-state performance of the system,The simulation results show that the harmonic suppression effect of this method is the best.