Research And Implementation Of Single-Phase PWM Rectifier For High Power Locomotive

The development of electric locomotives in our country is obvious to all,single-phase PWM rectifier has become a focus in the research and application of high-power rectifier for electric locomotive because of its stable DC bus voltage,effective control of the phase for grid side current,little current harmonics and bidirectional flow of energy.Combining the switching mode of single-phase PWM rectifier,the state space model of single-phase PWM rectifier is established and its stability is analyzed.Based on the analysis of the traditional direct current control and indirect current control schemes,and combined with the mathematical models of each link,the design method of controller parameters is given.The causes of secondary ripple on DC side are further analyzed,and the ripple suppression is realized by designing a notch filter.Based on decoupling control,the reasons of impulse current in single-phase PWM rectifier during steady-state switching are analyzed,and the scheme of transient impulse current suppression are proposed.Aiming at the problem of tardy response of indirect current control,a phase compensation strategies is proposed,which effectively improves the speed of phase correction.The above scheme is simulated on the MATLAB platform.The simulation results verify the feasibility of the scheme.The key technologies of single-phase PWM rectifier,including grid voltage phase-locked loop and start-up strategy are studied in this thesis.Aiming at the problems of amplitude change,frequency change,phase change,harmonic interference and DC bias of grid side voltage,this thesis proposes a phase detection scheme based on discrete Fourier transform,and verifies the effectiveness of the scheme through simulation.Aiming at the problem of grid-side current impulse during the start-up of single-phase PWM rectifier,the causes of current impulse in uncontrolled rectification and controlledrectification phases are analysed in this thesis,the strategies of adding charging resistor,selecting appropriate switching point in uncontrolled rectification phase,selecting appropriate phase as starting point,appropriately reducing the slope of soft start in controllable rectifier stage are given.The feasibility of PLL scheme and the effectiveness of start-up strategy are verified by simulation.Based on the application requirements of the actual system,the design method of main circuit for the high-power experimental platform as well as the hardware structure and the software for control unit are given in this thesis.Then,the validation tests of no-load startup,on-load operation and energy feedback are carried out on the experimental platform.The experimental results prove the validity of the proposed scheme.