Control And Implementation Of Four-quadrant Converter With Low-switching Frequency In Hybrid EMU

With the rapid development of China's high-speed rail technology,the requirements of the speed of the train and the power of four-quadrant converter are increasing.But limited to the switching losses and temperature of IGBT,it is required to keep the switching frequency of the four-quadrant converter as low as possible.This thesis is supported by National Key Technologies R&D Program for the "12th Five-year Plan"—"Research on Hybrid EMU Traction Technology",research on control and implementation of four-quadrant converter with low-switching frequency in Hybrid EMU.The control methods and implementation of four-quadrant converter with low-switching frequency in Hybrid EMU are proposed,and the feasibility and effectiveness of the proposed methods are verified by simulation and experiment.The main work as follows:Firstly,the sampling method of the four-quadrant converter is researched.The traditional sampling method and high sampling frequency sampling method are introduced,and the influence of the two sampling methods on the control of the four-quadrant converter is analyzed.Based on the analysis of AC current waveforms under unipolar frequency doubling SPWM modulation,an optimized sampling method is proposed,which is more suitable for low-switching frequency.By comparing the simulation results,it is proved that the fundamental components of the AC current can be sampled more accurately than the previous two sampling methods,which can make the four-quadrant converter controlled much better.Seondlv.the influence of the control delay is analyzed.A current prediction control method based on modified z-transform is proposed to reduce the influence of' control delay.The effectiveness of the current prediction control method mentioned is verified by the simulation results on Matlab/Simulink.Thirdly,limited to the shortcomings of traditional carrier phase shifting scheme in the aspects of convenience and flexibility,an FM carrier phase shift scheme based on voltage zero crossing detection is proposed.The scheme doesn't need hard-line to transmit carrier synchronization signal between the four quadrant converters,and it ensures the consistency of the converter program,it's good for the modular production and the reduction of the cost.Finally,the optimized sampling method,the current prediction control based on modified z-transform and the FM carrier phase shift technique based on voltage zero crossing detection are experimentally verified by using the "Ground intermodalation experimental platform of the hybrid EMU traction drive system".The experimental results are consistent with the previous simulation results,which proves that the control and implementation methods proposed are feasible and effective.