Design And Research Of Full SiC Auxiliary Converter For Trams

The auxiliary converter is an important part in trams.Its efficiency and power density have always been the focus of attention.With the development of SiC devices,the power electronic system using SiC devices has made significant breakthroughs in switching frequency,efficiency and power density.In this thesis,the author focuses on the design and development of the full SiC auxiliary converter system,completes research on the working characteristics of SiC devices and the establishment of the loss model,completes the loss model building of the auxiliary converter topology,the optimization design,the switching frequency selection,the control scheme design and the simulation verification.Finally the 40kVA full SiC auxiliary converter prototype is developed and debugged,and compared with the original Si system.In this thesis,the characteristics of SiC MOSFET device are studied,and the test comparison of the same grade SiC/Si devices is made.The test contents include switch loss,saturation voltage drop and diode forward voltage drop.The test results show that SiC MOSFET has excellent characteristics of low saturation pressure drop and low switching loss,and then the calculation method of device loss is deduced based on SiC MOSFET and verified by the test data.Then,this thesis focues on the full SiC auxiliary converter,optimizes the structure of DC/DC module by the loss model,studies,analysises and optimizes the mechanism of voltage oscillation and the suppression scheme of the rectifier.The system topology is determined by the phase shift full bridge converter +RCD buffer absorption circuit +three-phase inverter,and the switching frequency of the system is determined that the DC/DC module is 40kHz and DC/AC module is 10kHz;then the main circuit parameter design and control system design are completed.In the prototype design process,the main circuit parameters and control strategy,the voltage oscillation suppression scheme and the system loss of the rectifier are simulated and verified by Matlab,PSIM and PLECS software.Finally,the author completes the experimental verification of the 40kVA full SiC auxiliary converter.The content of the test includes the rated working condition of the prototype,the verification of the suppression effect of the rectifier voltage oscillation and the measurement of the loss distribution in the system.And the author compares the size of the Si/SiC system and some key elements.The conclusion is drawn that the efficiency of the auxiliary converter is increased by 1.76%after the application of the SiC device,and the power density is increased by 50%.