Research Of Electromagnetic Compatibility In Traction Converter

Electromagnetic pollution generated by electrical locomotive on the environment has been attached great attention by Rolling Stock Manufacturing Industry at home and abroad. Traction converter is one of severe electromagnetic interference(EMI) sources. So research of electromagnetic compatibility(EMC) strategy in traction converter is especially important. This thesis focuses on EMI generation and propagation mechanisms, cause and spread route of conducted EMI, harm of common mode(CM) EMI and modulation strategy to reduce common mode EMI in traction converter.The EMI of traction converter is classified as conduction EMI and radiating EMI. The main interference is conduction EMI in the two interferences. The conduction EMI is classified as common mode EMI and differential mode (DM) EMI. Differential EMI is due to the ripple current from the fast switch and common mode EMI is due to the dv/dt charging and discharging the parasitic capacitor. Common mode EMI is main interference in conduction EMI.CM voltage and CM current will lead to generate bearing voltage and bearing current in traction motor. Other earth connection devices will also be interfered by them. In order to decrease the harm of common mode EMI, the dissertation firstly analysed the structure and control strategy of traction converter. And described the cause of EMI generated by traction converter ,main spread route and suppression measure of EMI. Then the generation and propagation mechanisms of conduction EMI and the EMI caused by modulation strategy were analysed in detail. New modulation technologies are proposed to reduce common mode EMI of PWM inverter. Basing on the traditional SVPWM ,the new modulation technologies include digital vector action time modulation technology and improved SVPWM in three-phase inverter with four bridge legs. Efficiency of DC voltage and harmonic content of output current were analysed in detail on the new modulation technologies.Simulation was made on the two new modulation technologies by use of Matlab/Simulink, The simulation result shows that improved SVPWM in three-phase inverter with four bridge legs can attenuation common mode interference effectively without changing efficiency of DC voltage and harmonic content of output current. So it is fit to control traction converter.