Research On Electromagnetic Interference Of PWM Traction Inverter In Locomotive

Because of its advantages of high switching frequency, low losses and good performance etc, IGBT modules of high-power traction inverters in locomotive was widely applied in railway field. These advantages have been possible thanks to the reduction of switching time and the increase of voltage and current change rate (du/dt and di/dt) when switching on-and-off. From the perspective of EMI, this greatly increased the common-mode interference which aroused from charging and discharging parasitic capacitance from the traction inverter and the motor to the ground (namely common-mode EMI). In this paper, the research on EMI of PWM traction inverter in locomotive was listed mainly as following:Firstly, the formation mechanism of common-mode voltage of PWM traction inverter had been introduced, and a discovery was given that the increase of level number could decrease the inverter's common-mode voltage to a certain extent by comparing the common-mode voltage of two types of inverter with different circuit topology, but the common-mode voltage is still relatively high. The problem needed of further research.Secondly, the characteristics and propagation path of common-mode EMI of PWM inverter were analyzed, and according to the propagation path of common-mode current, the equivalent circuit of inverter-side common-mode current based on Buck circuit was given. Then, the time domain and frequency domain analysis for this equivalent circuit were made, and pointed out the influence's factors of common-mode current.Thirdly, with the actual parameters of the specific locomotive's traction inverter, the simulation model of common-mode EMI with the real-time simulation tool SIMULINK was established. And the common-mode current's time domain and frequency domain which showed by the inverter was analyzed, at the same time, the influence's factors of common-mode current were discussed which verified the previous theoretical analysis. In addition, the motor-side common-mode EMI was analyzed in the time domain and frequency domain, by measuring the common-mode disturbances on the input cable of Yongji motor (YJ87A).Finally, this paper discussed briefly the suppression measures of common-mode EMI of PWM traction inverter from two aspects:reducing the emission of the interference source and cutting off the transmission of interference signals.