Electromagnetic noise generated in the electrified railway propulsion system

Abstract: The electromagnetic compatibility (EMC) problem in the railway propulsion system is a significant safety issue of high concern. The problems can be caused by any part of the propulsion system as well as any combination of the sub systems. Simulation is a fast economical way to understand the system and to predict the EMC performance. In this thesis, the propulsion system is studied partly from the rectifier to the motor. To simulate the rectifier, a two level pulse width modulation (PWM) controlled rectifier is built in Simulink. Time domain line current as well as frequency domain spectra is studied. The spectrum changing according to time variation is obtained. In order to study the high derivative of switching pulse in the insulated gate bipolar transistor (IGBT), a simple circuit is proposed to investigate it. The high frequency noise spectrum is given and the variation of the spectrum due to the reverse recovery time of the ant-parallel diode is also demonstrated.Transmission line theory is used to model the cable used to connect the inverter and motor. The method to extract the characteristic capacitance and inductance matrices of the cable system is presented. Decoupling these characteristic matrices is required for modeling the multiconductor transmission line (MTL) in PSpice. A simple way to decouple them is thus proposed here. Through the simulation studies, we analyze the oscillation and overvoltage in the cable. A fourth cable with optimized layout is also illustrated here to reduce the oscillation on the line. Furthermore, the relationship between the length of line and the noise frequency is studied.Shielding is another way to reduce the electromagnetic (EM) coupling of power lines. The method to model shielded cables in PSpice is given in this thesis. Based on the model we have investigated the shielding effect and analyzed the impact of different grounding conditions on the shielding performance.