Wavelet analysis of line current for a four-quadrant AC locomotive

The analysis performed in this paper is related to a four-quadrant AC converter used to drive the motors of a railway locomotive in modern traction systems. The main aspect highlighted by the research is related to the instantaneous harmonic content of the input current and the secondary effects on the power line. Analytical relationships studied by means of wavelet analysis lead to the definition of the time-frequency evolution of the harmonic content inside the input current. In this way it is possible to better understand the dynamic behaviour of electrical power supply variations during transient working condition of the system and the possible influence on the whole electromagnetic compatibility (EMC) characteristics of the AC drive.