Harmonic analysis of EMUs in railway systems

The increasing use of power electronic drives and devices in electric multiple units (EMU) of railway systems has increased the levels of harmonics in the electricity feeding systems of railways. While the harmonic current for a single EMU can be easily measured or simulated, it is not easy to estimate the possible worst case for a number of trains of EMU operating simultaneously on a line according to a time schedule, but with statistical variation. This paper presents a systematic approach to estimate harmonic distortion, which incorporates a novel directional track shift method to deal with the train schedule. The railway simulation is performed in the ATP version of the electromagnetic transient program (EMTP) and the results of the harmonic simulation are compared with measurements made on a railway system. Summaries of the parameters affecting the harmonic performance of the traction system and estimates of the most predominant harmonics in network are also presented.