Modification of the selective harmonic elimination method for effective catenary current harmonics reduction

The paper proposes an application of a well-known method of Selective Harmonic Elimination in inverter´s output voltage to influence an input traction current spectrum in a DC supplied traction vehicle with asynchronous motors. The aim is to reduce the values of current harmonics in frequency bands that are subject to limitations applicable on Polish railways. This paper introduces the possibility of modifying the method (Selective Harmonics Elimination - SHE) in such a way as to replace elimination of selective harmonics with their reduction (Selective Harmonics Reduction - SHR). Comparative analysis of the effectiveness of both these methods was based on computer simulation results. The important advantage of the SHR method, in comparison with the SHE methods, is the reduction of the required switching angles number with obtaining the aim of the application, i.e. current harmonics amplitudes below the defined limits. Some exemplary results of effectiveness of the proposed method are as well presented and discussed.