Multilevel power filter in new electronics locomotive

The authors analyze the validity of active filtering systems in the presence of DC drives. In these drive systems harmonics are generated by one or more choppers duly shifted out of phase. This means that the current ripple frequency of the first harmonic is generally constant and it is linked to the frequency of the carrier wave with which the chopper is modulated. Results obtained so far have shown the flexibility of such a filtering technique. The purpose of reducing filter weights and dimensions seems to be achieved through a nonexcessively complex system