Suppression of time-varying resonances in the power supply line of AC locomotives by inverter control

The harmonic currents generated by the line-side converter of an electric locomotive are injected into the overhead supply system. Although low in magnitude, they give rise to traveling waves that start propagating in both directions along the overhead line. The traveling waves are reflected at various electrical discontinuities along the line such as the feeding substations and other traction vehicles, the positions of which are time varying. This produces eigenresonances at multiple frequencies. High resonant currents may be generated that cause problems of electromagnetic interference with railway communication and signaling systems. It is demonstrated that the time-varying eigenresonances can be identified in real time. Methods of optimal adaptive inverter control are employed in order to avoid the excitation of the line resonances