Active power filters for inverter locomotives-a concept for improved efficiency and low distortion currents

A concept study for an inverter locomotive equipped with an active power filter is presented. It is shown that the installation of the active power filter, i.e. a small power converter which eliminates most of the distortion current produced by the main converter, is an appropriate method not only for improving the line current spectrum but also for reducing the overall losses of the system. This is shown by means of a simple mathematical model which includes the main effects and allows the system to be optimized for a maximum efficiency. The study is concluded by a sensitivity analysis and proposals for adapted control methods