Active filter for single-phase overhead contact wire energized locomotive

An active filter for filtering the current and improving the power factor of a single-phase voltage overhead contact wire-energized locomotive having an input transformer for collecting the voltage supplied by said overhead contact wire and for distributing voltages to traction equipment and auxiliary equipment of said locomotive, said active filter comprising:

• two or more forced switching mode bridge inverter circuits (10, 11) which are connected to a dedicated secondary winding of said input transformer, which are in series on the alternating current sides thereof and which are fed with respective independent direct current voltages;
• and
• a control system which forces switching of said bridge circuits to produce an alternating current on the single-phase side from different voltage levels resulting from combination of the direct current voltages from said bridge circuits, said produced alternating current being fed to said input transformer to compensate harmonic frequencies generated, and the reactive power consumed, by said traction equipment and said auxiliary equipment of said locomotive and retransmitted to said overhead contact wire;
• wherein the direct current voltages feeding said bridge circuits are provided by a direct current generator for one of said bridge circuits and by a capacitor for the other of said bridge circuits;
• and
• wherein said control system comprises:
• a processor (28) enabling selection of the harmonic frequencies to be compensated a harmonic frequency processor closed loop (20);
• and a capacitor-voltage control closed loop (21).