Repetitive Control Method for Suppression of Higher Harmonics in Supply Current of Subway Couches

Moscow Metro has signal systems that ensure the safety of train traffic, such as automatic speed control system and centralization and interlocking systems. The traction electric drive of a metro train should not interfere with the operation of rail devices during standstill or movement. The main harmonics of the traction current are harmonics multiple of 300 Hz, appearing during rectification of the alternating voltage, and harmonics multiple of 50 Hz, in case of partial faults in traction substation. To reduce the influence of the harmonic composition of the traction electric drive, the frequencies encoding the information signals are chosen in intermediate ranges. However, during the movement of the train, the frequency of the motor and, consequently, of the currents change. Being superimposed on the main harmonic of 300 Hz, the amplitude of these frequencies can be amplified and create interference in the signals of automatic speed control and collision prevention control systems. This paper proposes an algorithmic way to reduce the harmonic composition of traction current, based on the repetitive control method. The algorithm was tested on the traction electric drive of a subway train couch and showed a 10-fold decrease in the harmonic amplitude of 300 Hz.