Harmonic suppression in electric traction system based on a single-phase hybrid active filter

A practical single-phase hybrid active power filter for electric traction system is proposed. This system consists of an active filter, a passive filter, fundamental series resonance circuit (FSRC) and a coupling transformer. With FSRC in parallel and a capacitor of 3^th-order filtering branch in series, the active power filter is immune to the effects of high fundamental voltage and current. Thus, the capacity of the active power filter is greatly reduced. This type of hybrid active power filter can compensate reactive power at the same time. The adopted harmonic current detecting method can guarantee the speed and precision of harmonic detection, and is immune to the effects of voltage distortion caused by electric locomotives. The current control strategy is a realtime and close-loop control, based on PWM control method. Simulation based on PACAD/EMTDC verifies the effectiveness and reliability of proposed system.