Traction transformer integrated LCL filtering method for high-frequency harmonic and resonance suppression in AC train

•Traction transformer integrated LCL filtering method with less filter inductors and capacitors is proposed.•Filtering mechanism is revealed by building electromagnetic decoupled equivalent circuit model of innovative transformer.•Prototype of traction transformer with integrated filter windings is designed and manufactured for validation.•Good filtering performance of the proposed method is verified by real-time field-circuit coupling simulation.