High-Order Harmonic Elimination and Resonance Damping Based on Inductive-Filtering Transformer for Electrified Railway Transportation System

This article focuses on the high-frequency resonance and harmonic elimination in the electrified railway transportation system. The high-order harmonic currents, which are generated by the grid-side converter in the locomotives' drive system, will inject into the traction power supply system (TPSS). These injected harmonic currents are harmful to electrical equipment along the transmission line in the TPSS, causing vibration, overheating, increased losses of the traction transformer, and deteriorating the power quality of TPSS. Even worse, these harmonics can be amplified in the locomotive-TPSS coupling system when their frequency matches the inherent frequency of TPSS, resulting in system resonance. To absorb the high frequency and avoid the resonance phenomenon, an inductive-filtering-based onboard traction transformer (IFTT) is proposed. The IFTT is designed for the restricted installation space by adding extra filtering windings to a convention onboard traction transformer. A detailed design process of the harmonic low-impedance loop is provided, which is the precondition of inductive filtering. Simulation and experimental results are shown to verify the feasibility of the proposed method.