Theoretical Analysis of Harmonic Voltage Resonance in AC Electric Traction System

This study investigated the harmonic voltage resonance in an AC electric traction supply system. With the introduction of vehicles with voltage stiff converters using pulse width modulation (PWM), resonances can sometimes be observed in the AC electric traction supply system, affecting the electromagnetic interference. Considering the characteristics of the distributed constant circuit, a novel theoretical equation was introduced to evaluate the harmonics produced by vehicles with voltage stiff converters in the AT-fed AC electric traction supply system. Analyzing the harmonics, which were produced by vehicles in the AT-fed AC electric traction supply system, using the proposed theoretical equation revealed that the resonance frequency may be affected not only by traditional theory, but also by the leakage impedance of on-board transformers. Furthermore, the magnification ratio of the harmonic voltages varies depending on the location of the train sets in the traction circuits.