Study on harmonic resonance of traction line in electrified high-speed traction system

Modern pulse width-modulated (PWM) converter-fed locomotives generate current harmonics which propagate along traction line. The traction line is distributed at high frequencies, so the injected harmonics may cause resonances. This paper presents a way for analyzing resonance in electrified high-speed traction system, by calculating the harmonic current along the traction line. According to harmonic voltage generation process and distributed characteristics of traction line, the formulas representing the harmonic spectra of PWM converter input voltage and harmonic impedance of traction system are presented. Frequency spectrum characteristics of traction voltage and current are simulated and analyzed while the locomotive runs along the traction line. Results indicate that properties of both harmonic current and voltage vary, the former has greater variation; series resonances occur at some frequency and the position depends on locomotive position along the line; harmonic current contents are small, the mains are 3-9th harmonics and series resonances ones.