Frequency-Scanning Harmonic Generator for (Inter)Harmonic Impedance Tests and Its Implementation in Actual 2 x 25 kV Railway Systems

Measurements of (inter)harmonic impedances of the traction power supply system (TPSS) play important roles in the validation of TPSS modeling, suppression of resonances, stability analysis of locomotives converters, etc. A harmonic generator (HG) and its construction are proposed in this article to directly measure the impedance of TPSSs. Compared to other experimental setups, the HG can emit a fully controlled single-tone (inter)harmonic current at the high voltage level in a wide frequency range, i.e., at least covering 150-3750 Hz. Field tests have been carried out in the actual 2 x 25 kV railway considering the influence of locations and lengths that are scarcely presented in existing literatures. Both the implementation process and test waveforms have verified the effectiveness and feasibility of the HG. The test results, which denotes that locations do not change the resonant frequency while railway lengths will shift resonant frequencies distinctly, can be a basis for developing techniques aimed to improve the power quality.

Automated summary

This article proposes a harmonic generator to directly measure the impedance of traction power supply systems. Field tests on actual railways have verified the effectiveness and feasibility of this method. The study found that locations do not change resonant frequencies, while railway lengths distinctly shift resonant frequencies.