Using a passive filter to suppress harmonic and resonance effects on railway power systems

Abstract

The motivation for this research was to find methods for suppressing harmonics and harmonic resonance in traction power systems. System parameters determined through actual field measurements from a traction substation in China were used to develop mathematical models of a special connection transformer, a traction load, and a traction line. Potential power quality problems arising from traction load operation, including harmonic currents and waveform distortions at the point of common coupling in the power grid, are described. Using frequency scan analysis, the harmonic resonance frequency and high distortion current waveform generated by a system undergoing harmonic resonance were estimated and found to be identical to simulation results. Detuned, single-tuned, and damping passive filters were studied as means of reducing harmonic currents and thus eliminating harmonics. Field measurements and simulation results showed that, although the detuned filter could not provide effective harmonic reduction, the single-tuned filter effectively eliminated harmonics and reduced amplification of the parallel harmonic resonance frequency of a traction network. Although the damping filter was effective in eliminating high-frequency harmonics, the additional power losses it incurred were not economical. These harmonic analyses were simulated using MATLAB/SIMULINK.