Implications of resonant circuit adjustment errors to the DC-link voltage in single-phase 16.7-Hz-railway applications

Traction vehicles operating in the single-phase 16.7-Hz-railway grid - typical for central Europe - employ a resonant circuit connected in parallel to the DC-link capacitor. The resonant circuit is necessary to take up the unavoidable grid power pulsation with double frequency, leaving a smooth DC-link voltage. In reality grid-voltage frequency and resonance frequency of the resonant circuit do not fit accurately: Manufacturing tolerances of resonant-circuit capacitor and inductance lead to an adjustment error and the railway-grid frequency moves within a defined intervall, due to the power-frequency control, independent from the European interconnected mains. In this paper implications of the adjustment error are analysed. Additionally instructions for parameter identification are given and backed by measurement results.