Measurement of harmonic currents and evaluation of the DC filter performance of the New England-Hydro-Quebec Phase I HVDC project

Measurements were conducted to determine the cause of increased telephone interference and to evaluate the DC filter performance. The measurements revealed unexpected high levels of three-pulse harmonic currents in the DC pole conductors. The cause is attributed to imbalances within the six-pulse bridges caused by the converter transformer and valve stray capacitances to ground. The conventional model of the converter power circuit used as the basis for the DC filter design does not reproduce the measured three-pulse harmonics.<
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