HVDC Converter Transformers Protection - Part 1: Signal Processing Aspects

This paper addresses the challenge of commutation failure (CF) in Line-Commutated Converter (LCC) High-Voltage Direct Current (HVDC) technology, which causes distortions in nearby AC system current waveforms. The research analyzes current signal characteristics in converter transformers, assesses how this distortion affects phasor estimation algorithms during transients, and examines harmonic components in short-circuit scenarios. The study employs Discrete Fourier Transform (DFT) techniques and estimates har-monic content. The results reveal that anti-aliasing filters modify the original signal, CFs lead to inaccuracies in phasor estimation, and the introduction of harmonics in the signal may block the trip command issuing for internal faults in conventional transformer protections.