Impact of DFT-Based phasor estimation errors due to commutation failures of LCC-HVDC links on the protection of AC lines in the near vicinity

Abstract

Commutation failure (CF) is an inherent issue for Line-Commutated Converter (LCC) HVDC technology. Whenever it happens, voltage and current waveforms throughout the AC system in the near vicinity of LCC-HVDC links become quite distorted. In this paper, it is assessed the impact of such kind of distortion on transient response of phasor estimation algorithms and, in turn, on the performance of AC transmission lines protection. Different discrete Fourier transform (DFT) based algorithms are implemented, and distance, differential and directional protection functions are evaluated. The obtained results reveal that phasor estimation errors arise whenever CFs take place, which may lead protection functions to misoperate, such that false trip command may be issued for external faults.