Harmonic distortion of LCC-HVDC and VSC-HVDC link in Eskom's Cahora Bassa HVDC Scheme

Abstract

Cahora Bassa, a thyristors based HVDC link transmits 1,920 MW of power from hydropower plant located in Zambezi river, north of Mozambique to Johannesburg, South Africa. This HVDC converter suffer few deficiency in its high level of harmonics distortion that transferred into its AC side of the transmission network couple with persistence rate of commutation failure. AC and DC filters with rugged controller are often used to minimize this effect but are limited in some aspect. Modern converter technology used for different HVDC links reduces harmonics content level, increases power transfer capabilities, enhances network stability and finally reduced the rate of commutation failure. This paper therefore investigate the level of harmonic distortion in line commutated converter used in Cahora Bassa link and thus proffer a suitable solution with the use of VSC-HVDC link. Current waveform characteristics and latest developments was also addressed. Simulation analysis was carried out using DigSILENT PowerFactory.