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Author: search.filters.author.Oni, Oluwafemi E.Subject: search.filters.subject.HVDC

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    Harmonic distortion of LCC-HVDC and VSC-HVDC link in Eskom's Cahora Bassa HVDC Scheme
    (IEEE, 2016-11) Oni, Oluwafemi E.; Davidson, Innocent Ewaen
    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.
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    Dynamic voltage stability studies using a modified IEEE 30-Bus system
    (IEEE, 2016) Oni, Oluwafemi E.; Davidson, Innocent Ewaen; Mbangula, Kamati N. I.
    Power System stability is an essential study in the planning and operation of an efficient, economic, reliable and secure electric power system because it encompasses all the facet of power systems operations, from planning, to conceptual design stages of the project as well as during the systems operating life span. This paper presents different scenario of power system stability studies on a modified IEEE 30-bus system which is subjected to different faults conditions. A scenario whereby the longest high voltage alternating current (HVAC) line is replaced with a high voltage direct current (HVDC) line was implemented. The results obtained show that the HVDC line enhances system stability more compared to the contemporary HVAC line. Dynamic analysis using RMS simulation tool was used on DigSILENT PowerFactory.
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    A review of LCC-HVDC and VSC-HVDC technologies and applications
    (IEEE, 2016) Oni, Oluwafemi E.; Davidson, Innocent E.; Mbangula, Kamati N.I.
    High Voltage Direct Current (HVDC) systems has been an alternative method of transmitting electric power from one location to another with some inherent advantages over AC transmission systems. The efficiency and rated power carrying capacity of direct current transmission lines highly depends on the converter used in transforming the current from one form to another (AC to DC and vice versa). A well configured converter reduces harmonics, increases power transfer capabilities, and reliability in that it offers high tolerance to fault along the line. Different HVDC converter topologies have been proposed, built and utilised all over the world. The two dominant types are the line commutated converter LCC and the voltage source converter VSC. This review paper evaluates these two types of converters, their operational characteristics, power rating capability, control capability and losses. The balance of the paper addresses their applications, advantages, limitations and latest developments with these technologies.