Enhancing the Performance of Eskom’s Cahora Bassa HVDC Scheme and Harmonic Distortion Minimization of LCC-HVDC Scheme Using the VSC-HVDC Link

Abstract

Cahora Bassa, a thyristor-based High Voltage Direct (HVDC) link, transmits 1920 MW of power from a hydro-power plant in Zambezi River, north of Mozambique, to Apollo Substation in Johannesburg, South Africa. The high degree of harmonics distortion that is transferred into the AC side of the transmission network and the continuous increase in the rate at which commutation failure occurs during systems disturbance are both flaws in the utilization of this HVDC converter technology. AC and DC filters with rugged controllers are often used to minimize this effect but are limited in scope. Modern converter technology, such as the Voltage Source Converter (VSC), was proposed in this study to reduce harmonics content level, increase power transfer capabilities, enhance network stability, and reduce the rate of commutation failure occurrence. This paper, therefore, evaluates the performance analysis of the Cahora Bassa HVDC link and its level of harmonic distortion in the line commutated converters. A proposed method of utilizing VSC HVDC is provided as a suitable solution using three modular-level voltage source converter technology. Current and voltage waveform characteristics during a three-phase short circuits fault were analyzed, and the latest developments in the area of VSC HVDC were discussed. The results show a lower total harmonics distortion with the usage of VSC HVDC converter technology at the inverter station. The continuous occurrence of commutation failure was minimized by implementing a new converter architecture. The network simulation and analysis were carried out using the DIgSILENT PowerFactory engineering software tool.

Protection of HVDC Transmission Systems for Integrating Renewable Energy Resources

“…represents the initially determined fault location. It corresponds to the location at which @ is minimized, as indicated in (7).…”

“…Voltage Source Converter-based High Voltage Direct Current (VSC-HVDC) transmission systems are widely employed worldwide for the efficient transmission of large power quantities. HVDC systems offer numerous advantages compared to traditional HVAC transmission systems [1][2][3][4][5][6][7][8][9][10]. One notable advantage is that the length of the DC transmission circuit is not limited, thanks to the absence of charging currents, especially with underground cables.…”

Critical Technical Issues with a Voltage-Source-Converter-Based High Voltage Direct Current Transmission System for the Onshore Integration of Offshore Wind Farms

“…Due to its high level of flexibility and inherent capacity to adjust both its reactive and active power, it is more beneficial in locations with metropolitan power networks. The majority of converter stations for the VSC-HVDC technology employ multilayer converter circuits [78,79], as seen in Figures 8 and 9 [80].…”

Network Coordination between High-Voltage DC and High-Voltage AC Transmission Systems Using Flexible AC Transmission System Controllers

“…It is located in South Africa, but the rectifier is 1414 km to the north in Mozambique. The present HVDC transmission line rating is 1920 MW with 533 kV [48].…”