A review of the performance of VSC-HVDC and MTDC systems

For decades, high voltage alternating current (HVAC) has been the more conventional method of power delivery. With recent advances in power electronics, high voltage direct current (HVDC) is an established technology in long-distance bulk power transmission. It is re-emerging to be the better option due to improved system operation and better support in the development of onshore and offshore transmission grids. Because of its speed and flexibility, the HVDC technology is able to provide the transmission system with several advantages such as transfer capacity enhancement, better power flow control, transient stability improvement, damping of power oscillations; rejection of cascading disturbances, enhanced stability/control, and the absence of reactive power generation or absorption by the line or cable. The objective of this study paper is to provide an overview of VSC-HVDC systems in terms of their overall performance, control methods and to highlight multi-terminal DC systems as the gateway to future DC grids in Africa.