VSC Conversion Technology for HVDC & FACTS, State of the Art and Future Trend

This speech is intended to describe the present State of the Art and future trend of Voltage Source Conversion (VSC) Technology applied to Transmission and Distribution (T&D) Lines in particular to High Voltage Direct Current (VSC-HVDC) and Flexible AC Transmission Systems (FACTS). Taking into consideration the present state and future trend of Power Semiconductor devices development, Conversion Topology and main Applications. The applications, where VSC-HVDC technology has been applied with major success, until now are: Interconnectors between countries and transmission by submarine cables from Off Shore Wind Farms to On Shore Grid (main locations in North Europe) , Multi-terminals (MTDC) and Back to Back (B2B) Ties (mainly in China). In near future we foresee important application of VSC technology also in Long Distance Transmission (LDT) (China, India and Brazil or between continentals). Some comparisons in terms of power rating, performances, space and losses has been evaluated between VSC-HVDC technology and the traditional one based on Current Source Thyristor conversion commonly known as Line Commutated Conversion (LCC-HVDC), in China some Hybrid solutions VSC+LCC has been already applied in B2B and others will be applied also in LTD in near future. We think Hybrid will become more and more important in the future to guarantee the best performances at lower cost and losses. Regarding FACTS many solutions have proposed and deeply studied based on VSC Converter in Series (SSSC), in Shunt (Statcom) or both in Series+Shunt position (UPFC) to stabilize high voltage AC line in transmission operation or against bad contingences. At present only Statcom has been extensively applied in real T&D projects and now is also entering in heavy duty industrial sectors to improve Power Quality of MV industrial feeding lines.