Modular Multilevel Converters for HVDC power stations SERBIA, Nicola Institut National Polytechnique de Toulouse (INP Toulouse)

SUMMARY
This work was performed in the frame of collaboration between the Laboratory on Plasma and Energy Conversion (LAPLACE), University of Toulouse, and the Second University of Naples (SUN). This work was supported by Rongxin Power Electronic Company (China) and concerns the use of multilevel converters in High Voltage Direct Current (HVDC) transmission. For more than one hundred years, the generation, the transmission, distribution and uses of electrical energy were principally based on AC systems. HVDC systems were considered some 50 years ago for technical and economic reasons. Nowadays, it is well known that HVDC is more convenient than AC for overhead transmission lines from 800 - 1000 km long. This break-even distance decreases up to 50 km for underground or submarine cables. Over the twenty-first century, HVDC transmissions will be a key point in green electric energy development. Due to the limitation in current capability of semiconductors and electrical cables, high power applications require high voltage converters. Thanks to the development of high voltage semiconductor devices, it is now possible to achieve high power converters for AC/DC conversion in the GW power range. For several years, multilevel voltage source converters allow working at high voltage level and draw a quasi-sinusoidal voltage waveform. Classical multilevel topologies such as NPC and Flying Capacitor VSIs were introduced twenty years ago and are nowadays widely used in Medium Power applications such as traction drives. In the scope of High Voltage AC/DC converters, the Modular Multilevel Converter (MMC), proposed ten years ago by Professor R. Marquardt from the University of Munich (Germany), appeared particularly interesting for HVDC transmissions.
LINK
http://hal.archives-ouvertes.fr/docs/00/94/53/75/PDF/SERBIA_2014.pdf