Multilevel Converters

Multilevel converters were conceived to address the need to increase the operating voltage of power converters without exceeding the limits of existing power semiconductors. This is achieved by arranging the semiconductors and capacitors in special configurations, which can distribute the stress more appropriately and generate different output voltage levels. This also improves significantly the quality of the generated voltage waveforms and enables the reduction of the switching frequency of the power semiconductors. Improvements in power quality and efficiency, together with higher voltage to operation have made these converters very popular in high-power medium-voltage drives, such as pumps, fans, conveyors, train traction and wind energy conversion. At Powerlab much work on design, modeling, topology development, modulation and control of these converters has been carried out since 2002. Powerlab is recognized as one of the most active groups in this area, with dozens of contributions, which include: new modulation methods, fault-tolerant operation, and their use in high performance applications such as regenerative conveyor belts, photovoltaic energy conversion systems and HVDC transmission. Powerlab has organized several special sections in journals, tutorial courses at conferences and highly cited review articles related to this type of converters.