The power electronic converter, especially the power semiconductor, is a major contributor to the failure rates of the wind turbine drivetrain. As the temperature is a major driving factor behind the failure mechanisms of these power semiconductors, the choice of topology and switching strategy can have a significant effect on the reliability of the converter. This paper presents a detailed comparison of several three-level converter topologies and switching strategies on the basis of loss distribution, thermal, and lifetime performance. This investigation is done through simulations on a 10-MW direct drive permanent magnet drivetrain. The study shows that overrating in the form of using overrated topologies, or the use of overrated components can result in large gains in lifetime expectancy and quantifies these gains. It concludes that the improvements offered by overrated topologies and overrated components are comparable and this use of the overrated topologies do not offer a significant advantage over the use of topologies with overrated components.

Published in: IEEE Journal of Emerging and Selected Topics in Power Electronics ( Volume: 6 , Issue: 3, Sept. 2018)