Comparison of Wind Power Converter Reliability with Low-Speed and Medium-Speed Permanent-Magnet Synchronous Generators

More and more wind turbine manufacturers turn to use the full-scale power electronics converter due to the stricter grid code requirements in order to thoroughly decouple the generator from the grid connection. However, a common used type of the generator is still unclear, where the selections of the low-speed (direct-drive) and medium-speed (one-stage) permanent-magnet synchronous generators are both promising solutions. This paper will assess and compare the reliability metrics for the machine-side converter for those two configurations. First, a translation from the mission profile of the turbine to the current and voltage loading of the each power semiconductor is achieved based on the synchronous generator modeling. Afterwards, a simplified approach to calculate the loss profile and the thermal profile is used to determine the most stressed power semiconductors in the converter. Finally, according to the lifetime power cycles, the lifespan can be calculated when operating in various wind classes. It is concluded that, although the low-speed permanent-magnet synchronous generator is able to eliminate the gearbox, the lifespan of its machine-side converter is lower than the one-stage medium-speed generator.