Thermal Cycling Overview of Multi-Megawatt Two-Level Wind Power Converter at Full Grid Code Operation

In this paper, two promising multi-megawatt wind turbines equipped with a doubly-fed induction generator-based partial-scale and a permanent magnet synchronous generator-based full-scale two-level power converter are designed and compared. Simulations of the two configurations with respect to loss distribution and junction temperature variation for the power device over the entire wind speed range are presented and analyzed both for normal operation and operation with various specific grid codes. It is concluded that in both partial-scale and full-scale power converters, the most thermal stressed power device in the generator-side converter will have a higher mean junction temperature and also junction temperature variation compared to the grid-side converter at the rated wind speed, and the thermal performance of the generator-side converter in the partial-scale power converter becomes crucial around the synchronous operating point and needs to be considered carefully. Moreover, reactive power injection directed by the grid codes will affect the thermal profile of the power semiconductors, especially at lower wind speeds.