Device loading of modular multilevel converter MMC in wind power application

Modular multilevel converter (MMC) is a recently emerged multilevel topology for high-voltage high-power applications. However, in wind power application the performance of the MMC has not been deeply investigated. In this paper the application of MMC in wind energy systems is studied. The converters used to connect the wind turbine to the grid having the rated active powers of 2MW and 10MW are designed and investigated. Electrical losses and thermal loading of the power devices in the proposed converter solutions are analyzed. The efficiency of the MMC converter under different P/Q boundaries defined by grid codes is investigated and compared with two-level and three-level NPC converters. It is concluded that it is possible to use the MMC in wind power application and the losses are distributed evenly between the sub-modules of the MMC converter. However, inside a sub-module the losses of the power devices are not equal that can lead to the de-rating of the converter.