Medium-Voltage versus Low-Voltage Converter Reliability in Wind Turbines: A Field-Data Based Study

Abstract:
High failure rates of typical IGBT-based low-voltage converters remain a challenge for wind-turbine reliability. For the first time, we present a field-data based reliability study for IGCT-based medium-voltage converters in offshore wind turbines. Compared with low-voltage converters, these are found to exhibit lower failure rates per MW of converter capacity and fewer components with susceptibility to climatic influences. The failure behavior through time of both the medium- and low-voltage converters is mostly characterized by early-failure behavior in the first years of turbine operation and subsequent reliability deterioration. In case of the medium-voltage converters, these trends are less pronounced so that the reliability behavior is more stable. Overall, the findings support the potential for wider adoption of medium- voltage converter technology in wind turbines.