Trends and Influencing Factors in Power-Converter Reliability of Wind Turbines: A Deepened Analysis

Based on comprehensive field data covering more than 22,000 operating years of onshore and offshore wind turbines on five different continents, we present failure rates for the main components of the converter system, investigate their failure behavior with respect to trends and identify both design-related and site-specific factors having a significant effect on converter reliability. All converter components show prominent early failure behavior followed by a transition straight to degradation failures. Several design factors are identified as significant reliability drivers: namely the cooling concept of the converter, its position inside the wind turbine, its rated capacity as well as the IGBT-module manufacturer. In addition, a susceptibility to the environmental influences of mean absolute ambient humidity, mean ambient temperature, installation height and mean capacity factor is identified and quantified.