Converter-Level Reliability of Wind Turbine With Low Sample Rate Mission Profile

The thermal dynamics of power semiconductors and power capacitors are closely related to the reliability and affect the cost of power electronic converter. However, the component loading in a wind turbine system is disturbed by many factors of the power converter, which presents various time constants from microseconds to hours. To determine the system availability in such system is a challenge and need detailed analysis. In the case of a mission profile with 1-hour sample rate, a simplified circuit model, loss model, and thermal model of the active power switches and passive capacitors are needed and described. According to the long-term electrothermal profile, the percentile lifetime of a single component can be predicted. The Weibull function based time-to-failure distribution can then be used to link from component-level to converter-level reliability. From analysis of a 2 MW wind turbine system, it can be seen that the dc-link capacitor bank dominates the converter-level reliability.