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 the cost of power electronic converter. However, the component loading in a wind turbine system is disturbed by many factors of the converter system, which is present at various time-constants from microseconds to years. In the case of a mission profile with 1-hour sample rate, the circuit model, loss model, and thermal model of the active power switches and passive capacitors are described and presented. The percentile lifetime of a single component can be predicted according to the long-term electro-thermal profile, and the Weibull function based time-to-failure distribution of the active component and passive component can be obtained. In a 2 MW wind turbine system, it can be seen that the dc-link capacitor bank dominates the converter-level reliability.