Design of power converter in DFIG wind turbine with enhanced system-level reliability

With the increasing penetration of wind power, reliable and cost-effective wind energy production are of more and more importance. As one of the promising configurations, the doubly-fed induction generator based partial-scale wind power converter is still dominating in the existing wind farms, and its reliability assessment is studied considering the annual wind profile. According to an electro-thermal stress evaluation, by using lifetime models and Monte Carlo based variation analysis, the time-to-failure distribution of the key power semiconductors is predicted. Aiming for the system-level reliability analysis, a Weibull distribution based component-level model is applied by using a reliability block diagram. A case study of a 2 MW wind power converter shows that the optimal selection of power module may be different viewed from the reliability perspective compared to the electrical stress margin. It can be seen that the B1 lifetime of the grid-side converter and the rotor-side converter deviates a lot by considering the electrical stresses, while they become more balanced by using an optimized reliable design. The system-level lifetime significantly increases with an appropriate design of the back-to-back power converters.