Reliability Model Development for Wind Turbine Drivetrain with Brushless Doubly-Fed Induction Machine as Generator

Brushless doubly-fed induction machines (BDFIM) are attractive generators to be used in wind turbines due to the absence of brushes and slip rings. Furthermore, the BDFIM is a medium-speed generator and hence only requires one or two-stage gearbox. This feature simplifies the gearbox system and therefore improve reliability and reduce maintenance costs for the wind turbine. Although the design and operation of the BDFIM has been widely studied in the literature, there are only few studies on reliability assessment of the machine as a wind turbine generator. This paper proposes a comprehensive reliability model for two wind turbine drivetrain configurations: One with doubly-fed induction generator, and the other when the BDFIM is employed as the generator. The model is capable of evaluating the failure rate and repair rate indexes for the both configurations. Real field survey data from a 90 MW wind farm as well as calculated reliability data are then utilised to determine the reliability index values for the two drivetrain configurations in order to compare their reliability performance.