Harmonics in Brushless Doubly Fed Induction Generator for Torque Ripple Analysis and Modeling

Brushless doubly fed induction generator (BDFIG) is promising for off-shore wind turbine application because of the high reliability without brush and slip ring. Because of the special structure of two isolated stator windings of different pole number and complex rotor configuration, the analysis of BDFIG is different from a conventional induction machine. The conductor distribution function is adopted to analyze the harmonics generated by stator and rotor windings. Furthermore, the torque ripple is deduced on the basis of the harmonics, and a multireference generic vector model is established to describe the harmonic behavior. All theories and predictions are validated using finite element method in Ansoft/Maxwell.