Analysis on Nonlinear Factors of Variable Speed Constant Frequency Doubly Fed Wind Turbine Generator System

A doubly fed wind turbine generator system mainly consists of a doubly fed induction generator(DFIG) and back-to-back voltage source converters(VSCs).The DFIG is a nonlinear and strong-coupled system with multi-variables and due to the coupling of capacitors of DC bus the VSCs also contain nonlinear factors.The authors systematically research nonlinear factors of DFIG system according to their mathematical models and analyze the advantages and defects of traditional vector control strategy, meanwhile investigate the feasibility of the nonlinear decoupling control based control strategy for DFIG units.The effect of attenuating nonlinear components by coordinate transformation is pointed out.