Design and Analysis of Current Control Methods for Brushless Doubly Fed Induction Machines

Brushless doubly fed induction machine (BDFIM) with apparent cost advantage and high potential in reliability is regarded as a viable alternative to the commonly applied doubly fed induction machine in modern energy conversion systems. Design and analysis of the current controller, which are key points for effective control of BDFIM, are for the first time intensively studied in this paper. The complete model of control winding current loop is developed in form of complex transfer function, and its differences from the conventional simplified model are clearly revealed. An improved feedforward current control method is proposed based on the complete model, offering simple and compact control structure with only few parameters involved. Stability and transient performance analysis is carried out on both conventional and improved current controllers, which theoretically proves stability improvement and faster dynamic performance of the improved current controller. The effectiveness and superiority of the proposed current controller, as well as the consistence between theoretical analysis and actual performance, are validated by experimental results performed on a prototype BDFIM system.