Bdfm Speed Control System

The brushless doubly-fed machine(BDFM), with simple structure and favorable reliability, has gained renewed attention in adjustable-speed drive and variable-speed constant-frequency generator applications in recent years for it features adjustable power factor and high efficiency. In BDFM, since both power winding and control winding are mounted in stator, current is doubly fed into the machine without electric brush and slip ring hence improving robustness and security can be achieved in this configuration. Up to now, the domestic study on BDFM is just confined to laboratory and there is no practical system used in industrial applications, so it is necessary to go deep into its research. In this paper, systematic research on variable-frequency adjustable-speed drive based on BDFM is carried out. Beginning with its historical development, this paper presents the BDFM抯 calculating model and variable calculating method based on its operating principle. And a simulation is carried out to verify its open-loop performance. And then, the research is focused on the control strategy of the BDFM. On the fundament of analyzing its open-loop characteristics and the normal induction machine抯 vector control method, a field orientation control scheme of BDFM is presented. A double-synchronous frame d-q model has been proposed where variables are transformed into either the BDFM power or control winding synchronous reference frame, which makes the field-oriented control methods feasible. A system controller block diagram and hardware structure diagram are proposed in this paper according to the synchronous frame d-q model. The simulation to the torque and frequency characteristics illustrates the effectiveness of the proposed method. The research in this paper has established a ftindamental for the practical application of BDFM, and will promote the BDFM抯 designing, modeling and controlling.