Study On Control Strategy For Brushless Doubly-Fed Machine Adjustable Speed Drive System

The Brushless Doubly-Fed Machine(BDFM) is a new type machine which has different design technology and control strategy with traditional induction machines. The BDFM system has the robust mechanical configuration and controllable speed and power factor as well as a relatively low rating power converter. These benefits attract more and more researchers' attention.In this paper, the steady state operation performance and control strategy of the BDFM with cage rotor is developed. Three parts are included.First of all, based on the summarizing of current researches on BDFM and operation principle of BDFM, some further studies had been done. Using MATLAB/Simulink simulation tools, based on the BDFM d-q model established on the rotor reference frame, the BDFM transient state simulation mode was established. Afterwards the operation performances in various operation modes were simulated. In order to extend the stable operation range of the BDFM, a method to determine the control relationship between the voltage amplitude and frequency of the control winding by the transient state model of BDFM was presented in this paper. Meanwhile the steady state performances in the stable operation range for the different voltage value were calculated by the steady state model of BDFM. According to the perfection performances, the final voltage value for the every operation frequency was decided. By means of the method presented in this paper, the calculation results for the stable operation range and the steady state operation performance of a sample BDFM are carried out and compared with the control strategy of constant V/Hz ratio. Results showed that the method presented in this paper appears good in the extending stable operation range and the steady state performances for BDFM. Together with the method of control strategy research proposed in this paper and the electromagnetic design of BDFM can construct a foundation for development of the BDFM adjustable-speed drive system and the variable speed constant frequency power generation system.Finally, the harmonics and its' effects in BDFM adjustable-speed drive system were analyzed. Harmonic model was established. According to harmonic analysis method, current harmonics and torque harmonics in system were calculated. Results showed that harmonics have a small effect on stability and steady state performance of BDFM.