Research On Magnetic Field Modulation Type Of Doubly-Fed Brushless Machine

The magnetic field modulation type of Doubly-Fed Brushless Machine (DFBM) not only features simplicity, robustness and reliability, but also can realize easily soft starting, asynchronous or synchronous operation, cascade or doubly-fed adjustable speed. Compared to an adjustable speed system using conventional AC machine, the DFBM system controls only the slip power of DFBM, a small fraction of the overall system power, through the stator auxiliary winding.The research on DFBM in our country just starts. The work of this thesis focuses mainly the theory analysis, parameter calculation and performance simulation of the DFBM. Four parts are included.First of all, based on analyzing the various structure types and operation modes of the DFBM, the basic theory about DFBM is studied. The magnetic coupling function and equivalent relationship between reluctance rotor and cage rotor have been analyzed. Without limiting to conventional analysis method that the DFBM came from two cascade induction motors, this thesis studies the principle of electromagnetic energy conversion of the DFBM using magnetic field modulation theory, which gather the principles of doubly-fed brushless machine with cage rotor and reluctance rotor into one. The air gap magnetic field of the DFBM with different structure rotors is analyzed. The unique equivalent circuit and torque formula of the DFBM with different rotor structure are also derived. The power, loss and energy flowchart in the DFBM are discussed. The comparison between the DFBM adjustable speed system and the traditional AC adjustable speed system is given in the thesis.Secondly, the performances of different operation modes for the DFBM with different structure rotor have been simulated. An universal mathematic model in ABC reference frame of the DFBM with reluctance rotor and cage rotor is put forward, and the voltage restriction is described. Based on above work, the simulation programs have been developed.Thirdly, the inductance parameters of the DFBM with different structure rotors, the salient pole reluctance rotor, ALA reluctance rotor and cage rotor, are studied in details. The models of calculating inductance parameter of the DFBM with different structure rotor are respectively derived, and the corresponding calculation softwares are carried out. The effects of rotor structure and other factors on stator winding inductance parameter have been studied by means of the parameter calculation program.Finally, the design principle and experiment method of the DFBM are studied. According to theoretical analysis and simulation study, the design principle of stator winding and rotor structure has been put forward. In order to study comparatively effects of different rotor structure on the operation behaviors of DFBM, a prototype machine has been designed and built The prototype machine has a common stator and two different structure rotors, the ALA reluctance rotor and the short-circuited cage rotor. The two rotors have the same size. The inductance parameter and operation performance in various operation modes of the prototype machine are also presented.