Research On The Rotor Circuit Of Wound Rotor Brushless Doubly-Fed Machine

The Brushless Doubly-Fed Machine(BDFM) is a novel AC induction machine with outstanding start-up performance and speed-regulation capability, whose structure and operation principle are similar with conventional AC machines, which makes it could operate under asynchronous, synchronous, doubly-fed mode as well as other operation modes. This type of machine is solid and reliable for being canceled the slip ring and brush, the rated converter it requires is fractional as well. Since all the mentioned advantages, BDFM will have wide application in hydroelectric and wind power generation systems, ship shaft generation systems and AC adjustable speed drive systems.The rotor of BDFM is the bridge of two magnetic fields inside the machine, thus, its structure has obvious effect on the performance of BDFM. Presently, there are 3 main kinds of BDFM rotor: special cage, reluctance structure and wound-rotor structure which is flexible in design and with low harmonic contents. Both the ‘Tooth Harmonic' principle and ‘Pole Changing' principle are design methods of wound rotor. The former one can realize high winding factor and flexible design, but it can't utilize all of the rotor-slot space; while the latter one is opposite.The wound rotor winding of BDFM designed of ‘Pole Changing' principle is taken as the research object in this paper, specific theoretical analysis and the simulation of the rotor circuit is stated. The main aims of the research are: analyzing the existing rotor designed of ‘Pole Changing' principle; analyzing the reason caused the unequal current of each circuit branch; presenting a new winding design to solve the mentioned problem.