A Brushless Doubly-fed Generator Based on Permanent Magnet Field Modulation

A brushless doubly fed generator (BDFG) for wind power applications with a double-rotor structure is presented in this paper. First, field modulation ring and its application in the proposed BDFG are introduced. The geometric constraints of the field modulation ring are analyzed. Then, the operation principle of a variable-speed constant-frequency BDFG system is presented. The design of the BDFG is discussed, and finite-element analysis for the BDFG is carried out to obtain the performance of the machine. Finally, a small-size prototype machine is designed and manufactured to verify the theoretical analysis. The proposed BDFG has some advantages, such as high efficiency and high reliability. It has good potential on the applications of future large-scale wind power generation systems.