Design and Performance Study of a Brushless Doubly Fed Generator Based on Differential Modulation

The brushless doubly fed generator (BDFG) has a good application prospect in the fields of ship shaft power generation and wind power generation due to its simple structure, safety, and reliability. In previous studies, the brushless doubly fed machine (BDFM) is all based on additive modulation and whose natural synchronous speed is 60 f
₁
/(p
₁
+ p
₂
). The natural synchronous speed and power density of BDFM are lower than those of traditional asynchronous machine. In order to increase the natural synchronous speed and expand the machine's operating range, this article proposes a BDFG based on differential modulation and whose natural synchronous speed is 60 f
₁
/|p
₁
- p
₂
|. First, this article analyzes the basic working principle of differential modulation BDFG and the key factors that prevent it from developing. Then, a design scheme of stator winding and rotor winding for differential modulation BDFG is presented. Finally, the finite-element model of the BDFG is established on the basis of the winding design example, and the experimental prototype is designed and manufactured. The steady-state performance of the differential modulation BDFG is analyzed according to the simulation and experiment, and the feasibility of the design scheme is verified.