Analytic Algorithm for Calculation of Saturated Inductances of Brushless Doubly-Fed Machine

Due to the complex winding structure and the magnetic field modulation mechanism of brushless doubly-fed machine (BDFM), as well as the difficulty of analytic solution about the saturated inductance parameters, this paper discussed the winding function method (WFM) at first. And then, analytic expressions of self-inductances and mutual-inductances among stator power winding (PW), stator control winding (CW) and loop of rotor short-circuited ring (RSCR) were devised respectively, in which the harmonics of airgap magnetomotive force (MMF) were considered. Furthermore, an improved equivalent magnetic circuit model of BDFM was analyzed and established by considering the core tooth saturation. Meanwhile, the core tooth permittivity was determined by an iterative algorithm and then the saturated inductances of BDFM were calculated by the improved WFM (IWFM). Finally, energy-perturbation finite element method was used to calculate the saturated inductances of BDFM by considering both the harmonics and the core saturation. The results were compared with those of the WFM and the IWFM, and verified the effectiveness of the IWFM. The IWFM proposed in this paper provides a novel analytic algorithm for fast calculation of the saturated inductances of BDFM and can be popularized to other AC machines.