Improved Current Control Structure for the Brushless Doubly-Fed Machine Based on aNew Equivalent Circuit Model

The Brushless Doubly-Fed Machine (BDFM) is a promising alternative to the common Doubly-Fed Induction Machine with slip rings and brushes (DFIM). In many scientific publications, a similar behavior of these machines has been noticed. In this paper, a new equivalent circuit model (ECM) for the BDFM is derived from a geometry-based coupled-circuit approach, which leads to an ECM with an equal structure as the well-known DFIM's ECM. On the one hand, this mathematically proves the similarities, and on the other hand the new ECM can be used for a new current control structure with a de-coupled d- and q-axis. The effectiveness of this new method is proven in both simulation and experiment, using a prototype machine.