A Digital Internal Model Current Controller for Salient Machines

The performance of anisotropic electrical machines is strongly dependent on the current loop characteristics. The problems for achieving robustness and fast response, without overshoot and oscillations, are mainly related to different values and behavior of the direct and quadrature inductances (L
_d
, L
_q
), as well as to high output frequencies. In this article, a novel current controller structure based on internal model control method is presented, taking into account the magnetic anisotropy (L
_d
≠ L
_q
). The model of salient machines is derived directly in the discrete domain and used to obtain a model-based controller. The controller derivation does not rely on transport-delay approximations, which enables improved decoupling of axes dynamics and the closed-loop robustness for very high output frequencies. The presented controller enables enhanced response for higher current loop bandwidth and output frequencies than the state-of-the-art methods. The experimental verification is performed on a three-phase synchronous machine, using a standard industrial three-phase inverter.