Robust current control of electrical machines considering saturation effects at high speed regimes

This paper considers a control approach for synchronous reluctance machines operating at variable speed regimes based on modern robust control tools. The main challenge arises from the inherent nonlinear magnetic behavior of the machine, caused by core saturation and cross saturation phenomena, resulting in a nonlinear dependence of the machine inductances from the instantaneous values of both direct and quadrature axis currents. The proposed method is based on a reformulation of the motor model as a linear parameter varying system. This allows transforming the controller design in a multivariable optimization problem, which can be solved with very efficient numeric tools. Depending on control objectives, several variants of the control law can be obtained, all mainly consisting of a standard proportional-integral feedback augmented with additional speed-dependent terms, and all providing guaranteed worst-case performances in the considered ranges of parameter uncertainties. The controllers are experimentally tested on a laboratory bench with a machine running at 50000rpm.