In recent years, reluctance synchronous machines (RSMs)have drawn attention from industry to their various appli-cations due to their compact design, high efficiency, andreliability. As both the efficiency requirementsand the price of rare earth materials are increasingly rising,RSMs are considered as a viable alternative to induction ma-chines (IMs) and permanent magnet synchronous machines(PMSMs).

For highly nonlinear machines,such as RSMs, the magnetic characteristics change significantly throughout the whole operation range dueto saturation and cross

-coupling effects. Therefore, the current controller tuning must be adapted online toachieve a fast and accurate tracking performance. The proposed current controllers are derived based onthe system theoretic concept of the exact input/output (I/O) linearization of the current dynamics. Thus,the nonlinear control system is simplified to an integrator which, in combination of proportional–integralcontrollers, can be tuned by means of pole placement similar to a phase-locked loop.

For I/O linearizationand control, the magnetic saturation and cross-coupling effects in the flux linkages and the differentialinductances must be considered which is done by the utilization of analytical flux linkage prototype functionsinstead of lookup tables. The performance of the developed nonlinear current control system is validatedby both, simulation and experimental results, for a highly nonlinear 1.5 kW RSM.

The results underpin the very high approximation accuracy and the continuity and differentiability of the flux linkage prototypefunctions over the whole operation range and the very fast and accurate tracking performance of thenonlinear I/O control system.

Read more details in the published article.