Sub-Optimal Flux-Weakening Control of Synchronous Reluctance Motors

This paper deals with the control of the synchronous reluctance motors in the flux-weakening operating range. Given the difficulties of implementing truly optimal control strategies, sub-optimal solutions, which require minimal parametrization and set-up efforts, are proposed and experienced. First, the proposed solutions are presented and discussed, considering the uncoupled, constant-inductances model of the motor in d-q components as an analytical basis. Then, the influence of the flux non-linearities is taken into account, considering a 75 kW motor designed for an electric vehicle as a test case. The deviation in performance compared with the computed maximum torque-to-current and maximum torque-to-voltage optimization criteria are outlined. Finally, experimental results are presented, demonstrating the practical implementation in a micro-controlled drive.