A new control strategy for high efficiency wide speed range synchronous reluctance motor drives

A synchronous reluctance motor drive exhibits an inherent unlimited speed range capability. In order to exploit this peculiar characteristic of the drive while assuring the lowest power losses, a proper control algorithm has to be used. In particular, while the working speed is increasing, the control must be able to command the reluctance motor under the maximum torque per ampere condition at first, into the flux weakening region, and then on the maximum torque per voltage trajectory. To this purpose, a novel voltage control loop is presented in this work. It is combined with a field oriented current control and profitably exploits a polar coordinate representation of the current reference to govern the drive working conditions. The result is a motor drive able to operate the reluctance machine in compliance with current and voltage rating constraints without speed limits. Additional merits of the proposed scheme are the ease of implementation and the simple design. The effectiveness of the proposed control algorithm is verified through simulations and experimental tests.