Impact of Rotor Excitation Current during Flux-Weakening Control of Hybrid-Excited Permanent Magnet Synchronous Motor

Hybrid-excited permanent magnet synchronous motors are particularly suitable for operating in the constant power region, thanks to the possibility to reduce the rotor flux when the speed increases. The flux-weakening control of such a motor is investigated in this paper. The flux-weakening operation is achieved by acting both on the stator winding currents and on the rotor excitation winding current. As in an interior permanent magnet motor, a voltage loop is designed for the stator current control, with a proper linearization of the loop. In addition, the excitation current reference is generated in a feed-forward manner by reducing the rotor flux so as to increase the working speed. The proposed flux-weakening control strategy is validated by means of simulations and experimental tests. The behavior of hybrid-excited permanent magnet motors is compared with that of an interior permanent magnet having equal rated parameters.