Loss-Minimization Strategy of Nonsinusoidal Back EMF PMSM in Multiple Synchronous Reference Frames

Traditional loss-minimization strategies of model-based control, copper loss minimization (CLM), and finite-element-based control suffer from respective problems of iron loss mismatch with a physical view, pseudominimization and amounts of efforts when they are applied to permanent magnet synchronous motor with nonsinusoidal back electromotive force (NS-PMSM). This article combines theories of multiple synchronous reference frames and iron loss resistance to develop a new model of NS-PMSM, based on which the stator iron loss is evaluated to match well with the physical view. Then, a current strategy is proposed to minimize the total stator loss under constraints of ripple-free torque and finite dc supply. The optimal current solution is solved in closed form and implemented effortlessly. A good robustness to phase resistance variation is also achieved. Compared to CLM, the proposed strategy realizes a true minimization with the stator loss reduced by 9% and the motor efficiency enhanced by 0.7% at rated operation of a 3.8-kW NS-PMSM. Precision of the iron loss evaluation and performances of the strategy are validated experimentally on the 3.8-kW motor setup.