Flux-Weakening Controller Design of Dual Three-phase PMSM Drive System with Copper Loss Minimization

The performance of flux-weakening controllers in the multiphase PM machines depends on the accurate fundamental voltage limit derivation, and the minimal copper loss design in the flux-weakening operation region has not been well discussed. In this paper, the accurate fundamental voltage limit with considering harmonic current suppression is derived at first. Then, two control concepts are addressed, and the corresponding flux-weakening control strategies are designed with the gradient descent method. In the first control strategy, both the fundamental and harmonic voltage vectors are feasible, resulting in the larger amplitude of the phase currents. The second control strategy obtains higher bus voltage utilization by an additional transition stage. At the same time, the harmonic currents cannot be further suppressed in the flux-weakening operation region. Thirdly, the copper loss per electrical cycle is calculated, and a switching scheme is designed to obtain lower copper loss in the flux-weakening operation region. Finally, both strategies are successfully implemented in a dual three-phase PMSM. Moreover, the proposed switching scheme obtains minimal copper loss in the whole flux-weakening operation region.