Maximum-Torque Optimization Control of Dual Three-Phase PMSM in Low-Frequency and Static Operations

In this article, a maximum-torque optimization control scheme is proposed for dual three-phase permanent-magnet synchronous motor (DTP-PMSM) drives in low-frequency and static operations. Both the winding configurations of isolated neutral points and open winding are studied in this article. In the conventional vector control scheme, the constraints of sinusoidal phase current may cause local overheating problems in low-frequency and static operations. By comparison, the proposed control scheme takes into account the high instantaneous single-phase copper loss to avoid local overheating problems and improve the torque output capability. First, the limit of phase current amplitudes is analyzed and calculated for different winding configurations without using any unnecessary constraints. Second, a nonlinear optimization problem is constructed to obtain the non-sinusoidal maximum-torque current references based on the objective of minimum instantaneous single-phase copper loss. Compared with the conventional vector control scheme, the proposed approach can improve the torque output capability of DTP-PMSM with isolated neutral points and open-winding DTP-PMSM in low-frequency and static operations by 5.5% and 17.3%, respectively.