Real-Time Torque Control of IPMSM Under Flux Variations

For interior permanent magnet synchronous motor (IPMSM) drives, accurate torque control and loss-minimizing operation are essential issues to keep up the excellent features of IPMSM. However, flux linkage variations owing to various operating conditions make it challenging to maintain their efficiency at the highest level during overall operating conditions. In this article, a real-time torque control is proposed to satisfy both torque control accuracy and high-efficiency operation in consideration of flux linkage variations. First, torque control under the minimum copper loss is modeled as a constrained optimization problem to satisfy both torque reference tracking and loss-minimizing operation in both maximum torque per ampere (MTPA) and flux-weakening regions. Current references are calculated through robust numerical and region identification algorithms in a command optimizer. Moreover, both stator flux linkages and dynamic inductances are estimated to reflect the flux variations in real time, which are the parts of a parameter estimator. The proposed estimators are designed to extract the fundamental flux linkages and their variations while maintaining high dynamic performance. The performance of the proposed methods is verified by the simulation and experimental results where premade lookup tables are not utilized at all.