An Accurate Full-Speed-Range Control Strategy for PMSM with Improved Virtual Signal Injection MTPA and Smooth Field-Weakening Transition

To improve the control accuracy of maximum torque per ampere (MTPA) in the constant-torque region and enhance the control performance in the field-weakening region for permanent magnet synchronous motors (PMSMs), this paper proposes a high-performance full-speed-range control strategy that integrates an improved virtual-signal-injection-based MTPA (VSIC-MTPA) approach with seamless field-weakening transition control. In the constant-torque region, the torque model employed by VSIC-MTPA is analytically refined by accounting for the effects of injected virtual signals and inverter nonlinear voltage drops. This analysis identifies key error terms in the original model, which are subsequently compensated to improve torque modeling accuracy and thereby enhance MTPA control precision. Furthermore, a novel switching mechanism and region-transition criterion are developed to enable smooth and rapid transitions between the constant-torque and field-weakening regions. The proposed design also reduces the current ripple during steady-state operation in the field-weakening region. Experimental results under various operating conditions validate the effectiveness and superior performance of the proposed method.