A Simple MTPA Operation Scheme for V/f Control of PMSMs

In this paper, a simple MTPA (Maximum Torque Per Ampere) operation scheme to improve the driving efficiency for the V/ f control of PMSMs is proposed. In PMSM drives, a proper distribution of the stator current on dq axis components is required for the MTPA operation. However, when PMSMs are driven by the V/f control, the proper current distribution for the MTPA operation cannot be assured depending on the magnitude of the stator voltage or the load. The proposed MTPA operation scheme adjusts the magnitude of the stator voltage by using the load information obtained from the deviation of the motor current from the d-axis MTPA current in the V/f control of PMSMs. Moreover, the variation of the d-axis current is used to damp the variation of the rotor speed for stable operation. The proposed scheme uses only a single controller for both the MTPA operation and the stabilization. The design of the controller is performed through the analysis of the MTPA operation system with a stabilization technique. Simulation and experimental results confirm the effectiveness of the proposed scheme for an 800W IPMSM.