MTPA operation scheme with current feedback in V/f control for PMSM drives

In this paper, an Maximum Torque Per Ampere (MTPA) operation scheme with current feedback to improve the driving efficiency in the V/f control for Permanent-Magnet Synchronous Motor (PMSM) drives is proposed. In the V/f control for PMSM drives, the proper current distribution of the MTPA currents is not assured depending on the magnitude of the stator voltage. Moreover, PMSM drives become unstable due to an absence of damper windings. In this paper, for both MTPA operation and stabilization, a scheme of using only a single Proportional Integral (PI) controller is proposed. The magnitude of the stator voltage, for the MTPA, is adjusted by employing the information of the load acquired from the PI controller, which uses the d-axis current deviation from the required MTPA current. For stable operation, the stator frequency is adjusted using the information on the rotor speed variation extracted from the proportional part of the controller. To obtain this information from the PI controller, its gains are designed through an analysis of the whole drive system. Simulation and experimental results confirm the effectiveness of the proposed scheme.