Stable Sensorless V/f and cosφ=1 Control for Permanent Magnet Synchronous Motor Drives

This paper proposes a novel control structure for scalar sensorless V/f controlled permanent magnetic synchronous motor (PMSM) drives with two feedback corrections in the new created d(v)q(v) reference frame: i) a speed stabilizing correction using input active power variation to moderate the stator applied frequency to ensure the stable operation, ii) a voltage amplitude correction employing the PI regulation of q(v)-axis current, that is the reactive current component, eventually realizes cos phi=1. The addition of PI regulator which also influences the stability of system is explored. Moreover, based on a basic V/f control, the scheme can greatly simplify the calculation and enhance insensitivity to the motor parameters. The proposed solution is simple, non-oscillatory and of good robustness. The simulation and experiments are carried out to prove the performance and validity.