Sensorless drives for permanent magnet synchronous motors

Abstract

Sensorless drives, in particular, Brushlesss DC (BLDC) drive, are applied onto permanent magnet synchronous motor despite existing drawbacks. The research work in this dissertation aims to address these drawbacks through analysis, simulations and implementations. Several schemes have been devised in this dissertation, namely, (1) Robust sensorless BLDC drive based on back-emf centering; (2) Low acoustics and torque ripple Q-BLDC drive through commutation current spike reduction, which gave significant torque ripple reduction; (3) Effective initial rotor position detection derived from induction and armature reaction, which can enhance sensorless starting capability effectively; (4) Robust crossover from open loop skew to BLDC using window masking, resulting in a significant improvement in starting times over the conventional method of gate turn-off; (5) Sensorless optimal sinusoidal BLDC through power angle control and freewheeling diode voltage sensing, which is significant in realizing compact sensorless PMSM drive with low cost and high efficiency.