Comparison of carrier signal injection methods for sensorless control of PMSM drives

Anti-clockwise pulsating injection method utilising the synergies of both pulsating injection and zero sequence voltage sensing has been proposed to enhance the rotor position estimation of permanent magnet synchronous machine (PMSM) drives. However, the detailed comparisons with the conventional carrier signal injection methods have not been carried out. Therefore, in this paper, for the three types of carrier signal injection methods, i.e., rotating injection in the stationary reference frame, pulsating injection in the estimated synchronous reference frame and in the estimated anti-clockwise rotating reference frame, comparative analyses are presented with the consideration of both carrier current and zero sequence carrier voltage sensing. Specifically, the influence of signal processing delays, cross-coupling effects, and multiple saliency effects on the position estimation accuracy are fully discussed and compared for the three methods. All the theoretical analyses are validated by either finite element (FE) analyses or experiments on a laboratory PM machine.