Improved rotating carrier signal injection method for sensorless control of PM brushless AC motors, accounting for cross-saturation effect

In carrier signal injection-based sensorless control of permanent magnet brushless AC (BLAC) motors, although cross-saturation effect is advantageous to extend the sensorless safety operation range, it results in load dependent error in the position estimation, and higher torque ripple as well. Considering the nonlinear behavior of estimated position error due to cross-saturation effect, an improved rotating carrier signal injection method is proposed in this paper, which pre-compensates the estimated position error resulting from cross-saturation effect by modifying the injected carrier voltage signal. Finally, experimental results show that a significant improvement in the position estimation can be achieved with the proposed method.