Implementation issues for fast initial position and magnet polarity identification of PM synchronous machines with near zero saliency

This paper presents a significant discussion of implementation details of an enhanced fast initial position and magnet polarity estimation method for low saliency PM synchronous machines. The carrier frequency operating-point model of the machine has been extended to include the effect of cross-saturation as part of the non-linear interactions of the machine inductance to an applied rotating voltage vector. The resulting carrier signal current components are isolated using synchronous reference frame filtering and the initial position and magnet polarity is estimated using a dual-vector tracking state filter. The paper also provides an extended discussion of design tradeoffs in tuning of the synchronous reference frame filters in conjunction with the dual-vector tracking state filter bandwidth. Experimental results demonstrate fast, reliable initial position and magnet polarity estimation with improved accuracy and speed of convergence