A Novel Method for Initial Rotor Position Estimation for IPM Synchronous Machine Drives

Novel methods for initial position estimation during startup are presented for interior permanent-magnet synchronous machine (IPMSM) drives. The magnet cavities in the IPMSM rotor create a sizable difference in the inductances of the two orthogonal rotor axes. This spatial saliency based on the rotor position makes it possible to use persistent, rotating or pulsating vector, carrier-frequency image tracking techniques to reliably identify and track the orientation of the d and q axes even when the rotor is at standstill. However, additional details in the saliency image must be used to identify the polarization of the magnets in order to distinguish the north and south poles. The magnet polarity is identified using magnetic saturation effects on the saliency image to uniquely identify the polarity being tracked. Carrier currents for both rotating and pulsating voltage carrier injection are derived by using IPM machine model including saturation and verified by measured carrier current components. Experimental results show that the proposed algorithms are capable of reliable and fast initial position estimation including the polarity at standstill.