Hybrid Position Estimation Strategy With a Smooth Transition for IPMSM Sensorless Drives in the Wide Speed Range

In this article, an innovative hybrid position estimation strategy along with the minimum voltage vector injection (MVVI) method and the back electromotive force (back EMF) based method is proposed for interior permanent magnet synchronous motors (IPMSMs) in full-speed regions. At zero- and low-speed, the MVVI method based on rotor saliency is used for position estimation; the inverter voltage error is counteracted in estimating the rotor position, minimizing the inverter nonlinearity effect without introducing external errors. For IPMSMs at the initial state, this article proposes to utilize the high frequency d-axis current excited by injection voltage itself directly for the polarity detection. The position estimation at low-speed based on the MVVI method has such advantages as no requirement for filters, fast convergence, and reliability of magnetic polarity detection. In addition, a smooth transition blends the MVVI method and the back EMF based method is proposed, and a compensation term based on q-axis feedback current is added on the error of both the reference and feedback speed to reject the load-disturbance within the low speed and transition region. Experimental results show that the proposed hybrid sensorless control strategy exhibits excellent performance in the full speed range for both steady-state and dynamic operations.