Combination of two different sensorless techniques for complete speed range sensorless drive and control of small sized PMSMs

A combination of two different sensorless techniques for small sized PMSMs are presented in this paper, namely, an alternate HFCI (High Frequency Current Injection) and a BEMF (Back Electro-Motive Force) based sensorless technique. The combination of the techniques is performed by means of two different switching functions. Through these functions the algorithm performs a complete speed-range sensorless drive and control of the electric motor including the standstill status. The switching algorithms use both the estimated angular speed and the estimated BEMF of the motor in order to perform the switching between the two sensorless techniques. The results in term of performance and reliability of the realized sensorless algorithms are presented within this work.