Abstract:

This paper proposes a systematic experimental procedure to exploit the torque capability of sensorless induction machine (IM) control at/near zero frequency/speed under high- frequency signal injection (HFSI). The key idea is to select the tilted injection angle by two criteria: (1) maintaining the polarity of the sensitivity of an error signal w.r.t. the rotor flux angle estimation error to ensure closed-loop stability, and (2) maximizing the sensitivity to ensure robustness against uncertainties. Three look-up tables (LUTs) of injection angles and error scalings are constructed regarding operating points and used for real-time HFSI implementation. We further integrate the proposed HFSI method with an adaptive flux observer (AFO) to enable a stable sensorless torque control at full-speed range. Experiment results validate the sensorless IM’s torque capability and demonstrate a smooth operation over the full speed range of the proposed unified observer.