This paper proposed a dual quasi-resonant controller position observer for conventional pulsating high frequency voltage injection method. The proposed position observer can not only improve the dynamic performance of the sensorless control, but can also compensate the position error fluctuation caused by the dead-time effect. To improve the dynamic performance, the digital bandpass filter in the traditional position observer used to extract high frequency current response is replaced by a quasi-resonant controller firstly. Moreover, an improved Luenberger observer without lowpass filter, which is usually used in traditional position observer to filter the noise in speed information, is adopted in the new position observer. Therefore, dynamic performances can be improved. Then, to reduce the sixth harmonic in the magnitude of position error and speed error caused by the dead-time effect, a frequency adaptive quasi-resonant controller is connected in parallel with the proportional-integral controller in the Luenberger observer. The experiment results verify that the proposed observer can reduce the position estimation error not only in steady state operation conditions, but in variable speed and variable load conditions, and the speed variation range can be widened as well.

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Due to the characteristics of inductance parameter mismatch and back electromotive force harmonics caused by novel leakage flux branches and other non-ideal factors for the variable-leakage-flux permanent magnet (VLF-PM) motor, its control system suffers from a deteriorated performance of the rotor position estimation. To overcome the problems mentioned above, an adaptive tracking estimator of the rotor position is proposed in this paper for the VLF-PM motor control system. First, the proposed method simplifies the VLF-PM motor mathematical model and reduces the effect of inductance parameter variations according to the active flux concept. Then, robust and gradient descent algorithms are utilized to maintain the robustness of inductance parameter variations and eliminate the specific order harmonics owing to the novel leakage flux branches. Meanwhile, the accuracy and stability are enhanced. Furthermore, the position compensation based on the current adaptive tracking strategy is proposed to compensate the rotor position error caused by other non-ideal factors. Finally, the feasibility of the proposed estimated system is verified.