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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This paper proposes a dual-harmonic pole-changing (PC) motor with split permanent magnet (PM) poles (DHPCM-SPMPs). By adopting a split PM pole structure, the amplitude of the third PM flux density is increased greatly. Therefore, when a PC winding is adopted to couple with the fundamental and third PM flux density components, respectively, the proposed motor can work as a PC PM motor to satisfy operating demands of electric tractors. The design and effect of the proposed split PM pole structure is introduced first. The winding topology is then designed according to the slot vector diagrams of the two PM flux density components, and the PC operation can be realized by electric switches. Aiming at a torque ratio design objective, the PM structure parameters can be determined based on mathematical derivation, and the speed-widening capability is proved based on the operation characteristic analysis. Finally, the electromagnetic performance of the DHPCM-SPMPs is investigated and compared by finite element analysis, which shows the high torque capability in eight-pole mode and the wide speed range in twenty-four-pole mode benefiting from the PC operation.

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