A Position Sensorless Control Strategy for BLDCM Driven by FSTPI Based on Flux-Linkage Function

This paper presents a new position sensorless control strategy for a brushless DC motor (BLDCM) driven by a four-switch three-phase inverter (FSTPI). This strategy introduces a flux-linkage function, which changes obviously at the time of the extremum jump. In the proposed strategy, the extremum jump edge determines the six commutation points needed for motor commutation. Then the high-precision and reliable commutation of the BLDCM is realized. This strategy can be used on BLDCM driven by FSTPI. Compared with other position sensorless control methods for BLDCM driven by FSTPI, the proposed method does not need to set a threshold value to detect the commutation point. It can obtain six commutation points required for motor commutation without interpolation. This avoids commutation errors caused by threshold value setting and interpolation. In addition, this strategy adopts a three-phase current control method for BLDCM driven by FSTPI. It can effectively restrain the current distortion of the capacitor middle point connection phase. And the terminal voltage is calculated. It can avoid the error caused by hardware sampling and improve the accuracy of the position sensorless control strategy. The experimental results verify the correctness of the theory and the effectiveness of the method.