基于无位置传感器的无刷直流电机换相续流研究

A Study on Commutated Freewheel of Position-sensorless Brushless DC Motors

无刷直流电机(brushless DC motor,简称BLDCM)换相时刻关断相电流续流会引起电机端电压波形畸变。当采用无位置传感器反电动势过零检测法时,端电压波形畸变会使位置检测信号相位超前,偏离最佳换相时刻,电机负载转矩和转速较大时增加了转矩脉动,甚至会造成换相失败,限制了反电动势检测法的无刷直流电机功率应用范围。因此,针对电流续流引起的位置信号相位超前的机理加以分析,推导出了超前角度与负载转矩和转速的关系,并给出了位置检测信号相位超前的补偿算法,并对电机在不同负载转矩和转速下位置信号进行相位补偿,拓宽了无位置无刷直流电机的运行范围。仿真和实验结果表明,在不同负载转矩和转速下经过补偿后的位置信号与最佳换相信号一致,电机负载转矩和转速较大情况下运行平稳。

Waveform distortion of motor terminal voltage will occur when phase current freewheel is switched off during commutation of the brushless DC motor （ BLDCM ）. Such distortion will result in phase lead of position detection signal and deviate from the best commutation time, thus increasing torque ripple and even causing communication failure in case of high load torque and speed, and limiting application scope of BLDCM power of the back-EMF detection method. In this background, this paper analyzes the mechanism for position signal phase lead caused by current freewheel, derives the relationship between lead angle and load torque and speed, and makes phase compensation for position signal under different motor load torques and speeds, thus extending operating range of the position sensorless BLDCM. Simulation and experimental results show that compensated position signal under different load torques and speeds is consistent to the optimal commutation signal and achieves smooth operation in the case of high motor load torque and speed.