A novel load variation compensation algorithm in a sensor-less brushless DC motor drive for a reciprocating compressor

This paper presents a novel load variation compensation algorithm in a sensor-less BLDC motor drive for a reciprocating compressor. Periodic load variation of a reciprocating compressor leads to commutation position error and instantaneous speed variation and causes large peak currents. The major concept of this study includes tracking the pattern of load torque and controlling the motor input voltage by the commutation point and PWM depending on the tracked load torque. The suggested method can reduce the cost because this method does not require additional current sensing or voltage comparison circuit. The utility of the suggested algorithm was confirmed by simulation and experimental results of a sensor-less BLDC motor drive.