Research On BLDCM Torque Ripple Suppression Based On Direct Torque And Current Prediction

Brushless DC motor(BLDCM)is widely used in transportation,medical equipment,household appliances and other fields,such as electric vehicles,hospital CT beds,inverter washing machines,etc.due to its simple structure,simple control,high efficiency,and low noise.However,BLDCM is driven by square wave.During normal operation,the two phases are turned on,which causes the motor to generate torque ripple during commutation.Because of this shortcoming,BLDCM cannot be used in high-precision applications,so it is very important for the motor to suppress torque ripple.Based on the operation principle and mathematical model of BLDCM,the causes of torque ripple were analyzed,and the different methods to restrain the torque ripple were compared.The improved direct torque control and current prediction control were used to restrain the torque ripple.Direct torque control is to control the torque of BLDCM as feedback quantity.On the basis of the traditional direct torque control,the voltage space vector of three-phase conduction was added during motor commutation.The simulation model was built on the Simulink simulation platform.The simulation results indicated that the two-three-phase hybrid conduction could obviously restrain the torque ripple of the motor.Current prediction control is to calculate the voltage required for the desired current value at the next moment according to the current current value,and convert the voltage into duty ratio to control the motor.Current prediction method and overlap commutation method were combined.Through theoretical analysis,the method could restrain torque ripple at full speed range.By improving the above method,the torque ripple would be further reduced by restraining the negative continuous current of the dc bus.The experimental results indicated that the torque ripple was further restrained by restraining negative continuous current of DC bus.