Research On Torque Ripple Suppression Of BLDCM DTC System Based On Zero Vector Reconstruction

BLDCM is very suitable for various industrial applications because of its advantages of simple structure,high power density and low cost.But BLDCM has the disadvantage of large torque ripple in the existing control algorithm,which limits the application of BLDCM in the situation of high torque performance requirements.The ideal anti EMF of BLDCM is trapezoidal flat top wave,which can be achieved by twophase conduction operation mode.The optimization of torque performance of BLDCM under two-phase conduction mode has become a hot research issue in motor control field in recent years.In view of the problems of the existing BLDCM direct torque control(DTC)theory,the definition of zero vector is not perfect and the torque ripple is still large,this paper will focus on the two-phase conduction BLDCM DTC system torque ripple suppression method.1.through the analysis of the current variation law of BLDCM DTC system with two-phase conduction under the action of the existing two-phase conduction zero vector,it is found that the reverse continuation flow will occur after the end of the positive continuation flow after the two-phase conduction and the opposite electromotive force,which will affect the torque performance.The theoretical analysis results are verified by simulation and experiment,which can not meet the requirements of zero vector.The paper optimizes the zero vector of double tube,establishes a single tube zero vector which can meet the requirements of zero vector in definition and electrical performance.A new voltage vector selection scheme is established based on the single tube zero vector.The effectiveness of the proposed zero vector and new voltage vector selection scheme for torque performance improvement is verified by simulation and experiment.2.it is found that BLDCM DTC system under traditional pure torque hysteresis control mode can only send a single positive vector or zero vector in a cycle,which leads to low torque control accuracy and control lag,and eventually causes excessive torque ripple.The paper introduces the duty cycle modulation strategy,improves the torque control method of BLDCM DTC system,and establishes a torque control scheme of BLDCM DTC system based on duty cycle modulation.The effectiveness of the torque control scheme is verified by simulation and experiment.3.in view of the problems of complex model and over dependence on motor parameters,the BLDCM commutation torque ripple control strategy is considered.Starting from the research of the causes of the commutation torque ripple of BLDCM,the PWM modulation strategy with full speed range is introduced during the commutation of the original duty cycle torque control scheme.Considering the serious lag of PWM commutation control,the current prediction control strategy is introduced to improve the commutation torque control method of BLDCM DTC system,A new torque control scheme of BLDCM DTC system based on current prediction commutation control is established.The effectiveness of the proposed scheme to suppress the commutation torque ripple of motor is verified by simulation and experiment.