Torque Ripple Suppression Of Brushless Dc Motor And Its High Performance Control Research

The conduction modes of brushless DC motor can be divided into two-phase conduction and three-phase conduction.Among them,two-phase conduction mode has become the main conduction mode of brushless DC motor due to its advantages of simple control,small switching loss and easy realization.The square wave current drive is often used in this conduction mode.However,the inherent commutation torque ripple problem under the square wave current drive seriously restricts the application of brushless DC motor in some precision and cutting-edge applications.Although the three-phase conduction method is slightly more complex to control than the three-phase conduction method,there is no commutation torque ripple in this conduction method and it is more conducive to the high performance of brushless DC motors.However,the conventional sinusoidal drive in this mode generates harmonic torque due to the non-sinusoidal counter potential of the brushless DC motor.To this end,this paper focuses on torque suppression and high performance control in two-phase and three-phase conduction,respectively,as follows:In order to solve the inherent commutation torque ripple problem under two-phase conduction,a regenerative boost inverter circuit is proposed based on the traditional three-phase bridge inverter circuit to suppress the torque ripple in a wide speed range.The stability of electromagnetic torque during non-commutation under the proposed control strategy is achieved by controlling the constant non-commutation current.When the motor is operating at a low speed,due to the bus voltage required for commutation is less than the DC power supply voltage,the smooth commutation of the motor can be achieved by pulse width modulation.At higher speeds,in order to achieve fast commutation and effectively suppress commutation torque ripple,the DC bus voltage can be raised using the proposed topology during commutation,where the additional compensation energy comes from the motor feedback during non-commutation.On this basis,a wide speed range torque ripple suppression system based on feedback boost inverter circuit is built.A high-performance instantaneous torque control scheme for brushless DC motor based on harmonic decomposition is proposed in order to suppress torque ripple and simultaneously achieve high-performance operation in three-phase conduction mode.From the point of view of harmonic utilization,the scheme proposed that injecting suitable fifth and seventh harmonic currents into fundamental wave current is sufficient to suppress torque ripple.In the event that torque ripple suppression is attained,the sum of the injected fifth and seventh harmonic currents is a constant value.Based on this,performance selection parameters are defined to distribute the proportion of the fifth and seventh harmonic currents required for high-performance operation such as no d-axis armature reaction and minimum copper consumption.A high-performance instantaneous torque control system based on harmonic decomposition is constructed.The above two schemes are designed to suppress the torque ripple under two different conduction modes.At the end of the paper,the relevant simulation and experimental verification for the two schemes are performed,and compared them with the traditional square wave closed-loop control system.The simulation and experimental findings demonstrate that the suggested control system efficiently suppresses torque ripple within 10%,and the second scheme can achieve high performance operation of the motor while achieving torque ripple suppression.