The Research On PM Brushless DC Motor Control Based On The Instantaneous Power Theory

Permanent magnet brushless DC motor(PMBLDCM)has advantages including simple structure,high performance of speed control and high efficiency etc.However,the electromagnetic torque of PMBLDCM can make fluctuations,which results in some problems such as noise and vibration.Moreover,under some special circumstances,the speed range can't satisfy the requirements of the system at the rated speed or below.So torque ripple suppression and expanding speed ability of PMBLDCM become the main research contents in this paper.A control strategy of PMBLDCM based on instantaneous power theory is proposed,which can primly suppress the torque ripple and boost speed operation on field-weakening.Firstly,the structure and basic operation principle of PMBLDCM is introduced.The mathematical model of the motor is constructed.On the basis of demonstrating the fundamental definition of instantaneous power theory,combining with the mathematics model of motor,the constant torque control strategy and flux-weakening speed expansion control strategy of PMBLDCM based on instantaneous power theory is proposed in this paper.The content of constant torque control strategy is constructing the relation among torque,electric current and flux linkage function by using instantaneous power theory.According to the given torque and flux linkage function,the corresponding reference current can be gained.By applying hysteresis current control,the actual current can track the reference current to make output torque constant.The flux-weakening speed expansion control strategy increases the direct axis demagnetization current to obtain the effect of equivalent flux-weakening by changing the reactive component so that the function of wide flux weakening speed range can be achieved.In order to verify the correctness and superiority of control strategy mentioned in this paper,Matlab/Simulink software is used to build a motor model that possesses non-ideal back electromotive force.This model is respectively applied in traditional double closed-loop control and constant torque control.The simulation results show that constant torque can suppress inherent torque ripple caused by the traditional control.In addition,the relational table of maximum speed,reactivecomponent and load torque is established by simulation.By using the look-up table,flux-weakening speed expansion control of PMBLDCM is verified.Finally,By using the TMS320F2812 as the control core,the hardware and software design schemes of control system of PMBLDCM is given.Based on using CCS3.3 software as the development environment for program debugging,the constant torque control and flux-weakening speed expansion control can be experimented and analyzed.Experiment results show the control strategy of PMBLDCM based on instantaneous power theory proposed in this paper can inhibit torque ripple effectively and expand the range of speed regulating.