Research On Model Predictive Torque Control Strategy Of Permanent Magnet Brushless DC Moto

Permanent Magnet Brushless DC Motor(BLDCM)has the advantages of small size,high efficiency,simple control,high power density and good reliability.It is widely used in new energy electric vehicles,industrial control,precision servo and many other fields.In order to solve the problem of large torque ripple during the operation of the Permanent Magnet Brushless DC Motor,this paper introduces Direct Torque Control(DTC)into the control system of Permanent Magnet Brushless DC Motor.Based on the research of torque flux double closed-loop control,the Direct Torque Control strategy based on model predictive control is studied.The specific research work is as follows:First of all,this paper analyzes the basic mathematical model of BLDCM and compares the calculation methods of the stator flux linkage.In addition,this paper proposes an improved integrator stator flux linkage observer.Aiming at the DC bias caused by low-pass filter in traditional voltage stator flux observer,the tracking performance of the stator flux linkage can be improved under the condition of low speed operation and sudden speed change of the motor through twice compensations.Secondly,the Space Vector Modulation Direct Torque Control(SVM-DTC)method based on second-order sliding mode is studied,which adopts second-order sliding mode regulators in the speed,torque and flux linkage to improve the dynamic control performance of the system.The second-order sliding mode SVM-DTC control has a fixed switching frequency and its control performance is better than the traditional DTC control,but it still has the problems of difficult parameter adjustment,large amount of calculation,and can not meet the parameter optimization control of wide speed regulation and wide load range.Therefore,in order to further improve the motor control performance,using the advantages of high controllability and fast response of Model Predictive Control,and the finite set Model Predictive Torque Control(FCS-MPTC)method is studied.The results show that this method is helpful to improve the dynamic and steady-state performance of the system,but it still has the problem of large torque ripple.Finally,based on FCS-MPTC,this paper proposes a control scheme of FCS-MPTC without flux linkage.In this method,the torque is preferentially tracked and the flux linkage is limited,which is beneficial to further reduce the torque ripple of the Brushless DC Motor.In order to further reduce the switching loss,a logic optimized hysteresis control strategy is applied to the no flux loop FCS-MPTC control.In order to avoid the large drop of flux amplitude and affect the motor control performance,a no flux loop FCS-MPTC with dynamic flux interval is also proposed.The results show that the no flux loop FCS-MPTC control method in the dynamic flux range inherits the high-performance torque control of the no flux loop FCS-MPTC,can effectively limit the flux,avoid the problem of excessive current caused by flux drop under different loads,and ensure the reliability of motor operation.