Research On The System Of Direct Torque Control For Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor has been widely applied in various AC drive systems for itsmerits of high efficiency,high power factor as well as high power density and the development ofpermanent synchronous magnet synchronous drive systems with high performance has societyvalue.As a motor control method with high performance,direct torque control(DTC) can directlycontrol motor torque,known that the essence of motor control is the control of torque.That is why thismethod is widely discussed.After DTC was applied successfully for induction motor,DTC forpermanent magnet synchronous motor was introduced in1997by Nanjing University of Aeronauticsand Astronautics and University of New South Wales,which has been the hot research issue sincethen.This thesis focuses on the sinusoidal motors, with the main content about direct torque control.Itcan furtherly improve the theory and help to promote development and application of DTC.In previous study of permanent magnet synchronous motor direct torque control,zero voltagevector was considered to keep the torque stable.The torque variation and the stator flux variationwithin one control period are analyzed detailedly in this thesis and quantitative analysis has beenmade for the impact of zero voltage vector.The result shows that when the motor runs with highspeed,zero voltage vector actually reduces the torque.The higher the rotor speed is,the more obviousthe effect of reducing the torque is..Then the result is verified by simulation and experiments..It is asignificant guide for understanding correctly the function of zero voltage vector in PMSM DTC andoptimizing the design of zero voltage vector working zone in the future.Stator flux observer has been one of the hot issues in DTC for permanent magnet synchronousmotor,especially when motors run with low speed.Focusing on the problem with the traditional fluxobserver,two common improved flux observer are been analyzed and both observer results in differentspeed ranges are compared.It is shown that the flux observer with amplitude limited compensation ismore adaptable and has wider speed range.The simulation and experiments all verify the results.Ithelps to lay foundation for further improvement and optimization of stator flux observer.With reluctance torque,it is more complex on the research of DTC for interior permanent magnetsynchronous motors compared with that for non-salient-pole motors.Discussing the differencesbetween torque formula,a method called stator flux adaptive DTC is introduced.Interior motors areequivalent to non-salient-pole motors so that simplified the analysis about variation of motor torque.This method can also obtain low loss and high efficiency.Simulation verifies the application of this method.Direct torque control and vector control are both high performance control methods and themethods with high performance can save energy for motors.Under the background of energy savingand discharge reducing,it is significant for discussing influences on parameters saving such as powerfactor and efficiency.On the basis of studying relatively mature theory,vector control,the two methodscalled id=0and UPF are compared with power factor and efficiency.The permanent magnet synchronous motor experimental platform for DTC is designed based onFreescale DSP56F8037and the stability is verified by experiments mentioned above.