Research On The Method Of Restraining Torque Ripple In The Direct Torque Control Of Asynchronous Motor

Compared with other motors,induction motors have been widely used in all fields of social life because of their simple structure,reliable operation,low price and many other advantages.In the research of induction motor high performance control method,direct torque control(DTC)is directly controlled by the motor torque.The system structure is simple.The control means is direct and the torque response is rapid.Foreign scholars pay close attention and research.However,the traditional DTC itself has the problem of excessive torque ripple,which in turn severely limits its application range.Therefore,in this thesis,the DTC of induction motor is taken as the research object,and the method of torque ripple suppression is mainly studied.The main contents are as follows:Firstly,the mathematic models of asynchronous motors in different coordinate systems are introduced in detail.The basic theory of DTC is expounded,and the modeling and simulation research based on MATLAB is carried out.Through the simulation analysis,the factors causing the torque ripple of DTC of asynchronous motor are determined.Secondly,two kinds of torque ripple suppression methods are introduced in detail.These methods include the combination of space vector modulation(SVPWM)and DTC to suppress torque ripple.On the basis of this,an improved adaptive flux observer is used to replace pure integrator and First-order low-pass filter method improves induction motor torque performance.The two methods are analyzed theoretically in detail,and the simulation model is built based on the analysis results.The simulation results under the same operating conditions verify the correctness of the analysis and the feasibility of the proposed method.Then,the hardware control platform of induction motor based on TMS320F28335_DSP is designed.The designing of DSP core board,peripheral circuit conditioning board and the main power board are completed,and the relevant commissioning work is completed.Finally,three experiments of traditional DTC,SVM-DTC and SVM-DTC based on adaptive flux observer are carried out respectively.By comparing the experimental waveforms,the correctness of the theoretical analysis,the simulation model and the reliability of the hardware control system were verified,which laid the foundation for the follow-up work.