Research On Direct Torque Control System Of Asynchronous Motor

In recent years,in many fields such as military industry,production and life,as the requirements for its control ability and precision are getting higher and higher,frequency control technology is widely seen.In the 1980 s,direct torque control(DTC)technology was born,with its simple and efficient control characteristics,has been widely concerned.The structure of direct torque control system is simpler than that of vetor control system,faster torque response,less influence by motor parameters,and better robustness.Although the direct torque control technology has obvious advantages,it also has some disadvantages:Due to the influence of its structure,the traditional flux observer is easy to produce large errors,and the torque fluctuation is large.The control precision of traditional controller is not high.These problems will affect the application effect of direct torque control system.To this end,this paper studies and analyzes the above problems.The main research contents are as follows:First of all,direct torque control technology and the necessary components of the system are briefly introduced,and its necessary model structure(dynamic mathematical model)is built.and the performance of DTC control system is studied and analyzed from the perspective of flux observer,stator flux and electromagnetic torque controller.Then,aiming at the problems existing in the traditional pure integrator flux observer,three improved observation methods are studied:The voltage model method(low pass filter method),double low pass stator flux method and full order closed loop flux observation method are improved,and the simulation verification analysis to select the most appropriate method.In addition,the answer to the question of the controller based on the analysis of the traditional PI controller of DTC control system and on the basis of variable structure control theory,this article selects the variable structure control technology to replace the PI control technology,as a result,compared with the traditional DTC control method,the improved DTC based on variable structure control method has better robustness and faster dynamic response.Finally,aiming at the improved design scheme in this paper,the feasibility of transforming the theory and technology into practical results is verified.this paper builds the structure block diagram of the improved system on the basis of the space vector pulse width modulation DTC control system,and the simulation comparison is carried out through Matlab/Simulink software and through the waveform to verify and analyze.