Research On Speed Sensorless Vector Control Strategy

Speed sensorless vector control technology not only plays a key role in smooth operation of the train,but is one of the important research points of the traction drive system.Supported by National Key Technologies R&D Program for the "12th Five-year Plan"—"Energy Saving Key Technology and Engineering Application Demonstration of Rail Transit Train",this thesis focuses on the study of the rotor flux observation and the speed estimation.The speed sensorless vector control strategy is designed and the feasibility and effectiveness of the strategy are verified through the simulation and experiment.For the research on traditional vector control strategy.The vector control theory and the method of coordinate transformation are analyzed.In addition,the different vector control scheme of the asynchronous motor as well as the mathematical model of the asynchronous motor is studied and established.The simple and feasible voltage reconstruction method is designed,and the motor stator voltage is obtained accurately,which provides the theoretical basis for the realization of the speed sensorless vector control strategy.As to the study on the rotor flux observation of asynchronous motor,an improved optimization method involving discrete filter is proposed according to the error analysis of voltage-model rotor flux observer.What’s more,the integral saturation and DC bias are eliminated by setting the proper cut-off frequency and compensation methods,the motor speed properties,however,hasn’t been completely improved yet.In order to solve the problems of the improved flux observer,on the basis of the stability theory,the full-order flux observer is designed,and the precision and stability of the flux observer are guaranteed by the pole configuration of the feedback gain matrix.The parameters sensitivity of rotor flux observer is analyzed,and the dynamic performance and parameters sensitivity of the flux observer are improved based on the method of stator resistance identification.Research on the realization of the speed sensorless vector control.The method of speed estimation and digital realization of the slip speed estimation are analyzed.In particular,the closed-loop speed estimation method based on stator current Model Reference Adaptive System is mainly studied.The adaptive rate is designed by Lyapunov stability and the stability analysis of the model is carried out.In addition,the parameters sensitivity of speed estimation is analyzed,and the method to restrain the sensitivity is proposed,which improves the dynamic performance and the stability of the system,and the speed sensorless vector control strategy is realized.As to the verification of the speed sensorless vector control strategy,the correctness and effectiveness of the speed sensorless vector control strategy proposed in this paper are verified by MATLAB simulation software and metro traction drive system experimental platform.