Research On Model Predictive Torque Control Of Induction Motor Based On Amplitude-phase Dynamics

Considering the five aspects of high-speed operation ability,efficiency,controllability,reliability and cost,induction motors have the highest comprehensive score and have been widely used in the field of high-performance traction and transmission.Model predictive control(MPC)has the advantages of simple concept,easy to contain multivariable control and easy to deal with various non-linear constraints.Therefore,in the field of high-performance AC motor drive,MPC is considered as a powerful alternative to vector control and direct torque control.Firstly,the basic principle of MPC is analyzed,and the specific scheme of conventional model predictive torque control and the method of model building are given.By discretizing the established mathematical model of induction motor in static coordinate system,the predictive equations of torque and flux are derived,the cost function representing the control performance of the system is designed,the principle of delay compensation is analyzed,and the concrete model establishment and the method of MATLAB simulation are given.It lays a theoretical foundation for improving the model predictive torque control method of induction motor.Secondly,in order to solve the tedious adjustment of weighting factor in conventional model predictive torque control,based on ghost operator theory and the basic principle of amplitude-phase dynamics,the dual variable of torque,reactive torque,is derived,and the amplitude-phase dynamic equation of induction motor is studied.A new cost function without weighting factor is constructed.The specific design method of the improved model predictive torque control method based on amplitude and phase dynamics of induction motor is given,and the superiority of the improved strategy is analyzed.On the basis of theoretical analysis,a simulation model is built and compared with the conventional model predictive torque control.The advantages of improved model predictive torque control in weighting factor adjustment are analyzed.Then,to solve the problem that the steady-state performance of model predictive torque control needs to be improved,the method of increasing the number of vectors is studied,and a simple and effective three-vector control strategy is proposed.Three adjacent basic voltage vectors are applied in a control cycle,including two effective voltage vectors and one zero voltage vector.The duration of the basic voltage vectors is deduced according to the target of simultaneous deadbeat control of torque and flux.The three-vector strategy can adjust the magnitude and direction of the voltage vector at the same time,effectively expanding the coverage of the feasible area of MPC.The simulation model is built based on the three-vector strategy and compared with the traditional single-vector method.The effectiveness and superiority of the proposed strategy are verified.Finally,an experimental platform of induction motor system is built,which is based on dSPACE rapid control prototype and its control software ControlDesk.The effectiveness and feasibility of the improved model predictive torque control method based on amplitude-phase dynamics and the proposed three-vector strategy are further verified by systematic experiments.