Flux And Torque Control Of Induction Motor Based On The Ghost Operator Theory

The control methods of induction motor(IM)drive systems require high accuracy of motor model and parameters.Field-oriented control(FOC)or direct torque control(DTC)for specific tasks(such as fast torque response,low torque ripple,and low current harmonics)have formed industrial standards in the field of IM control,and have also become the preferred solutions for IM drive systems in electrified transportation.Significant progress has been made in areas such as parameter estimaiton,sensorless control,robust control and predictive control.But for most current control methods,there are still obvious limitations in generalized control design.This paper focuses on developing the potential of instantaneous reactive power for simplifying the high-performance control design,so as to eventually realize the generalized control design of IM,including flux and torque control and parameter estimation method.By introducing the ghost operator theory which reflects the physical meaning of reactive power,this paper reveals the key role of real and reactive power in flux and torque control of induction motor.To simplify the control design for induction motors,the concept of the ghost operator is extended from power theory to torque theory and the ghost torque is thus defined.The control method of flux and torque is studied based on the ghost torque.A control model which can clearly describe the mechanism among flux,current and torque of IM is mathematically and physically established.On the other hand,the ghost torque is directly applied to flux and torque control design,and preliminary results has been achieved.Firstly,a generalized flux and torque control method in multi-time scales for IM based on the ghost torque is proposed according to the magnitude/phase dynamics theory.The advantages of FOC and DTC are retaind in this method,and the dynamic and static performance of IM drive system is further improved.Secondly,an online estimation algorithm of stator resistance is proposed based on the ghost torque.This method combines physical-and model-based methods to eliminate the error of reactive torque caused by stator resistance mismatch through measurement and calculation at the motor terminal.Thus,the accurate value of stator resistance can be obtained iteratively.Compared with the current obervers based on reactive power,the reactive-torque-based observer improves the convergence speed of estimation process,and has the characteristics of clear concept,clear physical meaning,and simple calculation.Furthermore,the proposed control methods and estimation algorithm are verified by MATLAB/Simulink simulations and experiments through dSPACE rapid control prototype(RCP).The feasibility and correctness of the proposed methods is verified by the simulation and experimental results.And once again,the potential of the instantaneous reactive power for simplifying the high performance control design of IM is demonstrated.