Research On Fuzzy Prediction And Fault Tolerant Control Of Induction Motor Based On Speed Sensorless

Induction motor AC drive system is widely used in daily life.At present,the traditional high-performance control methods of induction motor mainly include Vector Control(VC)and Direct Torqe Control(DTC).With the development and application of microprocessors,model predictive control is gradually applied to motor control.Among them,Finite Control Set Model Predictive Control(FCS-MPC)has become a research hotspot in AC drive system control because it can directly utilize the discrete characteristics of converters and the limited switching state.Compared with FOC and DTC,FCS-MPC can reduce current harmonic distortion and torque ripple simultaneously,and has the advantages of fast dynamic response,complete internal decoupling and easy introduction of non-linear constraints.Therefore,FCS-MPC is adopted as the high performance control strategy of the system.In order to further improve the system performance,the following aspects are studied in this thesis:(1)The configuration of the weighting factors in the traditional induction motor predictive control system will directly affect the control performance of the system and the weighting factor is difficult to determine.Therefore,based on the in-depth analysis of the influence of the selection of weighting factors on the system,the fuzzy control algorithm is applied to realize the dynamic adjustment of the weighting factor.The results show that the proposed strategy can smooth the stator current and flux output.(2)The three-phase four-switch drive induction motor fault-tolerant control system has fewer switch vectors and small output power,which is difficult to meet the system response speed and control performance requirements when the bridge arm switch fails.In this thesis,a three-phase six-switch fault-tolerant control strategy is proposed by improving the control strategy without changing its topology.The simulation results are compared and verified in the predictive control system of induction motor.The results show that compared with the traditional three-phase four-switch fault-tolerant control strategy,the system reaches the steady state for a shorter time,the torque ripple is smaller,and the stator current and flux linkage output are smoother.(3)In order to realize sensorless control of induction motors,a fractional sliding mode flux observer is designed based on sliding mode control theory and fractional calculus theory,and its stability is proved by Lyapunov principle.On this basis,the speed estimation is realized.Secondly,a new reaching law function is selected to replace the traditional symbolic function to weaken the chattering that exists universally in sliding mode variable structure.The simulation results show that the designed observer can accurately identify the motor speed and has good tracking performance.Then it is applied to the predictive control system of induction motor,and the speed sensorless control of induction motor is realized.