Research On Speed Sensorless Control Of Induction Motor Based On Sliding-mode Observer

Induction motor speed sensorless vector control system is widely used in textile,water pump and fan fields due to its low cost,high reliability and simple control.Accurate motor parameters and speed flux linkage estimation are the basis for efficient and stable operation of the system.To this end,this thesis estimates the rotational speed and flux linkage based on the sliding mode observer,and studies and realizes the high-performance,high-stability and wide-range induction motor speed sensorless digital control system.Firstly,in order to accurately estimate the rotational speed and flux of the induction motor,this thesis proposes a simple sliding mode observer based on the sliding mode variable structure control theory,and the design basis of the observer parameters is given by using the Lyapunov stability theorem.Aiming at the chattering problem of the estimated speed of the observer,a smooth saturation function is designed instead of the traditional switching function to suppress the chattering.Secondly,after analyzing the influence of motor parameter variation on the estimation performance of sliding mode observer,the off-line parameter identification technology of induction motor is studied.Aiming at the problem that the high-frequency current used for parameter identification cannot be effectively controlled by PI,a novel current amplitude adaptive strategy is proposed.Aiming at the influence of spectrum leakage on the identification results,a current frequency optimization scheme is proposed to achieve simultaneous sampling.Thirdly,in order to realize the sliding mode observer in the actual digital control system of induction motor,the traditional discretization method of sliding mode observer is analyzed.It is pointed out that the traditional method has the contradiction problem of discretization error and complexity,and a improvement based on the new discretization method of the ternary lattice method,the new method achieves a balance between complexity and precision,and has strong practicability and wide applicability.Finally,the physics experiment platform is built,and a series of methods are proposed.The speed sensorless vector control system of induction motor based on sliding-mode observer is realized.The operating condition of the system under various working conditions is tested.The results show that the system has good dynamics and stability.