Research And Design Of Direct Torque Control System For Permanent Magnet Synchronous Motor

PMSM has the advantages of small size and high power density,has attracted wide attention in the fields of electric vehicles and mechanical traction.The speed control relies on sensors to measure speed and rotor position in PMSM speed control system for electric vehicles,however,position sensors increase system cost and structural complexity,and are prone to sensor failure under extreme harsh conditions,which reduces the reliability and stability of the speed control system.Therefore,the study of position sensorless PMSM control plays an important role in reducing costs and improving system reliability.To this end,this paper studies the position estimation of PMSM sensorless control and the strategy of torque and flux ripple suppression.The main research contents are as follows:（1）The basic structure and coordinate transformation method of PMSM are introduced,the mathematical model of PMSM is established in three coordinate systems.The basic principle of direct torque control is introduced in detail,which lays the foundation for the subsequent improvement of PMSM control algorithm.（2）Aiming at the problem of poor anti-disturbance performance and low estimation accuracy of position estimation algorithm in the control of positionless PMSM under complex working conditions,a position estimation algorithm based on sliding mode MRAS is designed.Firstly,the speed and rotor position are estimated by MRAS,then a sliding-mode MRAS observer is constructed by improving the PI link in MRAS using sliding-mode control based on a novel convergence law.Finally,the proposed algorithm is verified on the simulation platform.The experiment results show that the position-free PMSM-DTC system based on the sliding-mode MRAS observer is more resistant to disturbances and can estimate the speed and rotor position more accurately than the MRAS observer.（3）Aiming at the problem of large torque and flux ripple in positionless PMSM-DTC system,two hysteresis controllers in DTC are replaced by FSTSMCs,and a super-twisting sliding mode controller is designed to suppress torque and flux ripple.Then,for the chattering caused by switching control in the super-twisting sliding mode algorithm,fuzzy control is introduced to output the appropriate sliding mode gain to solve the problem of parameter uncertainty and effectively reduce the chattering.Finally,the proposed algorithm is verified on the simulation platform.The experiment results show that FSTSMC can suppress torque and flux ripple more effectively than traditional DTC,and improve the stability of the system.（4）The hardware-in-the-loop simulation platform based on c SPACE is built,and the selection of some devices is given.The hardware circuit design is completed,and the software design flow chart and experimental steps are introduced.The sliding-mode MRAS algorithm and FSTSMC algorithm are verified on the hardware-in-the-loop simulation platform.The experimental results show that the improved PMSM-DTC system can operate safely and reliably,and the estimation of speed and rotor position and the suppression of torque and flux ripple are realized.The effectiveness and feasibility of the proposed algorithm are verified.