Research On Direct Torque Control Of Permanent Magnet Synchronous Motor Based On Second Order Sliding Mode

Permanent magnet synchronous motor has been widely used in civil,aerospace and other fields because of its simple structure,low loss,high efficiency,flexible shape and size.However,in order to achieve better control performance,it is necessary to choose the parameters of a complex permanent magnet motor.Based on the selection of direct torque control system as a closed-loop framework design,in order to solve the shortcomings of traditional direct torque control system,such as large torque and flux ripple,poor anti load disturbance ability,this thesis makes improvement and optimization design,and verifies the effectiveness of the solution through simulation and practice.In order to solve the complex problem of large fluctuation of stator flux and electromagnetic torque in traditional direct torque control system,a direct torque control solution based on sliding mode variable structure is proposed.Second order sliding mode controller of torque and flux linkage and space vector pulse width modulation can replace hysteresis control and switch table.In the traditional sliding mode control,the system is easy to produce serious chattering when it maintains the normal steady state.The nonlinear smooth function control FS is used to replace the step sign function,which can effectively reduce and reduce the high-frequency chattering.Through the analysis of Simulink simulation results,it is proved that the control algorithm reduces the ripple of flux and torque,makes the motor speed more stable and has good robustness.In order to solve the problem of high cost of sensors and easy to be affected by the environment in the control system,a speed sensorless controller based on sliding mode control is designed.In order to improve the dynamic quality of the speed control system,a sliding mode speed controller is designed by using the advantages of sliding mode control,such as insensitive to disturbance and parameters,fast response speed and so on.In order to avoid or weaken chattering fundamentally,quasi sliding mode control is adopted.SGN(s)is replaced by continuous function(s).The simulation results show that the proposed scheme is feasible.Finally,the RT-LAB hardware in the loop simulation experiment is carried out.After many experiments and debugging,the test waveform is analyzed.The experimental results show that the improved control system can effectively reduce the torque and flux ripple,and obtain a more stable speed.