The Application And Research Of Sliding Mode Variable Structure Theory In The Permanent Magnet Synchronous Motor-Direct Torque Control

With the advantages of well-robustness and easy-implementation,SMVS has been an independent and important offset of modern control theory system,and it is also widely used in the field of AC motor control.In recent years,with the increasing performance of the permanent magnetic synchronous motor,its application area also continues to expand,so the requirement for its control also becomes higher and higher.This article takes the permanent magnet synchronous motor direct torque control system as the background,and studies the application of sliding mode variable structure theory based on fractional order in the permanent magnet synchronous motor direct torque control in order to further enhance the control performance of the system.Research content of this article as follows:First,it states the mathematical model of the permanent magnet synchronous motor under different coordinate systems and the basic principle of direct matrix control.Focusing on greater torque,flux ripple and other shortcomings which exist in traditional direct torque control.The method of Integral sliding mode variable structure-direct torque control(SMVS-DTC)is introduced in detail.It replaces the hysteresis controller in traditional direct torque control by using integral sliding mode controller and instead of selection table of offline switch vector,it introduces algorithm of space vector pulse width modulation(SVPWM)and controls the dc-to-ac converter in order to achieve smoother output voltage.Secondly,problems like integral saturation effect as well as system chattering brought by sliding mode controlling existed aiming at the integral sliding mode controller.Based on the existing integer order integral sliding mode controller,a new fractional order sliding mode controller(FOSMVS-DTC)is proposed.First,the fractional integral term is introduced into the sliding surface design.Using the property of that the smaller the fractional order in the integral equation is,the faster the descent speed is,while the slower the speed of becoming stable will be,the integral saturation effect of the original integral sliding mode controller is restrained.Then,a new reaching law combined with fractional differential equation and exponential reaching law is adopted to improve the convergence speed to reduce the overshoot in the transient process.The simulation result shows that,the improved fractional-order sliding mode controller has combined both advantages of integral sliding mode controller and fractional-order calculus,which can further improve the control performance of the motor,expanding the application range of the system.Again,aiming at the fact that the rotor position estimation of the traditional sliding mode observer is not accurate,and there are problems such as dead zone in prediction,we have generalized the mathematical model of permanent magnet synchronous motor to fractional order,and established a more accurate mathematical model.And based on such mathematical model,we have designed a new type of sliding mode observer of fractional order,and at the same time better solved the problem of phase lag and so on combining the improved phase-locked loop technology.The simulation result shows that the sliding-mode observer of fractional order after improvement can not only predict the rotor position more precisely but also reduce the dead time in the prediction.Finally,based on the above research findings,we designed and invented the PMSM using TMS320F2812 of Texas Instrument Company as its core that directly twists the hardware circuit of the control system.We simply introduced the software structure diagram that studying algoruthm in this essay to lay foundations for the experimental verification that controls the algoruthm in the future.