Research On Direct Torque Control Of Permanent Magnet Motor To Suppress Low Speed Torque Ripple

Permanent magnet synchronous motors have the advantages of small size and high efficiency compared to other AC motors.During operation,the speed is more stable and the dynamic response is fast,making it widely used in various fields.The direct torque control avoids the shortcomings in vector control,and its control structure is simple and clear,and the response speed is fast.In this paper,direct torque control is applied to the permanent magnet synchronous motor control system,and based on the existing theory,the causes of torque and speed pulsation generated by the system during low speed operation are analyzed.In response to several major problems causing torque ripple,corresponding improvement measures are proposed to improve the overall performance of the system at low speeds.This paper first briefly introduces the basic structure and characteristics of permanent magnet synchronous motor and establishes its mathematical model.On this basis,the theory of direct torque control is expounded,and the direct torque control system of permanent magnet synchronous motor is simulated.The system is simulated at low speed to analyze the problems of system performance during low speed operation.Then,the problem of low-speed torque ripple in the system is analyzed,which mainly improves the two problems of stator flux linkage observation and voltage vector selection.Among them,in the stator flux observation,there are mainly problems of stator resistance calculation error and DC offset.In the improvement of stator flux linkage observation,the specific method is to use an improved integrator with amplitude limitation,and use the fuzzy control method to compensate the flux angle,so that the observation of the stator flux linkage is more accurate.On the other hand,the super-slip sliding mode controller is used in the calculation of the voltage vector to optimize the control performance of the flux linkage and torque,and effectively reduce the ripple problem of the torque.The SVPWM algorithm is used on the voltage vector output to make the output voltage vector more precise,thus reducing the torque ripple.The fuzzy sliding mode algorithm is used to improve the speed regulator to improve the overall response performance and anti-disturbance performance of the system.Finally,the simulation of the permanent magnet synchronous motor control system with improved algorithm is carried out.The simulation results show that the improved system effectively reduces the torque ripple of the permanent magnet synchronous motor at low speed,and the improved system has good dynamic response performance and robustness.