Research On Control Method Of Torque Ripple Suppression Of Permanent Magnet Synchronous Motor

With the wide application of permanent magnet synchronous motors(PMSM)in electric vehicles,demands of control quality for motor drive system are becoming higher and higher.Torque ripple in drive system is an important source of vibration and noise in PMSM,and reducing the torque ripple is one of key problems to improve quality of drive system and NVH performance of vehicle.In order to reduce torque ripple,this paper analyzes the generation mechanism of permanent magnet synchronous motor torque ripple,studies the torque ripple suppression strategy in the direct torque control system,and proposes corresponding improvement methods.Firstly,based on mathematical theoretical model of PMSM,the mechanism of the torque ripple caused by the motor body,inverter and sensor are studied respectively.Results show that motor body and inverter will produce integer times harmonics of 6.The load,asymmetry of cogging and manufacturing process affect cogging torque.Current sensor has offset error and calibration error,and calibration error causes 2-fold frequency torque ripple.Amplitude imbalance phenomenon of resolver cause s 2-fold frequency torque ripple.Then,based on the direct torque control system of permanent magnet synchronous motor,the basic principle,torque ripple generation mechanism and the corresponding improvement direction are analyzed.The improvement direction includes the selection of refined voltage vector,optimization or replacement of hysteresis modulator.The regional voltage vector table method can refine the selection of voltage vectors.By analyzing the torque ripple mechanism of the non-zero voltage vector acting time,an improved control strategy is proposed.The simulation results show that the proposed strategy can significantly reduce torque ripple.The model predictive direct torque control is used instead of the traditional hysteresis modulator.By analyzing the stator current mathematical model and the number of voltage vector selections,the calculation amount is optimized,and the optimal combination of duty cycle and voltage vector is selected to achieve counter rotation.The suppression of moment pulsation,simulation and experimental results have verified the correctness of the control strategy.Finally,the difficulty of testing torque ripple is analyzed.The torque ripple is analyzed by collecting q-axis current,and the test data is processed by M / J method to quantify the torque ripple.Build a permanent magnet synchronous motor test bench,complete the hardware and software design,and verify some of the improved control strategies proposed in this paper.