Reduced Torque Ripple In The Direct Torque Control Of Matrix Converter-Fed Permanent Magnet Synchronous Motor Drives

Matrix converter fed permanent magnet synchronous motor drive system received is suitable for fields with strict requirements on the volume and weight of equipment,due to their advantages such as high power density,motor energy regeneration and feedback,etc.In this paper,a series of researches are conducted on the problems such as large torque ripples and unfixed switching frequency in the conventional direct torque control.The relationships between stator voltage,electromagnetic torque and stator flux linkage of permanent magnet synchronous motor under direct torque control are analyzed.Based on this,the expressions of 18 effective voltage vectors of matrix converter on the electromagnetic torque and stator flux linkage of permanent magnet synchronous motor are derived.Taking into account the demand of the motor system for the reactive power on the input side,the regulation of the input current vector of the matrix converter on the reactive power of the power supply side of the motor system is further analyzed.Combined with the characteristics of matrix converter vector amplitude variation with time,the factors affecting the direct torque control torque ripples and the unfixed switching frequency are analyzed.By comparing the existing strategies for realizing fixed switching frequency,a constant switching frequency torque controller is proposed to replace the traditional three-level hysteresis torque comparator.In this paper,the modeling,averaging and linearization of the torque loop containing the proposed controller are present.According to the classical control theory,combined with the characteristics of matrix converter vector amplitude variation with time,the method of torque controller parameters and triangular-wave waveform is proposed to form a reduced torque ripple direct torque control strategy for matrix converter-permanent magnet synchronous motor system..In order to verify the effectiveness of the reduced torque ripple in direct torque control,the matrix converter-permanent magnet synchronous motor system simulation model is designed in this paper by Matlab/Simulink.Then the matrix converter-permanent magnet synchronous motor experimental system platform is built,and the simulation and experimental results of the proposed strategy and traditional direct torque control strategy are compared.The results show that the proposed strategy can achieve good suppression of torque ripple.