Research On Torque Ripple Reduction Of Three-Level Inverter In Direct Torque Control System

Direct torque control is another high performance control technique of AC motor, it adapt flux oriented control and transient space vector theory, directly control stator flux and torque, it has the advantage of rapid torque response and less relying on stator parameters, but has the disadvantage of bigger torque ripple.Direct torque control system which control core is TMS320LF2407A DSP and object is three-phase asynchronous motor is implemented in this paper. On the basis on analyzing of asynchronous motor, DTC principle and torque ripple characteristic, some methods for the topo of three-level that can reduce the torque ripple is researched.Finally, all the methods that based on synthesizing vectors , included synthesizing vectors control method, torque predictive control method, torque predictive control method based on the amplitude and phase compensation of the stator flux linkage, discrete duty ratio control technology are researched by MATLAB simulation; the control circuits based on TMS320 LF2407A are designed. Synthesizing vectors control method, torque predictive control method and discrete duty ratio control technology have been implemented on 1.1kW induction motor by assembly language. The simulation and experiment results prove that at the same sampling frequency and hysteresis width of stator flux and torque, comparing with synthesizing vectors control method, the methods which have been discussed can better reduce the torque ripple, improve the motor performance.