The Direct Torque Control For Asynchronous Motor

The Direct Torque Control(DTC) which is firstly used in the last century presents many advantages,such as fast torque response and high robustness to the variation of parameters. The three-level neutral-point-clamped(NPC) inventer has the significant advantages of lower switch frequency,less distorted output and lower voltage request. In the last few years,it is widely used in medium-voltage adjustedable apeed drive applications. According to Direct Torque Control for asynchronous motor ,the following acpects are made in this paper:According to the theory of Direct Torque Control (DTC), a changed method of the space sector is proposed. It is simple to get SN. With the new SVPWM table,the simulation model of DTC Based on Matlab6.5 / Simulink for asynchronous motor is developed. Then all simulation blocks are stated detailedly. Finally , The reasonability and validity of the simulation model are testified by the three different simulation results.To reducing the torque ripple of machine in conventional Direct Torque Control strategy, according to duty ratio control, a changed vector table was proposed in Direct Torque Control based on the new ATR. The changed strategies of Direct Torque Control can reduce the torque ripple largely. Finally the reasonability and validity of the changed strategy are testified by the simulation results Based on Matlab 6.5 / Simulink.Finally, according to the problems of voltage unbalance of neutral point and high dv/dt of output voltage,a method are used in the the system of the three-level Direct Torque Control of diode Netrual-Point-Clamp(NPC) three-level inverter.