The Simulation Reserch Of Direct Torque Control For Induction Motor System Based On The Three-level Inverter

Following the Vector Control (VC) technique, Direct Torque Control (DTC) of asynchronous motor is a new and high-powered AC driving control technique, which has been developed rapidly in the recent decades. The DTC technique has many advantages, such as the idea of DTC is novel, the structure is simple, and the control method of DTC is directly. DTC is an excellent AC driving control technique, which has high static and dynamic performance and has been successfully applied in many occasions up to now. However, the applications of this method are limited due to some disadvantages, such as, the large ripple of electromagnetic torque, the great harmonic components, and the distortion of the stator flux track. Three-level neutral-point-champed inverter is applied to DTC system for improving control performance of DTC system. However, higher dv/dt and neutral point voltage floating often occur at the common three-level inverter, therefore, the modified modulate strategy is first studied for an induction motor system (IM) fed by a three-level inverter to implement direct torque control (DTC), and then the SIMULINK model is set up for the direct torque controlled induction motor system fed by the modified three-level inverter's modulate strategy. Simulation results show that the modified modulate strategy can not only overcome the shortage of neutral point voltage floating and higher dv/dt in the common three-level inverter, but also reduce the torque ripple, therefore, improve the dynamic performance of a direct torque controlled IM system markedly.